B1.1M03 Presentation V1.0 Dated 02.02.09

PART 66 CATEGORY B1.1 MODULE 3 : ELECTRICAL FUNDAMENTALS

ELECTRON THEORY (EASA Ref : 3.1)

B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 2

EASA Ref:3.1

ATOMIC STRUCTURE -

smallest part of an element (solar system)

-

element, molecules and compound nucleus consists of PROTONS and NEUTRONS electrons – around the orbit of an atom

-

Charge of proton – positive Charge of electron – negative Charge of neutron – neutral

-

Proton and Neutron makes up app. 98% of the mass


Slide No 3

EASA Ref :3.1


Slide No 4

EASA Ref :3.1


Slide No 5

EASA Ref :3.1


Slide No 6

EASA Ref :3.1

IONISATION FACTORS AFFECTING IONISATION: HEAT LIGHT ELECTRIC FIELDS MAGNETIC FIELDS CHEMICAL ACTION PRESSURE CAN BE: POSITIVE ION (LOSS OF ELECTRON) or NEGATIVE ION (GAIN OF ELECTRON) MOVEMENT OF ELECTRON IS CURRENT FLOW


Slide No 7

EASA Ref :3.1


Slide No 8

EASA Ref :3.1


Slide No 9

EASA Ref :3.1

MOLECULAR STRUCTURE OF CONDUCTOR, INSULATOR AND SEMICONDUCTOR A MATERIAL WHICH ALLOW ELECTRONS TO FLOW IS KNOWN AS CONDUCTOR. EX: GOLD, COPPER, SILVER and ALUMINUM A MATERIAL WHICH PREVENTS ELECTRON FLOW IS KNOWN AS INSULATOR. EX: DRY AIR, MICA, EBOLITE, PORCELIN and RUBBER A MATERIAL WHICH RESTRICTS ELECTRON FLOW IS KNOWN AS SEMICONDUCTOR. EX: SILICON, GERMANIUM and TELLURIUM


Slide No 10

STATIC ELECTRICITY AND CONDUCTION ( EASA Ref : 3.2 )


Slide No 11

EASA Ref : 3.2

STATIC ELECTRICITY AND DISTRIBUION OF ELECTROSTATIC CHARGES FRICTION: RUBBING OF 2 DIFFERENT MATERIALS, WHEREBY ONE MATERIAL LOSSES ELECTRONS AND THE OTHER GAINS ELECTRONS MATERIAL WITH LESS ELECTRONS IS CALLED POSITIVELY CHARGED MATERIAL WITH GAINED ELECTRONS IS CALLED NEGATIVELY CHARGED


Slide No 12

EASA Ref : 3.2

MATERIALS THAT ACQUIRE A CHARGE OF STATIC ELECTRICITY: GLASS,AMBER, HARD RUBBER,WAXES, NYLON,RAYON, SILK, FLANNEL. EX: HARD RUBBER RUBBED AGAINST FUR. ROD – NEGATIVE CHARGE FUR – POSITIVE CHARGE


Slide No 13

EASA Ref : 3.2

ELECTROSTATIC LAW OF ATRACTION AND REPULSION: (COULOMB’S LAW) LIKE CHARGES REPELS and UNLIKE CHARGES ATTRACTS

COULOMB’S LAW – UNITS OF CHARGE: QUANTITY (UNIT OF CHARGE) OF ELECTRICITY = COULOMB SYMBOL FOR COULOMB = Q 1 COULOMB = 6,290,000,000,000,000,000 ELECTRONS = 6.29 x1018 ELECTRONS


Slide No 14

EASA Ref : 3.2

CONDUCTION OF ELECTRICITY IN SOLIDS – ELECTRONS IN LIQUIDS – POSITIVE IONS OR NEGATIVE IONS IN GASES – ELECTRONS AND IONS IN A VACUUM – ELECTRONS AND IONS


Slide No 15

ELECTRICAL TERMINOLOGY (EASA Ref : 3.3 )

ELECTRICAL TERMINOLOGY, UNIT and AFFECTIVE FACTORS: DIFFERENCE IN POSITIVE AND NEGATIVE CHARGE = POTENTIAL DIFFERENCE (PD) UNIT OF PD - VOLTS 120 VOLTS WITH 0 VOLTS = A PD of 120 VOLTS - 120 VOLTS WITH 0 VOLTS = A PD of 120 VOLTS

+ 120 VOLTS WITH - 120 VOLTS = A PD of 240 VOLTS THIS PD CAN FORCE ELECTRONS TO FLOW FROM NEGATIVE CHARGE TO POSITIVE CHARGE DUE TO ELECTRICAL PRESSURE


Slide No 16

EASA Ref : 3.3


Slide No 17

EASA Ref : 3.3


Slide No 18

EASA Ref : 3.3

CONVERSION OF ENERGY: -

CHEMICAL ENERGY CONVERTED TO ELECTRICAL ENERGY

-

ELECTRICAL ENERGY CONVERTED TO LIGHT ENERGY

-

LIGHT ENERGY CONVERTED TO HEAT ENERGY


Slide No 19

EASA Ref : 3.3


Slide No 20

EASA Ref : 3.3

EMF CAN BE MEASURED WHEN NO CURRENT FLOWS PD CAN BE DETERMINED Reason: voltage will be dropped across the internal resistor of the battery EMF = PD + INTERNAL VOLTAGE DROP NO CURRENT FLOWS , EMF =PD UNIT FOR EMF AND PD IS VOLTS


Slide No 21

EASA Ref : 3.3


Slide No 22

EASA Ref : 3.3

VOLTAGE:

ELECTRICAL POTENTIAL = JOULES PER COULOMB (VOLTS) CURRENT:

1 AMPERE = 1 COULOMB PER SECOND (Q = AMPERE X TIME) , Q=I/t UNIT FOR CURRENT = AMPERE (Amp)

SYMBOL FOR CURRENT = I


Slide No 23

EASA Ref : 3.3

PREFIXES: 0.1 Amp = 100 milliamp 0.010 Amp = 10 milliamp 0.001 Amp = 1 milliamp 0.000001 Amp = 1 microamps

3 TYPES OF CURRENT: -

DIRECT CURRENT (DC)

-

PULSATING CURRENT (PULSATING DC )

-

ALTERNATING CURRENT (AC)


Slide No 24

EASA Ref : 3.3

DC - CURRENT FLOWS CONTINUOUSLY IN ONE DIRECTION

PULSATING DC - CURRENT FLOWS IN ONE DIRECTION BUT VARIES IN AMPLITUDE BUT DOES NOT GO BELOW ZERO

AC - CURRENT FLOWS IN ONE DIRECTION , THEN IN THE OTHER DIRECTION AND CHANGES FROM POSITIVE TO NEGATIVE AND THEN POSITIVE AGAIN AND SO FORTH


Slide No 25

EASA Ref : 3.3

FREQUENCY:

1 HERTZ = 1 CYCLE PER SECOND UNIT FOR FREQUENCY = HERTZ (Hz)


Slide No 26

EASA Ref : 3.3


Slide No 27

EASA Ref : 3.3


Slide No 28

EASA Ref : 3.3

RESISTANCE: THE PROPERTY OF A MATERIAL WHICH OPPOSSES ELECTRON FLOW. DIFFERENT MATERIAL HAVE DIFFERENT VALUE OF RESISTANCE SILVER = VERY LOW RESISTANCE RUBBER = VERY HIGH RESISTANCE SYMBOL = R UNIT = OHMS (Ω)


Slide No 29

EASA Ref : 3.3

Prefixes: 1 MICRO OHM = 0.000001 OHM = 1µΩ 1 milliohm = 0.001 OHM = 1 mΩ 1000 ohms = 1 kilo ohm = 1 k Ω 1000000 ohm = 1 M Ω

Note: resistor are used to control current flow


Slide No 30

EASA Ref : 3.3

3 FACTORS AFFECTING RESISTANCE: -

LENGTH

-

CROSS-SECTION

-

MATERIAL ρ (rho)

Rho = the resistance of 1 meter of the material and the cross-section of 1 millimeter square


Slide No 31

EASA Ref : 3.3

CONDUCTANCE: -

OPPOSITE TO RESISTANCE – THE EASE OF CURRENT FLOW

-

IT IS THE RECIPROCAL OF RESISTANCE

-

UNIT FOR CONDUCTANCE = SIEMENS (S)

G= 1/R

or

R = 1/G

G= V / I


Slide No 32

EASA Ref : 3.3

ELECTRIC CHARGES: ELECTRIC CHARGES GIVES A MATERIAL ITS ELECTROMAGNETIC PROPERTIES

PROTON - POSITIVE CHARGE ELECTRON - NEGATIVE CHARGE NEUTRON - ZERO CHARGE / NEUTRAL


Slide No 33

EASA Ref : 3.3

2 TYPES OF CURRENT FLOW:

ELECTRON FLOW - ELECTRONS FLOW FROM NEGATIVE TO POSITIVE CONVENTIONAL CURRENT FLOW - HOLES TRAVEL FROM POSITIVE TO NEGATIVE


Slide No 34

EASA Ref : 3.3


Slide No 35

EASA Ref : 3.3


Slide No 36

EASA Ref : 3.3

WHEN A BATTERY IS CONNECTED TO A LOAD ELECTRONS FLOW FROM NEGATIVE TO POSITIVE AT THE TERMINALS.

CURRENT (ELECTRONS) FLOWS FROM THE POSITIVE ROD TO THE NEGATIVE ROD INSIDE THE BATTERY THROUGH THE ELECTROLYTE.


Slide No 37

EASA Ref : 3.3


Slide No 38

GENERATON OF ELECTRICITY ( EASA Ref : 3.4 )

6 BASIC MEANS OF GENERATING ELECTRICITY FRICTION -

PRESSURE

-

HEAT

-

LIGHT

-

MAGNETISM

-

CHEMICAL ACTION


Slide No 39

EASA Ref : 3.4


Slide No 40

EASA Ref : 3.4

FRICTION:

WHEN 2 DIFFERENT MATERIALS ARE RUBBED TOGETHER ELECTRONS TEND TO TRANSFER FROM ONE MATERIAL TO ANOTHER ONE BECOMES POSITIVE AND THE OTHER WILL BE NEGATIVE


Slide No 41

EASA Ref : 3.4


Slide No 42

EASA Ref : 3.4

MAGNETISM

WHEN A MAGNET IS MOVED INTO A COIL AND REMOVED, A VOLTAGE IS PRODUCED KNOWN AS INDUCED VOLTAGE. THE PROCESS IS KNOWN AS INDUCTION THE VALUE OF VOLTAGE INDUCED DEPANDS ON THE SPEED OF MOVEMENT AND NUMBER OF COILS FREE ELECTRONS ARE FORCED TO MOVE WITHIN THE WIRE


Slide No 43

EASA Ref : 3.4


Slide No 44

EASA Ref : 3.4


Slide No 45

EASA Ref : 3.4

HEAT: WHEN HEAT IS APPLIED TO A JUNCTION OF 2 DIFFERENT MATERIAL, ELECTRONS ARE FORCED TO MOVE. 2 JUNCTIONS, COLD AND HOT JUNCTION THE EFFECT IS KNOWN AS THERMO-ELECTRIC EFFECT USED IN ENGINES, EXHAUST GASES, OVENS and FURNACES


Slide No 46

EASA Ref : 3.4


Slide No 47

EASA Ref : 3.4

PRESSURE: WHEN QUARTZ PLATE IS COMPRESSED, A VOLTAGE IS PRODUCED WHEN A VOLTAGE IS APPLIED, COMPRESSION OF THE QUARTZ IS PRODUCED THIS EFFECT IS KNOWN AS PIEZOELECTRIC EFFECT USED FOR TRANSMISSION AND RECEPTION OF ULTRASONIC VIBRATION IN WATER (SONAR, ECHO SOUNDER )


Slide No 48

EASA Ref : 3.4


Slide No 49

EASA Ref : 3.4

LIGHT

WHEN LIGHT STRIKES A PHOTO-VOLTAC MATERIAL, A VOLTAGE IS

PRODUCED

THIS EFFECT IS KNOWN AS PHOTO-ELECTRIC EFFECT USED IN PHOTO-DIODES, PHOTO-TRANSISTORS, SOLAR CELLS AND SILICON CELLS ALSO SMOKE DETECTOR.


Slide No 50

EASA Ref : 3.4


Slide No 51

EASA Ref : 3.4

CHEMICAL EFFECT WHEN 2 DISSIMILAR METALS ARE PLACED SIDE BY SIDE, ELECTRONS TEND TO FLOW. ELECTRONS FROM THE NEGATIVE POLARITY WILL MOVE TOWARDS THE POSITIVE POLARITY. WHEN 2 PLATES OF DISSIMILAR METALS ARE PLACED IN AN ELECTROLYTE, OPPOSITE ELECTRIC CHARGES WILL BE ESTABLISHED ON THE PLATES, RESULTING AN ELECTRICAL VOLTAGE(PD)


Slide No 52

EASA Ref : 3.4


Slide No 53

DC SOURCES OF ELECTRICITY ( EASA Ref : 3.5 )

DC SOURCES OF ELECTRICITY: WHEN 2 DISSIMILAR METALS ARE PLACED IN A CHEMICAL (ELECTROLYTE), AN ELECTRIC CELL IS FORMED KNOWN AS SIMPLE CELL WHEN MORE THAN 2 CELLS JOINT TOGETHER, IT IS KNOWN AS A BATTERY WHEN CERTAIN SUBSTANCES ARE DISSOLVED IN WATER +ION OR -ION IS PRODUCED. THIS EFFECT IS KNOWN AS ELECTROLYTIC DISSOCIATION AND THIS SUBSTANCE IS KNOWN AS ELECTROLYTE THEY CAN BE ACID OR ALKALINE


Slide No 54

EASA Ref : 3.5

THE RELATIONSHIP BETWEEN DISSIMILAR METALS IS KNOWN AS ELECTROCHEMICAL SERIES.

EX: A NICKEL CADMIUM BATTERY NICKEL = -0.22V CADMIUM = - 0.40V PD OF THE CELL = - 0.22 – (- 0.40) = 0.18V


Slide No 55

EASA Ref : 3.5


Slide No 56

EASA Ref : 3.5 ENERGY CONVERSION: CHEMICAL ENERGY IS CONVERTED TO ELECTRICAL ENERGY AS ZINC DISSOLVES, THE +IONS MOVE TOWARDS THE COPPER ELECTRODE (ZINC BECOMES EVEN MORE NEGATIVE WITH RESPECT TO THE ELECTROLYTE 1.1 V IS PRESENT AT THE TERMINALS (ANODE AND CATHODE ) 2 CONDITIONS WHEN ELECTRICITY CAN BE EXHAUSTED a) ZINC FULLY DISSOLVED or b) ELECTROLYTE EXHAUSTED (THE IONS USED UP)


Slide No 57

EASA Ref : 3.5

HYDROGEN BUBBLES FORM WHEN ELECTRIC CURRENT IS GENERATED

BUBBLES FORM BARRIER AT THE ANODE CAUSING A REDUCTION IN CURRENT FLOW

THIS EFFECT IS KNOWN AS POLARIZATION FORMATION OF HYDROGEN BUBBLES AT THE ANODE OF THE CELL


Slide No 58

EASA Ref : 3.5


Slide No 59

EASA Ref : 3.5


Slide No 60

EASA Ref : 3.5

CLASSES OF CELLS PRIMARY CELL = NOT RECHARGEABLE = CAN BE USED ONLY ONCE SECONDARY CELL = RECHARGEABLE = CAN BE REUSED MANY TIMES


Slide No 61

EASA Ref : 3.5

CELLS CAN BE CONNECTED IN 2 WAYS

SERIES = EX: 3 CELLS OF 1.2V = 3.6V, HIGHER OUTPUT VOLTAGE AND CAPACITY OUTPUT (AH )THE SAME PARALLEL = EX: 3 CELLS OF 1.2V = 1.2V ,OVERALL VOLTAGE THE SAME BUT CAPACITY OUTPUT ( AH ) INCREASED


Slide No 62

EASA Ref : 3.5


Slide No 63

EASA Ref : 3.5


Slide No 64

EASA Ref : 3.5


Slide No 65

EASA Ref : 3.5


Slide No 66

EASA Ref : 3.5

INTERNAL RESISTANCE OF BATTERY Ri = 0.5Ω

Rex = 5.5 Ω

EMF = 12 V

RT = 0.5 + 5.5 = 6Ω IT = EMF/RT = 12/6 = 2Amp Uri = IT X Ri = 2 X 0.5 = 1V PD = 12 – 1 V = 11V


Slide No 67

EASA Ref : 3.5


Slide No 68

EASA Ref : 3.5


Slide No 69

EASA Ref : 3.5

AIRCRAFT BATTERIES A device composed of two or more cells that convert chemical energy into electrical energy. has 2 terminals: - negative terminal with excess of electrons - positive terminal with lack of electrons -output is steady DC voltage -purpose on aircraft: - stand-by power - auxiliary power start up


Slide No 70

EASA Ref : 3.5

Dry cell also known as leclanche cell -produced by a French, Georges leclanche in 1839-1889 -commonly used but can be used only once (primary cell)


Slide No 71

EASA Ref : 3.5


Slide No 72

EASA Ref : 3.5

Secondary cell also called storage batteries -can be recharged -do not produce electrical energy but can be recharged by storing in chemical form -after a certain number of charges and discharges the battery should be replaced e.g. - lead acid battery nickel cadmium battery etc


Slide No 73

EASA Ref : 3.5

Lead Acid


Slide No 74

EASA Ref : 3.5

LEAD ACD BATTERIES

-

positive plate is made of lead peroxide (PbO2) negative plate is made of pure spongy lead (Pb)

-

the electrolyte is made up of sulphuric acid (30%) and distilled water (70%)

-

the 2 plates are separated by plates known as separators purpose of the porous separators is to prevent short circuit

-

offer minimum resistance to current flow due to the material of the separators (porous )


Slide No 75

EASA Ref : 3.5


Slide No 76

EASA Ref : 3.5

Lead acid battery construction -consists of a group of lead acid cells connected in series. -the positive plates are connected together to a plate strap, the negative plates are also connected together to a different plate strap -they are both insulated from each other


Slide No 77

EASA Ref : 3.5

Lead acid


Slide No 78

EASA Ref : 3.5

the 3 elements are placed inside a hard rubber of plastic composite container the container are sealed to prevent leakage or spillage and loss of electrolyte ventilation caps are located at the top to let the gasses due to chemical action.


Slide No 79

EASA Ref : 3.5

Construction


Slide No 80

EASA Ref : 3.5

Specific Gravity Test Procedure

-

wear goggles to protect eyes

-

ventilation caps to be removed

-

squeeze the hydrometer rubber bulb hard and insert it into the cell hole closest to the positive terminal. (to be repeated at all cell holes)

-

release the bulb slowly without removing the tube out of the electrolyte

-

the float movement should not be restricted

-

observe the reading at eye level.


Slide No 81

EASA Ref : 3.5

Specific gravity


Slide No 82

EASA Ref : 3.5

Lead Acid Battery Inspection and Service -inspect for cracks on supporting structure -inspect for corrosion and evidence of leakage by opening the covers -refill electrolyte if the level is below the level -check for defect by carrying out load test or hydrometer test -check that the terminals are not corroded -check that the cables are in good condition (not cracked or broken) -check that the ventilation of the aircraft and battery box is good


Slide No 83

EASA Ref : 3.5

Lead acid


Slide No 84

EASA Ref : 3.5

ALKALINE BATTERIES -

positive plate, nickel hydroxide , NI(OH)2

-

negative plate, metallic cadmium (Cd)

-

electrolyte, potassium hydroxide (KOH)

-

plates are made by sintering process

-

active material impregnated into the plate by chemical deposition


Slide No 85

EASA Ref : 3.5

Alkaline Battery


Slide No 86

EASA Ref : 3.5 Nickel cadmium battery


Slide No 87

EASA Ref : 3.5

Connections of cells


Slide No 88

EASA Ref : 3.5

Different capacity batteries


Slide No 89

EASA Ref : 3.5

Inspection of Alkaline Battery -inspections -

are based on: flying hours annual inspection periodic inspection (normally 28 days)

-what is to be inspected: the case proper airflow of the vent system the cells (clean if required) the cell connector for corrosion, cracks and overheating the cell caps are clean and not clogged for correct electrolyte level


Slide No 90

EASA Ref : 3.5

CHARGING OF BATTERY 2 methods (constant voltage or constant current) constant -

voltage charging voltage is held constant always. current diminishes as the battery is charged the electron flow resistance is reduced as the charge increases as the battery voltage increases, the charger current reduces

-

on the aircraft, batteries are normally constant voltage charged.

-

if more than one battery is to be charged at one time, they must be connected in parallel


Slide No 91

EASA Ref : 3.5

Constant Current Charging

current is held constant but voltage varies equipment monitors the current constant while the voltage decreases if more than one battery is to be charged, it should be in series over charging is to be prevented


Slide No 92

EASA Ref : 3.5

THERMOCOUPLES -a sensor for the measure of temperature -consists of 2 dissimilar metals (also in the form of alloy wires) -voltage is formed either heated or cooled and correlated back to temperature -a voltage produced by heating is known as Peltier Seeback Effect (thermoelectric effect )


Slide No 93

EASA Ref : 3.5

Operation of Thermocouples voltage depends on: -types of material used -temperature difference between hot and cold junctions Connected in a closed loop parallel circuit: -when heated the resistance changes at a known rate -voltage is proportional to the temperature


Slide No 94

EASA Ref : 3.5

Measuring and Reference junctions -measuring junction is the hot junction exposed to temperature -reference junction is the cold junction where the temperature is held constant


Slide No 95

EASA Ref : 3.5

Thermocouple


Slide No 96

EASA Ref : 3.5

Types of Thermocouple surface contact type -

measures temperatures of solid components

-

cylinder head temperature-indicating systems of air cooled engines

immersion type -

measures gases and liquid temperatures (engine oil) gas temperature-indicating system of turbine engines


Slide No 97

EASA Ref : 3.5

Thermocouples


Slide No 98

EASA Ref : 3.5

– Copper – Constantan (T curve) Thermocouples

-copper wire is positive and constantan is negative wire -used in mildly oxidizing and reducing temp. of up to 400º C -suitable at moist and low temp. areas -due to the low temp. the homogeneity of the component wire can be maintained. -errors are very low


Slide No 99

EASA Ref : 3.5

Chromel-Alumel (K Curve) -chromel : 90% nickel, 10% chromium -alumel : 95% nickel, 2% maganese, 2% aluminium and 1% silicon -positive is the chromel wire and the negative is the alumel wire -used in clean oxidizing atmosphere -operating temp. for the largest wire size is 1260ºC -smaller wires operate at lower temp.


Slide No 100

EASA Ref : 3.5

– Voltages produced by Thermocouples C – tungstan rhenium = 15 µV / ºC E – chromel constantan = 68 µV / º C J – iron constantan = 52 µV / º C K – chromel alumel = 41 µV / º C R – platinum radium (13% platinum) = 10 µV / ºC S – platinum rhodium (10% platinum) = 10 µV / ºC T – copper constantan = 42 µ V / ºC N – nicrosi (nickel, chromium and silicon) = 40 V /ºC


Slide No 101

EASA Ref : 3.5

Temperature versus Voltage


Slide No 102

EASA Ref : 3.5


Slide No 103

EASA Ref : 3.5

PHOTOCELLS -also known as Solar Cell or Photovoltaic cell -converts ultra violet and infra red light directly into voltage uses of photocells (known as electric eye) -light activated counters -automatic door opener -intrusion alarms


Slide No 104

EASA Ref : 3.5

Construction of photocell -P-type Silicon the metal rib is the positive electrode , metal backing is the negative electrode (N type Silicon) -each solar cell can produce about 1 watt of power and 0.5 volts


Slide No 105

EASA Ref : 3.5

Operation of photocell -P-type and N-type semiconductor are sandwiched together -produces low power -reacts to light in a short time period - accurately controlling a great number of operations Used in: -video camera -automatic manufacturing process controls -door openers -burglar alarms -smoke detector


Slide No 106

DC CIRCUITS ( EASA Ref : 3.6 )

DIRECT CURRENT ELECTRICAL CIRCUITS A DC circuit is necessary for DC electricity to exist

Types of DC circuits: -

series parallel combination of series and parallel


Slide No 107

EASA Ref : 3.6

Simple circuits:

If a load is connected to a battery, current flows from the pos. term. to the neg. terminal. the load, if it is a bulb, it should light up until the battery is discharged or the bulb has blown. keeping in mind that electron flow from cathode to anode whereas conventional flow holes travel from anode to cathode


Slide No 108

EASA Ref : 3.6


Slide No 109

EASA Ref : 3.6

Sources of DC power supply: -

battery

-

DC generator

-

rectifier output

3 components associated with a circuit: -

voltage => unit volts

-

current => unit amperes or amps

-

resistance => ohms


Slide No 110

EASA Ref : 3.6

Conductors: wires are normally made of copper but it can also be aluminum or any other low resistance elements tungsten is also a conductor but has a very high resistance to current therefore it heats and lights up


Slide No 111

EASA Ref : 3.6

Series circuit


Slide No 112

EASA Ref : 3.6

SERIES DC CIRCUIT when 2 or more components are connected one after the other in a line, it is said that they are in series the current that flows in this circuit is the same in all components but the voltage is divided among them components cannot be controlled individually disadvantage is that if one component fails, than all will not function


Slide No 113

EASA Ref : 3.6

schematic


Slide No 114

EASA Ref : 3.6

SCHEMATIC The circuit elements in fig. 51 are connected end to end The current flows through each element is the same, but volt drops different. A component (ex. Bulb) will be represented as a resistor and drawn as a rectangular block or zig-zag line.


Slide No 115

EASA Ref : 3.6

parallel


Slide No 116

EASA Ref : 3.6

PARALLEL DC CIRCUIT

2 or more components are connected side by side with each other.

if any one fails than the others will still be operational all components can be controlled individually


Slide No 117

EASA Ref : 3.6


Slide No 118

EASA Ref : 3.6


Slide No 119

EASA Ref : 3.6

When the series circuits and the parallel circuits are connected together, they are said to be a combination.


Slide No 120

EASA Ref : 3.6 OHM’S LAW the current passing thru’ a conductor from one terminal to another is directly proportional to the PD across the 2 terminals and inversely proportional to the resistance of the conductor between the 2 points it is true only for lower current and voltage at high current and voltages the law does not apply (due to heat) Formula: I = V/R


Slide No 121

EASA Ref : 3.6

sometimes the potential difference is also known as the voltage drop, abbreviated as E or U instead of V when 1 amp of current flows thru’ an ohm resistor with 1 volt is known as one volt per ampere.


Slide No 122

EASA Ref : 3.6

Figure 54 :Ohm’s Law


Slide No 123

EASA Ref : 3.6

Using the equation when 2 variables are known, the 3rd variable can be calculated. voltage = current x resistance current = voltage / resistance resistance = voltage / current B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 124

EASA Ref : 3.6

Figure 55 : Solving Circle


Slide No 125

EASA Ref : 3.6

– To find resistance:

R=V/I = 6V / 2A =3Ω


Slide No 126

EASA Ref : 3.6

I= E/R = 1.5V / 10Ω = 0.15 Amp = 150mA


Slide No 127

EASA Ref : 3.6

ANALOGY:

E = I X R (constant)

(constant) E = I X R (constant) E =I X R B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 128

EASA Ref : 3.6


Slide No 129

EASA Ref : 3.6

KIRCHHOFF’S LAW KIRCHHOFF’S LAW IS DIVIDED INTO 2 -

CURRENT LAW

-

VOLTAGE LAW

KIRCHHOFF’S CURRENT LAW = KIRCHHOFF’S JUNCTION LAW = KIRCHHOFF’S FIRST LAW STATES: THE ALGEBRAIC SUM OF CURRENT INTO ANY JUNCTION IS ZERO (This also means that the sum of current flowing into a junction equals the sum of current flowing out of the junction)


Slide No 130

EASA Ref : 3.6

i1=5amp, i2=5amp, i3=8amp, i4=5amp, i5=4amp, i6=11amp

i2

i1

i3 OUT FLOWING

i6 i4

IN FLOWING

i5 SUM: i1 + i2 +i4 + i5 = i3 + i6 => 5A + 5A + 5A + 4 A = 8A + 11A => 19A = 19A ALGEBRAIC: i1 + i2 - i3 + i4 + i5 - i6 = 0 => 5A + 5A -8A + 5A + 4A - 11A =0 => 0 = 0


Slide No 131

EASA Ref : 3.6

– KIRCHHOFF’S CURRENT LAW


Slide No 132

EASA Ref : 3.6

KIRCHHOFF’S VOLTAGE LAW STATES: THE ALGEBRAIC SUM OF THE VOLTAGE (POTENTIAL DIFFERENCES) IN ANY LOOP MUST EQUAL ZERO VR1 + VR2 + VR3 = 18 V => 6V + 6V + 6V = 18V 6V +

2K

6V _+

R 1 3 mA

2K R 2

=> 18V = 18V => 0 = 0

6V _+

2K

_

R 3

18V B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 133

EASA Ref : 3.6


Slide No 134

EASA Ref : 3.6


Slide No 135

EASA Ref : 3.6


Slide No 136

EASA Ref : 3.6

SIGNIFICANCE OF THE INTERNAL RESISTANCE OF A SUPPLY

NEW BATTERIES WITHOUT INTERNAL RESISTANCE WILL PRODUCE AN EMF THAT IS EQUAL TO THE PD. WHEN THE RESISTANCE OF THE ELECTOLYTE INCREASES THE PD WILL DECREASE AS THE INTERNAL RESISTANCE INCREASES EVEN MORE, THE VOLTAGE DROP WITHIN THE BATTERY INCREASES EVEN MORE.


Slide No 137

EASA Ref : 3.6

EX: NEW BATTERY VOLTAGE = 12V AND THE INTERNAL RESISTANCE = 1Ω. THE LOAD TAKES UP 0.5 Amp. WHAT IS THE INTERNAL VOLTAGE DROP? INT. VOLT DROP = 0.5 Amp X 1 Ω = 0.5 V AND THEREFORE, THE TERMINAL VOLTAGE = 12V – 0.5 V = 11.5V FORMULA: V = E – (I X r) BULB I =0.5 Amp

E = 12 VOLTS

r=1Ω


Slide No 138

EASA Ref : 3.6


Slide No 139

RESISTANCE / RESISTORS ( EASA Ref : 3.7 )

RESISTORS and RESISTANCE COMES IN MANY -

SHAPES

-

SIZES

-

VALUES

-

WATTAGES


Slide No 140

EASA Ref : 3.7

SYMBOLS


Slide No 141

EASA Ref : 3.7

SI UNIT for RESISTANCE – Ohm 1 OHM = 1 VOLT OF PRESSURE THAT CAN PUSH 1 AMP OF CURRENT THRU’ A RESISTOR IN A SECOND 18 1 AMP OF CURRENT = 6.24150629 X 10 ELECTRONS PER SEC MULTIPLES: Ex: 1K Ω = 1000 Ω 1M Ω = 1000000 Ω = 1 X 10 6 Ω 170K Ω =170000 Ω 1M5 = 1500000 Ω SI => Systeme international d’unites or International system of unit Body responsible => bureau international des poits et mesures (BIPM)


Slide No 142

EASA Ref : 3.7


Slide No 143

EASA Ref : 3.7

IF A RESISTOR HAS A NUMBER SUCH AS 10, 15 or 110 , IT MEANS THAT IT IS 10 Ω 15 Ω 110 Ω or 10R 15R AND 110R R CAN ALSO BE REPRESENTED BY THE LETTER E. i.e: 10R 15R AND 110R. IT CAN BE REPRENENTED BY 10E 15E AND 110E 1.1 = 1E1 or 1R1

2.5 = 2E5 or 2R5


9.7 = 9E7 or 9R7

Slide No 144

EASA Ref : 3.7

IDEAL RESISTOR DOES NOT CHANGE IN RESISTANCE IN THE CIRCUIT IN ANY CIRCUMTANCES. RESISTANCE VALUES ARE AFFECTED BY THE APPLIED VOLTAGE, CURRENT, TEMPERATURE AND OTHER ENVIRONMENTAL FACTORS EVERY RESISTOR OPERATES WITHIN THE TOLERENCE IT IS MEANT TO. IF IT EXCEEDS THE WATTAGE TOLERENCE IT WILL BE DAMAGED WATTAGE FOR CARBON FILM OR METAL FILM RESISTORS ARE 1/8, 1/4 OR 1/2 WATT METAL FILM AND CARBON FILM RESISTORS ARE MORE STABLE WITH TEMPERATUE CHANGE THAN CARBON RESISTORS LARGER ONES ARE HIGHER POWERED ex: WIRE WOUND AND CERAMIC RESISTORS


Slide No 145

EASA Ref : 3.7 VARIABLES AFFECTING ELECTRICAL RESISTANCE LENGTH RESISTANCE INCREASES WITH LENGTH CROSS-SECTIONAL AREA OF THE WIRE RESISTANCE DECREASES WITH INCREASE IN AREA THE RHO OF THE MATERIAL DIFFERENT MATERIALS HAVE DIFFERENT RESISTANCE (CONDUCTIVE ABILITY) RESISTIVITY: DEPENDS ON THE MATERIALS ELECTRICAL STRUCTURE AND ITS TEMPERATURE TEMPERATURE MOST MATERIALS USED AS CONDUCTORS INCREASE IN RESISTANCE VALUE AS TEMPERATURE INCREASES. BUT THERE ARE MATERIALS THAT THEIR RESISTANCE DECREASE AS TEMPERATURE INCREASES


Slide No 146

EASA Ref : 3.7

RESISTIVITY


Slide No 147

EASA Ref : 3.7

LOWER RESISTIVITY =>HIGHER CONDUCTIVITY => HIGHER ELECTRON FLOW HIGHER RESISTIVITY => LOWER CONDUCTIVITY => LESS ELECTRON FLOW TEMPERATURE: EFFECTS RESISTANCE THE MOST MOST CONDUCTORS INCREASE IN RESISTANCE WITH INCREASE IN TEMPERATURE CARBON DECREASES, CONSTANTAN AND MANGANIN CHANGES VERY LITTLE WITH TEMPERATURE.


Slide No 148

EASA Ref : 3.7

TEMPERATURE COEFFICIENT: with the increase of the temp. by 1 degree from 0 degree causes one ohm to be increases in a conductor is known as temperature coefficient. when the resistance increases with the increase in temperature it is known as positive temperature coefficient. Ex: silver, aluminum and copper when the resistance decreases with the increase of temperature is known as negative temperature coefficient ex: insulators, semiconductors and thermistors manganin and constantan changes very little over their working temperature


Slide No 149

EASA Ref : 3.7

SPECIFIC RESISTANCE (RESISTIVITY)

THE RESISTANCE OFFERED BY A UNIT VOLUME. i.e *CIRCULAR-MIL-FOOT or CENTIMETER CUBE, THAT RESIST CURRENT FLOW IS KNOWN AS SPECIFIC RESISTANCE RESISTIVITY IS THE RECIPROCAL OF CONDUCTIVITY FORMULA: R= ρL/A (ρ – specific resistance in ohms per circular mil foot, L – length in feet and A – circular area in circular mils) * Circular mils => 1 thousandth of an inch


Slide No 150

EASA Ref : 3.7

SELECTION OF WIRE IF THE PROPER WIRE IS NOT SELECTED, THERE CAN BE A SEVERE DAMAGE TO AIRCRAFT OR OTHER EQUIPMENT EX: IF THE SUPPLY IS 28VDC AND THE LOAD REQUIRES A MIN. OF 26VDC WITH 5 AMP, WHAT IS THE MAXIMUM RESISTANCE THE WIRE CAN HAVE (2 WAYS)? R = E / I = 2V/5A = 0.4Ω IF THE LENGTH OF THE WIRE IS 20FT LONG AND THE RHO FOR STEEL IS 100 Ohm – cmil / ft , what is the area? A=ρXL R

= 100 Ω-cm/ft X 2O = 5000cmil 0.4


Slide No 151

EASA Ref : 3.7


Slide No 152

EASA Ref : 3.7

Ex 1: IN AN ALUMINUM WIRED CIRCUIT, AL 000 SWG IS USED. THE Rho OF THIS MATERIAL IS 0.920 Ω – cmil/ft AND WITH AN AREA OF 168872 cmil. THE LENGTH OF THE WIRE IS 20 ft. WHAT IS THE RESISTANCE OF THIS WIRE? R = ρ L = 0.920Ω-cmil/ft X 20ft A 168872 cmil

= 108.958 µΩ

Ex 2: IN AN ALUMINUM WIRED CIRCUIT, AL 6 SWG IS USED. THE RESISTANCE IS 641 µΩ, AREA IS 28280 cmil AND THE LENGTH IS 30 ft. WHAT IS THE Rho OF THIS MATERIAL.

ρ = R X A = 641 µΩ X 28280cmil = 0.60425 Ω-cmil/ft L

30ft


Slide No 153

EASA Ref : 3.7


Slide No 154

EASA Ref : 3.7

Figure 68


Slide No 155

EASA Ref : 3.7 BUSBAR (ALUMINUM)

3CM 4CM 125CM

AREA = WIDTH X HEIGHT

A = 4CM X 3CM = 12 CM²

SPECIFIC RESISTANCE: R=pL/A 2.65 µΩ-cm x 125cm / 12cm² R = 27.604 µΩ


Slide No 156

EASA Ref : 3.7

RESISTOR COLOUR CODE

4 COLOUR BANDS -

3 BAND FOR OHMS => 1st AND 2nd BANDS FOR VALUE THE 3rd BAND AS MULTIPLIER ( NUMBER OF ZEROES )

-

4th BAND FOR TOLERANCE 5%, 2% AND 1%


Slide No 157

EASA Ref : 3.7


Slide No 158

EASA Ref : 3.7

4 CODED RESISTORS

-

1001 = 100 + 0 = 1000 Ω = 1K Ω 1002 = 100 + 00 = 10000 Ω = 10K Ω

-

1003 = 100 + 000 = 100000 Ω = 100K Ω

-

4992 = 499 + 00 = 49900 Ω = 49.9K Ω


Slide No 159

EASA Ref : 3.7


Slide No 160

EASA Ref : 3.7

5 BAND RESISTORS

FOR MILITARY USE -

1st, 2nd AND 3rd BANDS DETERMINE THE FIRST 3 DIGITS

-

4th BAND IS THE MULTIPLIER

-

5th BAND IS THE TOLERANCE


Slide No 161

EASA Ref : 3.7

TOLERANCE FOR 5 CODED RESISTORS (BS 18520)

B = 0.1 % C = 0.25 % D = 0.5 % F=1% G=2% J=5% K = 10 % M = 20 %


Slide No 162

EASA Ref : 3.7

CYLINDRICAL SMD RESISTOR

-

1st, 2nd AND 3rd DIGITS ARE THE VALUE

-

4th BAND IS THE MULTIPLIER

-

5th BAND IS THE TOLERANCE

-

6th TEMPERATURE COEFFICIENT


Slide No 163

EASA Ref : 3.7

SURFACE MOUNTED DEVICE

563 -

THE SPACE AVAILABLE ON THE DEVICE IS LIMITED -

3 DIGIT CODE HAS A 5% TOLERANCE

-

4 DIGIT CODE HAS A 1% TOLERANCE

-

CERTAIN CIRCUITS TOLERANCES IS NOT IMPORTANT

-

CERTAIN CIRCUITS TOLERANCE IS IMPORTANT


Slide No 164

EASA Ref : 3.7

WATTAGE RATINGS WHEN CURRENT FLOWS THROUGH A RESISTOR, IT HEATS UP. IF THE TEMPERATURE EXCEEDS A CERTAIN CRITICAL VALUE THE RESISTOR WILL BE DAMAGED WATTAGE RATINGS OF A RESISTOR THE POWER THE RESISTOR CAN DISSIPATE OVER A LONG PERIOD OF TIME THEY ARE PRINTED ONLY ON LARGE RESISTORS


Slide No 165

EASA Ref : 3.7


Slide No 166

EASA Ref : 3.7

WATTAGE RATING

-1/16W, 1/8W, 1/2W, 1/4W RESISTORS ARE USED FOR ELECTRONICS -1W, 2W, 5W, 10W etc ARE USED FOR HEAVY DUTY CIRCUITS LIKE THE POWER SUPPLY. -IF REQUIRED A SMALL WATTAGE RESISTOR CAN BE REPLACE WITH A LARGER WATTAGE RESISTOR FOR THE SAME VALUE.


Slide No 167

EASA Ref : 3.7

WATTAGE CALCULATION: 1.

P = VxI

2.

P = V² / R

3.

P =I²xR

IF THE VOLATGE ACROSS A 250R RESISTOR IS 6 VOLTS, BATTERY POWER IS 15V, WHAT IS THE POWER DESSIPATED BY THIS RESISTOR? P = V² / R = 6² / 250 = 36 / 250 = 0.144 Watts = 144mW (RESISTOR REQUIRED IS ¼ Watt RESISTOR) NORMALLY POWER DESSIPATION IS CALCULATED WITH THE BATTERY POWER P = V² / R = 15² / R = 225 / 250 = 0.9Watts = 900mW (RESISTOR REQUIRED IS 1 Watt RESISTOR)


Slide No 168

EASA Ref : 3.7

RESISTORS CIRCUIT PATTERNS

RESISTORS ARE FOUND IN ALL ELECTRONIC CIRCUITS IN THE FORM OF: -SERIES -PARALLEL -SERIES PARALLEL COMBINATION


Slide No 169

EASA Ref : 3.7

SERIES CONFIGURATION

-CURRENT IS CONSTANT BUT THE VOLTAGE IS VARIABLE ACROSS EACH RESISTOR -THE RESISTORS ARE FITTED ONE AFTER THE OTHER - ELECTRONS FLOW ONLY IN ONE DIRECTION -THE TOTAL RESISTANCE IS THE SUM OF ALL THE RESISTORS R1 + R2 + R3 + …………….Rn


Slide No 170

EASA Ref : 3.7


Slide No 171

EASA Ref : 3.7 SERIES CONFIGURATION V1=5V

I=1A V2=8V V3=7V

R1 = V1/I = 5V/1A = 5 Ohms

R2 = V2/I = 8V/1A = 8Ohms

R3 = V3/I = 7V/1A = 7 Ohms

RT = 30 Ohms R4 = 30 – 5 – 8 – 7 = 10 Ohms THEREFORE V4 = I x R4 = 1 x 10 = 10V

THE TOTAL VOLTAGE IS = 5 + 8 + 7 + 10 = 30Volts


Slide No 172

EASA Ref : 3.7

PARALLEL CONFIGURATION -BRANCHED OUT FROM A SINGLE NODE AND RECOMBINE IN ANOTHER POINT -CURRENT DIVIDES BETWEEN THE BRANCHES WHEREAS THE VOLTAGE IS THE SAME FOR ALL BRANCHES 1 = Req

1 + 1 + 1 +…………. 1 R1 R2 R3 Rn

-symbol for parallel is //


Slide No 173

EASA Ref : 3.7

FORMULA -SINCE R1 // R2, Req = R1 x R2 R1 + R2 -IN A PARALLEL CCT THE TOTAL RESISTANCE IS LESS THAN THE SMALLEST RESISTOR.


Slide No 174

EASA Ref : 3.7 PARALLEL CONFIGURATION


Slide No 175

EASA Ref : 3.7

EMF = 12 V. SINCE VOLTAGE IS THE SAME IN ALL BRANCHES OF A PARALLEL CCT, R1, R2 AND R3 GETS 12V EACH

V1 = V2 = V3 = 12V

Ohms LAW STATES THAT I = V/R

THEREFORE I1 = 12/2 =6A

I2 = 12/3 = 4A

I3 = 12/6 = 2A

KIRCHHOFF’S LAW STATES: CURRENT INTO A JUNCTION IS EQUAL TO THE CURRENT OUT OF THE JUNCTION. IT =I1+I2+I3 = 6+4+2 = 12A


Slide No 176

EASA Ref : 3.7

COMBINATION CONFIGURATION (SERIES PARALLEL)

FORMULA: Req = (R1 // R2) + R3 = R1xR2 +R3 R1+R2


Slide No 177

EASA Ref : 3.7

COMBINATION

RAB = R1 + R2 (SERIES) RTOTAL= RAB x R3

(PARALLEL)

RAB + R3


Slide No 178

EASA Ref : 3.7

1/RAB = 1/R1 + 1/R2

1/RCD = 1/R4 + 1/R5


RTOTAL =RAB +R3 + RCD

Slide No 179

EASA Ref : 3.7

COMBINATION 1/RAB = 1/R1 + 1/R2 = 1/10 + 1/4.0 = 0.35 Therefore RAB=1/0.35 = 2.857 Ohms


1/RCD = 1/R4 +1/R5 = 1/8 +1/1 1.125 Therefore RCD = 1/1.125 = 0.889 Ohms

Slide No 180

EASA Ref : 3.7

RTOTAL = RAB + R3 + RCD = 2.857 + 3 + 0.889 = 6.7 Ohms


Slide No 181

EASA Ref : 3.7

EXAMPLE 2

RAB = R1 +R2 =1+2 = 3 Ohms

REF = R4 + R5 =4+5 = 9 Ohms


Slide No 182

EASA Ref : 3.7

1/RTot = 1/RAB + 1/R3 + 1/REF 1/RTot = 1/3 + 1/3 + 1/9 RTot = 1.286 Ohms


Slide No 183

EASA Ref : 3.7

FIXED RESISTORS -USED TO REDUCE CURRENT FLOW IN SOME PARTS OF A CIRCUIT -THE CURRENT AND VOLTAGE IS CONSTANT AT THE OUTPUT IF THE INPUT IS KEPT CONSTANT -COMES IN DIFFERENT VALUES - USED IN MOST ELECTRONIC EQUIPMENT AND ELECTRICAL DEVICES

INPUT


OUTPUT

Slide No 184

EASA Ref : 3.7

TOLERANCES AND LIMITATIONS CONDUCTING MATERIAL

CONDUCTING MATERIAL RESISTING MATERIAL

RESISTANCE IS PROPORTIONAL TO LENGTH AND Rho OF THE MATERIAL AND INVERSE TO THE X-SECTIONAL AREA -OHM’S LAW APPLIES -3 FACTOR WHEN SELECTING A RESISTOR: -TOLERANCE -POWER RATING -STABILITY B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 185

EASA Ref : 3.7

TOLERANCE

TOLERANCE -

SPECIFIES THE MAXIMUM AND MINIMUM VALUE OF RESISTANCE

-

A RESISTOR VALUE IS 1K Ohm AND HAS A TOLERANCE OF 20%. THEREFORE THE ACTUAL VALUE OF THE RESISTOR WILL BE WITHIN THE RANGE OF: 20% OF 1000 = 200 Ohms THEREFORE THE VALUE IS WITHIN 800 Ohms AND 1200Ohms


Slide No 186

EASA Ref : 3.7

POWER RATING POWER RATING 2 WATTS

1/4 WATT

-

INDICATES THE MAXIMUM POWER THE RESISTOR CAN HANDLE AT ROOM TEMPERATURE

-

SHOULD NOT EXCEED THE RATING OR ELSE IT WILL BE DAMAGED FOREVER

-

RATING CAN BE OF MANY VALUES Ex: ¼ W, ½ W, 1 W, 2W etc

-

BIGGER THE RESISTOR, THE LARGER IS THE RATING


Slide No 187

EASA Ref : 3.7

STABILITY -THE ABILITY TO MAINTAIN THE RESISTANCE OF THE CIRCUIT -CHANGES VERY LITTLE WITH CHANGE OF TEMPERATURE -IMPORTANT IN ELECTRONIC PRECISION CIRCUITS


Slide No 188

EASA Ref : 3.7 CONSTRUCTION METHODS

LOW POWER RESISTORS CARBON FILM RESISTOR IS MADE OF GRAPHITE CUT INTO BLOCKS OR WRAPPED OR GRAFTED INTO REQUIRED SHAPE X-SECT. DETERMINES THE POWER RATING TYPES OF CARBON FILM RESISTORS STANDARD FILM – BARREL OR CIRCULAR TYPE WITH PINS ON THE OPPOSITE SIDES CHIP TYPE – COMES UP TO 6 LAYERS NETWORK TYPE – CAN HAVE 12 RESISTORS IN 1 COMPACT SPACE. MAX VALUE 10 M Ohms. TOLERANCE +- 5%. RATINGS 0.125 W TO 1 WATT WITH GOOD STABILITY


Slide No 189

EASA Ref : 3.7


Slide No 190

EASA Ref : 3.7 HIGH POWER RESISTORS -

POWER RATING OF 5 TO 50 WATTS

-USED IN POWER SUPPLIES AND AMPLIFIERS GETS VERY HOT USES RESISTANT WIRE WRAPPED WITH CERAMIC MATERIAL SYMBOL IN CIRCUIT IS THE SAME AS OTHER CONVENTIONAL RESISTORS LOW TOLERANCE AND HIGH STABILITY MADE OF MAGANIN, NICHROME OR CONSTANTAN WIRE WOUND ON A FORMER AND A PROTECTIVE COATING VALUES - 1 Ohm TO 25K Ohms, POWER RATING O- 10 TO 20 WATTS B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 191

EASA Ref : 3.7


Slide No 192

EASA Ref : 3.7

VARIABLE RESISTORS RHEOSTATS -2 TERMINALS ( 1 MOVEABLE TERMINAL AND THE OTHER ONE CONNECTED TO THE TRACK END -MOVABLE TERMINAL PROVIDES THE VARIED RESISTANCE BY TURNING A SPINDLE -USED TO VARY CURRENT IN A CIRCUIT. Ex : VARY THE BRIGHTNESS OF A LAMP OR TO VARY THE CHARGING OF A CAPACITOR -2 TERMINALS FOR RIGIDITY OF WHICH 1 IS FOR INPUT. WIPER IS THE OUTPUT -USED WITH HIGH POWERED DEVICE > ½ WATT


Slide No 193

EASA Ref : 3.7

POTENTIOMETER -HAS 3 TERMINALS ( 2 FIXED AND 1 SLIDING TERMINAL ) -USED TO VARY VOLTAGES. Ex: VARY THE VOLUME OF AN AMPLIFIER, TO SET AS A PRESET TO A SENSOR -VOLTAGE CAN BE TAPPED ACROSS THE 2 FIXED TERMINALS -OUTPUT VOLTAGE CAN BE VARIED WITH THE WIPPER ROTATION FROM 0 UP TO THE SUPPLY VOLTAGE


Slide No 194

EASA Ref : 3.7


Slide No 195

EASA Ref : 3.7

PRESETS -VARIABLE RESISTORS BUT IN A MINIATURE FORM -MOUNTED ON THE CIRCUIT BOARD DIRECTLY -USED IN ALARM TONE SETTING, SENSITIVITY OF LIGHT SENSITIVE CIRCUITS ETC -DOES NOT HAVE SPINDLES BUT VALUE ADJUSTED WITH A SMALL SCREWDRIVER -CHEAP AND VERY ACCURATE -CAN BE 1 TURN TYPE OR MULTI TURN (10X) TYPE FOR FINE ADJ.


Slide No 196

EASA Ref : 3.7

Figure 87


Slide No 197

EASA Ref : 3.7

POTENTIOMETER CONSTRUCTION -2 TYPES: COATED TYPE -STRIP (ARC) OF INSULATING MATERIAL WITH A SLIDER MOVING OVER THE STRIP WHICH INCREASES AND DECREASES THE RESISTANCE AS IT MOVES OVER IT. RESISTANCE IS EITHER LINEAR, LOGARITHMIC (COMMONLY USED), INVERSE-LOGARITHMIC etc. USED FOR BALANCE, TONE AND VOL CONTROLS COILED TYPE -CONDUCTIVE WIRE WOUND OVER AN INSULATOR. BY MOVING THE SLIDER THE OUTPUT IS VARIED ACCORDINGLY. USED IN ACCURATE AND CONSTANCY CIRCUITS FUNCTIONS. USED FOR HIGH CURRENT APPLICATION WITH HIGHER POWER DISSIPATION


Slide No 198

EASA Ref : 3.7

RESISTANCE VALUE,TOLERANCE AND WATTAGE

RANGES FROM E6 SERIES = 1,2.2 AND 4.7. NORMALLY USED IN ELECTRONICS (1K, 2K, 5K, 10K, 1M, 10M, 50M etc) -

TOLERANCES RANGE FROM 30%, 20%, 10%, AND 5% (COILED POTS)

COMES IN DIFFERENT SHAPES AND SIZES AND WATTAGE FROM ¼ WATTS (COATED POTS FOR VOLUME CONTROL) TO 10s OF WATTS (REGULATING HIGH CURRENT )


Slide No 199

EASA Ref : 3.7


Slide No 200

EASA Ref : 3.7 POTENTIOMETERS

MONO POTENTIOMETER SYMBOL

STEREO POTENTIOMETER

RULER POTENTIOMETER


COILED POT (20W RHEOSTAT) REGULATES CURRENT

Slide No 201

EASA Ref : 3.7

TRIMMER POTENTIOMETERS (TRIMMERS) -GIVES VERY ACCURATE VOLTAGE AND CURRENT VALUES -ADJUSTABLE BY ADJ. SCREWS THAT HAS A SLIDING CONTACT -WATTAGE RANGE 0.1 TO 0.5 WATTS -NORMALLY USED FOR FINE ADJ. WITH MANY TURNS OF THE SCREW


Slide No 202

EASA Ref : 3.7


Slide No 203

EASA Ref : 3.7

OPERATION AND USE OF POTENTIOMETER (POTS) AND RHEOSTAT -HAS 3 TERMINALS USED FOR VOLTAGE REGULATORS AND ELECTRONIC CIRCUITS (VOLUME CONTROL) AND VOLTAGE DIVIDERS OR VARIABLE RESISTOR (USES 2 TERMINALS) -POTENTIOMETER CONVERTED TO VARIABLE RESISTORS ARE ALSO KNOWN AS RHEOSTAT (ONLY 2 TERMINALS ARE USED)


Slide No 204

EASA Ref : 3.7


Slide No 205

EASA Ref : 3.7

CONVERSION OF A POT TO RHEOSTAT -ONLY 2 TERMINAL ARE USED OF WHICH ONE IS THE WIPER -THE RESISTANCE CHANGES WITH THE POSITION OF THE WIPER -IF END TERMINALS ARE USED, IT BEHAVES AS A FIXED RESISTOR


Slide No 206

EASA Ref : 3.7


Slide No 207

EASA Ref : 3.7


Slide No 208

EASA Ref : 3.7

MOTOR CONTROLS

-IF A BULB IS CONNECTED TO THE 2 TERMINALS (ONE WIPER) IN SERIES AND THE RESISTANCE IS VARIED, THE BULB WILL CHANGE IN BRIGHTNESS. -IF A MOTOR IS CONNECTED TO THE 2 TERMINALS IN SERIES, AND THE RESISTANCE IS VARIED, THE SPEED OF THE MOTOR WILL VARY BUT WITH POWER WASTAGE AT THE RHEOSTAT -NORMALLY WHEN THE POT IS USED AS A RHEOSTAT THE UNUSED TERMINAL IS CONNECTED TO THE WIPER TO PREVENT COMPLETE OPEN CIRCUIT


Slide No 209

EASA Ref : 3.7

MOTOR SPEED CONTROLLER


Slide No 210

EASA Ref : 3.7

SPEED CONTROL


Slide No 211

EASA Ref : 3.7

WIPER TERMINAL DISCONNECTED


Slide No 212

EASA Ref : 3.7

THERMISTORS -RESISTOR THAT SENSES TEMPERATURE -MADE OF SINTERED SEMICONDUCTOR MATERIAL -2 TYPES OF THERMISTORS - POSITIVE COEFFICIENT (PTC) – RESISTANCE INCREASES WITH TEMPERATURE. USED IN TV DEMAGNETIZING COIL AND POLYSWITCH AS SELF REPAIR FUSE. - NEGATIVE COEFFICIENT (NTC) – RESISTANCE DECREASES AS TEMPERATURE INCREASE. USED IN TEMPERATURE DETECTORS AND MEASURING INSTRUMENTS


Slide No 213

EASA Ref : 3.7

-NTC, MADE OF OXIDES OF NICKEL, MANGANESE, COPPER, COBOLT AND OTHER SIMILAR MATERIAL. -COMES IN THE FORM OF BEADS, RODS OR DISC -USED IN AIRCRAFT AS TEMP SENSORS. Ex; IN HEATING, AIRCONDITIONING AND BATTERY SYSTEMS -PTC, MADE OF BARIUM TITANATE TO PREVENT OVER CURRENT IN CIRCUIT DUE TO TEMP RISE


Slide No 214

EASA Ref : 3.7

BENEFITS OF TERMISTORS -ACCURATE BUT WORKS WITH A TEMP RANGE OF 0 TO 100 DEGREES C -STABLE THEREFORE IS NOT EFFECTED BY AGING.


Slide No 215

EASA Ref : 3.7

VOLTAGE DEPENDENT RESISTORS (VARISTOR) -THE RESISTANCE IS INVERSLY PROPOTIONAL TO VOLTAGE -MADE OF SILICON CARBIDE -USED IN : -

VOLTAGE STABILIZATION CIRCUITS TRANSIENT VOLTAGE SUPPRESSION SWITCH CONTACT PROTECTION

-CONNECTED ACROSS THE PROTECTED DEVICE DUE TO SURGE CURRENT


Slide No 216

EASA Ref : 3.7

METAL OXIDE VARISTOR (MOV) -CONTAINS CERAMIC MASS OF ZINC OXIDE GRAINS IN A MATRIX OF OTHER METAL OXIDES. i.e. BISMUTH, MANGANESE AND COBALT. -IT IS SANDWICHED BET. 2 METAL PLATES (ELECTRODES) LIKE THE DIODE JUNCTION - CURRENT FLOWS ONLY IN ONE DIRECTION -USED FOR SHORT CIRCUIT PROTECTION


Slide No 217

EASA Ref : 3.7

WHEATSTONE BRIDGE CONSTRUCTION -CONSISTS OF 4 RESISTORS. i.e. 2 VOLTAGE DIVIDERS -BOTH DIVIDERS HAVE THE SAME VOLTAGE SUPPLY -A GAGE IS CONNECTED BETWEEN THE 2 DIVIDERS TO DETECT THE CURRENT WITH A GALVANOMETER -BALANCED CONDITION = VOLTAGE AT BOTH DIVIDERS ARE EQUAL. THEREFORE NO CURRENT FLOWS THRU’ THE METER. -UNBALANCED CONDITION= VOLTAGE IS NOT THE SAME IN BOTH DIVIDERS. THEREFORE CURRENT FLOWS THRU’ THE METER.


Slide No 218

EASA Ref : 3.7

FIGURE 97 : WHEATSTONE BRIDGE B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 219

EASA Ref : 3.7

WHEATSTONE BRIDGE OPERATION

I

A I2

I1

27K R2

R1

v

C

B I4

I3 RX

R3

27K

2.7K

D B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 220

EASA Ref : 3.7

APPLICATION OF WHEATSTONE BRIDGE -TO MEASURE THE INTERNAL RESISTANCE ACCORDANCE TO PRESSURE OR TEMPERATURE STRAIN -LOCATING BREAKS IN POWER LINES -ACTING AS TEMP. CONTROL DEVICE -MEAUREMENT OF ACFT WEIGHT AND C of G POSITION -MEASURING ELECTRICAL VALUES IN INSTRUMENTS


Slide No 221

POWER ( EASA Ref : 3.8 )

POWER AND ENERGY -VOLTAGE DROPS ACROSS A RESISTOR BUT DOES NOT PASS THRU’ -CURRENT PASSES THROUGH A CIRCUIT BUT NOT ACROSS -ENERGY IS THE CAPABILITY OF DOING WORK = ELECTRICAL ENERGY IS USED TO BE CONVERTED TO LIGHT OR HEAT ENERGY. ANOTHER IS THE MOVEMENT OF ELECTRIC MOTORS TO DO SOMETHING -TYPES MECHANICAL ENERGY -POTENTIAL ENERGY -KINETIC ENERGY


Slide No 222

EASA Ref : 3.8

POTENTIAL ENERGY

A BODY HAS BY VIRTUE OF ITS POSITION, POTENTIAL ENERGY


Slide No 223

EASA Ref : 3.8


Slide No 224

EASA Ref : 3.8

KINETIC ENERGY

-IF THE BOX IS KNOCKED OF THE TABLE, THE BOX HAS KINETIC ENERGY WHILE MOVING THRU’ SPACE. -POTENTIAL AND KINETIC ENERGY ARE CAPABLE OF DOING WORK ELECTRICAL ENERGY – JOULE(WATT/SEC ) - POWER IS = V X I BUT WORK IS DONE OVER A PERIOD OF TIME. THEREFORE, ENERGY = VOLTAGE X AMPERE X TIME W=UXIXt -CAN BE EXPRESSED IN Watt – Seconds (Ws) OR Watt – Hours (Wh)


Slide No 225

EASA Ref : 3.8

KINETIC ENERGY


Slide No 226

EASA Ref : 3.8

POWER -RATE OF ENERGY BEING USED OR WORK DONE WITH RESPECT TO TIME -POWER IS = ENERGY / TIME -SINCE ENERGY IS V X I X t, POWER = (V X I X t) / t -THEREFORE POWER IS = V X I, P = I²R, P = V² / R


Slide No 227

EASA Ref : 3.8 – POWER TRANSFER


Slide No 228

EASA Ref : 3.8

MAXIMUM POWER TRANSFER -

WHEN THE Ri = RLOAD , MAX POWER IS TRANSFERRED

-

THIS CONDITION IS KNOWN AS RESISTANCE MATCHING

-

P = V X I , I X R X I, I²R


Slide No 229

CAPACITANCE / CAPACITORS ( EASA Ref : 3.9 )

CAPACITORS AND CAPACITANCE OPERATION AND FUNCTION -A DEVICE THAT STORES ELECTRICAL ENERGY IN THE FORM OF ELECTRIC FIELD BETWEEN 2 CONDUCTING BODIES USES OF CAPACITORS -DC BLOCKER -STORES MEMORY IN COMPUTER CHIPS -STORE CHARGE FOR CAMERA FLASH -TUNED CIRCUIT IN RADIOS


Slide No 230

EASA Ref : 3.9

DESCRIPTION OF A CAPACITOR CONSISTS OF : -2 PLATES (1 NEG. AND 1 POS.) -1 DIELECTRIC WHEN POWERED: -THE NEG. PLATE GAINS ELECTRONS -THE POS. PLATE LOSES ELECTRONS -

ONCE THE PLATES ARE AT THE SOURCE VOLTAGE, THE CHARGING STOPS


Slide No 231

EASA Ref : 3.9

COMES IN: DIFF. SIZES -DIFF. ARRANGEMENT OF PLATES -DIFF. TYPES OF DIELECTRIC DIELECTRICS MADE OF: -PAPER -CERAMIC -AIR -MICA -ELECTROLYTIC MATERIALS TYPES: -FIXED -ADJUSTABLE


Slide No 232

EASA Ref : 3.9

CAPACITORS:


Slide No 233

EASA Ref : 3.9


Slide No 234

EASA Ref : 3.9

VARIABLE CAPACITOR

VARIABLE CAPACITOR


Slide No 235

EASA Ref : 3.9

CAPACITOR


Slide No 236

EASA Ref : 3.9

- AS THE CHARGE ON THE PLATES INCREASE, THE ELECTRIC FIELD ALSO INCREASES -THE ELECTRIC FIELDS CREATES A POTENTIAL DIFFERENCE BET. THE PLATES V=Exd or E=V/d or d=E/V


Slide No 237

EASA Ref : 3.9

PARALLEL PLATES


Slide No 238

EASA Ref : 3.9

• SYMBOLS


Slide No 239

EASA Ref : 3.9

ANALOGY

Q=VxC


Slide No 240

EASA Ref : 3.9

DIELECTRIC MATERIALS

-THE DIELECTRIC IS AN INSULATOR, IT PREVENTS DC CURRENT FROM FLOWING BET. THE PLATES -IT STORES ELECTROSTATIC CHARGES -DIELECTRIC’S ABILITY TO SUPPORT ELECTROSTATIC FORCES IS DIRECTLY PROPORTIONAL TO THE DIELECTRIC CONSTANT


Slide No 241

EASA Ref : 3.9


Slide No 242

EASA Ref : 3.9

CAPACITANCE

-ELECTRONS ARE REMOVED FROM 1 PLATE AND DEPOSITED ON THE OTHER. -AS THIS GOES ON, THE CHARGE INCREASES -THIS CHARGE IS STORED IN THE DIELECTRIC IN THE FORM OF ELECTRIC FIELDS -THEREFORE THE PLATES POSSESES A CERTAIN CAPACITANCE -CAPACITANCE IS THE CHARGE CAUSED BY A UNIT OF POTENTIAL (V) ON A CONDUCTOR (PLATE) -UNIT FOR CAPACITANCE IS THE FARADS (F)


Slide No 243

EASA Ref : 3.9

DEFINATION: -1 FARAD IS THE CONDUCTANCE OF A CONDUCTOR (PLATE) WITH A POTENTIAL DIFFERENCE OF 1 VOLT WHEN IT CARRIES A CHARGE OF 1 COULOMB (6.28 x 10¹⁸ ELECTRONS). -1 FARAD CAPACITOR STORES 1 COULOMB OF CHARGE WHEN A POTENTIAL OF 1 VOLT IS APPLIED ACROSS THE TERMINALS OF THE CAPACITOR CAPACITANCE (C) = CHARGE (Q) / VOLTAGE (V) CHARGE = CAPACITANCE x VOLTAGE VOLTAGE = CHARGE / CAPACITANCE (Q = QTY OF STORED ELECTRICAL CHARGE IN COULOMB; C = CAPACITANCE IN FARADS AND V = POTENTIAL DIFFERENCE IN VOLTS)


Slide No 244

EASA Ref : 3.9 FARADS (F) -1 FARAD IS TOO LARGE -THEREFORE SMALLER VALUE ARE USED: µ (MICRO) MEANS 1 MILLIONTH OF A FARAD n (NANO) MEANS 1 THOUSAND MILLIONTH => 1000nF = 1 µf P (PICO) MEANS 1 MILLION MILLIONTH => 1000 pF = 1 nF


Slide No 245

EASA Ref : 3.9

PERMITTIVITY OF SPACE (ABSOLUTE) ε0 = 8.854 x 10¯¹² F/m PERMITTIVITY OF DIELECTRIC MATERIAL εr or kε = DIELECTRIC CONSTANT

C = Q/V OR C = ε A/d = k ε0 A/d


Slide No 246

EASA Ref : 3.9 STORED ENERGY -WHEN OPPOSITE CHARGES ACCUMULATE ON THE PLATES, THERE WILL BE ELECTRIC FIELDS FORMED. THEREFORE A VOLTAGE IS DEVELOPED ENERGY STORED = ½ CV² ( JOULES ) -THE CAP. CAN BREAKDOWN IF THE MAX. WORKING VOLTAGE IS EXCEEDED AND THIS IS LIMITED BY THE ELECTRIC FIELD OF THE DIELECTRIC (JOULES OF ENERGY PER CUBIC METER) Ex: WHAT IS THE ENERGY STORED BY A CAP. OF 20µ F, IF THE VOLTAGE IS 24V. E = ½ CV ² = ½ x 20µF x 24V² = 5.7mJ


Slide No 247

EASA Ref : 3.9

FACTORS AFFECTING CAPACITANCE DEPANDS ON 3 FACTORS: -AREA OF THE PLATES -DISTANCE BETWEEN THE PLATES -DIELECTRIC CONSTANT OF THE MATERIAL

ε0 A C = kε d


Slide No 248

EASA Ref : 3.9

AREA -

THE LARGER THE AREA , THE LARGER IS THE CHARGE AND CAPACITANCE

DISTANCE THE CLOSER THE PLATES THE STRONGER IS THE ELECTROSTATIC LINES OF FORCE, THEREFORE THE CHARGE STORAGE IS GREATER DIELECTRIC CONSTANT -

DIELECTRIC IS AN INSULATOR. DIFF. MATERIALS HAVE DIFF. CONSTANT VALUES

-

HIGHER THE CONSTANT, HIGHER IS THE INSULATION


Slide No 249

EASA Ref : 3.9


Slide No 250

EASA Ref : 3.9

DIELECTRIC CONSTANT


Slide No 251

EASA Ref : 3.9

ABSOLUTE CONSTANT -ABSOLUTE CONSTANT = ε0 = 8.854 x 10¯¹² F/m IF A CAPACITOR HAS AIR AS DIELECTRIC, THE AREA OF THE PLATE IS 2 Sq m AND A DISTANCE OF 1 cm, WHAT IS THE CAPACITANCE?

C = ε0 KA

d = 8.854 x 10¯¹² F/m (1 x 2) 0.01m = 1771 pF


Slide No 252

EASA Ref : 3.9

C = ε0 KA/d


Slide No 253

EASA Ref : 3.9

C = ε0 KA/d

………… PicoFarads


Slide No 254

EASA Ref : 3.9

C = ε0 KA/d

Bakelite 4.8

0.1 sq m

1 cm

……..picoFarads


Slide No 255

EASA Ref : 3.9

C = ε0 KA/d

Mica 5.4

0.085 sq m

0.1 cm

…….picoFarads


Slide No 256

EASA Ref : 3.9

C = ε0 KA d

THE CAPACITANCE IS DIRECTLY PROPORTIONAL TO THE DIELECTRIC AND THE AREA BUT INVERSELY PROPORTIONAL TO THE DISTANCE


Slide No 257

EASA Ref : 3.9

VOLTAGE RATING -SELECTION OF CAPACITOR DEPANDS ON: CAPACITANCE

WORKING VOLTAGE

DESIRED CAPACITANCE IN THE CIRCUIT HOW MUCH VOLTAGE THE CAPACITOR CAN HANDLE (WORKING VOLTAGE) IN THE CIRCUIT -IF THE VOLTAGE RATING IS SMALLER THAN THE REQUIRED VALUE THEN THE CAPACITOR WILL BE DAMAGED AND ARCING WILL TAKE PLACE WITHIN THE CAPACITOR -IF THIS HAPPENS THAN IT CAN DAMAGE OTHER COMPONENTS -THICKER THE DIELECTRIC, LOWER IS THE CAPACITANCE -FREQUENCY INCREASES, THE LOSSES AND HEATING EFFECT INCREASES


Slide No 258

EASA Ref : 3.9

VOLTAGE RATING -20 VRMS = 28.28V PEAK. THEREFORE A 50 V CAPACITOR WILL BE MOST APPROPRIATE (30V CAP. WILL ALSO DO) -50 % OF THE RMS VALUE IS VERY SAFE

ONAS KONAS KONAS KONAS KO

CAPACITANCE


WORKING VOLTAGE

Slide No 259

EASA Ref : 3.9

CAPACITOR LOSSES 2 TYPES OF DIELECTRIC LOSSES HYSTERESIS LOSSES DUE TO THE RAPID CHANGE IN ELECTRON CHANGE -OVER IN THE CIRCUIT. LOSSES DEPANDS ON THE TYPE OF DIELECTRIC LEAKAGE LOSSES ALTHOUGH THE DIELECTRIC IS AN INSULATOR, CURRENT CAN STILL PASS THROUGH BUT IN A VERY SMALL AMOUNT. IF THE LEAKAGE IS TOO HIGH, THAN OVER HEATING TAKES PLACE AND IT CANNOT RETAIN THE CHARGE


Slide No 260

EASA Ref : 3.9

TYPE, CONSTRUCTION AND FUNCTION 2 TYPE OF CAPACITORS POLARIZED > ELECTROLYTIC UNPOLARIZED > NON ELECTROLYTIC POLARIZED CAPS HAS HIGHER POWER HANDLING CAPABILITY MUST BE CONNECTED ACCORDING TO THE POLARITY, OTHER WISE CAN CAUSE BODILY INJURIES THEY HAVE VERY LARGE VALUES (> 1 MICRO F). VALUE AND WORKING VOLTAGE IS PRINTED ON THE BODY NOT DAMAGED DUE TO HEAT WHILE SOLDERING


Slide No 261

EASA Ref : 3.9


Slide No 262

EASA Ref : 3.9

ELECTROLYTIC CAPACITORS -FIXED CAPACITIVE VALUE -RANGE FROM 1 TO SEVERAL 1000 MICRO FARADS -USED IN RECTIFIERS AS SMOOTHING CIRCUIT -2 DESIGNS OF E – CAPS => AXIAL AND RADIAL (SMALLER) + + + KONAS KONAS + + 5000 µf 25 v

1000 µF 50V

KONAS KONAS

-WORKING VOLTAGE CAN BE AS LOW AS 6 VOLTS -CHOOSE THE CAP ACCORDING TO THE POWER SUPPLY


Slide No 263

EASA Ref : 3.9

E – CAPS


Slide No 264

EASA Ref : 3.9

TANTALUM BEAD CAPACITOR -

SPECIAL TYPE OF ELECTROLYTIC CAPACITOR

-

HANDLES LOW VOLTAGES ONLY

-

SMALL IN SIZE BUT LARGE CAPACITANCE AND EXPENSIVE

-

BEAD CAPS ARE PRINTED WITH CAPACITY, VOLTAGE AND POLARITY IN FULL

-

OLD TYPE USES COLOUR CODES (BODY, TIP AND SPOT)


Slide No 265

EASA Ref : 3.9

CAP CODING

4 and 7 X 1000000 47,000,000 pF = 47µF with a WV of 35V


Slide No 266

EASA Ref : 3.9

COLOUR CODES SPOT => GREY MEANS X BY 0.01 AND WHITE MEANS X BY 0.1

VALUES OF LESS THAN 10 MICRO F CAN BE READ THIRD COLOUR STRIPE INDICATES VOLTAGE RATING YELLOW MEANS 6.3 V BLACK MEANS 10 V GREEN MEANS 16 V BLUE MEANS 20 V GREY MEANS 25 V WHITE MEANS 30 V and PINK MEANS 35 V


Slide No 267

EASA Ref : 3.9

SPOT NUMBER OF ZEROS TIP 2ND DIGIT BODY 1ST DIGIT VOLTAGE RATING

READING IN MICRO FARADS


Slide No 268

EASA Ref : 3.9

EXAMPLE: BLUE, GREY, BLACK AND YELLOW MEANS 68 MICRO F WITH A WORKING VOLTAGE OF 6.3 V BROWN, GREEN, WHITE AND PINK MEANS 1.5 MICRO F WITH WORKING VOLTAGE OF 35 V YELLOW, VIOLET, GREY AND GREEN MEANS 0.47 MICRO F WITH 10 WORKING VOLTS


Slide No 269

EASA Ref : 3.9

UNPOLARISED CAPACITOR -

CAN BE CONNECTED IN EITHER WAY

-

ITS ROBUST

-

CAN STANDS HEAT DURING SOLDERING EXCEPT FOR THE POLYSTYRENE TYPE

-

FROM 50 WORKING VOLTS TO 250 WORKING VOLTS

-

47 MEANS 47 MICRO F = 47000 NANO F 0.1 MEANS 0.1 MICRO F = 100 NANO F

-

4.7 n F CAN ALSO BE STATED AS 4n7


Slide No 270

EASA Ref : 3.9


Slide No 271

EASA Ref : 3.9

POLYSTYRENE CAPACITOR

-

VALUES ARE NORMALLY IN PICOFARADS ( pF)

-

CAN BE DAMAGED DUE TO HEAT

-

ONLY CERTAIN VALUES ARE POSSIBLE (E 3 SERIES) 10,22,47 => 100,220,470 =>1000,2200,4700 => 10000,22000,47000 (E 6 SERIES) 10,15,22,33,47,68 => 100,150,220,330,470,680 => 1000,1500,2200, 3300,4700,6800 => 10000,15000,33000,47000,68000


Slide No 272

EASA Ref : 3.9

-

READ IN PICOFARADS


Slide No 273

EASA Ref : 3.9 MICA CAPACITOR MICA SHEET

TIN FOIL PLATES

CAN BE MADE BY DEPOSITS OF SILVER FILM ON MICA OR INTERLEAVED SHEETS OF METAL FOIL (TIN,AL etc) -

POSSESES: HIGH STABILITY LOW TOLERANCE ( +_ 1% ) HIGH WORKING VOLTAGE LOW LEAKAGE CURRENT RANGE => 0.01µF TO 10 nF


Slide No 274

EASA Ref : 3.9

-

CERAMIC CAPACITOR: MANY SHAPES WITH CERAMIC DIELECTRIC OR BARIUM TITANATE DIELECTRIC DISC ROD PLATE -

SMALL IN CAPACITANCE (1pF TO 1 MICRO F)

-

LARGE WORKING VOLTAGE (TO A FEW THOUSAND VOLTS)

-

BARIUM TITANATE HAS V. HIGH CAPACITANCE ( DUE TO V. HIGH DIELECTRIC CONSTANT) BUT SMALL IN SIZE

-

HAS POOR STABILITY AND TOLERANCE


Slide No 275

EASA Ref : 3.9 VARIABLE CAPACITOR (TUNING CAPACITOR) -

CAPACITANCE CAN BE CHANGED IN VALUE, MECHANICALLY

-

USED IN THE RF AND OSCILLATOR STAGE OF THE RADIO

-

HAS A STATOR (IMMOBILE) AND A ROTOR (MOBILE) CONNECTED WITH A COMMON AXIS

-

SMALL IN VALUE, IN THE RANGE OF 100pF AND 500pF (0.0001 µF TO 0.00005 micro F )

-

HIGHER THE MESH, HIGHER IS THE CAPACITANCE

-

CAPACITORS CONTAINED IN PLASTIC CONTAINERS HAVE VALUES OF 12 pF TO 218pF


Slide No 276

EASA Ref : 3.9

GANGED DUAL CAPACITORS

SINGLE CAPACITANCE QUADRUPLE CAPACITANCE 2 VARIACS AND 2 TRIMMERS


Slide No 277

EASA Ref : 3.9

PRESET (TRIMMER) CAPACITORS -

MINIATURE CAP. WITH VERY SMALL CAPACITANCE = 2 TO 100 pF

-

USED FOR FREQUENCY FINE TUNING IN TRANSCIEVERS AND OSCILLATORS

-

CCT BOARD MOUNTED

-

ADJUSTED WITH NON-MAGNETIC SCREWDRIVER

-

SPECIFIED BY THE MINIMUM AND MAXIMUM VALUES


Slide No 278

EASA Ref : 3.9

PRESET (TRIMMERS) CAPACITORS


Slide No 279

EASA Ref : 3.9 COLOUR CODING (CERAMIC) (JOINT ARMY-NAVY AND RADIO MANUFACTURERS CODE) -

CAPACITORS ARE MARKED WITH NUMBERS FOR: VALUE WORKING VOLTAGE TOLERANCE TEMPERATURE COEFFICIENT

-

SMALL CAPS ARE MARKED WITH COLOURS LIKE THE RESISTOR CODING 1ST 2 COLOURS REPRESENT THE 1ST 2 DIGITS 3RD COLOUR REPRESENTD THE MULTIPLIER 4TH COLOUR REPRESENTS TOLERENCE 5TH COLOUR REPRESENT WORKING VOLTAGE DISC CERAMIC AND TUBULAR CAPS DOES NOT HAVE WORKING VOLTAGE- USED IN LOW OR NODC VOLTAGE IF 5 COLOUR RING, THEN 1ST RING IS THE TEMP COEFF. AND THE OTHER 4 ARE AS THE NUMBERING SYSTEM

-


Slide No 280

EASA Ref : 3.9

10 nF


Slide No 281

EASA Ref : 3.9 MICA OR MOULDED PAPER CAPACITORS -

COMES WITH 3 DOTS OR 6 DOTS

-

3 DOT REPRESENTS 1ST, 2ND DOTS FOR 1ST 2 DIGITS 3RD DOT FOR MULTIPLIER 6 DOTS REPRESENTS 1ST (OR TYPE), 2ND, AND 3RD DOTS FOR FIRST 3 DIGITS 4TH DOT FOR MULTIPLIER 5TH DOT FOR TOLERENCE 6TH DOT FOR VOLTAGE RATING -

ALWAYS SELECT A CAP OF A VALUE ABOVE THE SUPPLY VOLTAGE


Slide No 282

EASA Ref : 3.9

FIRST DOT BLACK OR WHITE FOR MICA SILVER OR BODY COLOUR FOR PAPER


IN PICOFARADS

Slide No 283

EASA Ref : 3.9


Slide No 284

EASA Ref : 3.9


Slide No 285

EASA Ref : 3.9

WHAT IS THE VALUE?

MICA CAP WITH 1.2 nF +- 6% B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 286

EASA Ref : 3.9


Slide No 287

EASA Ref : 3.9


Slide No 288

EASA Ref : 3.9

CAPS NUMBER CODING -

1ST AND 2ND NUMBER IS THE DIGITS

-

3RD NUMBER IS THE NUMBER OF ZEROS

-

LETTER STANDS FOR TOLERENCE

-

READINGS IN PICOFARADS

-

WORKING VOLTAGE, 25 VOLTS


103M 25V

10000 p F (0.01µ F), 20%, 25V

Slide No 289

EASA Ref : 3.9

WHAT IS THE VALUE OF EACH CAPACITOR

26 mF OR 260,000 pF

630 pF

9600 pF

683J

68000 pF


Slide No 290

EASA Ref : 3.9

CAPS IN SERIES BY CONNECTING IN SERIES THE PLATES ARE SEPERATED, THEREFORE CAPACITANCE IS REDUCED THE CAPACITANCE IS FELT ACROSS THE LEFT PLATE OF C1 AND RIGHT PLATE OF C2

1000 µF 50V


C1 C2

KONAS KONAS

CT = C1XC2 C1+C2

1000 µF 50V

SERIES CAPACITANCE - 1/CT = (1/C1) + (1/C2) + (1/C3) ………….OR

KONAS KONAS

THE FORMULA FOR SERIES CAPACITANCE IS THE SAME AS FOR RESISTANCE IN PARALLEL

NEUTRAL

Slide No 291

EASA Ref : 3.9


Slide No 292

EASA Ref : 3.9

AS FOR RESISTANCE, THE CAPACITANCE SHOULD BE CONVERTED TO FARADS FIRST THE TOTAL CAPACITANCE SHOULD BE BELOW THE SMALLEST CAPACITANCE CALCULATE THE TOTAL CAPACITANCE 1.

C1 = 0.47 µF , C2 = 0.68p F, AND C3 = 50n F

2.

C1 = 10µF, C2 = 0.47µF


Slide No 293

EASA Ref : 3.9

CAPS IN PARALLEL

-

TOTAL CAPACITANCE OF THE CAPACITORS IS: CT = C1 + C2 + C3 ………………

-

ALL CAPS SHOULD BE CONVERTED TO THE SAME UNIT

C1 = 68µF, C2 = 0.01nF AND C3 = 47pF C1 = 0.25µF, C2 = 0.03µF, C3 = 2µF


1000 µF 50V

1. 2.

KONAS KONAS

CALCULATE THE TOTAL CAPACITANCE

1000 µF 50V

CONNECTING CAPACITORS IN PARALLEL ADDS UP THE TOTAL AREA OF THE CAPACITORS,THEREFORE THE AREA IS BIGGER.

KONAS KONAS

-

Slide No 294

EASA Ref : 3.9


Slide No 295

EASA Ref : 3.9

-

WHEN PARALLELED THE TOTAL CHARGE INCREASES ENERGY STORED = 0.5 X C X V ² WHEN MORE THAN 2 CAPS ARE CONNECTED IN SERIES THE OVERALL WORKING VOLTAGE WILL ADD UP


Slide No 296

EASA Ref : 3.9

75V 1.667m F 5000 µf 25 v

+

KONAS KONAS

5000 µf 25 v

+

KONAS KONAS

5000 µf 25 v

+

KONAS KONAS

75V 1.667m F 5000 µf 25 v

25V 5 mF

+

KONAS KONAS

5000 µf 25 v

+

KONAS KONAS

5000 µf 25 v

+

KONAS KONAS

75V 1.667m F 5000 µf 25 v

+

KONAS KONAS

5000 µf 25 v

+

KONAS KONAS

5000 µf 25 v

+

KONAS KONAS

3 X 3 MATRIX OF CAPACITORS


Slide No 297

EASA Ref : 3.9

CHARGING OF THE CAPACITOR

OFF CHARGE

NO POWER CONNECTED TO CAP BOTH PLATES ARE NEUTRAL

NO ELECTRIC FIELDS BETWEEN THE PLATES


Slide No 298

EASA Ref : 3.9

ON CHARGE -

POWER IS CONNECTED ACROSS THE PLATES

-

CAP WILL CHARGE UP AT 5 TIMES CONSTANT

-

ELECTRONS ARE REMOVED FROM THE POSITIVE PLATE AND FED TO THE NEGATIVE PLATE.

-

THE BUILD UP OF CURRENT OPPOSES THE SOURCE VOLTAGE

-

THE CAP CONT. TO CHARGE UNTIL SOURCE VOLTAGE AND CURRENT STOPS FLOWING


Slide No 299

EASA Ref : 3.9

DISCHARGING OF THE CAPACITOR -

CHARGE ON THE 2 PLATES SHOULD BE NEUTRALIZES

-

THE ELECTROSTATIC FIELD WILL VANISH

-

THE SOURCE ENERGY IS RECOVERED FROM THE CAPACITOR WHEN DISCHARGED

-

CAPACITORS DO NOT CONSUME POWER, IT ONLY STORES ENERGY


Slide No 300

EASA Ref : 3.9

RESISTOR / CAPACITOR TIME CONSTANT

FORMULA: 1TC = R x C


Slide No 301

EASA Ref : 3.9

CHARACTERISTIC CURVE OF THE CHARGE


Slide No 302

EASA Ref : 3.9

CHARGING THE CURRENT WILL BE MAX AND THE VOLTAGE WILL BE MIN AS SOON AS THE VOLTAGE IS APPLIED TO THE CAP (INITIALLY)

THE VOLTAGE WILL BE MAX AND THE CURRENT WILL BE MIN WHEN THE CAP IS FULLY CHARGED


Slide No 303

EASA Ref : 3.9

CHARACTERISTIC CURVE OF VOLTAGE AND CURRENT

CHARGING


Slide No 304

EASA Ref : 3.9

DISCHARGING THE VOLTAGE WILL BE MAX. AND THE CURRENT WILL ALSO BE MAX. AS SOON AS THE LOAD IS APPLIED (INITIALLY)

THE VOLTAGE WILL BE MIN. AND THE CURRENT WILL ALSO BE MIN. WHEN THE CAP. HAS FULLY DISCHARGED


Slide No 305

EASA Ref : 3.9

CHARACTERISTIC CURVE OF VOLTAGE AND CURRENT

C DIS


G IN R HA

G

Slide No 306

EASA Ref : 3.9

TESTING OF CAPACITORS

MULTIMETER (EITHER ANALOGUE OR DIGITAL) SHOULD BE AT VERY HIGH RANGE NON-POLARIZED


Slide No 307

MAGNETISM ( EASA Ref : 3.10 )

MAGNETISM -

CAN PRODUCE ELECTRICITY OR ELECTRICITY CAN PRODUCE MAGNETISM

-

CONVERTING A METAL INTO A MAGNET IS THE PROCESS OF CONVERTION OF ELECTRICAL ENERGY INTO MECHANICAL ENERGY. Ex; GENERATOR

-

MOVING A MAGNET THROUGH A COIL CAUSES AN ELECTRIC CURRENT TO FLOW. THIS PROCESS IS THE CONVERTION OF MECHANICAL ENERGY TO ELECTRICAL ENERGY. Ex; MOTOR


Slide No 308

EASA Ref : 3.10

PROPERTIES OF MAGNETISM NATURE OF MAGNETISM -

IT IS AN ELECTRIC CHARGE IN MOTION (ELECTRONS)

-

ELECTRONS ARE MAGNETS SPINNING ON ITS AXIS

-

SOME SPIN CLOCKWISE AND EQUAL AMOUNT IN ANTICLOCKWISE

-

THEY ARE MAGNETICALLY NEUTRAL, THEREFORE NO MAGNETIC CHARACTERISTICS


Slide No 309

EASA Ref : 3.10

SUSPENDED MAGNET (PERMANENT MAGNET) -

EARTH IS A MAGNET ITSELF

-

WHEN SUSPENDED THE MAGNET LIES IN THE NORTH-SOUTH DIRECTION

-

MAGNETIC FIELDS (INVISIBLE) ARE ALSO KNOWN AS LINES OF FORCE


Slide No 310

EASA Ref : 3.10

Magnet in earth magnetic field B1.1M03 Presentation V1.0 dated 02.02.09

Magnetic field and poles of the earth Slide No 311

EASA Ref : 3.10

SHAPES OF MAGNETS MADE OF STEEL -

COMPASS NEEDLES BARS RODS HORSE SHOES RINGS (CIRCULAR)


Slide No 312

EASA Ref : 3.10

Shapes of magnets B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 313

EASA Ref : 3.10

MAGNETIC POLES

-

MAGNETS HAVE 2 ENDS, 1 NORTH SEEKING POLE AND 1 SOUTH SEEKING POLE

-

WHEN SUSPENDED THE END THAT POINTS TO THE NORTH POLE OF THE EARTH IS NORTH POLE. THE ONE THAT POINTS SOUTH IS SOUTH POLE


Slide No 314

EASA Ref : 3.10 MAGNETISM BY INDUCTION -

ANOTHR NAME FOR NATURAL MAGNET -LODESTONE

-

THEY CAN PICK UP IRON AND STEEL

-

WHEN A SOFT IRON IS PLACED NEXT TO A MAGENT IT GETS INDUCED AND SLIGHTLY MAGNETIZED

-

IF THE MAGNET IS STROKED A NUMBER OF TIMES, IT WILL BE EVEN MORE INDUCED AND MORE MAGNETIZED


Slide No 315

EASA Ref : 3.10

MAGNETIC SHIELDING -

ALSO CALLED MAGNETIC SCREENING

-

SOFT IRON IS USED AS MAGNETIC SCREEN FOR SHIELDING THE EFFECT OF CONCENTRATING THE FLUX TO PREVENT STRAY MAGNETIC FIELDS CAUSING INACCURATE OPERATION.


Slide No 316

EASA Ref : 3.10 SCREENING OF COMPONENTS -

-

-

SINCE MAGNETIC FLUX CAN BE CONCENTRATED INTO IRON, THE CENTER PART OF THE IRON RING HAS NO MAGNETIC FLUX OUTSIDE THE IRON CORE THE ABILITY OF THE SOFT IRON TO CONCENTRATE THE MAGNETIC FLUX IS KNOWN AS PERMEABILITY. SOFT IRON – HIGH PERMEABILITY AND AIR - LOW PERMEABILITY


Slide No 317

EASA Ref : 3.10

TYPES OF MAGNETIC MATERIALS -

FERROMAGNETIC MATERIALS – CAN ATTRACT OTHER KIND OF METALS LIKE IRON, NICKEL AND COBOLT

-

PARAMAGNETIC MATERIALS – CANNOT ATTRCT OTHER KINDS OF METAL, PAPER OR WOOD

-

DIAMANGNETIC MATERIAL – REPELS ITSELF FROM MAGNETS (NOT IN USE) IF AN IRON IS MAGETIZED BY A LOADSTONE, THAT IRON IS KNOWN AS ARTIFICIAL MAGNET. THEY LOSE THEIR MAGNETISM EASILY (SOFT IRON)

-

SOME IRONS CAN RETAIN THEIR MAGNETISM FOR A LONG PERIOD OF TIME. THEY ARE KNOWN AS PERMANENT MAGNET


Slide No 318

EASA Ref : 3.10

TYPES OF MAGNETIC MATERIALS B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 319

EASA Ref : 3.10

RELAY -

CONSISTS OF A TEMPERORY MAGNET, COIL, ARMATURE AND CONTACTS

-

CAN BE NORMALLY OPEN OR NORMALLY CLOSED TYPE


Slide No 320

EASA Ref : 3.10

CONSTRUCTION OF RELAY


Slide No 321

EASA Ref : 3.10

CIRCUIT SYMBOL AND CONTACTS OF A RELAY


Slide No 322

EASA Ref : 3.10

OPERATION -

CURRENT FED TO THE COIL

-

SORF IRON BECOMES MAGNET

-

ATTRACTS THE ARMATURE

-

CONTACTS EITHER CLOSES OR OPENS

-

CURRENT DISRUPTED IRON LOSSES MAGNETISM

-

ARMATURE RELEASED DUE TO SRINGY ACTION

-

CONTACTS EITHER OPENS OR CLOSES


Slide No 323

EASA Ref : 3.10


Slide No 324

EASA Ref : 3.10

USES OF RELAY REMOTE SWITCHING -

HIGH VOLTAGE DROP CAN BE EXPERIENCED IN LONG WIRES

-

A RELAY CAN BE USED TO CONTROL EQUIPMENT AT A DISTANCE

-

SINCE RELAY TAKES ONLY A SMALL CURRENT

-

POWER LOSS AT THE EQUIPMENT WILL BE LESS


Slide No 325

EASA Ref : 3.10

REMOTE SWITCHING USING A RELAY B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 326

EASA Ref : 3.10

HEAVY WORKING CURRENT SWITCHING -

EQUIPMENT CAN BE SWITCHED ON AND OFF WITH SMALL CURRENT

-

CAN BE HEAVY DUTY RELAY OR LIGHT DUTY RELAY.

-

USED IN

-

PROTECTIVE CIRCUITS INDICATING SYSTEMS POWER CONTROL SYSTEMS TELEGRAPHIC CONTROL SYSTEMS


Slide No 327

EASA Ref : 3.10

HEAVY WORKING CURRENT SWITCHING B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 328

EASA Ref : 3.10

MAGNETIC FIELDS ON CURRENT CARRYING CONDUCTORS -

CURRENT FLOWS, A MAGNETIC FIELD IS PRODUCED

2 METHODS TO DETERMINE THE FIELD DIRECTION -

RIGHT HAND RULE WIRE GRASPED WITH RIGHT HAND THUMB POINTS TO THE DIRECTION OF CURRENT FINGERS POINT TO THE DIRECTION OF THE MAGNETIC FIELDS


Slide No 329

EASA Ref : 3.10

MAGNETIC FIELD AROUND A CONDUCTOR B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 330

EASA Ref : 3.10

RIGHT HAND RULE B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 331

EASA Ref : 3.10

CORKSCREW RULE -

WHEN THE CORKSCREW IS SCREWED INTO THE PAPER, THE CURRENT WILL FLOW INTO THE PAPER

-

THE DIRECTION THE CORKSCREW IS TURNED , IS THE DIRECTION OF THE MAGNETIC FIELDS (CLOCKWISE)

-

WHEN THE CORKSCREW IS REMOVED, THE CURRENT WILL FLOW OUT OF THE PAPER

-

THE DIRECTION OF THE CORKSCREW IS THE DIRECTION OF THE MAGNETIC FIELDS (ANTI-CLOCKWISE)


Slide No 332

EASA Ref : 3.10

COCKSCREW RULE B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 333

EASA Ref : 3.10

MAGNETOMOTIVE FORCE (MMF) -

THE FORCE THAT TENDS TO PRODUCE A MAGNETIC FIELD

-

UNIT FOR MMF IS THE GILBERT, SYMBOL IS F

-

1 GILBERT IS EQUAL TO THE MAGNETIC FORCE THAT IS REQ. TO ESTABLISH AFLUX DENSITY OF 1 MAXWELL IN A FLUX PATH OR MAGNETIC CCT. HAVING A RELUCTANCE OF 1 UNIT

MAGNETIC CIRCUIT


Slide No 334

EASA Ref : 3.10

FIELD STRENGTH -

MAGNETIC FIELDS ARE CONTINOUS, THEY CAN PASS THRU’ THE CORE AND ALSO THE AIR GAP

-

SYMBOL FOR MAGNETIC FIELD STRENGTH IS H (UNIT IS TESLA)

-

SYMBOL FOR MAGNETIC FLUX DENSITY IS B (LIKE THE VOLTAGE) (UNIT IS WEBER) H =

AMPERES x TURNS

= IN/L Tesla

LENGTH (MAGNETIC CCT)


Slide No 335

EASA Ref : 3.10 OUTSIDE –THE MAGNETIC LINES OF FORCE TRAVEL FROM NORTH SEEKING POLE TO THE SOUTH SEEKING POLE INSIDE – THE MAGNETIC LINES OF FORCE TRAVELS FROM SOUTH TO NORTH


Slide No 336

EASA Ref : 3.10

FLUX DENSITY (SYMBOL B) MAGNETIC FLUX -

THE ENTIRE GROUP OF MAGNETIC FIELD LINES, WHICH CAN BE CONSIDERED TO FLOW OUTWARD FROM THE NORTH POLE OF A MAGNET, IS CALLED MAGNETIC FLUX

-

SYMBOL IS Φ

-

A STRONG FIELD HAS MORE LINES OF FORCE AND MORE FLUX THAN A WEAK MAGNETIC FIELD

(phi)


Slide No 337

EASA Ref : 3.10

PERMEABILITY -

THE ABILITY OF A MATERIAL TO BECOME A MAGNET IS THE PERMEABILITY. DIFFERENT MATERIAL HAVE DIFFERENT PERMEABILITY.

-

WHEN AN IRON BECOMES A MAGNET IT PRODUCES MAGNETIC FIELDS OF ITS OWN, HENCE INCREASING THE FLUX DENSITY

-

THE MULTIPLYING FACTOR OF A MATERIAL IS µ (mu) =B/H

-

RANGES FROM 1 (AIR) TO A FEW THOUSANDS


Slide No 338

EASA Ref : 3.10

EFFECT OF IRON IN MAGNETIC FIELD


Slide No 339

EASA Ref : 3.10

HYSTERESIS LOOP

-

WHEN A SOFT IRON IS SUBJECTED TO CURRENT AROUND IT, IT BECOMES A MAGNET

-

IF THE MAGNETIC FIELDS ARE INCREASED EVEN MORE INTO SATURATION, TME IRON IS FULLY MAGNETIZED

-

NOW IF THE CURRENT IS REMOVED, THE IRON STILL HOLDS SOME RESIDUAL MAGNETISM. THIS EFFECT IS KNOWN AS HYSTERESIS

-

IT CAN BE SAID THAT THE LAG OF FLUX DENSITY (B) BEHIND THE MAGNETIC FIELD STRENGTH (H) IS HYSTERESIS


Slide No 340

EASA Ref : 3.10

B-H CURVE ONCE AT SATURATION AND THE MAGNETISM IS REMOVED THE ‘B’ DOES NOT DROP TO ZERO, INSTEAD IT HOLDS VALUE OF ‘B’. THIS VALUE OF ‘B’ IS KNOWN AS REMNANT OR RESIDUAL MAGNETISM. KEEP IN MIND, ONLY IF IT REACHES SATURATION.

-

REMNANT OR RESIDUAL MAGNETISM WILL REDUCE TO ZERO QUITE FAST UNDER NORMAL CONDITION.

IF THE INCREASE OF THE ‘H’ STRENGTH IS NOT TO SATURATION AND REMOVED, IT IS KNOWN AS REMNANT FLUX DENSITY


Slide No 341

EASA Ref : 3.10

B-H CURVE

INITIAL BEFORE MAGNETISM

AFTER INCREASING TO MAX. MAGNETISM (SATURATION)

Remanence or Residual Magnetism B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 342

EASA Ref : 3.10

RETENTIVITY -

WHEN THE MAGNETISM IS HELD FOR A LONG PERIOD OF TIME, IT IS KNOWN AS RETENTIVITY

-

RESIDUAL / REMNANT IS NOT THE SAME AS RETENTIVITY.

-

IN NORMAL CONDITIONS THE REMNANT CAN DECREASE TO ZERO BUT THE RETENTIVE MAGNETISM MAY LAST A VERY LONG TIME DEPANDING ON THE TYPE OF MATERIAL USED


Slide No 343

EASA Ref : 3.10

COERCIVE FORCE

-

TO REMOVE THE REMNANT MAGNETISM, A NEGATIVE MAGNETISING FORCE IS REQUIRED

-

THE AMOUNT OF NEGATIVE FORCE REQUIRED IS KNOWN AS COERCIVE FORCE

-

IF THE FIRST TIME IT REACHED SATURATION, THAN THIS VALUE IS KNOWN AS COERCIVITY OF THE MATERIAL.


Slide No 344

EASA Ref : 3.10

COERCIVE FORCE


Slide No 345

EASA Ref : 3.10

MAGNETIC ATTRACTION

-

-

WHEN 2 UNLIKE POLES ARE PLACED CLOSE TOGETHER, THEY ATTRACT EACH OTHER. MAGNETIC FIELDS COMBINE


Slide No 346

EASA Ref : 3.10

MAGNETIC POLES


Slide No 347

EASA Ref : 3.10

MAGNETIC REPULSION

-

WHEN 2 LIKE POLES ARE PLACED CLOSE TOGETHER, THEY REPEL

-

MAGNETIC FIELDS REPEL EACH OTHER


Slide No 348

EASA Ref : 3.10

REPULSION


Slide No 349

EASA Ref : 3.10

SATURATION POINTS

-

A CERTAIN AMOUNT OF FORCE IS REQUIRED TO REMOVE THE RESIDUAL MAGNETISM.

-

IF THE FORCE IS TOO HIGH, THAN THE IRON WILL BE SATURATED IN THE OPPOSITE DIRECTION (NEGATIVE SATURATION)

-

TO REMOVE THE MAGNETISM OF A PERMANANT MAGNET, A LARGE FORCE IS REQUIRED HARD IRON REQUIRES A LARGE FORCE TO ENERGIZE AND DEENERGIZE

-


Slide No 350

EASA Ref : 3.10

NEGATIVE SATURATION B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 351

EASA Ref : 3.10

EDDY CURRENT

IN A TRANSFORMER, WHEN THE MAGNETIC FIELD EXPENDS AND COLLAPSES, THE CORE IS INDUCED WITH VOLTAGE. THIS VOLTAGE IN TURN ESTABLISHES A CURRENT. THIS CURRENT IS KNOWN AS EDDY CURRENT THAT FLOWS IN A CIRCULAR PATH.


Slide No 352

EASA Ref : 3.10

CARE AND STORAGE OF MAGNETS

-

TO PREVENT THE LOSS OF MAGNETIC ENERGY OF A PERMANENT MAGNET A KEEPER IS REQUIRED

-

A KEEPER CAN BE A SOFT IRON OR EVEN ANOTHER MAGNET

-

WITH THE KEEPER, THE MAGNETIC CIRCUIT IS COMPLETE. THEREFORE THERE IS NO STRAYING OF THE MAGNETIC FIELDS


Slide No 353

EASA Ref : 3.10

MAGNET WITH KEEPERS B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 354

EASA Ref : 3.10

DIRECTION OF CURRENT FLOW IN A WIRE -

WHEN CURRENT FLOWS THROUGH A WIRE, ELECTRONS (HOLES) SHOULD FLOW FROM POSITIVE TO NEGATIVE (CONVENTIONAL)

-

ARROW SYMBOLIZES THE TAIL AS POSITIVE AND THE HEAD AS NEGATIVE


Slide No 355

EASA Ref : 3.10

DIRECTION OF CURRENT FLOW


Slide No 356

EASA Ref : 3.10

MAGNETIC FIELDS IN A COIL -

-

A PIECE OF STRAIGHT WIRE CARRYING CURRENT HAS MAGNETIC FIELDS AROUND IT , BUT VERY SMALL FOR PRACTICAL USE IF THE SAME WIRE IS TWISTED INTO A LOOP, THE MAGNETIC FIELDS WILL BE CONCENTRATED INTO A SMALL AREA -

ONCE CONCENTRATED, IT WILL HAVE 3 PROPERTIES

-

BRINGS THE FLUX LINES TOGETHER CREATES NORTH AND SOUTH POLES CONCENTRATES THE FLUX LINES IN THE CENTRE


Slide No 357

EASA Ref : 3.10

MAGNETIC FIELDS IN A COIL


Slide No 358

EASA Ref : 3.10 RIGHT HAND GRASP RULE -

USING THE RIGHT HAND AND GRASPING THE COIL IN THE DIRECTION OF CURRENT FLOW, THE THUMB POINTS TO THE NORTH -

THE FLUX DENSITY DEPANDS ON:

-

VALUE OF THE CURRENT IN THE COIL NUMBER OF TURNS IN THE COIL THE TYPE OF CORE MATERIAL

-

IF A CORE IS USED, THE MAGNETIC FORCE STRENGTH IS INCREASED

-

IF THE NUMBER OF TURNS INCREASE, THE MAGNETIC FORCE STRONGER TOO. (STRONGER ELECROMAGNETS)

-

THE LEVEL OF CURRENT CAN ALSO VARY THE STRENGTH OF THE MAGNETIC FORCE


Slide No 359

EASA Ref : 3.10

RIGHT HAND GRASP RULE


Slide No 360

EASA Ref : 3.10

MAGNETIC CHARACTERISTICS RELUCTANCE (S) (IT IS THE SAME AS RESISTANCE IN AN ELECTRICAL CIRCUIT) -

IT IS THE OPPOSITE TO MAGNETIC FLUX IT IS RECIPROCAL OF THE PERMEABILITY FORMULA : PERMEABILITY = 1/ RELUCTANCE S=1/µ OR µ = 1/S Ex: IF THE RELUCTANCE IS 0.0002, WHAT IS THE PERMEABILITY OF THIS MATERIAL. µ = 1 / 0.0002 = 5000


Slide No 361

EASA Ref : 3.10

MAGNETIC MATERIALS -

2 TYPES OF USEFUL MAGNETIC MATERIALS

-

FERROMAGNETIC MATERIAL MATERIAL THAT CAN BECOME MAGNET ( NICKLE, COBALT, IRON etc). THEY HAVE THE ABILITY OF CONCECNTRATING AND MULTIPLING THE FLUX

-

NON-FERROMAGNETIC MATERIALS MATERIAL THAT CANNOT BECOME MAGNET ( ALLUMINUM WATER AIR etc). IT CANNOT CONCENTRATE THE MAGNETIC FLUX AND DOES NOT HAVE THE ABILITY OF MULTIPLING THE FLUX. - AIR HAS A µ OF 1


Slide No 362

EASA Ref : 3.10

MAGNETIC FIELD STRENGTH/ FLUX DENSITY CURVE ( B-H CURVE )


Slide No 363

EASA Ref : 3.10

STRAIGHT LINE GRAPH BECAUSE AIR HAS A PERMEABILITY OF 1


Slide No 364

EASA Ref : 3.10

B-H CURVE OF FERROMAGNETIC MATERIAL

Large increase of H causes a small increase of B

Small increase of H causes a large increase of B

Large increase of H causes a small increase of B


Slide No 365

EASA Ref : 3.10 CLASSIFICATION OF FERROMAGNETIC MATERIALS 2 TYPES OF MAGNETIC MATERIALS: HARD MAGNETIC MATERIALMAKES A GOOD PERMANENT MAGNET, HIGH RETENTIVITY LARGER HYSTERESIS LOSSES ALNICO MAKES A GOOD PERMANENT MAGNET ALNICO CONSISTS OF ALU, COBALT, NICKEL AND IRON SOFT MAGNETIC MATERIAL LOW RETENTIVITY, LOW HYSTERESIS LOSSES AND HIGH PERMEABILITY SUITABLE WITH AC DEVICES ex; ELECTRIC MOTOR,GENERATOR AND TRANSFORMER STEEL ALLOYS (PERMALLOY OR STALLOY) FOR AC USE SORT IRON FOR DC USE,HAS HIGH PERMEABILITY BUT RELATIVELY HIGH HYSTERESIS LOSS


Slide No 366

EASA Ref : 3.10

HYSTERESIS LOOP


Slide No 367

EASA Ref : 3.10

HYSTERERIS LOOP


Slide No 368

INDUCTANCE / INDUCTOR ( EASA Ref : 3.11)

INDUCTANCE AND INDUCTOR BY THE MOVEMENT OF A CONDUCTOR IN A MAGNETIC FIELD, ELECTRICAL ENERGY CAN BE PRODUCED BY MOVEMENT OF A MAGNET INTO A COIL, ELECTRICAL ENERGY CAN BE PRODUCED TOO. Ex; GENERATOR AND TRANSFORMER


Slide No 369

EASA Ref : 3.11 INDUCING A VOLTAGE -

WHEN A CONDUCTOR IS MOVED INTO A MAGNETIC FIELD AT 90° THE ELECTRONS ARE FORCED TOWARDS THE RIGHT OF THE CONDUCTOR, WHILE LACK OF ELECTRONS AT THE LEFT. A PD IS DEVELOPED.

-

WHEN THE CONDUCTOR IS MOVED OUT OF THE MAGNETIC FIELDS, THE ELECTRONS MOVE IN THE OPPOSITE DIRECTION AND THE PD DISAPPEARS WHENTHE CONDUCTOR IS OUT OF THE FIELDS

-

IF THE CONDUCTOR STOPS IN THE FIELDS, THERE WILL BE NO PD

-

THEREFORE PD IS CREATED ONLY WHEN THE CONDUCTOR IS MOVED

-

MECHANICAL FORCE IS CONVERTED TO ELECTROMOTIVE FORCE BY ELECTROMAGNETIC INDUCTION


Slide No 370

EASA Ref : 3.11


Slide No 371

EASA Ref : 3.11

EFFECT OF MAGNETIC FIELD STRENGTH ON THE INDUCED VOLTAGE -

WHEN THE CONDUCTOR MOVEMENT AND THE MAGNETIC FLUX ARE IN THE SAME DIRECTION, THERE WILL BE NO EMF INDUCED IN THE OTHER CIRCUIT


Slide No 372

EASA Ref : 3.11

MAGNETIC FIELD STRENGTH


Slide No 373

EASA Ref : 3.11

EFFECT OF RATE OF CHANGE OF FLUX ON INDUCED VOLTAGE

-

MOVING THE COIL AT 45 DEG. WILL INCREASE THE INDUCTION AND WHEN MOVED TO 90 DEG., THE INDUCTION WILL BE INCREASED TO MAXIMUM.

-

TURNING A FURTHER 90 DEG. WILL PRODUCE ZERO INDUCTION


Slide No 374

EASA Ref : 3.11


Slide No 375

EASA Ref : 3.11

FACTORS AFFECTING THE RATE OF CHANGE OF FLUX -

SPEED OF CONDUCTOR MOVEMENT THRU’ THE FIELDS THE STRENGTH OF THE MAGNETIC FIELDS THE ANGLE BETWEEN THE CONDUCTOR AND FIELD THE LENGTH (# OF TURNS) OF THE CONDUCTOR IN THE FIELD

FARADAY’S LAW: WHEN A CONDUCTOR CUTS OR IS CUT BY THE MAGNETIC FLUX, THERE WILL BE INDUCED EMF PRODUCED. THIS IS PROPORTIONAL TO THE RATE OF MOVEMENT THRU’ THE FIELDS FORMULA: EMF = B x I x V


Slide No 376

EASA Ref : 3.11

LENZ’S LAW

-

WHEN A CURRENT IS SET UP IN AN INDUCED EMF CLOSED CIRCUIT, THE CONDUCTOR WILL PRODUCE ITS OWN MAGNETIC FIELDS

-

THE MAGNETIC FIELDS IN FRONT OF THE CONDUCTOR’S MOTION IS STRENGTHENED

-

BEHIND THE CONDUCTOR’S MOTION IS WEAKENED


Slide No 377

EASA Ref : 3.11


Slide No 378

EASA Ref : 3.11

FIELDS OF PARALLEL CONDUCTORS CARRYING CURRENT -

CURRENT CARRYING CONDUCTOR’S MAGNETIC FIELDS WILL ATTRACT EACH OTHER IF THEY ARE IN THE SAME DIRECTION

-

CURRENT CARRYING CONDUCTOR’S MAGNETIC FIELDS WILL REPEL EACH OTHER IF THEY ARE IN THE OPPOSITE DIRECTION

-

THE DIRECTION OF THE MAGNETIC FIELDS ARE IN ACCORDANCE WITH THE RIGHT HAND AND CORKSCREW RULE


Slide No 379

EASA Ref : 3.11

FIELDS OF PARALLEL CONDUCTORS


Slide No 380

EASA Ref : 3.11

FORCE ON A CURRENT CARRYING CONDUCTOR IN A MAGNETIC FIELD -

A CONDUCTOR CARRYING CURRENT IS PUT INTO THE MAGNETIC FIELDS, INTERACTION BETWEEN THE 2 FIELDS TAKE PLACE

-

THE CONDUCTOR HAS ITS OWN FIELDS, THEREFORE ON 1 SIDE IT AIDS THE MAGNETIC FIELDS AND ON THE OTHER SIDE IT OPPOSES

-

THE AIDED SIDE HAS A GREATER FORCE COMPARED TO THE OPPOSED SIDE. THEREFORE THE CONDUCTOR IS FORCED TOWARDS THE WEAKER SIDE

-

ELECTRICAL ENERGY IS CONVERTED TO MECHANICAL ENERGY


Slide No 381

EASA Ref : 3.11


Slide No 382

EASA Ref : 3.11

THE CORKSCREW RULE IS USED TO DETERMINE THE FELD DIRECTION OF THE CONDUCTOR ANOTHER WAY TO DETERMINING THE DIRECTION OF FORCE IS BY THE LEFT HAND RULE

MAGNETIC FLUX IS FROM NORTH TO SOUTH THE DIRECTION OF CURRENT FLOW IN THE CONDUCTOR (DIRECTION OF THE FINGERS) WHEREBY THE THUMB DETERMINE THE DIRECTION OF FORCE


Slide No 383

EASA Ref : 3.11

LEFT HAND MOTOR RULE


Slide No 384

EASA Ref : 3.11

MAGNITUDE OF THE FORCE THE MAGNITUDE IS PROPORTIONAL TO 3 FACTORS: THE FLUX DENSITY OF THE MAGNET’S POLES THE FLUX DENSITY OF THE CONDUCTOR (PROPORTIONAL TO THE CURRENT) LENGTH OF THE CONDUCTOR THEREFORE FORCE IS EQUAL TO (FORMULA): FORCE = FLUX DENSITY (B) x CURRENT (I) x LENGTH (l) = B. I. l NEWTONS


Slide No 385

EASA Ref : 3.11

LENZ’S LAW

AN ELECTROMAGNETIC FIELD INTERACTING WITH A CONDUCTOR WILL GENERATE ELECTRICAL CURRENT THAT INDUCES A COUNTER MAGNETIC FIELD THAT OPPOSES THE MAGNETIC FIELD GENERATING THE CURRENT ( THE INDUCED CURRENT ALWAYS OPPOSES THE MOTION OR CHANGE PRODUCING IT )


Slide No 386

EASA Ref : 3.11

LENZ’S LAW


Slide No 387

EASA Ref : 3.11

DETERMINATION OF THE INDUCED CURRENT FLOW WITH LENZ’S LAW

-

FIRST THE DIRECTION OF THE CONDUCTOR MOVEMENT SHOULD BE KNOWN

-

THE DIRECTION OF THE FIELD IN THE CONDUCTOR SHOULD ALSO BE KNOWN

-

USING THE RIGHT HAND OR THE CORKSCREW RULE IN REVERSE TO DETERMINE THE INDUCED CURRENT


Slide No 388

EASA Ref : 3.11

BACK EMF WHEN A CURRENT CARRYING CONDUCTOR MOVES THROUGH THE MAGNET’S MAGNETIC FIELDS, THE CONDUCTOR’S FIELD WILL CHANGE (RATE OF CHANGE OF FLUX). THIS CHANGE WILL INDUCE AN EMF (BACK EMF) WHICH WILL OPPOSE THE APPLIED EMF AND IN TURN, THE CURRENT OF THE CONDUCTOR. -

THIS CAUSES THE CONDUCTOR TO MOVE BACK EMF IS ALSO KNOWN AS –EMF or COUNTER EMF FORMULA: -EMF = B x I x V


Slide No 389

EASA Ref : 3.11 MAGNETIC LINE OF FLUX AROUND A LOOP -

IF CURRENT IS CHANGED IN A LOOP, THE FLUX ALSO CHANGES IN STRENGTH

-

THE CHANGE CAUSES AN EMF (BACK) THAT OPPOSES THE EMF

-

IF THE VOLTAGE AND CURRENT INCREASES THE OPPOSITION ALSO INCREASES AND VICE VERSA

-

IF THE CURRENT INCREASES IN AN INDUCTOR, THE ENERGY IS STORED IN THE FIELDS AND WHEN THE CURRENT DECREASES, THE FIELD GIVES UP THE ENERGY.

-

ENERGY STORED IN THE MAGNETIC FIELDS DEPEND ON THE INDUCTANCE AND COIL CURRENT


Slide No 390

EASA Ref : 3.11 INDUCTANCE THE OPPOSITION TO A CHANGE OF CURRENT OR FLUX -

ANY IRCUIT WHICH HAS AN EMF INDUCED INTO IT BY A CHANGE OF CURRENT THROUGH THAT CCT POSSESS SELF INDUCTANCE.

-

A COIL IS AN INDUCTOR

-

SYMBOL FOR INDUCTANCE IS ‘L’ AND THE UNIT FOR INDUCTANCE IS HENRYS (H) IF 1 AMPERE FLOWS IN A CIRCUIT FOR 1 SECOND PRODUCES 1 VOLT – EMF THE CCT IS SAID TO HAVE AN INDUCTANCE OF 1 HENRY. FORMULA: - EMF(V ) INDUCTANCE = RATE OF CHANGE OF CURRENT (A) RATE OF CHANGE OF TIME (S)


Slide No 391

EASA Ref : 3.11

INDUCTANCE OF A CORED COIL -

WHEN CURRENT FLOWS IN A COIL INCREASES , THE INDUCTANCE INCREASES BUT WHEN THE COIL IS INSERTED WITH A CORE, THE INDUCTANCE INCREASES UNTIL SATURATION.

-

FURTHER INCREASE IN THE CURRENT WILL DRASTICALLY REDUCE THE INDUCTANCE

-

NON-MAGNETIC MATERIALS SUCH AS AIR, COPPER AND ALUMINUM DOES NOT MULTIPLY FLUX, THEREFORE THE CORE DOES NOT SATURATE. IT IS INDEPENDENT OF CURRENT


Slide No 392

EASA Ref : 3.11


Slide No 393

EASA Ref : 3.11 -

WHEN CURRENT FLOWS IN A COIL, A BACK EMF WILL BE PRODUCED -

THIS BACK EMF IS PROPORTIONAL TO THE AMOUNT OF MAGNETIC FORCE (RATE OF CHANGE) THAT CUTS THE COIL THE INDUCTANCE ‘CUTTING’ DEPENDS ON: -

NUMBER OF TURNS (GREATER THE NUMBER OF TURNS, GREATER IS THE CUTTING AND THEREFORE BACK EMF)

-

CROSS-SECTIONAL AREA OF THE CORE (THE GREATER THE A, THE GREATER IS THE FLUX THAT CUTS THE CONDUCTOR)

-

PERMEABILITY (GREATER IS THE MU, THE GREATER IS THE FLUX CUTTING CONDUCTOR AND THEREFORE GREATER –EMF

-

LENGTH OF THE CORE (SHORTER THE CORE, LESS IS THE FLUX)


Slide No 394

EASA Ref : 3.11

FORMULA L = N2 A µ Henrys H l


Slide No 395

EASA Ref : 3.11

FORMULA:

L = N² x A x µ Henrys H l Ex : 1 IF AN INDUCTOR HAS AIR AS ITS CORE AND THE NUMBER OF TURNS IT HAS IS 100 WITH A X-SECTIONAL AREA OF 0.2 x 10‫־‬³, WHAT IS THE INDUCTANCE OF THIS INDUCTOR (µ OF AIR = 1.26 X 10‫־‬6 ) N² x A x µ L = l 100² X ( 0.2 x 10‫־‬³) x (1.26 X 10‫־‬6 ) L= 0.2 = 12.6 X 10‫־‬6 or 12.6 µ H


Slide No 396

EASA Ref : 3.11 CALCULATION: Ex: 2 IF N = 100 TURNS, A = 3µ METERS, l = 0.5 METERS, AND THE FERRITE CORE HAS mu=1000. FIND THE INDUCTANCE. N² x A x µ L = l

(100)² X (3 X 10‫־‬6) X (1.26 X 10‫־‬6 ) X 1000 = 0.5 = 756 mH or 0.756 µH


Slide No 397

EASA Ref : 3.11

Inductor symbol


Slide No 398

EASA Ref : 3.11

TIME CONSTANT -

as discussed earlier, the current that flows in an inductor is opposed by the induced current

-

as the current is increased, the opposed current also increases

-

therefore this causes the current to delay in the circuit


Slide No 399

EASA Ref : 3.11

RISE TIME -

WHEN POWER IS APPLIED TO AN INDUCTIVE CIRCUIT, THE CURRENT INCREASES AT A HIGH SPEED IN 1 TIME CONSTANT. IT IS 63.2%

-

AS THE CURRENT INCREASES THE BACK EMF WILL BE REDUCED FROM MAXIMUM. INITIALLY WHEN POWER IS APPLIED:

-

TIME IS 0 RATE OF CURRENT CHANGE IS MAXIMUM BACK EMF AND THE APPLIED VOLTAGE ARE ALMOST EQUAL THAT IS MAXIMUM THE VOLTAGE DROP (I X R) ACROSS R IS MINIMUM FORMULA:

t = L (Henrys) R (OHMS)


Slide No 400

EASA Ref : 3.11

5 TIME CONSTANT

-

THE VOLTAGE IS MAX. WHEN THE APPLIED CURRENT WAS MIN.

-

IN 1 TC THE EMF HAS DROPPED FROM 100% TO 63.2%, THEREFORE THE BACK EMF IS 36.8%

-

IT TAKES 5 TC TO INCREASE THE CURRENT TO MAX. WHERE THE VOLTAGE DROPS TO ALMOST ZERO. L FORMULA: 5TC = 5 X R


Slide No 401

EASA Ref : 3.11

AT 5 TC -

BACK EMF OF THE INDUCTOR IS MINIMUM

-

RATE OF CURRENT CHANGE IS MINIMUM

-

CURRENT FLOW IS MAXIMUM

-

APPLIED VOLTAGE DROP ACROSS THE R IS MAXIMUM


Slide No 402

EASA Ref : 3.11

Time constant


Slide No 403

EASA Ref : 3.11 DECAY TIME -

WHEN POWER IS REMOVED FROM THE CIRCUIT, THE CURRENT WILL DROP FROM MAX. TO 36.8 % OF THE MAX VALUE. THAT IS CURRENT FLOWS FROM THE COLLAPSING MAGNETIC FIELDS

-

THE BACK EMF IS MAX AND IT TRIES TO KEEP THE CURRENT FLOW IT TAKES 1 TC TO DROP 63.2%. THEREFORE THE VOLTAGE DROP ACROSS THE R IS 36.8%

-

THE BACK EMF IS ALSO 36.8% AT 5 TC THE CURRENT IS ALMOST ZERO AND ALL THE ENERGY IS DISCHARGED THRU’ THE RESISTOR

-

SMALLER RESISTOR VALUE MAKES THE DECAY TIME LONGER

-

BACK EMF (MANY TIMES HIGHER THAN THE APP. VOLTAGE) CAN BE DANGEROUS AND CAN CAUSE DAMAGE TO EQUIPMENT AND PERSONAL


Slide No 404

EASA Ref : 3.11

Example INDUCTANCE = 10 H AND RESISTANCE IS 1K. WHAT IS THE 5 TC OF THIS CIRCUIT L Formula:

5TC = 5 R 5 x 10/1000 = 5 x 0.01 = 0.05 seconds


Slide No 405

EASA Ref : 3.11

Example 2

IF THE INDUCTOR IS 10 H AND THE RESISTANCE IS 10 OHMS, WHAT IS THE TIME REQUIRED TO RISE THE CURRENT TO MAXIMUM. L Formula: 5TC = 5 x R = 5 x 10 / 10 =5x1 = 5 seconds


Slide No 406

EASA Ref : 3.11

Decay time


Slide No 407

EASA Ref : 3.11

INDUCTANCE IN SERIES -

-

-

WHEN 2 OR MORE INDUCTORS ARE CONNECTED IN SERIES, THE TOTAL VOLTAGE IS THE SUM OF THE VOLTAGE ACROSS EACH INDUCTOR UT = U1 + U2 + U3 +………………..Un WHEN 2 OR MORE INDUCTORS ARE CONNECTED IN SERIES THEY SHOULD BE ADDED UP JUST LIKE RESISTORS IN SERIES LT = L1 + L2 + L3 +………………Ln TO CALCULATE, FIRST OF ALL THE VALUES OF THE INDUCTORS SHOULD BE CONVERTED TO THE SAME DENOMINATION 10 µH + 100 mH = 10 µH + 100000 µH = 100010 µH Or 0.01mH + 100 mH = 100.01mH


Slide No 408

EASA Ref : 3.11

MUTUAL INDUCTION WHEN TWO INDUCTORS ARE PLACED CLOSE TO ONE ANOTHER,THE FLUX GENERATED WHEN A CHANGING CURRENT FLOWS INTHE FIRST INDUCTOR WILL CUT THROUGH THE OTHER INDUCTOR. THE CHANGING FLUX WILL INDUCE A CURRENT IN THE SECOND INDUCTOR. THIS EFFECT IS KNOWN AS MUTUAL INDUCTANCE


Slide No 409

EASA Ref : 3.11

THE EFFECT OF THE RATE OF CHANGE OF PRIMARY CURRENT AND MUTUAL INDUCTANCE ON INDUCED VOLTAGE

INDUCED VOLTAGE = MUTUAL INDUCTANCE X RATE OF CHANGE PRIMARY CURRENT = M di dt


Slide No 410

EASA Ref : 3.11

FACTORS AFFECTING MUTUAL INDUCTANCE 1. NUMBER OF TURNS OF COIL 2. PHYSICAL SIZE OF COIL 3. PERMEABILITY OF COIL 4. POSITION OF COIL WITH RESPECT TO EACH OTHER


Slide No 411

EASA Ref : 3.11

PRINCIPLES USES OF INDUCTORS 1. TUNED CIRCUITS 2. FILTERS 3. TRANSFORMERS 4. CHOKES


Slide No 412

DC MOTOR / GENERATOR THEORY ( EASA Ref : 3.12)

FORCE ON CONDUCTOR N A MAGNETIC FIELD


Slide No 413

EASA Ref : 3.12

BASIC MOTOR THEORY WHEN THE CURRENT CARRYING CONDUCTOR IS PLACED WITHIN THE MAGNETIC FIELD,THE TWO FIELDS CANNOT EXIST INDEPENDENTLY A CURRENT CARRYING CONDUCTOR HAS A MAGNETIC FIELD SURROUNDING IT. THE FIELD IS CLOCKWISE- CURRENT IN –COCKSCREW RULE THE MAGNETIC FIELD BETWEEN THE TWO POLES OF A BAR MAGNET MOVES FROM NORTH TO SOUTH THE RESULT WILL BE,STRONG FIELDS ON THE LEFT WHILE FIELDS ON THE RIGHT BECOMES WEAK( OPPOSE EACH OTHER ). THEREFORE, THE CONDUCTOR WILL BE FORCED TO MOVE TOTHE RIGHT HAND SIDE. –FLEMING’S LEFT HAND RULE


Slide No 414

EASA Ref : 3.12


Slide No 415

EASA Ref : 3.12

THE PRINCIPLE OF ELECTRIC MOTOR THE FORCE ON THE CONDUCTOR , F = B I l NEWTONS F = FORCE ON CONDUCTOR, IN NEWTONS (N ) B = FLUX DENSITY OF MAGNETIC FIELD, IN TESLA I = CURRENT FLOW IN CONDUCTOR, IN AMPERES l = LENGTH OF CONDUCTOR , IN METERS FLUX DDENSITY ,B =θ/A F =θIl A


Slide No 416

EASA Ref : 3.12

A PRACTICAL DC MOTOR The construction of a dc motor is identical to that of a dc generator. It consists of : a) Armature assembly ( shaft, iron core, armature winding and commutator) b) Field assembly ( pole pieces , yoke, fields windings) c) Brushes assembly ( brushes, brush holders, brush rockers and brush spring ) d) Bearings


Slide No 417

EASA Ref : 3.12

POWER POWER IS PROPORTIONAL TO THE TORQUE AND THE SPEED STRONG TORQUE AT LOW SPEED, LOW TORQUE AT HIGH SPEED TORQUE TORQUE IS PROPORTIONAL TO Φ X Ia OUTPUT TORQUE (SHAFT TORQUE ) =ARMATURE TORQUE – LOST TORQUE LOST TORQUE WILL VARY WITH SPEED


Slide No 418

EASA Ref : 3.12

BACK EMF BACK EMF IS THE INDUCED EMF OPPOSES THE APPLIED VOLTAGE (LENZ’S LAW ) BACK EMF PUSHING ONE WAY AND APPLIED VOLTAGE THE OTHER WAY, SO THE DIFFERENCE BETWEEN THESE TWO ACTUALLY DRIVES CURRENT THROUGH THE ARMATURE CCT KNOWN AS EFFECTIVE VOLTAGE OR ARMATURE VOLTAGE EFFECTIVE VOLTAGE = APPLIED VOLTAGE – BACK EMF EX. A 28 VOLTS DC MOTOR HAS A 1 OHM ARMATURE RESISTANCE AND ARMATURE CURRENT OF 2 AMPS FLOWING. FIND THE BACK EMF BACK EMF = APPLIED VOLTAGE – EFFECTIVE VOLTAGE = 28 – 2X 1 = 26 VOLTS


Slide No 419

EASA Ref : 3.12

SPEED CONTROL OF A DC MOTOR SPEED CONTROL MAY BE OBTAINED BY CONTROLLING THE FIELD CURRENT OR ARMATURE CURRENT BY INSERTING VARIABLE RESISTORS IN THE FIELD CCTS OR ARMATURE CCTS


Slide No 420

EASA Ref : 3.12

TO REVERSE THE DIRECTION OF ROTATION OF A MOTOR IS TO REVERSE THE DIRECTION OF CURRENT FLOW THROUGH THE ARMATURE OR THE FIELDS IF THE CURRENT FLOW THROUGH THE ARMATURE AND THE FIELD ARE BOTH REVERSED THE MOTOR CONTINUES IN THE SAME DIRECTION ON AIRCRAFT IT IS NORMAL TO REVERSE THE DIRECTION OF CURRENT THROUGH THE ARMATURE BY MEANS OF REVERSING RELAYS USE TWO FIELDS BOTH WOUND ON THE SAME POLE PIECES BUT WITH ONE GIVING OPPOSITE POLARITY TO THE OTHER


Slide No 421

EASA Ref : 3.12

TYPES OF DC MOTORS 1. SERIES MOTOR The field is connected in series with the armature, so the torque is proportional to the square of the armature current Large starting torque, High torque at low speed – starting an a/c engine The motor must be connected to a load permanently as the off load speed will be very high On engine starter motors a small shunt winding is incorporated to limit this off load speed as the starter is disconnected from the engine.


Slide No 422

EASA Ref : 3.12

SERIES MOTOR CHARACTERISTICS B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 423

EASA Ref : 3.12

2. SHUNT MOTOR The field is connected in parallel with the armature and of fairly high resistance. Considered to be a constant speed machine It is a self regulating machine,( when a new load is placed on the motor’ the motor automatically adjusts its own effective voltage) Starting torque is small- slow build up of the field strength and restricted armature current Should be started on light load or no load conditions. Used in inverter drives, windscreen wipers and fuel pumps


Slide No 424

EASA Ref : 3.12

SHUNT MOTOR CHARACTERISTICS


Slide No 425

EASA Ref : 3.12

3.COMPOUND WOUND MOTOR Has two windings wound on the same pole pieces .They are wound to assist one another (cumulative ) or to oppose one another (differential ) a)Cumulative Compound i )Predominantly shunt field winding, the series winding enables a fairly high starting torque and a constant torque machine Used on fuel pumps and heavy duty actuators ii) Shunt limited type – high torque at low speed. When the motor is disconnected from the load ,the minor shunt limits the off load speed.


Slide No 426

EASA Ref : 3.12

b) Differential Compound The shunt and series field windings are wound to oppose one another. Fairly constant speed/load characteristic which is fairly constant but increases speed as the load becomes too great Low starting torque, but if overloaded, the series field winding will cancel the shunt field winding. There will be no torque the motor will stop even though taking excessive current. Has a problem on starting.


Slide No 427

EASA Ref : 3.12

COMPOUND MOTOR CHARACTERISTICS B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 428

EASA Ref : 3.12

BASIC GENERATOR THEORY When a conductor cuts a magnetic field, an emf is induced in the conductor (Faraday’s Law ) A single coil which can be rotated between a magnetic field, the ends of the coil are connected to slip rings, brushes spring on the slip rings make the connection to the external circuit (load The loop is rotated through 360 degrees and an alternating emf is generated. The magnitude of the emf generated depends on : - B = Flux Density in Tesla -l = length of conductor in meters v = velocity (speed ) of conductor in meters/sec e= B l v


Slide No 429

EASA Ref : 3.12

FLEMING’S RIGHT HAND RULE TO FIND THE DIRECTION OF THE INDUCED EMF (HENCE THE CURRENT ) OF A CONDUCTOR ROTATED IN A MAGNETIC FIELD FIRST FINGER – DIRECTION OF MAGNETIC FIELD SECOND FINGER – DIRECTION OF CURRENT FLOW (CONVENTIONAL) THUMB - DIRECTION OF CONDUCTOR MOVEMENT


Slide No 430

EASA Ref : 3.12

FLEMING’S RIGHT HAND RULE


Slide No 431

EASA Ref : 3.12

CONSTRUCTION AND PURPOSE OF COMPONENTS IN DC GENERATOR 1.

ARMATURE ASSEMBLY a) Shaft b) Iron Core - provides low reluctance path, core laminated –to reduce eddy currents c) Armature Windings ( output windings) –wound in longitudinal slots in the core and wedged. Wave windings – high voltage and low current output Lap windings - high current and low voltage output. d) Commutator – consists of a number of copper segments on the shaft they are insulated from one another by strips of mica rectify ac to dc


Slide No 432

EASA Ref : 3.12

2.

FIELD ASSEMBLY a) Yoke – cylindrical frame of the machine.-part of the magnetic cct. Made of cast or rolled steel. b) Pole Pieces – forms the core of the magnet coils. Bolted inside the yoke. laminated- reduces eddy currents c) Field Windings – pre-formed coils mounted on the pole pieces. provide the North and South polarity alternately

3.

BRUSHES GEAR ASSEMBLY a) Brush - made of material of low contact resistance, low specific resistance, low coefficient of friction, and good lubricating propertiesgraphite carbon. b) Brush Holders - metal boxes for brush to fit in. Brush holders is secured to brush rockers. c) Brush Spring - maintain good contact with commutator

4.

BEARINGS

-supported the armature. Ball or roller


Slide No 433

EASA Ref : 3.12

TYPICAL DC GENERATOR B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 434

EASA Ref : 3.12

CLASSIFICATION OF DC GENERATORS 1. PERMANENT MAGNET 2. SEPARATELY EXCITED 3. SELF EXCITED SELF EXCITED DC GENERATORS THE FIELD IS EXCITED BY CURRENT OBTAINED FROM THE ARMATURE OF THE MACHINE ITSELF. THESE GENERATORS HAS A SMALL AMOUNT OF RESIDUAL MAGNETISM IN THE POLE PIECES DUE TO PREVIOUS MAGNETISATIONS A)

SERIES WOUND FIELD COILS ARE WOUND IN SERIES WITH THE ARMATURE. FEW TURNS OF HEAVY WIRE OR COPPER STRIP OF LARGE CROSS SECTION AREA OF VERY LOW RESISTANCE. HAVE POOR VOLTAGE REGULATION –NOT NORMALLY USED ON A/C


Slide No 435

EASA Ref : 3.12

SERIES WOUND GENERATOR


Slide No 436

EASA Ref : 3.12

B ) SHUNT WOUND FIELD WINDINGS CONNECTED IN PARALLEL TO THE ARMATRE AND ALSO TO THE EXTERNAL CCT.CONTAINS MANY TURNS OF SMALL WIRE OF HIGH RESISTANCE. SHUNTGENERATOR SHOULD BE ALLOWED TO BULD UP TO THEIR CORRECT VOLTAGE BEFORE THE LOAD IS APPLIED. IF THE LOAD IS INCREASED ABOVE THE FULL CONDITION THEN ,THE VOLTAGE DROPS TO ZERO. HAS A FALLING VOLTS/LOAD CHARACTERISTICS DUE TO IR DROP IN THE ARMATURE WINDINGS USED ON A/C AS ITS DC POWER SOURCE


Slide No 437

EASA Ref : 3.12

SHUNT WOUND GENERATOR


Slide No 438

EASA Ref : 3.12

C)

COMPOUND WOUND COMBINATION OF A SERIES WINDING AND A SHUNT WINDING. IF THE SERIES FIELD ASSISTS THE SHUNT FIELD, THE GEN IS SAID TO BE CUMULATIVE COMPOUND a) FLAT COMPOUND – THE ‘NO-LOAD’ AND ‘FULL LOAD’ VOLTAGES ARE OF THE SAME VALUE. b) UNDER COMPOUND – THE ‘FULL LOAD’ VOLTAGE IS LESS THAN THE ‘NO LOAD’. c) OVER COMPOUND – THE’FULL LOAD’ VOLTAGE IS HIGHER THAN THE ‘NO LOAD’ VALUE IF THE SERIES FIELD OPPOSES THE SHUNT FIELD, THE GEN IS SAID TO BE DIFFERENTIAL COMPOUND USED WHERE VOLTAGE REGULATION IS OF PRIMARY IMPORTANCE


Slide No 439

EASA Ref : 3.12

COMPOUND WOUND GENERATOR


Slide No 440

EASA Ref : 3.12

REGULATION OF GENERATOR VOLTAGE


Slide No 441

EASA Ref : 3.12

VIBRATING TYPE VOLTAGE REGULATOR


Slide No 442

EASA Ref : 3.12

STARTER GENERATOR CONSTRUCTION CONSISTS OF SELF EXCITED COMPOUND WOUND GENERATOR WITH COMPENSATING AND INTERPOLE WINDINGS AND INTEGRAL FAN COOLING. IT IS COOLED BY RAM AIR SPEED SENSOR –SIGNAL FOR STARTER CUTOFF START AS COMPOUND MOTOR SERIES MOTOR FOR TORQUE SHUNT GENERATOR – CONNECTED TO BUS BAR


Slide No 443

AC THEORY ( EASA Ref : 3.13 )

LOOP IN A MAGNETIC FIELD B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 444

EASA Ref : 3.13

EMF GENERATION B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 445

EASA Ref : 3.13

Flux Cut by a Loop in a Magnetic Field B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 446

EASA Ref : 3.13

Lines Cut against Loop Position B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 447

EASA Ref : 3.13

EMF against Loop Position B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 448

EASA Ref : 3.13

Peak Value of a Sinusoidal Wave B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 449

EASA Ref : 3.13

Peak to Peak Value of a Sinusoidal Wave B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 450

EASA Ref : 3.13

ROOT MEAN SQUARE VALUE AN ALTERNATING CURRENT THAT WILL GENERATE THE SAME AMOUNT OF HEAT AS DIRECT CURRENT THAT HAS A VALUE OF ONE AMPERE IS CONSIDERED TO HAVE AN EFFECTIVE VALUE OR RMS VALUE OF ONE AMPERE. RMS VALUE = PEAK VALUE √2 AVERAGE VALUE =0.637 PEAK VALUE INSTANTANEOUS EMF (U) =EMF max x Sinθ


Slide No 451

EASA Ref : 3.13

Period of a Sinusoidal Wave B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 452

EASA Ref : 3.13

Frequency of a Sinusoidal Wave B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 453

EASA Ref : 3.13

Period and Frequency B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 454

EASA Ref : 3.13

Frequency Band B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 455

EASA Ref : 3.13

ANGULAR VELOCITY ANGULAR VELOCITY (ω ) = 2 π f rad /sec 360 Degrees = π radians

RADIAN


Slide No 456

EASA Ref : 3.13

Sine Waves in Phase B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 457

EASA Ref : 3.13

Sine Waves Out of Phase


Slide No 458

EASA Ref : 3.13

Typical Waveforms B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 459

EASA Ref : 3.13

PRT and Mark to Space Ratio B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 460

EASA Ref : 3.13

Generation of Three Phase Alternating Current B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 461

RESISTIVE ( R ), CAPACITANCE ( C ), AND INDUCTANCE ( L ) (EASA Ref : 3.14 )

RESISTORS,CAPACITORS AND INDUCTORS ARE IMPORTANT COMPONENTS IN ELECTRICAL AND ELECTRONIC ENGINEERINGS. IF A RESISTOR IS CONNECTED TO A SINUSOIDAL VOLTAGE, THE CURRENT AND VOLTAGE ARE ALWAYS IN PHASE. WITH A CAPACITOR,THE VOLTAGE LAGS THE CURRENT BY 90 DEGREES WHEREAS WITH A COIL, THE VOLTAGE LEADS THE CURRENT BY 90 DEGREES ALL THE ABOVE CAN BE REPRESENTED IN GRAPHS AND IN PHASOR DIAGRAMS.


Slide No 462

EASA Ref : 3.14

RC Series Connection B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 463

EASA Ref : 3.14


Slide No 464

EASA Ref : 3.14


Slide No 465

EASA Ref : 3.14


Slide No 466

EASA Ref : 3.14

Power Triangles for RC and RL Series Circuit


Slide No 467

EASA Ref : 3.14

Mathematical Relationship for Power in RC/RL Series Circuits


Slide No 468

EASA Ref : 3.14

Resistor/ Capacitor in Parallel


Slide No 469

EASA Ref : 3.14

Resistor/Coil in Parallel


Slide No 470

EASA Ref : 3.14

Mathematical Relationship for Current in RC/RL Parallel Circuits


Slide No 471

EASA Ref : 3.14

Mathematical Relationship for Admittance, Conductance and Susceptances


Slide No 472

EASA Ref : 3.14

RC/RL Frequency dependent Current Divider


Slide No 473

EASA Ref : 3.14

Power Triangles for RC and RL Parallel Circuits


Slide No 474

EASA Ref : 3.14

Mathematical Relationship for Power in RC/RL Parallel Circuits


Slide No 475

EASA Ref : 3.14


Slide No 476

EASA Ref : 3.14


Slide No 477

EASA Ref : 3.14


Slide No 478

EASA Ref : 3.14


Slide No 479

EASA Ref : 3.14


Slide No 480

EASA Ref : 3.14


Slide No 481

EASA Ref : 3.14


Slide No 482

EASA Ref : 3.14


Slide No 483

EASA Ref : 3.14


Slide No 484

TRANSFORMER ( EASA Ref : 3.15 )

TRANSFORMER PRINCIPLES A TRANSFORMER IS AN ELECTRICAL DEVICE FOR TRANSFERRING ELECTRICAL ENERGY FROM ONE CIRCUIT TO ANOTHER CIRCUIT BY MUTUAL INDUCTANCE. (ELECTROMAGNETIC INDUCTION ). THE ELECTRICAL ENERGY IS TRANSFERRED WITHOUT A CHANGE IN FREQUENCY. A TRANSFOERMER WILL NOT OPERATE WITH A STEADY CURRENT IN THE PRIMARY. (DC ) WHEN AC IS USED,THE VOLTAGE AND CURRENT LEVELS CAN BE INCREASED OR DECREASED.(STEP-UP OR STEP –DOWN).


Slide No 485

EASA Ref : 3.15

Transformer Principles


Slide No 486

EASA Ref : 3.15

BASIC CONSTRUCTION OF A TRANSFORMER 1.

CORE - SUPPORTS THE WINDINGS AND PROVIDES A PATH FOR MAGNETIC FLUX -AIR –CORE – USED WHEN HIGH FREQUENCY ABOVE 20 KHz -IRON –CORE – FREQUENCY BELOW 20KH -STEEL- CORE- LAMINATED FOR EFFICIENT POWER TRANSFER SHAPE OF CORE- HOLLOW SQUARE THROUGH THE CENTER - SHELL –CONSISTS OF E AND I SHAPED SECTIONS OF METAL

2.

WINDINGS – WRAPPED AROUND THE A CORE - PRIMARY – RECEIVES ENERGY FROM THE AC SOURCE - SECONDARY- RECEIVES ENERGY FROM THE PRIMARY WINDING AND DELIVERS TO THE LOAD

3.

ENCLOSURE- PROTECTION FROM DIRT , MOISTURE, AND MECHANICAL DAMAGE.


Slide No 487

EASA Ref : 3.15

(a) (c )

Hollow –core construction (b) Windings wrapped around laminations Shell-type core construction


Slide No 488

EASA Ref : 3.15

BASIC OPERATION OF A TRANSFORMER

WHEN AN ALTERNATING VOLTAGE IS APPLIED TO THE PRIMARY WINDING,IT PRODUCES AN ALTERNATING CURRENT , WHICH SETS UP ALTERNATING MAGNETIC FLUX (EXPANDING AND CONTRACTING ) THROUGH THE CORE. THE MAGNETIC FLUX INDUCES AN EMF INTO THE SECONDARY WINDING. ( MUTUAL INDUCTANCE ). THE VOLTAGE MAY BE STEPPED UP OR DOWN DEPENDING ON THE DESIGN OF THE PRIMARY AND THE SECONDARY WINDINGS.


Slide No 489

EASA Ref : 3.15

Mutual Inductance


Slide No 490

EASA Ref : 3.15

Schematic symbols for transformer


Slide No 491

EASA Ref : 3.15

TRANSFORMER LOSSES 1.

COPPER LOSSES ( I2R LOSS ) - PRODUCED BY CURRENTS FLOW IN THE TRANSFORMER WINDINGS. ( RESISTANCE OF THE WINDINGS)

2.

CORE LOSSES –IRON LOSSES A) HYSTERESIS LOSS – THE BUILD UP AND COLLAPSE OF THE MAGNETIC FLUX IN THE CORE. B) EDDY CURRENT LOSSES – CIRCULATING CURRENTS PRODUCED IN THE CORE BY THE CHANGING MAGNETIC FLUX.

3.

STRAY LOSSES – POWER IS LOST IN AN INDUCTOR.(VARIOUS KINDS )


Slide No 492

EASA Ref : 3.15

METHODS OF OVERCOMING LOSSES COPPER LOSSES MINIMISED BY USING LARGE DIAMETER CONDUCTORS FOR THE WINDINGS HYSTERESIS LOSSES THE CORES ARE FORMED INTO SQUARE OR RECTANGULAR BLOCK TO PROVIDE A COMPLETE CLOSED PATH FOR THE MAGNETIC FLUX. USED OF SOFT MAGNETIC MATERIALS- ADD 3% OF SILICON TO IRON EDDY CURRENT LOSSES THE IRON CORE IS LAMINATED AND INSULATING THE SEPARATE LAMINATIONS FROM EACH OTHER.


Slide No 493

EASA Ref : 3.15

PRIMARY AND SECONDARY VOLTAGE, PRIMARY AND SECONDARY CURRENT,TURNS RATIO, POWER AND EFFICIENCY RELATION OF THE PRIMARY AND THE SECONDARY VOLTAGE US =NS UP NP RELATION BETWEEN THE PRIMARY AND THE SECONDARY CURRENT IP =NS IS NP TURNS RATIO = N S NP POWER, P =U S. I S = U P . I P


EFFICIENCY , η = P S PP

Slide No 494

EASA Ref : 3.15

TRANSFORMER ACTION UNDER LOAD AND NO LOAD CONDITIONS TRANSFORMER ON NO LOAD CONDITION When the supply voltage is applied to the primary, an induced emf (back emf ) is produced in the primary which opposes the supply voltage. Very small excitation current ( I e ) will flow in the primary winding to overcome losses and to magnetise the core The primary and secondary voltages are in anti-phase. The off load primary current (I o ) lags the primary voltage with a large angle. ( poor power factor for a transformer on no load )


Slide No 495

EASA Ref : 3.15

TRANSFORMER ON LOAD CONDITION When a load is applied to the secondary, a secondary current will flow . This current opposes the primary flux so reduce the total flux in the core. The primary back emf is reduced and increase in effective emf in the primary so increase in primary current. The secondary current is 180 degrees out of phase to the primary current. The total primary current is the phasor sum of off load primary current and excitation current (I o ) .


Slide No 496

EASA Ref : 3.15

POLARITY MARKINGS PHASING DOTS The dots at the ends of the winding are called the phasing dots. The positioning of the dots is used to indicate the similar instantaneous polarities. When an instantaneous positive voltage is applied to the primary terminals ( dot) there will be an instantaneous positive voltage produced at the secondary terminals (dot).


Slide No 497

EASA Ref : 3.15

AUTOTRANSFORMER IS ONE IN WHICH PART OF THE WINDING IS COMMON TO BOTH THE PRIMARY AND SECONDARY CIRCUITS. SUITABLE FOR APPLICATIONS THAT REQUIRE A VOLTAGE TRANSFORMATION. OF NEAR UNITY, AND TO REDUCE THE APPLIED VOLTAGE TO AN AC MOTOR DURING STARTING. ADVANTAGE – REQUIRE LESS COPPER WIRE, SO LESS I2R LOSS DISADVANTAGE – NOT SAFE FOR INTERCONNECTING HIGH-VOLTAGE AND LOW –VOLTAGE CIRCUITS, BECAUSE OF THE COMMON WINDING. A VARIABLE AUTOTRANSFORMER- PROVIDES AN ADJUSTABLE AC VOLTAGE.


Slide No 498

EASA Ref : 3.15


Slide No 499

EASA Ref : 3.15

EFFICIENCY THE EFFICIENCY OF A TRANSFORMER IS η = OUTPUT POWER INPUT POWER = OUTPUT POWER OUTPUT POWER + LOSSES( COPPER + IRON ) REGULATION = NO LOAD VOLTAGE – FULL LOAD VOLTAGE FULL LOAD VOLTAGE


Slide No 500

EASA Ref : 3.15

LINE AND PHASE VOLTAGES STAR CONNECTIONS LINE VOLTAGE = 3 PHASE VOLTAGE UL = 3 UP DELTA CONNECTIONS LINE VOLTAGE = PHASE VOLTAGE UL = UP


Slide No 501

EASA Ref : 3.15

LINE AND PHASE CURRENTS STAR CONNECTIONS LINE CURRENT = PHASE CURRENT IL = IP DELTA CONNECTIONS LINE CURRENT = √3 PHASE CURRENT IL = √3 IP


Slide No 502

EASA Ref : 3.15

CALCULATION OF POWER IN A PHASE SYSTEM STAR CONNECTIONS POWER = 3 UP IP COS θ WATTS ALSO = 3 UP IL COSθ ,UP = UL/√ 3 COS θ , IL =IP =√3 UL IL COS WATTS DELTA CONNECTIONS POWER = 3 UP IP COSθ WATTS ALSO = 3 UL IP COSθ ‘ UP =UL, IP =IL/√3 = √3 UL IL COSθ WATTS


Slide No 503

FILTERS ( EASA Ref : 3.16 )

A FILTER IS ANY CIRCUIT THAT WILL REMOVE SOME PARTS OF A SIGNAL OR POWER SOURCE, WHILE ALLOWING OTHER PARTS TO CARRY ON WITHOUT HINDRANCE. EQUALIZERS, CROSSOVER NETWORKS, TWEETER, AND POWER CONDITIONING. LOW PASS FILTER PASSES LOW FREQUENCIES BUT BLOCKS FREQUENCIES HIGHER THAN THE CUTOFF FREQUENCY 1. INDUCTIVE LOW PASS ( LR FILTER ) USE IN AC DC POWER SUPPLIES. 2. CAPACITIVE LOW PASS ( RC FILTER ) USED IN AUDIO FREQUENCIES 3. T TYPE TWO INDUCTORS AND A CAPACITOR 4. Π TYPE AN INDUCTOR AND TWO CAPACITORS . B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 504

EASA Ref : 3.16

Main characteristic of low pass filter


Slide No 505

EASA Ref : 3.16

HIGH PASS FILTER OFFER EASY PASSAGE OF HIGH FREQUENCY SIGNAL AND BLOCK LOW FREQUENCY SIGNAL 1. CAPACITIVE HIGH PASS ( CR FILTER ) HIGH IMPEDANCE IN SERIES BLOCK LOW FREQUENCY SIGNALS 2. INDUCTIVE HIGH PASS (RL FILTER ) LOW IMPEDANCE INPARALLE SHORT OUT LOW FREQUENCY SIGNAL 3. T TYPE 2 SERIES CAPACITORS AND AN INDUCTOR 4. Π TYPE A CAPACITOR AND PARALLEL CAPACITORS


Slide No 506

EASA Ref : 3.16

High pass frequency response curve


Slide No 507

EASA Ref : 3.16

BAND PASS FILTER BLOCKS FREQUENCIES THAT ARE TOO HIGH AND FREQUENCIES THAT ARE TOO LOW SIGNAL INPUT -------LOW PASS--------HIGH PASS------------SIGNAL OUTPUT 1. CAPACITIVE BAND PASS LOW PASS –RC , HIGH PASS –CR 2. INDUCTIVE BAND PASS HIGH PASS – RL , LOW PASS – LR 3. MADE UP OF INDUCTORS AND CAPACITORS CR –HIGH PASS , RC – LOW PASS


Slide No 508

EASA Ref : 3.16

Band pass frequency response


Slide No 509

EASA Ref : 3.16

BAND STOP FILTER STOPS TRANSMISSION OF FREQUNCIES BETWEEN f co1 AND F co 2 ALSO KNOWN AS A NOTCH , BAND REJCT OR BAND ELIMINATION FILTER. SERIES ELEMENT – PARALLEL RESONANT CCTS ( 2 TUNED CCTS ) SHUNT ELEMENT – A SERIES RESONANT CCT AT LOW FR THE SERIES RESONANT CCT IMPEDANCE ( Z ) IS HIGH, PARALLEL CCT IMPEDANCE IS LOW. FREQUENCY PASSED. AT RESONANT, THE PARALLEL CCT Z IS HIGH , SERIES RESONANT Z IS LOW. THEREFORE FREQUENCIES ARE BLOCKED IN THESE RANGE AT HIGH FR, THE PARALLEL CCT Z LOW, SERIES ONE INCREASED, SO FREQUENCIES PASSED AGAIN.

B1.1M03 . Presentation V1.0 dated 02.02.09

Slide No 510

EASA Ref : 3.16

Characteristics of band stop filter


Slide No 511

EASA Ref : 3.16

APPLICATIONS OF FILTERS IN AIRCRAFT

HF COMMUNICATION TRANSCEIVER VOR RECEIVERS MARKER BEACON RECEIVER ILS RECEIVER ENGINE VIBRATION MONITORING SYSTEMS AUTOMATIC FLIGHT CONTROL SYSTEMS FLIGHT DIRECTOR SYSTEMS VOICE RECORDER


Slide No 512

AC GENERATORS ( EASA Ref : 3.17 )

ROTATION OF A LOOP IN A MAGNETIC FIELD AND WAVE FORM PRODUCED WHEN LOOP OF COIL ROTATED IN A MAGNETIC FIELD, THE COIL CUTS THROUGH A MAGNETIC FIELD,GENERATING AN EMF. THE EMF PRODUCED ARE CONNECTED TO SLIP RINGS WHICH CAUSE CURRENT TO FLOW ALTERNATELY FIRST IN ONE DIRECTION AND THEN IN THE OTHER DIRECTION IN ONE COMPLETE REVOLUTION. THESE IS THE BASIC AC GENERATOR PRINCIPLE THE WAVEFORM PRODUCED IS A SINOSOIDAL ( ALTERNATING )


Slide No 513

EASA Ref : 3.17

Rotation of a loop in a magnetic field and waveform produced B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 514

EASA Ref : 3.17

CONSTRUCTION OF REVOLVING (ROTATING ) ARMATURE TYPE GENERATOR STATOR - STATIONARY PART OF THE GENERATOR – FIELD WINDINGS DC EXCITATION ON POLE PIECE TO CREATE NORTH AND SOUTH POLES AROUND THE STATOR. ROTOR -

ROTATING PART OF THE GENERATOR – ARMATURE WINDINGS IN SLOTS

SLIP RINGS - OUTPUT


Slide No 515

EASA Ref : 3.17

OPERATION OF REVOLVING ARMATURE TYPE GENERATOR THE ROTOR CUTS THE MAGNETIC FIELD AND PRODUCES AN AC EMF IN THE STATOR. THE GENERATED EMF IS BROUGHT TO THE LOAD BY SLIP RINGS LOW POWER RATING SELDOM USED ON A/C


Slide No 516

EASA Ref : 3.17

Rotating armature alternator


Slide No 517

EASA Ref : 3.17

CONSTRUCTION OF REVOLVING (ROTATING ) FIELD TYPE GENERATOR STATOR – ARMATURE WINDINGS –OUTPUT ROTOR - FIELD WINDINGS- FED VIA SLIP RINGS AND BRUSHES WITD DC OPERATION OF REVOLVING FIELD TYPE THE FIELD IS ROTATED AND CUTS THE STATIONARY WINDINGS. AN AC IS PRODUCED IN THE STATOR WINDINGS –OUTPUT IT IS PREFFERED THAN REVOLVING ARMATURE TYPE BECAUSE: THE OUTPUT CAN BE CONNECTED DIRECTLY TO THE LOAD PROBLEM OF HIGH VOLTAGE ARCING AT THE SLIP RINGS ARE ELIMINATED


Slide No 518

EASA Ref : 3.17

Rotating field alternator B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 519

EASA Ref : 3.17

SINGLE PHASE ALTERNATOR A GENERATOR THAT PRODUCES A SINGLE CONTINUOSLY ALTERNATING VOLTAGE. THE STATOR WINDINGS ARE CONNECTED IN SERIES. THE INDIVIDUAL VOLTAGE THEREFORE ADD ,TO PRODUCE A SINGLE PHASE AC VOLTAGE


Slide No 520

EASA Ref : 3.17

TWPO PHASE ALERNATOR IF ANOTHER SET OF SINGLE PHASE WINDINGS AT 90° TO ONE ANOTHER IS ADDED TO THE SINGLE PHASE, A TWO PHASE OUTPUT IS PRODUCED 90° OUT OF PHASE WITH EACH OTHER.

THREE PHASE ALTERNATOR THREE PAIRS OF COILS ARE USED. EACH PAIR OF COILS IS SPACED AT 120° TO ONE ANOTHER SO 3 PHASES ARE PRODUCED WHERE THE OUTPUTS ARE 120° OUT OF PHASE


Slide No 521

EASA Ref : 3.17

Single phase alternator


Two phase alternator

Slide No 522

EASA Ref : 3.17

3 Phase rotating field generator


Slide No 523

EASA Ref : 3.17

THREE PHASE STAR CONNECTION LINE CURRENT = PHASE CURRENT IL = IP LINE VOLTAGE = √ 3 PHASE VOLTAGE UL =√3UP ADVANTAGE 2 VOLTAGES – 200 V AC AND 115 V AC USES –IN A/C POWER SUPPLIES


Slide No 524

EASA Ref : 3.17

THREE PHASE DELTA CONNECTIONS LINE CURRENT = √3 PHASE CURRENT IL = √3 IP LINE VOLTAGE = PHASE VOLTAGE UL =UP ADVANTAGE 2 VALUE OF CURRENTS – HIGHER CURRENT OUTPUT


Slide No 525

EASA Ref : 3.17

PERMANENT MAGNET GENERATOR ALSO CALLED BRUSHLESS GENERATOR CONSISTS OF PMG, MAIN EXCITER GENERATOR AND MAIN GENERATOR OPERATION OF BRUSHLESS GENERATOR WHEN GENERATOR SHAFT ROTATES, PMG WILL ROTATE, ITS FIELD CUTS THE STATOR FIELD WINDING, INDUCES AC INTO IT. THE OUTPUT FED TO THE V/R IN THE GCU. THE AC RECTIFIED AND GOES TO MAIN EXCITER STATOR FIELD. THE EXCITER FIELD INDUCES VOLTAGE INTO THE EXCITER INPUT WINDING. THE OUTPUT IS RECTIFIED BY 6 SILICON DIODES SENT TO OUTPUT FIELD WINDING VOLTAGE IS INDUCED IN THE MAIN OUTOUT WINDING


Slide No 526

EASA Ref : 3.17

Brushless Generator


Slide No 527

AC MOTORS ( EASA Ref : 3.18 )

CONSTRUCTION OF THREE PHASE SYNCHRONOUS MOTOR CONSISTS OF 1. STATOR FIELD WNDING 2. ROTOR- PERMANENT MAGNET OR ELECTROMAGNET SALIENT POLE – WINDING RECEIVED DC THROUGH SLIP RINGS


Slide No 528

EASA Ref : 3.18

Synchronous motor


Slide No 529

EASA Ref : 3.18

OPERATION OF AC SYNCHRONOUS MOTOR WHEN 3 PHASE AC POWER IS APPLIED TO THE STATOR, ROTATING MAGNETIC FIELD IS SET UP AROUND THE ROTOR THE ROTOR IS ENERGISED WITH DC ( ACTS AS A BAR OF MAGNET ) ATTRACTED BY THE ROTATING STATOR FIELD THIS ATTRACTION WILL EXERT A TORQUE ON THE ROTOR CAUSE THE ROTOR TO ROTATE WITH THE FIELD.


Slide No 530

EASA Ref : 3.18

Action of synchronous motor


Slide No 531

EASA Ref : 3.18

CHARACTERISTICS OF AC SYNCHRONOUS MOTOR 1. NOT SELF STARTNG 2. CONSTANT SPEED DEPENDS ON THE FREQUENCY OF THE POWER SUPPLY F = NP/60 HZ 3. USE AS MOTR IN ENGINE SPEED INDICATORS 4. DIRECTION OF ROTATION CAN BE ACHIEVED BY CHANGING ANY TWO OF THE 3 PHASE INPUTS


Slide No 532

EASA Ref : 3.18

CONSTRUCTION OF 3 PHASE INDUCTION MOTOR 1. STATOR FIELD WINDING 2. ROTOR – NOT CONNECTED TO EXTERNAL SOURCE VOLTAGE - SQUIRREL CAGE ROTOR - WOUND ROTOR


Slide No 533

EASA Ref : 3.18

Types of ac induction motor rotors


Slide No 534

EASA Ref : 3.18

OPERATION OF INDUCTION MOTOR CURRENT IS INDUCED IN THE ROTOR BY THE ACTION OF THE ROTATING MAGNETIC FIELD CUTTING THE ROTOR CONDUCTORS. ROTOR CURRENT GENERATE A MAGNETIC FIELD INTEACTS WITH THE STATOR. TORQUE EXERTED ON THE ROTOR AND CAUSE IT TO ROTATE AS THE STATOR FIELD IS ROTATING, THE ROTOR FOLLOW A LITTLE BEHIND. IF THERE IS NO RELATIVE MOTION, NO CURRENT AND NO ROTOR MOVEMENT. THE DIFFERENCE BETWEEN THE ROTOR SPEED AND ROTATING MAGNETIC FIELD SPEED ( SYNCHRONOUS SPEED ) IS THE SLIP SPEED. SLIP SPEED = Ns – Nr ( SYN SPEED – ROTOR SPEED ) SLIP = Ns – Nr x100 Ns


Slide No 535

EASA Ref : 3.18

Production of motor torque


Slide No 536

EASA Ref : 3.18

CHARACTERISTICS OF INDUCTION MOTOR 1. SELF STARTING 2. CONSTANT SPEED USE AS HYDRAULIC PUMPS, FUEL PUMPS AND FLAP MOTOR TO REVERSE THE DIRECTION OF ROTATION, CHABGE OVER ANY 2 CONNECTIONS OF THE 3 PHASE INPUTS .


Slide No 537

EASA Ref : 3.18

Speed/Torque characteristic of induction motor


Slide No 538

EASA Ref : 3.18

Induction motor characteristics torque and current vs speed


Slide No 539

EASA Ref : 3.18

CONSTRUCTION OF SINGLE PHASE INDUCTION MOTOR (SPLIT PHASE ) CAPACITOR START STATOR - MAIN WINDING AND START WINDING-PARALLEL, 90 DEGREES PHASE DIFFERENCE CAPACITOR –IN SERIES WITH CENTRIFUGAL SWITCH OPERATION THE CURRENTS ARE 90 DEGREES OUT OF PHASE, SO MAGNETIC FIELDS ALSO THE SAME. THE TWO WINDINGS ACT LIKE A TWO PHASE STATOR AND PRODUCE THE ROTATING FIELD REQUIRED TO START THE MOTOR. THE SWITCH OPENS AND CUTS OUT THE START WINDING WHEN THE MOTOR NEARLY AT FULL SPEED. THE DIRECTION OF ROTATION –REVERSED BY CHANGING OVER THE TWO LEADS OF ANY ONE WINDING. USES FOR VACUUM CLEANERS, WORKSHOP PEDASTAL DRILLS,REFRIGERATOR AND AIR COMPRESSORS.


Slide No 540

EASA Ref : 3.18

Single phase induction motor


Slide No 541

EASA Ref : 3.18

Capacitor start induction motor


Slide No 542

EASA Ref : 3.18

SHADED POLE CONSTRUCTION STATOR- PROJECTINGPOLE PIECES – SPLIT INTO TWO - ONE HALF FITTED WITH COPPER OR ALUMINIUM RING ( SHADING ) ROTOR- SQUIRREL CAGE OPERATION AS THE SUPPLY CURRENT RISES AN INDUCED VOLTAGE IS SET UP IN THE SHADING RING.FLUX PRODUCED IN THE RING OPPOSES THE BUILD UP OF MAIN FLUX. MAIN FLUX CONCENTRATES IN THE UNSHADED POLE. AS THE SUPPLY CURRENT DROPS, AN INDUCED VOLTAGE IS SET UP IN THE SHADING RING. FLUX PRODUCED OPPOSES THE COLLAPSE OF THE MAIN FLUX.MAIN FLUX CONCENTRATED IN THE SHADED POLE. THE NEXT HALF CYCLE, THIS IS REPEATED,CREATING FLUX SHIFTING FROM UNSHADED TO THE SHADED POLE, SIMILAR TO A ROTATING FIELD. SPEED IS DETERMINED BY THE INPUT FREQUENCY. CAN BE VARIED WITHIN LIMITED RANGE BY A SERIES RESISTOR OR INDUCTOR. REVERSAL OF ROTATION – BY TRANFERRING THE SHADING RINGS TO THE OTHER HALF OF THE POLEPIECES (NOT PRACTICAL ) USE FOR FANS, BLOWERS, CLOCKS AND ENGINE INDICATION INSTRUMENT.


Slide No 543

EASA Ref : 3.18

Shaded pole induction motor B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 544

EASA Ref : 3.18

Line of flux moves towards the shaded ring (effect of moving field ) B1.1M03 Presentation V1.0 dated 02.02.09

Slide No 545

EASA Ref : 3.18

CONSTRUCTION OF HYTERESIS MOTOR STATOR – TWO WINDINGS 90° TO EACH OTHER- REFERENCE AND CONTROL PHASE ROTOR - COBALT STEEL- HIGH MAGNETIC RETENTIVITY AND LARGE HYTERESIS LOOP. OPERATION IF REFERENCE PHASE IS MAXIMUM, CONTROL PHASE NO CURRENT AT THIS TIME ROTOR RETAINS THE FLUX POLARITY WHEN THE REFERENCE PHASE REDUCES. THE CONTROL PHASE NOW BUILDS UP-ROTATING FIELD CREATED. THE ROTOR WILL BE ATTRACTED TO THE STATOR OF THE OPPOSITE POLARITIES. AS CONTROL CURRENT DIES AWAY, THE CURRENT BUILDS UP ON THE REFERENCE PHASE. ROTOR CONTINUES TO TURN AS THE FIELD ROTATES THE SPEED OF THE MOTOR DEPENDS ON THE SUPPLY FREQUENCY. DIRECTION OR ROTATION IS DONE BY CHANGING THE PHASE RELATIONSHIP OF THE CONTROL PHASE BY 180 DEGREES USED AS SERVO MOTORS AND MINIATURE RATE GYROS.


Slide No 546

EASA Ref : 3.18

Hysteresis motor


Slide No 547

EASA Ref : 3.18

METHODS OF SPEED CONTROL OF INDUCTION MOTOR 1. WOUND ROTOR - VARYING THE AMOUNT OF EXTERNAL RESISTANCE IN THE ROTOR CIRCUIT. - USED OF HEAVY DUTY RESISTORS 2. SQIRREL CAGE ROTOR - TWO SPEED MOTOR WINDING - ELECTRONIC CONYROL UNIT


Slide No 548

EASA Ref : 3.18


Slide No 549

EASA Ref : 3.18


Slide No 550

B1.1M03 Presentation V1.0 Dated 02.02.09

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