A Project Report on
Control of BLDC Motor For Thread Traversing T raversing In Texturising Machine
DEPARTMENT OF ELECTRICAL ENGINEERING C. K. PITHAWALLA COLLEGE OF ENGINEERING & TECHNOLOGY
SURAT-395007 ACADEMIC YEAR 2015-2016
Major Project Report on
Control of BLDC Motor For Thread Traversing T raversing In Texturising Machine BACHLOR OF ENGINEERING IN ELECTRICAL ENGINEERING Submitted By Adak Ankit SwapanKumar
130093109001 130093109001
Patel Mukund Kishorbhai
130093109009 130093109009
Bhalodia Vivek Rasiklal
130093109004 130093109004
Mistry Chirag Mohanbhai
130093109006 130093109006
Saraswala Rajat Jawahar
130093109013 130093109013
DEPARTMENT OF ELECTRICAL ENGINEERING C. K. PITHAWALLA COLLEGE OF ENGINEERING & TECHNOLOGY
SURAT-395007 JUNE – JUNE – 2016 2016
ii
C. K. PITHAWALLA COLLEGE OF ENGINEERING AND TECHNOLOGY
DEPARTMENT OF ELECTRICAL ENGINEERING
This is to certify that following students :
1
130093109001 130093109001
Adak Ankit SwapanKumar
2
130093109009 130093109009
Patel Mukund Kishorbhai
3
130093109004 130093109004
Bhalodia Vivek Rasiklal
4
130093109006
Mistry Chirag Mohanbhai
5
130093109013 130093109013
Saraswala Rajat Jawahar
of Final year, Seventh semester Electrical Engineering have successfully completed the Industry Defined Problem (IDP) - identification report and presented the same as per guidelines of Gujarat Technological University (GTU) on
Control of BLDC Motor For Thread Traversing In Texturising
Machine”
The work done by them is found satisfactory. Surat
.............................
.............................
.............................
Guide
Jury
HOD, EED
iii
Dr. N. K. Zaveri
Prof.
ACKNOWLEDGEMENT
Knowledge in itself is a continuous process. Research is hard but involves great joy as well. The greatest of joys has been working with the people here at C. K. Pithawalla College and Technology. An observer might have thought we were working alone but the critical mass of people here in Electrical Department meant that we could always find the help and encouragement on all issues. For achieving success, man is not an independent identity. The guidance and support of their colleagues, peer and teachers which helps him to find the way of success. Keeping this in mind, first of all, we are thankful and grateful to our project guides Prof. Chetan k. Lad
& Prof. Amisha H. Kapadia
for their immense support and
providing their deep, core knowledge knowledge to us regarding to our project work and layout. layout. My sincere thanks to all faculty members as they spent their valuable time in guiding us in our project. We would also like to present our gratitude to Department Head, Dr. Naimish K. Zaveri for providing us all the facilities that would cherish our project.
And last but not least our sincere thanks to all friends who supported us and inestimable help us in providing us the necessary information and help during the preparation of our project. Because without their support, the completion of our project was not possible. Adak Ankit SwapanKumar Patel Mukund Kishorbhai Bhalodia Vivek Rasiklal Mistry Chirag Mohanbhai Saraswala Rajat Jawahar
iv
ABSTRACT
We have visited the company named ALIDHRA TEXTILE ENGINEERING LIMITED.is located at Road No. 6 ,Udhyognagar, Udhna Surat on date 25/07/2015. It is area production company. In Alidhra the thread traversing in texturising machine is done by using induction motor and gear box to achieve the low speed control and for the position control system such as forward, reverse and locking in different pattern. Now a days in the recent development of the world the BRUSHLESS DC MOTOR drives are becoming more popular in Industries, Traction, Automotive, Aerospace, Automation equipment & Instrumentation. Our main aspect is to use the BLDC motor for thread traversing in texturising machine. This motor has permanent magnet at rotor & 3-phase winding at stator. Due to the elimination of brushes BLDC motor has advantages of noiseless operation, high dynamic response, high-efficiency etc. BLDC motor can operate in four steady states modes of torque-speed plane. In 1 st& 3 rd quadrant, the supply voltage is greater than the back emf which is forward & reverse motoring modes respectively. In 2 nd& 4th quadrant the back emf generated by motor should be greater than the supplied voltage, which are the forward braking and reverse braking modes of operation. By using the BLDC motor the gear mechanism can be neglected so that the maintenance reduces, overall cost reduces, and the efficiency increases and the requirement of high torque is fulfilled. Our project group is going to verify the performance of BLDC motor with various modes of operation specially forward, reverse and locking in THREAD TRAVERSING IN TEXTURISING MACHINE and also the simulation using MATLAB.
v
CONTENTS Content
Page no.
ACKNOWLEDGEMENT
iv
ABSTRACT
v
CONTENTS
vi
LIST OF TABLE
vii
LIST OF FIGURE
vii
ABBREVIATION
x
NOMENCLATURE
xi
CHAPTER : 1
CHAPTER : 2
CHAPTER : 3
CHAPTER : 4
CHAPTER : 5
INTRODUCTION
1
1.1 Industrial Visit At Alidhra
1
1.2 Operation In Textile Industries
1
1.3 Requirement of Motor Speed Control
2
1.4 Generalized Block Diagram of Bldc Motor Based Thread Traversing In Textile Industry
2
1.5 Organization of Chapter
3
CONCEPT OF THREAD TRAVERSING IN TEXTILE INDUSTRY
4
2.1 Traversing Mechanism Used On Winding Machines
4
3.1 GENERAL DETAILS OF BLDC
9
3.2 Construction
10
3.3 Four Quadrant Control Operation
14
3.4 Theory of Operation
15
3.5 Torque/Speed Characteristics
18
HARDWARE AND SOFTWARE IMPLEMENTATIONS
19
4.1 Simulation Machine Parameter
19
4.2 Simulation Model
20
4.3 Hardware
25
4.4 Testing and speed control of BLDC Motor
33
CONCLUSION AND FUTURE WORK
40
5.1 Conclusion
40
REFERENCES
41
APPENDIX
42
vi
LIST OF TABLE
Table no.
Table
Page no.
1
Parameters of BLDC Motor
19
2
Open Circuit Test Results
27
3
Load Test Results
27
4
Testing results of hardware
39
vii
LIST OF FIGURES Fig no.
Figure
Page no.
1.1
Generalized Block Diagram
2
2.1
Precision Type Winding Mechanism
4
2.2
Traverse Roll
5
2.3
Gear And Shaft Mechanism
5
2.4
Thread Guide Assembly
6
2.5
Traverse Bar Driver
6
2.6
Roll Driver
7
2.7
Traverse Cam
8
3.1
Stator of BLDC Motor
10
3.2
Trapezoidal Back Emf
11
3.3
Sinusoidal Back Emf
11
3.4
Rotor Magnet Cross Section
12
3.5
BLDC Motor Transverse Section
12
3.6
(A) Schematic Representation of A Three Branches Hall Sensor (B) Three Branches Vertical Hall Device Mounted As Angular Position Sensor For Brushless Motor Control
14
3.7
Four Quadrants of Operation
15
3.8
Electronically Commutated BLDC Motor Drive
16
3.9
Hall-Sensor Signal,Back Emf,O/P Torque & Phase Current
17
3.10
Torque/Speed Characteristics
18
4.1
Simulink Model of BLDCM
20
4.2
Three-Phase Inverter Circuit
21
4.3
Hall Sensor Pulses
23
4.4
Gate Pulses
23
4.5
Speed And Torque Characteristics
24
4.6
Back Emf And Current Waveforms
24
4.7
Power Supply
25
4.8
Transformer
26
4.9
Testing of Transformer
27
4.10
Bridge Rectifier
28
viii
4.11
Bridge Rectifier With Capacitor Filter
29
4.12
Rectifier Testing (A) Input Voltage (B) Output Voltage
29
4.13
15 Volt Supply
30
4.14
Three-Phase Inverter Card
31
4.15
Micro-Controller Card
31
4.16
Gate pulse g1 and g4
33
4.17
Gate pulse g1 and g3
33
4.18
Current Ia
33
4.19
Hall sensor signal Ha and H b
34
4.20
Hall sensor signal H b and Hc
34
4.21
Hall sensor signal Ha and Hc
34
4.22
Gate signal g1 and g4 at 750rpm
35
4.23
Gate signal g1 and g3 at 750rpm
35
4.24
Current Ia at 750rpm with loading
35
4.25
Gate signal g1 and g4 at 950rpm
36
4.26
Gate signal g1 and g3 at 950rpm
36
4.27
Current Ia at 950rpm with loading
36
4.28
Line voltage Vab and Vac
37
4.29
Line voltage Vab and Vac
37
4.30
Gate signal g1-g3, g1 and g3
37
A.1
Block Diagram of P89V51RD2
43
A.2
Pin Diagram of P89V51RD2
44
ix
ABBREVIATIONS
BLDCM …………………………………………….BRUSHLESS DC MOTOR RPM ……………………………………….......REVOLUTION PER MINUTE IM……………………………………………………......INDUCTION MOTOR EMC………………………………ELECTRO MAGNETIC COMPATIBILITY SRM……………………………………SWITCHED RELUCTANCE MOTOR SPM………………………………….......SURFACE PERMANENT MAGNET IPM………………………………….......INTERIOR PERMANENT MAGNET EMF……………………………………………….ELECTROMOTIVE FORCE
x
NOMENCLATURE
Vin……………………………………………………………INPUT VOLTAGE Vout………………………………………………………..OUTPUT VOLTAGE Iin…………………………………………………………….INPUT CURRENT Iout………………………………………………………...OUTPUT CURRENT T p………………………………………………………………PEAK TORQUE Tr ……………………………………………………………RATED TORQUE Vdc………………………………………………………………DC VOLTAGE
xi
CHAPTER : 1
INTRODUCTION
1.1 Industrial Visit At Alidhra : The
project
group
visited
the
company
named
ALIDHRA
TEXTILE
ENGINEERING LIMITED. Which is located at Road No. 6 Udhyognagar, Udhna Surat. In
alidhra textile industries there is a method of thread traversing used in the texturising machine. Thread Traversing means the thread is wound up in the bobbin having a lateral motion in which they are adjusted laterally that is the thread‟s adapted for giving lateral motion. As they are using conventional induction motor with the VFD CONTROL LOGIC and they were getting as the high speed and low torque but their requirement was low speed and high torque which was fulfilled by the gear mechanism connected at the shaft of the induction motor.
1.2 Operation in Textile Industries : There are various basic operations in textile industries. They are as follows:1. Carding 2. Spinning 3. Slashing (Sizing) 4. Weaving 5. Knitting 6. Tufting 7. Designing 8. Scouring 9. Wool Carbonizing 10. Filling 11. Bleaching 12. Mercerizing 13. Dyeing 14. Printing 15. Finishing
1.3 Requirement of Motor Speed Control : As conventional induction motor has no brush, so no such problem of brush friction generation arcing and sparking, but its starting torque is small at below base speed, efficiency is low and speed response is bad. To overcome these drawbacks we recommended them to use BRUSHLESS DC MOTOR (BLDC) instead of induction motor and gear box combine to use in texturising machine. BLDC without brush, commutated by electronic control method, having higher efficiency and speed – torque response. Efficiency is an important indicator of energy saving and carbon reduction. There are two types of permanent magnet configuration used in the BLDC motor structure named : 1. SURFACE MOUNTED PERMANENT MAGNET (SPM) 2. INTERNAL EMBEDDED PERMANENT MAGNET (IPM) SPM BLDC have magnets on the rotor surface, while the IPM BLDC have magnets inside the rotor. Obviously, due to the high speed requirement, the IPM structure is selected to be used in the Thread Traversing in the Texturis ing Machine. Our main aim of this project is controlling the speed of BRUSHLESS DC MOTOR at low speed and high torque such that gear box can be removed and also the size will be reduced.
1.4 Generalized Block Diagram of BLDC Motor Based Thread Traversing In Textile Industry : -
FIG 1.1 GENERALIZED BLOCK DIAGRAM
2
As shown in (fig : 1.1) 1-phase AC input is given to the transformer which converts the 230 volt Ac to the 12volt Ac. Supply. This single phase 12volt Ac supply is given to the rectifier which convert single Ac supply into equivalent DC output which will be measure across output terminal of rectifier. A capacitor is connected for the ripple free output dc voltage. This Dc output voltage is given to the 3-phase inverter circuit which converts dc voltage into 3-phase ac voltage and this output ac voltage is given to the BLDC motor. In BLDC motor hall sensors is used which gives control signal which is useful for control operation in the control circuit. Output of the control circuit is given to the 6-step operation block. This step operation gives output in the form of pulse. This pulse is given to the 3-phase inverter circuit. 24 volt supply from rectifier is given to the input of inverter to drive the inverter circuit. BLDC motor work with the help of this output signal from 3-phase inverter by proper switching combinations so that BLDC motor rotates in clockwise or anticlockwise direction.
1.5 Organization of Chapter : CH : - 2 Concept of Thread Traversing In Textile Industries CH : - 3 Basic Concept of IM BLDC Motor CH : - 4 Implementation and Simulation Results CH : - 5 Conclusion and Future Work
3
CHAPTER : 2
CONCEPT OF THREAD TRAVERSING IN TEXTILE INDUSTRY
2.1 Traversing Mechanism Used on Winding Machines : The seven mechanism are used on different types of yarn and coil winding machines. Their fundamentals, however , may be applicable to other machines which require similar changes of motion, Except for the lead screw as used, for example on lathes, these seven represent the principles of all well-known, mechanical types of traversing devices .
2.1.1 Winding Mechanism : -
FIG
2.1
PRECISION
TYPE
WINDING
As seen in fig 2.1 package is mounted on belt driven shaft on this precision type winding mechanism. Cam shaft imparts reciprocating motion to traverse bar by means of cam roll that runs in cam groove. Gears determine speed ratio between cam and package. Thread guide is attached to traverse bar. Counterweight keeps t hread guide against package.
2.1.2 Traverse Roll : Package is friction-driven from traverse roll. Yarn is drawn from the supply source by traverse roll and is transferred to package from the continuous groove in the roll different winds 4
winds are obtained by varying the groove path .
FIG 2.2 TRAVERSE ROLL
2.1.3 Gear and Shaft Mechanism : Reversing bevel gears which are driven by a common bevel gear , drive the shaft carrying the traverse screw as shown in fig 2.3 . Traverse nut mates with this screw and is connected to the yarn guide. Guide slides along the reversing rod . When nut reaches end of its travel , the thread guide compresses the spring that pawl and the reversing lever. this engages
FIG 2.3 GEAR AND SHAFT MECHANISM
the clutch that rotates the traverse screw in the opposite direction . as indicated by the large pitch on the screw, this mechanism is limited to low speeds, but permits longer lengths of traverse than most of the others shown .
5
2.1.4 Thread Guide : -
FIG 2.4 THREAD GUIDE ASSEMBLY
As seen in fig 2.4 drum drives package by friction . pointed cam shoe which pivots in the bottom side of the thread guide assembly rides in cam grooves and produces reciprocating motion of the thread guide assembly on the traverse bar . plastic cams have proved quite satisfactory even with fast traverse speeds interchangeable cams permit a wide variety of winds.
2.1.5 Traverse Bar Driver Assembly : -
FIG 2.5 TRAVERSE BAR DRIVER
6
Roll that rides in heart-shaped cam groove engages slot in traverse bar driver which is attached to the traverse bar shown in fig 2.5. Maximum traverse is obtained when adjusting guide is perpendicular to the driver . As angle between guide and driver is decreased , traverse decreases proportionately . Inertia effects limit this type mechanism to slow speed .
2.1.6 Traverse roll driver : -
FIG 2.6 ROLL DRIVER
Two cam rolls that engages heart shaped cam are attached to the slide . Slide has a driver roll that engages a slot in the traverse bar driver . Maximum traverse (to capacity of cam) occurs when adjusting disk is set so slide is parallel to traverse bar . As angle between traverse bar and slide increases, traverse decreases . At 90 deg traverse is zero .
2.1.7 Traverse Cam : Traverse cam ( fig 2.7 ) imparts reciprocating motion to can follower which drives thread guides on traverse guide rods . Package is friction driven from drum . Yarn is drawn from the supply source through thread guide and transferred to the drum-driven package . speed
7
FIG 2.7 TRAVERSE CAM
of this type of mechanism is determined by the weight of the reciprocating parts .
8
CHAPTER : 3
BLDC MOTOR
3.1 General Details of BLDC : BLDC motor, also called Permanent Magnet DC Synchronous motor, are one of the motor types that have more rapidly gained popularity, mainly because of their better characteristics and performance. These motors are used in a great amount of industrial sectors because their architecture is suitable for any safety critical applications. The brushless DC motor is a synchronous electric motor that, from a modelling perspective, looks exactly like a DC motor, having a linear relationship between current and torque, voltage and rpm. It is an electronically controlled commutation system, instead of having a mechanical commutation, which is typical of brushed motors. Additionally, the electromagnets do not move, the permanent magnets rotate and the armature remains static. This gets around the problem of how to transfer current to a moving armature. In order to do this, the brush-system/commutator assembly is replaced by an intelligent electronic controller, which performs the same power distribution as a brushed DC motor. BLDC motors have many advantages over brushed DC motors and induction motors, such as :
Better speed versus torque characteristics
High dynamic response
High efficiency and reliability
Long operating life
Noiseless operation
Higher speed ranges
In addition, the ratio of delivered torque to the size of the motor is higher, making it useful in applications where space and weight are critical factors, especially in aerospace applications.
9
3.2 Construction : BLDC motors are a type of synchronous motor. This means the magnetic field generated by the stator and the magnetic field generated by the rotor rotates at the same frequency. BLDC motors do not experience the “slip” that is normally seen in induction motors. BLDC motors come in single-phase, 2-phase and 3-phase configurations. Corresponding to its type, the stator has the same number of windings. Out of these, 3-phase motors are the most popular and widely used.
3.2.1 Stator : The stator of a BLDC motor consists of stacked steel laminations with windings placed in the slots that are axially cut along the inner periphery as shown in (Fig 3.1). Traditionally, the stator resembles that of an induction motor; however, the windings are distributed in a different manner. Most BLDC motors have three stator windings connected in star fashion. Each of these windings are constructed with numerous coils interconnected to form a winding. One or more coils are placed in the slots and they are interconnected to make a winding. Each of these windings are distributed over the stator periphery to form an even numbers of poles. There are two types of stator windings variants: trapezoidal and sinusoidal motors. This differentiation is made on the basis of the interconnection of coils in the stator windings to give the different types of back Electromotive Force (EMF).
FIG 3.1 STATOR OF BLDC MOTOR
As their names indicate, the trapezoidal motor gives a back EMF in trapezoidal fashion and the sinusoidal motor‟s back EMF is sinusoidal, as shown in (Fig 3.2) and (Fig 3.3) In addition to the back EMF, the phase current also has trapezoidal and sinusoidal variations in the respective types of motor. This makes the torque output by a sinusoidal 10
motor smoother than that of a trapezoidal motor. However, this comes with an extra cost, as the sinusoidal motors take extra winding interconnections because of the coils distribution on the stator periphery, thereby increasing the copper intake by the stator windings.
FIG 3.2 TRAPEZOIDAL BACK EMF
FIG 3.3 SINUSOIDAL BACK EMF
Depending upon the control power supply capability, the motor with the correct voltage rating of the stator can be chosen. Forty-eight volts, or less voltage rated motors are used in automotive, robotics, small arm movements and so on. Motors with 100 volts, or higher ratings, are used in appliances, automation and in industrial a pplications.
11
3.2.2 Rotor : -
FIG 3.4 ROTOR MAGNET CROSS SECTION
The rotor is made of permanent magnet and can vary from two to eight pole pairs with alternate North (N) and South (S) poles. Based on the required magnetic field density in the rotor, the proper magnetic material is chosen to make the rotor. Ferrite magnets are traditionally used to make permanent magnets. As the technology advances, rare earth alloy magnets are gaining popularity. The ferrite magnets are less expensive but they have the disadvantage of low flux density for a given volume. In contrast, the alloy material has high magnetic density per volume and enables the rotor to compress further for the same torque. Also, these alloy magnets improve the size-to-weight ratio and give higher torque for the same size motor using ferrite magnets. Neodymium (N d), Samarium Cobalt (S mCo) and the alloy of Neodymium, Ferrite and Boron (N dFeB) are some examples of rare earth alloy magnets. Continuous research is going on to improve the flux density to compress the rotor further. (Fig. 3.4) Shows cross sections of different arrangements of magnets in a rotor.
3.2.3 Hall Sensors : -
FIG 3.5 BLDC MOTOR TRANSVERSE SECTION
12
Unlike a brushed DC motor, the commutation of a BLDC motor is controlled electronically. To rotate the BLDC motor, the stator windings should be energized in a sequence. It is important to know the rotor position in order to understand which winding will be energized following the energizing sequence. Rotor position is sensed using Hall Effect sensors embedded into the stator. Most BLDC motors have three Hall sensors embedded into the stator on the nondriving end of the motor. Whenever the rotor magnetic poles pass near the Hall sensors, they give a high or low signal, indicating the N or S pole is passing near the sensors. Based on the combination of these three Hall sensor signals, the exact sequence of commutation can be determined. (Fig:-3.5) shows a transverse section of a BLDC motor with a rotor that has alternate N and S permanent magnets. Hall sensors are embedded into the stationary part of the motor. Embedding the Hall sensors into the stator is a complex process because any misalignment in these Hall sensors, with respect to the rotor magnets, will generate an error in determination of the rotor position. To simplify the process of mounting the Hall sensors onto the stator, some motors may have the Hall sensor magnets on the rotor, in addition to the main rotor magnets. These are a scaled down replica version of the rotor. Therefore, whenever the rotor rotates, the Hall sensor magnets give the same effect as the main magnets. The Hall sensors are normally mounted on a PC board and fixed to the enclosure cap on the non-driving end. This enables users to adjust the complete assembly of Hall sensors, to align with the rotor magnets, in order to achieve the best performance. Based on the physical position of the Hall sensors, there are two versions of output. The Hall sensors may be at 60° or 120° phase shift to each other. Based on this, the motor manufacturer defines the commutation sequence, which should be followed when controlling the motor. Nowadays, because miniaturized brushless motors are introduced in many applications, new position sensors are being developed, such as a three branches vertical Hall sensor depicted in (fig:-3.6(a)). The connecting principle between the brushless motor and this sensor is reminiscent of the miniaturized magnetic angular encoder based on 3-D Hall sensors. A permanent magnet is fixed at the end of a rotary shaft and the magnetic sensor is placed below, and the magnet creates a magnetic field parallel to the sensor surface. This surface corresponds to the sensitive directions of the magnetic sensor. Three-phase brushless motors need three signals with a phase shift of 120° for control, so a closed-loop regulation 13
may be used to improve the motor performance. Each branch could be interpreted as a half of a vertical Hall sensor and are rotated by 120° in comparison to the other. Only a half of a vertical Hall sensor is used since little space is available for the five electrical contacts(two for the supply voltage and three to extract the Hall voltages). This sensor automatically creates three signals with a phase shift of 120°, which directly correspond to the motor driving signals, to simplify the motor control in a closed-loop configuration. A drawing of this device‟s use as angular position sensor for brushless motor control is given in (fig:3.6(b)) A first alignment is between the rotor orientation and the permanent magnet, and a second alignment is between the stator and the sensor. This alignment will allow the motion information for the motor and the information about its shaft angular position.
FIG 3.6 (a) SCHEMATIC REPRESENTATION OF A THREE BRANCHES HALL SENSOR (b) THREE BRANCHES VERTICAL HALL DEVICE MOUNTED AS ANGULAR POSITION SENSOR FOR BRUSHLESS MOTOR CONTROL
3.3 Four Quadrant Control Operation : There are four possible modes or quadrants of operation using a three phase Brushless DC (BLDC) Motor. In 1 st Quadrant positive speed and the torque is positive hence the motor rotates in the forward direction. In 2nd Quadrant motor is rotating in the forward direction, but torque is being applied in reverse. Reverse Torque is applied to “brake” the motor, and the motor is now generating power. In 3rd Quadrant negative speed and negative torque. In this condition the motor is rotating in reverse direction. In 4th Quadrant exactly the opposite, the motor rotates in the reverse direction, but the torque is being applied in the forward direction. Again, torque is being applied to attempt to slow the motor and change its direction to forward again. Once again, power is being generated by the motor.
14
FIG 3.7 FOUR QUADRANTS OF OPERATION
The three phase brushless DC (BLDC) motor is initially made to rotate in forward direction, but when the speed command is given reverse, the control goes into the forward braking mode hence current flows from motor to battery , in this case the rotor comes to the standstill position is term named as forward braking or regenerative braking. Instead of waiting for the absolute standstill position, continuous energization of the main phase is attempted. This rapidly slows down the rotor to a standstill position. Similarly for when the motor rotates in the reverse direction, but when the speed command is given positive, the controller goes into reverse regeneration mode, in this case the current is flows from motor to source.
3.4 Theory of Operation : A BLDC motor is driven by voltage strokes coupled with the rotor position. These strokes must be properly applied to the active phases of the three-phase winding system so that the angle between the stator flux and the rotor flux is kept close to 90° to get the 15
maximum generated torque. Therefore, the controller needs some means of determining the rotor's orientation/position (relative to the stator coils), such as Hall-effect sensors, which are mounted in or near the machine‟s air gap to detect the magnetic field of the passing rotor magnets. Each sensor outputs a high level for 180° of an electrical rotation, and a low level for the other 180°. The three sensors have a 60° relative offset from each other. This divides a rotation into six phases (3-bit code).
FIG 3.8 ELECTRONICALLY COMMUTATED BLDC MOTOR DRIVE
The process of switching the current to flow through only two phases for every 60 electrical degree rotation of the rotor is called electronic commutation. The motor is supplied from a three-phase inverter, and the switching actions can be simply triggered by the use of signals from position sensors that are mounted at appropriate points around the stator. When mounted at 60 electrical degree intervals and aligned properly with the stator phase windings these Hall switches deliver digital pulses that can be decoded into the desired three-phase switching sequence. A BLDC motor drive with a six -step inverter and Hall position sensors is shown in (Fig:-3.8). Such a drive usually also has a current loop to regulate the stator current, and an outer speed loop for speed control. The speed of the motor can be controlled if the voltage across the motor is changed, which can be achieved easily varying the duty cycle of the PWM signal used to control the six switches of the three-phase bridge. 16
FIG 3.9 HALL-SENSOR SIGNAL,BACK EMF,O/P TORQUE & PHASE CURRENT
17
Only two inverter switches, one in the upper inverter bank and one in the lower inverter bank, are conducting at any instant. These discrete switching events ensure that the sequence of conducting pairs of stator terminals is maintained. (Fig:-3.8) shows an example of Hall sensor signals with respect to back-EMF and the phase current. One of the hall sensors changes the state every 60 electrical degrees of rotation. Given this, it takes six steps to complete an electrical cycle. However one electrical cycle may not correspond to a complete a mechanical rotation is determined by the rotor pole pairs. For each rotor pole pair, one electrical cycle is completed. The number of electrical cycles\rotations equals the rotor pole pairs. This sequence of conducting pairs is essential to the production of a constant output torque.
3.5 Torque/Speed Characteristics : (Fig:-3.10) shows an example of torque/speed characteristics. There are two torque parameters used to define a BLDC motor, peak torque (TP) and rated torque (TR ).During continuous operations, the motor can be loaded up to the rated torque. As discussed earlier, in a BLDC motor, the torque remains constant for a speed range up to the rated speed. The motor can be run up to the maximum speed, which can be up to 150% of the rated speed, but the torque starts dropping. Applications that have frequent starts and stops and frequent reversals of rotation with load on the motor, demand more torque than the rated torque. This requirement comes for a brief period, especially when the motor starts from a standstill and during acceleration. During this period, extra torque is required to overcome the inertia of the load and the rotor itself.
FIG
3.10
TORQUE/SPEED
18
CHAPTER : 4
HARDWARE AND SOFTWARE IMPLEMENTATIONS
4.1 Simulation Machine Parameter : -
TABLE : 1 PARAMETERS OF BLDC MOTOR
SR NO.
BLDC MOTOR
1
Back EMF waveform
Trapezoidal
2
Mechanical Input
Torque Tm
3
Stator phase inductance Ls [h]
4
Stator phase resistance Rs [ohm]
5
Back emf flat area [degree]
6
Inertia, friction factor, pole pairs [j(kg.m^2) F(N.m.s) p()]
7
Flux linkage established by magnets (V.s)
8
Voltage constant (V_peak L-L/ krpm)
9
Torque constant (N.m/A_peak)
8.50E-03 2.875 120 degree
[0.0008 0.001 4]
0.175 146.6077 1.4
19
4.2 Simulation Model : -
FIG 4.1 SIMULINK MODEL OF BLDCM
20
(Fig : 4.1) shows a block diagram of Simulation Model of BLDC motor based Thread Traversing in textile industry. With the help of this type of connection we performed six-step operation. In which different block are used like 3-phase Inverter circuit, BLDC motor block, and Control circuit block. A 300 Volt DC supply is given to the 3-phase inverter circuit Block. In inverter circuit 6 Ideal switches are used to form 3-phase inverter circuit as shown in (fig : 4.2).
FIG 4.2 THREE-PHASE INVERTER CIRCUIT
In inverter circuit switch S1, S3, S5 are connected in Upper side while switch S4, S6, S2 are connected in lower side of the circuit. In ideal switch terminal 1 and g are input signal while terminal 2 and m are output signal. In switch gate pulses (g1, g2, g3, g4, g5, g6) are applied from the Hall sensor signal of the BLDC motor. Terminal „m‟ of the IDEAL switch is terminating through Terminator Block.
21
Output of the inverter is taken from Terminal a, b, c as shown in (fig:-4.2). Output of this inverter circuit is given to the 3-phase BLDC motor. The parameter of BLDC motor is given in (table no. 1) Output of the BLDC motor is given to the Bus selector block which gives output as Hall effect signal (ha, hb, hc), Back emf (ea, eb, ec) in volt, Current(Ia, Ib, Ic) in ampere, electromagnetic torque Te (N*m) and rotor speed wm (rad/s). In Hall sensor, logical operation will be performed and which gives output as gate pulses. This gate pulses are used to drive 3-phase inverter circuit. In control circuit step input and repeating sequence are used which gives out control signal and this signal is given to the switch S1, S2 and S3 of the 3-phase inverter circuit. This way we get six step output operation of BLDC Motor .
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4.2.1 Simulink Results : 1. Hall Sensor Pulses for forward and reverse rotat ion
Reverse Rotation Waveform After This Intersection
FIG 4.3 HALL SENSOR PULSES
2. Gate Pulses for forward and reverse rotation
Reverse Rotation Waveform After This Intersection
FIG 4.4 GATE PULSES
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3. Speed and Torque for forward and reverse rotation Reverse Rotation Waveform After This Intersection
FIG 4.5 SPEED AND TORQUE CHARACTERISTICS
4. Back Emf and Current for forward and reverse rotation
Reverse Rotation Waveform After This Intersection
FIG 4.6 BACK EMF AND CURRENT WAVEFORMS
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4.3 Hardware : 4.3.1 24 volt DC supply : The power supply is designed to convert high voltage ac mains electricity to a suitable low voltage supply for electronics circuit and other device the RPS (regulated power supply) is the power supply with rectification, filtering and regulation being done on the ac mains to get a regulated power supply for a microcontroller and for the other devices being interfaced to it. A power supply can be broken down into a service of blocks, each of which performs a particular function. A DC power supply which maintains the output voltage constant respective of ac mains fluctuations or load variations is known as „regulated power supply‟ . (Fig : 4.7) shows a regulated power supply.
FIG 4.7 POWER SUPPLY
4.3.2 Transformer : Transformer is an electrical device which is used to convert electrical power from one electrical circuit to another without change in frequency. Transformer convert ac electricity from one voltage to another with little loss of power. Transformers work only with ac and this is one of the reasons why mains electricit y is
25
ac. Step up transformer increase in output voltage, most power supplies use a step down transformer to reduce the dangerously high mains voltage to a safer low voltage. Input coils called a primary and the output coils is called the secondary. There is a no electrical connection between the two coils instant they are linked by the alternating magnetic field crated in the soft iron core of the transformer. The two lines in the middle of the circuit symbol represent the core. The transformer waste the very little power so power out is equal to the power in note that as voltage is step down current is stepped up. The ratio of the number of the turns on each coils called the turns ratio determine the ratio of the voltage. A stepped down transformer large number of turns on the its primary coil which is connected to the high voltage main supply, and a less number of turns in secondary(output) coil to give a low output voltage. Turns ratio = Vp/Vs = Np/Ns Power out = power in Vp = primary (input) voltage Np = no. of turns on primary coil Ip = primary (input) current
FIG 4.8 TRANSFORMER
In project transformer are used with rating of 230/24 V and current rating of 10 A. For testing of transformer two type of test will be performed
Open Circuit Test
Load test
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FIG 4.9 TESTING OF TRANSFORMER TABLE : 2 OPEN CIRCUIT TEST RESULTS
INPUT (Volt)
OUTPUT (Volt)
235
25.2
TABLE : 3 LOAD TEST RESULTS
Sr No. 1 2 3 4 5 6 7 8 9 10
Vp 235 235 235 235 235 235 235 235 235 235
Vs 24.2 24.2 23.8 23.6 24.1 24.2 23.6 23.5 23.3 23.1
Is 3.25 4 4.5 5.1 5.5 6.2 6.55 7 7.5 8
4.3.3 Rectifier : A circuit which is used to convert AC to DC is known as RECTIFIER. The process of the conversion ac to dc called „rectification‟.
4.3.3.1 Bridge Rectifier : A bridge rectifier makes use of four diodes in bridge arrangements to achieve full wave rectification. This is widely used configuration; both with individual diodes wired as shown and with single component bridge were the diode bridge is wired internally. 27
FIG 4.10 BRIDGE RECTIFIER
A bridge rectifier makes use of four diodes in bridge arrangement as shown in (fig : 4.10) to achieve full wave rectification. This is widely used configuration both with individual diode wired is shown and signal component bridge where the diode bridge is wired internally.
Operation : -
During positive half cycle of secondary, the diode D2 and D3 are forward in biased while D1 and D4 are in reverse biased as shown in (fig : 4.10) .
During negative half cycles of secondary voltage, the diodes D1 and D4 are in forward biased while D2 and D3 are in reverse biased as shown in (fig : 4.10) .
Capacitor Filter : -
Capacitive filter is used in this project. It removes the ripples from the output of rectifier and smoothens the D.C. Output received from this filter is constant until the mains voltage and load is maintained constant. However, if either of the two is varied, D.C. voltage received at this point changes. Therefore a regulator is applied at the output stage.
The simple capacitor filter is the most basic type of power supply filter. The use of this filter is very limited. It is sometimes used on extremely high-voltage, low-current power supplies for cathode-ray and similar electron tubes that require very little load current from the supply. This filter is also used in circuits where the power-supply ripple frequency is not critical and can be relatively high. Below figure can show how the capacitor changes and discharges. 28
FIG 4.11 BRIDGE RECTIFIER WITH CAPACITOR FILTER
4.3.3.2 Rectifier Testing : In our circuit we are using 2200uf hence large value of capacitor is placed to reduce ripples and to improve the DC component. In rectifier circuit 35A Range Bridge, 50V, 2200µF Capacitor and transformer with the rating of 230/24V-10A are used.
(A)
(B)
FIG 4.12 RECTIFIER TESTING (A) INPUT VOLTAGE (B) OUTPUT VOLTAGE
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4.3.4 15 Volt DC supply for Inverter : For inverter a 15 volt DC supply is used for its operation. (Fig : 4.13) shows the 15 volt dc supply with 5 volt supply for Hall sensor signal amplification circuit.
FIG 4.13 15 VOLT SUPPLY
4.3.5 Hall Sensor Signal Amplification Circuit : BLDC motor has three Hall sensors inside the stator on the non-driving end of the motor. Whenever the rotor magnetic poles pass near the hall sensors they give a high or low signal indicating the N or S pole is passing near the sensors. Based on the combination of these three Hall sensor signals, the exact sequence of commutation can be determined. A 5 volt DC supply is given to Hall-sensor terminals.
4.3.6 3-phase Inverter : A three phase inverter consists of three single-phase inverter switches each connected to one of the three load terminals. For the most basic control scheme, the operation of the three switches is coordinated so that one switch operates at each 60 degree point of the fundamental output waveform. This creates a line-to-line output waveform that has six steps. The six steps waveform has a zero-voltage step between the positive and negative sections of the square-wave such that the harmonics that are multiples of three are eliminated. When carrier-based PWM techniques are applied to six-step waveforms, the basic overall shape, or
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envelop, of the waveform is retained so that the 3rd harmonics and its multiples are cancelled.
FIG 4.14 THREE-PHASE INVERTER CARD
4.3.7 8051 Micro-Controller : A microcontroller unit is a specialized type of digital computer used to provide automatic sequencing or control of a system.
FIG 4.15 MICRO-CONTROLLER CARD
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Microcontroller differ from ordinary digital computers in being very small (typical a single integrated circuit chip), with several dedicated pins for input and/or output of digital signals, and limited memory. Instructions programmed into the microcontroller‟s memory tell it how to react to input conditions, and what types of signals to send to t he outputs. The simplest type of signal understood by a microcontroller is a discrete voltage level: either “high” or “low” measured at a specified pin on the chip.
4.3.7.1 P89V51RD2 IC : The P89V51RD2 is 80C51 microcontroller with 64kB flash and 1024 B of data RAM. A key feature of P89V51RD2 is its X2 mode option. The design engineer can choose to run the application with the conventional 80C51 clock rate (12 clocks per machine cycle) or select the X2 mode (six clocks per machine cycle) to achieve twice the throughout at the same clock frequency by half, thus dramatically reducing the EMI. The flash program memory supports both parallel programming and in serial ISP. Parallel programming mode offers gang-programming at high speed, reducing programming costs and time to market. ISP allows a device to be reprogrammed in the end product under software control. The capability to field/update the application possible. The P89V51RD2 is also capable of IAP, allowing the flash program memory to be reconfigured even while the application is running.
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4.4 Testing and speed control of BLDC Motor : 4.4.1 Six step operation
Fig. 4.16 Gate pulse g1 and g4
Fig. 4.17 Gate pulse g1 and g3
Fig. 4.18 Current I a 33
Fig. 4.19 Hall sensor signal H a and H b
Fig. 4.20 Hall sensor signal H b and Hc
Fig. 4.21 Hall sensor signal H a and Hc
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4.4.2 Speed control by pwm
Fig.4.22 Gate signal g1 and g4 at 750rpm
Fig.4.23 gate signal g1 and g3 at 750rpm
Fig.4.24 current I a at 750rpm with loading
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Fig.4.25 gate signal g1 and g4 at 950rpm
Fig.4.26 Gate signal g1 and g3 at 950rpm
Fig.4.27 Current Ia at 950rpm with loading
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Fig.4.28 Line voltage Vab and Vac
Fig.4.29 Line voltage Vab and Vac
Fig.4.30 Gate signal g1-g3, g1 and g3
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4.4.3 Operation with pwm method : For the PWM method we used g1, g3, g5 as PWM pulses whereas g2, g4, g6 used as normal pulses (speed frequency) as input to the inverter. For the PWM mode we use PCA timer (8-bit) which is shown in fig.3.15 that has five modules, Modules0, Modules1…., in that we use 3 modules as PWM input that is Modules0 , Modules2, Modules4. This timer is 8-bit so, range is 0 to FF (0 to 255), for the PCA input we use f osc/12 as internal clock frequency. For calculating the frequency f,
= 7.2 KHz For the connection, Modules0 of the PCA timer is connected to pin P1.3 as g1, Modules1 is connected with P1.4 as g2 Modules2 is connected with P1.5 as g3 Pin P1.6 is connected as g4 Pin P1.7 is connected as g5 Pin P1.2 is connected as g6 For timer base key scanning 3 pin is used as an Increment, Decrement and Start/Stop. For Increment pin P2.0 is used. For Decrement pin P2.1 is used. For Start/Stop pin P2.2 is used. For the time variation 10 time we will take so for the 255 time we get 25 time speed variation is achieved. Suppose, the position of the key press is already as (1, 1, 1). 38
So, for the first position of the pin P2 is as 0x07 and when we compare 0x01 with it that time we get output as 0x01, for the second interval if P2 is compare with 0x02 then it gives out as 0x02, and for third interval if P2 is compare with 0x04 then it gives out as 0x04. For speed control (change the duty ratio), for increment and decrement we use + or – 10 step time variation so, we get 0 (minimum) to 250 (maximum) speed control in s tep wise. Table shows the testing of hardware
Table 4 Testing results of hardware DC link voltage: 24V
Fs= 7.2 kHz
Sr. No.
Line Voltage Vab
% Duty Ratio of PWM
1.
45.8
48
1800
2.
55
50
1925
3.
65
60
2171
4.
80
62
2280
5.
85
65
2430
6.
95
72
2780
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Speed N (rpm)
CHAPTER : 5
CONCLUSION
5.1 CONCLUSION : The simulation is carried out using MATLAB Simulink for six step operation of BLDC motor and motor simulation results are analyzed for forward and reverse motoring. Some hardware components like voltage regulator, transformer, rectifier and 3-phase inverter card have been made. We have use BRUSHLESS DC MOTOR (BLDC) instead of induction motor and gear box combine to use in texturizing machine. BLDC without brush, commutated by electronic control method, having higher efficiency and speed – torque response. Efficiency is an important indicator of ener gy saving and carbon reduction. We have finally completed the thread traversing with BLDC motor in the forward , reverse and forward-stop-reverse-stop operation.
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REFERENCES
[1] AN885, Microchip : AZ , “Brushless DC (BLDC) Motor Fundamentals Application Note” , USA. 2003. [2] AN10661, Rev. 01-17 October 2007 . [3] “3-Phase BLDC Motor Control with Hall Sensors using 56000/E Digital Signal Controllers Application Note” ; AN1916, Freescale Semiconductor: TX, USA, 2005. [4] Leonard N. Elevich , “3-Phase BLDC Motor Control With Hall Sensors Using 56800/E Digital Signal Controllers3-Phase BLDC Motor Control With Hall Sensors Using 56800/E Digital Signal Controllers”. [5] Dr. Inaam Ibrahim , “AC machine”. [6] V.U, S.Pola and K. P. Vittal , “Simulation of four quadrant operation & speed control of BLDC motor on MATLAB/SIMULINK ” , ‖ in Proc.IEEE Region 10 Conference , 2008, pp. 1 – 6. [7] Becerra R.C. ; Ehsani M. “High-Speed Torque Control of Brushless Permanent Magnet Motors” , IEEE Trans. Ind. Electron. 1988, 35, 402-406. [8] Krishnan R. ; Lee S. “PM Brushless DC Motor Drive with a New Power-Converter Topology” , IEEE Trans. Ind. Appl. 1997, 33, 973-982. [9] T.J.E. Miller , “Brushless Permanent Magnet and Reluctance Motor Drives” , (Book), Clarendon Press Oxford, 1989.
TEXT BOOK : -
[1] BIMAL K. BOSE , “Modern Power Electronics and AC Drives”
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APPENDIX
Features of P89V51RD2 :
80C51 CPU
5 V operating voltage from 0 MHz to 40 MHz
64kB of on-chip flash user code memory with ISP and IAP
Supports 12-clock(default) or 6-clock mode selection via software or ISP
SPI and enhanced UART
PCA with PWM and capture/compare functions
Four 8-bit I/O ports with three high-current port 1 pins (16 mA each)
Three 16-bit timers/counters
Programmable watchlog timer
Eight interrupt sources with four priority levels
Second DPTR register
Low EMI mode (ALE inhibit)
TTl and CMOS compatible logic levels
Brownout direction
Low power modes
Power-down mode with external interrupt wake-up
Idle mode
PDIP40, PLCC44 and TQFP44 packages
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BLOCK DIAGRAM : -
FIG A.1 BLOCK DIAGRAM OF P89V51RD2
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