Technical Guidelines ABB LT Motors
Contents
Product range Features of standard TEFC motors Manufacturing range summary Designs variants Features of standard SPDP motors
3 3 3 4 4
General Standards Tolerances Mounting arrangement Degree of protection Cooling methods Direction of rotation Insulation and insulation class Effect of voltage and frequency variation Permitted output in high ambient temperature and high altitudes Permitted output for voltage unbalance Motors for 60 Hz operation Winding connection
5 6 6 8 9 9 9 10 10 10 11 12
Electrical Electrical features Starting method for AC motors Typical motor current and torque curves Comparison between starting methods Starting time Example of starting performance with different load torques Electrical braking Duty types Protection accessories Guide for fuse protection Voltage drop along cable Negative sequence withstand characteristics Power factor improvement chart
13 14 15 15 16 17 18 20 22 22 23 23 24
Mechanical Mechanical Features Exploded view of HX motors Pulley diameter Permissible radial forces Permissible axial forces
25 26 27 28 29
Others Testing Motor for frequency converter drive Guide and check points for motor selection (mechanical aspects) Guide and check points for motor selection (electrical aspects) Ordering Information Frequently asked questions
30 31 33 34 35 37
Product Range
! ! ! ! ! ! ! ! ! ! !
Standard TEFC motor, IS : 325 - 1996 Crane duty motors Non sparking motors Type “EX-n” Increased Safety motors Type “Ex-e” Flame proof motors Type “Ex-d” Variable frequency drive motors Ring frame motors, IS : 2972 Part III Roller table motors for steel plants Auxiliary motors for a.c locomotives Custom build motors for textile, machine tools and various other applications. Standard SPDP motors, IS : 325 - 1996
Feature of standard TEFC Motors Type Enclosure Voltage ± variation Frequency ± variation Combined variation Mounting reference Frame dimensions Altitude Relative humidity Degree of protection Class of insulation Ambient temperature / temperature rise Duty Position of terminal box Connection / No of leads Direction of rotation Grease type Greasing arrangements Cooling Paint
Three phase squirrel cage induction motor Totally - enclosed fan cooled 415V ± 10% 50Hz ± 5% 10% (Absolute Sum) As per IS 4691 As per IS 1231; IS 2223 Up to 1000 M Up to 100% IP55 Class F 45ºC/75ºC Up to Frame 160 50ºC/70ºC Frame 180 to 400 S1/Continous Top at drive end Up to 2 HP - STAR / 3 Leads > 2 HP - DELTA / 6 Leads Bi-directional Lithium complex grease Online greasing arrangement for 225 and above IC 0141 (TEFC) Polyurethane (Shade: Munsell Blue)
Range Output Voltage Frequency Duty Ambient Temperature
0.18 ...500kW; 0.25 ...675hp; according to IS 325 220 ... 660V 25 ... 60Hz S1 ... S8 according to IS:325 -20ºC ... 65ºC
3
Design Variants
Electrical Non standard voltage and frequency variations AC variable speed drives High torque motors High slip motors Motors for frequent start / stops / reversals Frequency 25 to 60 Hz Special performance requirements Class H insulation Voltage 220V to 550V
Mechanical Non standard mounting dimensions Special shaft extension Double shaft extension Separately ventilated motors Low vibration and noise level Brake motors Special bearings and lubrications Tacho mounting / SPM mounting Non standard paint shade Alternative terminal box position IP 56 protection Special shaft material Special size of terminal box and terminal arrangements Surface cooled motors SS name plate Non standard keyway Epoxy gelcoat on overhangs Space heaters Thermistors, RTD , BTD Single compression / double compression glands
Note: Please refer to the company for details of special designs offered.
Feature of standard SPDP Motors Type Enclosure Voltage ± variation Frequency ± variation Combined variation Mounting reference Frame dimensions Altitude Relative humidity Degree of protection Class of insulation Ambient temperature Duty Position of terminal box Connection / No of leads Direction of rotation Grease type Cooling Paint
4
Three phase squirrel cage induction motor Screen protected drip proof 415V ± 10% 50Hz ± 5% 10% (Absolute Sum) As per IS 4691 As per IS 1231; IS 2223 Up to 1000 M above MSL Low / indoor applications IP 23 F, Temperature rise limited to CL.B 40ºC S1 Top DELTA / 6 Leads Bi-directional Li-complex grease IC 01 Polyurethane (Shade: Munsell Blue)
Standards
ABB Motors are designed to ensure that performance complies with IS:325. HX/M2BA Motors are totally-enclosed three-phase squirrel cage type complying with relevant Indian Standards. List of Indian Standards applicable to low-voltage induction motors are as given below:
IS No.
Title
IS 325:1996
Three-phase induction motors (fifth revision)
IS 900:1992
Code of practice for installation and maintenance of induction motors (second revision)
IS 1231:1974
Dimensions of three-phase foot-mounted induction motors (third revision)
IS 2223:1983
Dimensions of flange mounted a.c. induction motors (first revision)
IS 2253:1974
Designation for types of construction and mounting arrangement of rotation electrical machines (first revision)
IS 2254:1985
Dimensions of vertical shaft motors for pumps (second revision)
IS 2968:1968
Dimensions of slide rails for electric motors
IS 4029:1967
Guide for testing three-phase induction motors
IS 4691:1985
Degrees of protection provided by enclosure for rotation electrical machinery (first revision)
IS 4722:1992
Rotating electrical machines (first revision)
IS 4728:1975
Terminal marking and direction of rotation for rotating electrical machinery (first revision)
IS 4889:1968
Method of determination of efficiency of rotating electrical machines
IS 6362:1971
Designation of methods of cooling of rotating electrical machines
IS 7538:1975
Three-phase squirrel cage induction motors for centrifugal pumps for agricultural applications
IS 7816:1975
Guide for testing insulation resistance of rotating machines
IS 8151:1976
Single-speed three-phase induction motors for driving lifts
IS 8223:1976
Dimensions and output ratings for foot-mounted electrical machines with frame numbers 355 to 1000
IS 8789:1978
Values of performance characteristics for three-phase induction motors
IS 12065:1987
Permissible limits of noise level for rotating electrical machines
IS 12066:1987
Three-phase induction motors for machine tools
IS 12075:1986
Mechanical vibration of rotating electrical machines with shaft heights 56mm and higher-measurement, evaluation and limits of vibration severity (super ceding IS 4729:1968)
IS 12615:1989
Energy efficient three-phase squirrel cage induction motors
IS 12802:1989
Temperature rise measurement of rotating electrical machines
IS 12824:1989
Type of duty and classes of rating assigned to rotating electrical machines
IS 13107:1991
Guide for measurement of winding resistance of an a.c. machine during operation at alternating voltage
IS 13529:1992
Guide on effects of unbalanced voltages on the performance of three-phase cage induction motors
IS 13555:1993
Guide for selection and application of three-phase a.c. induction motors for different types of driven equipment 5
Tolerances (as per IS:325-1996)
Item
Tolerance
Efficiency (h) By summation of losses Motors up to 50kW Motors above 50kW
-15 percent of (1 - h) -10 percent of (1 - h)
By input output method
-15 percent of (1 - h)
Total losses applicable to motors above 50kW*
+10 percent of total losses
Power factor (cosf)
-1/6 of (1 - cosf) min 0.02 and max 0.07
Slip at full load and working temperature
±20 percent of the guaranteed value
Breakaway starting current with the specified starting method
±20 percent of the guaranteed starting current (no negative tolerance)
Breakaway torque
-15 to +25 percent of the guaranteed torque (+25 percent may be exceed by agreement)
Pullout torque
-10 percent of the guaranteed torque except that after applying this tolerance, the torque shall not be less than 1.6 or 1.5 times the rated torque
Moment of inertia or stored energy constant for motors above 315 frame
±10 per cent of the guaranteed value
* Upon agreement between manufacturer and purchaser
Mounting arrangements IS:2253 and technically identical IEC 60034-7 specify two possible ways of describing how a motor is mounted. Code I covers only motors with bearing end shields and one shaft extension. The code consists of letters IM, a further letter and a number. Code II is a general one applicable to all rotating machines. The code consists of letters IM and four characteristics numerals as illustrated below.
IM
1
00
1
Shaft extension, one cylindrical shaft extension Mounting arrangement, horizontal mounting with feet downward Type of construction, foot mounted motor with two endshield International mounting
6
Mounting arrangements
CodeI/CodeII Foot-mounted motor,
IM B 3 IM 1001
Flange -mounted motor, Large flange
IM B 5 IM 3001
Flange -mounted motor , Small flange
IM B 14 IM 3601
Foot and flange-mounted, Motor with feet, Large flange
IM B 35 IM 2001
Foot and flange-mounted, Motor with feet, Small flange
IM B 34 IM 2101
Foot-mounted motor, Shaft with free extensions
IM 1002
IM V 5 IM 1011
IM V 6 IM 1031
IM B 6 IM 1051
IM B 7 IM 1061
IM V 3 IM 3031
IM 3051
IM 3061
IM V 18 IM 3611
IM V 19 IM 3631
IM 3651
IM 3661
IM 3671
IM V 15 IM 2011
IM V 36 IM 2031
IM 2051
IM 2061
IM 2071
IM 2111
IM 2131
IM 2151
IM 2161
IM 1012
IM 1032
IM V 1 IM 3011
IM 1052
IM 1062
IM B 8 IM 1071
IM 3071
IM 2171
IM 1072
7
Degree of protection
Degree of protection for rotating machines are indicated according to IS:4691 using the characteristic letters ‘IP’ followed by two characteristic numerals for the degree of protection. The first numeral indicates protection against contact and ingress of foreign bodies. The second numeral indicates protection against ingress of water.
First characteristic numeral IP 2
Protected against solid objects greater than 12mm
IP 5
Dust protected motors, Ingress of dust is not fully protected, but dust can not enter in an amount sufficient to interface with satisfactory operations of the motor.
Second characteristic numeral IP 3
Protected against spraying water, sprayed up to angle of 600 from vertical shall have no harmful effect.
IP 5
Protected against water, jets by a nozzle from any direction shall have no harmful effect.
IP 6
Protected against heavy seas, powerful jets from all direction shall have no harmful effect.
Degree of protection - Schematic
1st Numeric
8
1st Numeric
0
No protection
0
No protection
1
Protected against solid objects greater that 50mm (e.g. hand)
1
Dripping water shall have no harmful effect.
2
Protected against solid objects greater that 12mm (e.g. fingers)
2
Protected against dripping water when enclosure is titled 150
3
Protected against solid objects greater that 2.5mm (e.g. tools, wires)
3
Protected against spraying water up to 600
4
Protected against solid objects greater that 1mm (e.g. wire or strips)
4
Water splashed from any direction shall have no harmful effect
5
Ingress of dust is not totally protected, but does not enter in sufficient quantities to harm equipment
5
Water hosed against the enclosure shall have no harmful effect (water jets)
6
No ingress of dust
6
Water from powerful jets of heavy seas shall have no harmful effects
Cooling Methods
D-end and N-end
Cooling methods of HX/M2BA Motors are in accordance with IS:6362. The motors are cooled by the method IC 0141, i.e. frame surface cooled, with external cooling fan on motor shaft.
The ends of motors are defined as D-end; the end that is normally the drive end of the motor and N-end; the end that is normally the non-drive end of the motor.
The fan is made of strong engineering plastic for frames upto 200 (aluminum alloy/cast iron option is also available). For frames 225 and above, aluminum alloy fans are used. Fans of all motors are bidirectional. The motors are provided with cooling ribs for increased surface area and improved cooling. An air gap is left between ribs and fan cover for cleaning purposes. The ribs are designed so that they keep the flow of air close to the surface of the motor along the entire length, thus improving self cleaning and cooling.
Direction of rotation
The external ventilation of the motors is obtained by means of the fan mounted to the shaft, which sucks in the ambient air through the fan cover on the N-end and blows it over the frame in between the ribs. Fans are axially and radially locked to prevent vibration. The internal cooling of motors is affected by the churning action of internal air by the ribs on the die-cast rotor.
In conformation with IS:4728, the terminals of the motor are marked such that when the alphabetic sequence of the terminals U1, V1, W1: U2, V2, W2 corresponds to the supply phase sequence L1, L2, L3 the motor runs in a clockwise direction, when seen from drive end. For anticlockwise operation of the motor, any two of the supply phase connections (L1, L2, L3) are exchanged to obviate the need for change of the terminal markings.
0
C
Insulation and insulation classes
180
Insulation materials are divided into insulation classes. Each class has a designation corresponding to the temperature that is the upper limit of the range of application of the insulating material under normal operating conditions.
155
The winding insulation of a motor is determined on the basis of the temperature rise in the motor and the ambient temperature. The insulation is normally dimensioned for the hottest point in the motor at its normal rated output and an ambient temperature of 45ºC/50ºC. Motors subjected to ambient temperatures above 45ºC/50ºC will generally have to be derated.
120
In most cases, the standard rated outputs of motors from ABB motors are based on the temperature rise for insulation class B. Where the temperature rise is according to class F, this is specified in the data tables. However, all the motors are designed with class F insulation, which permits a higher temperature rise than class B. The motors, therefore, have a generous overload margin. If temperature rise to class F is allowed, the outputs given in the tables can be increased by approximately 12%.
15
15 130
Hotspot temperature margin
10 75
95
120
Maximum ambient temperature
45
45
45
Insulation class Maximum winding temperature
B 130
F 155
H 180
Permissible temperature rise
45
Temperature limits are according to standards. The extra thermal margin when using class F insulation with class B temperature rise makes the motors more reliable. 9
Effect of voltage and frequency variation
Almost without exception, the starting current decreases slightly more in proportion to the voltage. Thus for example 90% of rated voltage the motor will draw slightly less than 90% of the starting current, approximately 87 to 89%. The starting torque is proportional to the square of the current, the torque delivered at 90% of rated voltage is therefore only 75% to 79% of the starting torque. Particular attention should be paid to these points if the electrical supply is weak and when starting techniques based on current reduction are being used. The pull out torque is roughly proportional to the voltage. If the saturation of the magnetic circuit is neglected, then the general effect of variation in voltage and frequency on the characteristics of induction motor can be given as per the table below. Table - Effect of variation of voltage and frequency on the characteristics of induction motor* Characteristics
Voltage
Frequency
110%
90%
105%
95%
Torque
Increased by 21%
Decrease 19%
Decrease 10%
Increase 11%
Speed Synchronous Full load Slip
No change Increase 1% Decrease 17%
No change Decrease 1.5% Increase 23%
Increase 5% Increase 5% Little change
Decrease 5% Decrease 5% Little change
Current Rated Starting No load Overload capability
Decrease 7% Increase 10-12% Increase 10-15% Increase 21%
Increase 1% Decrease 10-12% Decrease 10-15% Decrease 19%
Slight decrease Decrease 5-6% Decrease 5-6% Slight decrease
Slight increase Increase 5-6% Increase 5-6% Slight increase
Temperature rise
Decrease 3-4%
Increase 6-7%
Slight decrease
Slight increase
Starting & maximum
Magnetic noise
Slight increase
Slight Decrease
Slight decrease
Slight increase
Efficiency, full load
Increase 0.5-1.0%
Decrease 2%
Slight increase
Slight decrease
Increase 1%
Slight increase
Slight decrease
Power factor, full load Decrease 3%
*These variations are indicative in nature and are not uniformly applicable to all the designs.
Permitted output in high ambient temperature and high altitudes Motors of basic design are intended for operation in a maximum ambient temperature of 45°C and at maximum altitude of 1000 meters above mean sea level. If a motor is to be operated in higher ambient temperature or at higher altitude, it should normally be derated according to the following table. Ambient temperature (°C)
40
45
50
55
60*
65*
75*
85*
Permitted output (% of rated output)
107
100
96.5
93
90
86.5
79
70
Height above sea level (M)
1000
1500
2000
2500
3000
3500
4000
Permitted output (% of rated output)
100
96
92
88
84
80
76
*changes in the type of lubricant and lubrication interval required.
Permitted output for voltage unbalance The phase unbalance for voltage is calculated as follows: maximum difference in voltage compared to average voltage value % voltage imbalance = 100 x _____________________________________________________ average voltage value If this unbalance is known before the motor is purchased it is advisable to apply derating as per following table. Unbalance Derating
1% 100
2% 95
3% 90
4% 83
5% 76
Rerating S1 duty motors to S2 and S3 duty motors Standard motors can be used for S2 and S3 duties with increased outputs. However, the starting torque and pull out torque as a percentage of the full load torque would be reduced. S2
10
S3
60 min
30min
10min
60% CDF
40%CDF
25% CDF
100%
115%
120%
100%
105%
120%
Motors for 60 Hz operation
Motors wound for a certain voltage at 50 Hz can be operated at 60 Hz, without modification, subject to the following changes in their data. Motor wound for 50 Hz and
Connected to 60 Hz and
Data at 60 Hz in percentage of values at 50Hz
220 V
220 v 225 v
100 115
380 V
380 V 415 V 440 V 460 V
400 V
Output
rpm
TN
TS/TN
Tmax/TN1)
IN
IS/IN
120 120
98 100
83 100
83 96
70 95
85 98
100 110 115 120
120 120 120 120
98 98 100 100
83 95 100 105
83 91 96 100
70 85 95 100
85 93 98 103
380 V 400 V 415 V 440 V 460 V 480 V
100 100 105 110 115 120
120 120 120 120 120 120
100 98 100 100 100 100
80 83 88 95 100 105
83 83 86 91 96 100
66 70 78 85 95 100
80 85 88 93 98 100
415 V
415 V 460 V 480 V
100 110 115
120 120 120
98 98 100
83 95 100
83 91 96
70 85 95
85 94 98
500 V
500 V 550 V 575 V 600 V
100 110 115 120
120 120 120 120
98 98 100 100
83 95 100 105
83 91 96 100
70 85 95 100
85 94 98 103
Efficiency, power factor and temperature rise will be approximately the same as at 50 Hz. 1)
IN IS/IN TN Tmax/TN TS/TN
= = = = =
rated current starting current/rated current rated torque maximum torque/rated torque starting torque/rated torque
11
Winding Connection
Single speed Star connected windings for motors upto 2 hp and delta connected windings for motors above 2 hp are standard features. The connection diagrams for single speed motors are given below: D - connection
Y - connection
Double speed The difference in winding configuration and application necessitates different winding connections so as to accommodate maximum power in a given frame. -
Motors with two separate windings are normally Y/Y connected upto frame size 160, larger motors are D/D, Y/D or D/Y connected
-
Motors with Dahalander connection, are in D/YY when they are designed for constant torque drives and Y/YY when they are designed for fan drive.
The connection diagram for different combinations are given below: 1.
2.
3.
4.
Two separate windings Y/Y
Low speed
High speed
Low speed
Low speed
High speed
Low speed
High speed
Low speed
High speed
Low speed
High speed
Low speed
High speed
Two separate windings D/D
Dahlanderconnection D/YY
Dahlanderconnection Y/YY
Low speed 12
High speed
High speed
Electrical features
1. Voltage Rated voltage is the voltage between line terminals for which the motor is designed. Standard voltage for motors is 415V. Motors can, however, be made available for any supply voltage between 220V and 660V. Motors for two different supply voltages have non standard windings and are available on request.
7. Rated current It is the value of the current taken by the motor when delivering rated power at rated voltage and frequency. The value of rated currents are at specified voltage, for other voltages, Ux, the current Ix may be calculated as: 415.I Ix = Ux Where
2. Frequency Rated frequency is the frequency of the voltage for which the motor is designed. The basic design of the motor is suitable for a rated supply frequency of 50 Hz. HX/M2BA motors can be offered for any frequency in the range 25 Hz to 60 Hz, however, for supply frequency other than 50 Hz, they are made available on request.
3. Voltage and frequency variation Motors can be operated continuously at rated output, with a long term voltage variation of ±10%, frequency variations of ±5% and a combined voltage and frequency variation of 10%, over rated values. The temperature rise may increase by 10K at extreme voltage and frequency. If the motors are required to operate continuously at voltage approaching the limits of voltage tolerances without exceeding the temperature rise limit, this must be specified at the time of enquiry.
4. Number of poles Number of poles of the motor determine the basic speed (synchronous speed) of the motor. Standard motors are available in the configuration of 2,4,6 and 8-poles.
5. Power Rated power is the shaft power of the motor with an ambient temperature not exceeding 45°C/50°C and an altitude not exceeding 1000m above mean sea level.
6. Rated speed, slip Rated speed corresponds to the operating speed of the motor at the rated power when it is being fed at rated voltage and frequency. The synchronous speed of an induction motor depends on the supply frequency and the number of poles of the stator winding. Thus, hs=
f p
x 60(rpm)
where hs= synchronous speed (rpm) f = frequency (Hz) p = number of pair of poles note 2p = number of poles The rated speed given in the list is for motors operating at rated power under normal voltage and frequency. The difference between synchronous speed, hs and rotor speed, n; referred to the synchronous speed, is called slip. This slip, s, is expressed as a percentage;
Ux = new voltage Ix = new current I = current at 415V
The current consumption varies also with the loading of the motor, but it should be noted that the relationship is not linear.
8. Starting current Usually, given as a percentage or as a multiple of rated current, it is the value of the current drawn by the motor during starting. The value of the starting current is generally between 500-700% (5-7 per unit) of the rated current.
9. Torque characteristics Typical torque/speed characteristics of the motor is shown in figures on page no. 15 along with different relevant parameters. The nominal torque of the motor TN' is the torque developed by the motor at rated speed, n while delivering rated power P. The relationship between the torque TN' the power P, and the speed n is TN= 9550 x
415.I [Nm] Ux
Where
P = power (kW) n = motor speed (rpm) alternatively, torque T, in kgm can be given as TN= 974 x
P n
[kgm]
Starting torque of the motor TS' is the torque developed by the motor at zero speed when it is directly switched on. Value of starting torque is usually given as a percentage or as a multiple of nominal motor torque TN. Pull out torque of the motor Tmax' is the maximum torque that the motor can develop when it is operated directly on line. Value of pull out torque is usually given as a percentage or as a multiple of nominal motor torque TN.
10. Moment of inertia The moment of inertia J is given in Kgm2. The moment of inertia is numerically equal to 1/4 GD2. The moment of inertia JL of the driven machine at nL rpm when referred to motor speed n rpm is given by J = JL [nL/n]2
11. Overloads In accordance with IS:325 motors are rated to withstand an overload, an excess torque of 60% of their rated torque at rated voltage and frequency for 15 seconds.
hs - h x 100 (%) hs When the motor is partly loaded the slip varies almost linearly with the load. s=
13
Starting methods for AC motors
Reducing electrical and mechanical stress at start-up The starting current of an AC motor can vary from 3 to 7 times the nominal current. This is because a large amount of energy is required to magnetise the motor enough to overcome the inertia the system has at standstill. The high current drawn from the network can cause problems such as voltage drop, high transients and in some cases, uncontrolled shutdown. High starting current also causes great mechanical stress on the motor’s rotor bars and windings and can affect the driven equipment and the foundations. Several starting methods exist, all aiming to reduce these stresses. The load, the motor and the supply network determine the most appropriate starting method. When selecting and dimensioning the starting equipment and any protective devices, the following factors must be taken into account: • The voltage drop in the supply network when starting the motor • The required load torque during start • The required starting time
Direct-on-line (DOL) start: Direct on line starting is suitable for stable supplies and mechanically stiff and well dimensioned systems. It is the simplest, cheapest and most common starting method. Starting equipment for small motors that do not start and stop frequently is simple, often consisting of a hand operated motor protection circuit breaker. Larger motors and motors that start and stop frequently, or have some kind of control system, normally use a direct-on-line starter which can consist of a contactor plus overload protection, such as a thermal relay.
UN Ist UN = Rated net voltage Ist = Start current at full voltage
Star-Delta (Y/D) starting: UN
Most low voltage motors can be connected to run at either 400V with delta connection or at 690V with star connection. This flexibility can also be used to start the motor with a lower voltage. Star/delta connection gives a low starting current of only about one third of that during direct-online starting, although this also reduces the starting torque to about 25%. The motor is started with Y-connection and accelerated as far as possible, then switched to D-connection. This method can only be used with induction motors delta connected for the supply voltage.
Ist UN = Rated net voltage Ist = Start current at full voltage
Soft starters UN Soft starters are based on semiconductors, which, via a power circuit and a control circuit, initially reduce the motor voltage, resulting in lower motor torque. During the starting process, the soft starter progressively increases the motor voltage so that the motor becomes strong enough to accelerate the load to rated speed without causing torque or current peaks. Soft starters can also be used to control the stopping of a process. Soft starters are less costly than frequency converters but like frequency converters, they may inject harmonic currents into the grid, disrupting other processes.
Frequency converter start Although a frequency converter is designed for continuous feeding of motors, can also be used exclusively for start-up only. The frequency converter enables low starting current because the motor can produce rated torque at rated current from zero to full speed. As the price of frequency converters continues to drop, they are increasingly replacing soft starters. However in most cases they are still more expensive than soft starters, and like these, they inject harmonic currents into the network.
14
IstR UN = Rated net voltage UM
IstR = Start current at red. voltage UM = Motor voltage
UN IstR UN = Rated net voltage UM
IstR = Start current at red. voltage UM = Motor voltage
Typical motor current and torque curves
TM TMD TMY TL TL0 TN TS Tmin
= = = = = = = =
Motor torque Motor torque with direct-on-line starting Motor torque with start-delta starting Load torque Load breakaway torque Rated motor torque Breakaway torque or locked rotor torque Pull-up torque
Tmax Tacc I IN ID IY n nS
= = = = = = = =
Breakdown torque or pull-out torque Acceleration torque Current Rated current Current in D-connection Current in Y-connection Speed Synchronous speed
Comparison between starting methods Current
1 2 3
= = =
Torque
Direct-On-Line starter Y/D-starter Start with soft starter
15
Starting time
Theory The starting current of an induction motor is much higher than the rated current, and excessively long starting period causes harmful temperature rise in the motor. The high current also leads to electro-mechanical stresses. It is, therefore, of importance to know the time taken by the motor to accelerate the load to rated speed. This time is called starting time or acceleration time. Starting time depends upon: -
Total inertia of the system Torque speed curve of the motor Torque speed curve of load
If only the starting torque and maximum torque of the motor and the nature of the load are known, the starting time can be approximately calculated with the equation: K1 Tst = (JM + JL) x Tacc where
Speed Constant nM K1 nM K1
If the torque curves for the motor and the load are known, the starting time can be calculated by integrating the equation: T - TL = (JM + JL) x where
T TL JM JL W
= = = = =
¶w ¶t
Motor torque, Nm Load torque, Nm Moment of inertia of motor, kgm2 Moment of inertia of load, kgm2 Motor angular velocity
Tst = Tacc = K1 =
starting time acceleration torque as per diagrams, Nm as per table below
Poles 2 4 6 8 3000 1500 1000 750 345 157 104 78
10 600 62
3600 1800 1200 900 415 188 125 94
720 75
50 50
This method of calculation may be used for direct-on-line starting and for motors up to about 250kW. In other cases more points on the motor torque curves are required. In any case up to the point of maximum torque. If there is speed transformation between the motor and the driven machine, the load torque must be recalculated for the motor speed, by using the following formula:
TL' =
TL x nL nM
where TL' nM nL
= Recalculated load torque, Nm = Motor speed, rpm = Load speed, rpm
The moment of inertia must also be recalculated. JL'=JL' x (nL/nM)2 where JL'= Recalculated moment of inertia, kgm2
16
Frequency Hz
Example of starting performance with different load torques
4-pole motor, 160 kW, 1475krpm
The load is geared down in a ration of 1:2
1 = 800 Nm at nM rpm 2 Moment of inertia of load: nM JL = 80 kgm2 at nL = rpm 2 1 JL = 80 x ( ) 2 = 20 kgm2 at nM rpm 2 Total moment of inertia:
Torque of load:
JM + JL at nM r/min
TL
Torque of motor: TN = 1040 Nm, TS = 1,7 x 1040 = 1768 Nm Tmax = 2,8 x 1040 - 2912 Nm Moment of inertia of motor: JM = 2,5 kgm2
TL
=
1600 Nm at nL =
nM rpm 2
=
1600 x
2,5 + 20 = 22,5 kgm2
Example 1:
Example 3:
Lift motion
Fan Torque
Torque TL
TL
Speed TL
=
1600 Nm
T'L = 800 Nm
Speed TL
=
1600 Nm
T'L = 800 Nm
Constant during acceleration
Square-law increase during acceleration
Tacc
=
0,45 x (TS + Tmax) - T'L
Tacc
=
Tacc
=
Tacc
=
tst
=
tst
=
tst
=
0,45 x (1768 + 2912) - 800 = 1306 Nm K1 (JM + J'L) x Tacc 157 22,5 x 1360 = 2,7 s
tst
=
Example 2:
1 x T'L 3 1 0,45 x (1768 + 2912) x 800 = 1839 Nm 3 K1 (JM + J'L) x Tacc 157 22,5 x = 1,9 s 1839 0,45 x (TS + Tmax) -
Example 4:
Piston pump
Fly wheel Torque
Torque
TL
TL
Speed TL
=
1600 Nm
T'L = 800 Nm
Linear increase during acceleration Tacc
=
Tacc
=
tst
=
tst
=
1 0,45 x (TS + Tmax) T'L 2 1 0,45 x (1768 + 2912) €800 = 1706 Nm 2 K1 (JM + J'L) x T acc 157 22,5 x 1706 = 2,1 s
Speed TL
=
0
Tacc
=
0,45 x (TS + Tmax)
Tacc
=
tst
=
tst
=
0,45 x (1768 + 2912) = 2106 Nm K1 (JM + J'L) x T acc 157 22,5 x = 1,7 s 2106
17
Electrical braking
For slip-ring motors the starting and braking times are both determined by the dimensioning of the rheostatic starter.
Countercurrent braking (Plugging) With countercurrent braking, an ordinary standard motor is switched at full speed for the opposite direction of rotation. This can be done with a reversing switch. After braking to a standstill, the motor starts in the opposite direction of rotation, unless the current is switched off at the right moment. A low speed detector is therefore used to cut off the supply to the motor when the speed approaches zero.
Torque
Countercurrent braking gives a very high braking torque. The current during braking is about the same as during starting, so that there is a considerable temperature rise in the motor. Consequently the permitted frequency of braking with the countercurrent technique is only about one-quarter of the number of permitted braking can easily be exceeded with countercurrent braking, temperature sensors should always be used to protect the motor windings from overheating.
Braking torque
P2 P1
3600x X= Tbx where
4x
Ist I
x P2 P1 tb Ist/I
= = = = =
2
-
2
P2 P1
=
where
(In this case the load torque contributes to the braking torque. To be on the safe side, however, calculations are based on the braking torque being the same as the acceleration torque.) 2
Permitted number of brakings per hour Output taken from motor, kW Rated output of motor in continuous duty, kW Braking time, s Starting current / full load current
K1x (Jm + Jb) 0.45 x (Mmax + Mstart) tb K1
= =
Jm Jb
= =
Mmax = Mstart =
Torque
Braking torque
Countercurrent braking
Braking time, s Constant depending on number of poles, see table Moment of inertia of motor, kgm2 Moment of inertia of load, referred to speed of motor, kgm2 Maximum torque of motor, Nm Starting torque of motor, Nm
Frequency Hz
Constant K1 for different number of poles 2 4 6 8 10
50 60
345 415
157 188
104 125
78 94
62 75
Although the load torque contributes to the braking torque, making allowance for it complicates the calculation unduly if the braking time must be accurately known. It can therefore be said that the braking torque is approximately equal to the acceleration torque, when the load current is approximately zero.
18
Starting
Figure 1
For squirrel cage motors the braking time can be calculated approximately with the formula: tb
Mb
Acceleration torque
Speed
Countercurrent braking
The permitted number of counter current braking can be calculated approximately with the formula:
Torque
Torque
Acceleration torque
Starting
Speed
Figure 2 (It is a complicated matter to calculate theoretically the braking torque curve for countercurrent braking. In most cases it can be assumed that the braking torque is approximately equal to the acceleration torque, when the load current is approximately zero.)
With countercurrent braking there is no braking action in the event of power failure. The technique is therefore unsuitable for use in plant where loss of braking could cause danger.
Speed detector with countercurrent braking A low speed detector designed to cut off the supply to the motor when the speed approaches zero can be used to terminate countercurrent braking at the right instant. The speed detector is usually mounted on the N-end of the motor and is driven from the motor shaft via a coupling.
Direct-current braking
Regenerative braking
When braking with this technique, the a.c. supply to the motor is disconnected and the stator is excited with direct current; this causes the motor to produce a braking torque.
This is the method of braking multi-speed motors when changing down to lower speeds. The thermal stresses are approximately equal to those occuring when motors with dual speed connections are started at lower rated speed. With the motor at the lower speed working as a generator, it develops very high braking torque in the interval between operating speeds of motor corresponding to the two poles. The maximum braking torque is slightly higher than the starting torque of the motor at the lower speed. Regenerative braking is also used with variable speed drives.
An ordinary standard motor and suitable equipment for d.c. excitation may be used. The a.c. voltage follows a decay curve, and the d.c. voltage must not be connected until the a.c. voltage has fallen to a value at which it will not harm the d.c. equipment. The excitation current is determined by the braking time chosen, but is usually 1 to 2 times the rated current of the motor. However, saturation of the magnetic circuit imposes a limit on the braking torque. Direct-current braking gives a far longer braking time than countercurrent braking, however high the excitation current, but thermal losses are lower, so more frequent braking is permissible.
Based on the thermal stesses developed during different braking methods, with reference to those developed during direct-on-line starting, following thermal equivalence is drawn. Four jogs (or inching) One DC injection braking One plug stop One regenerative braking
= = = =
One start Two start Three start One start
If the d.c. voltage fails there will be no braking action. The technique is therefore unsuitable for use in plants where loss of braking could cause danger.
Time
Figure 3
(The lower curve shows the output voltage from the stator winding of a small induction motor after disconnection from the supply. Only half the curve is shown. The upper curve is a 50 Hz scale. With countercurrent braking, the d.c. voltage must not be connected until the a.c. voltage has fallen to a value at which it will not harm the d.c. equipment.)
Torque
Braking torque
Torque
Acceleration torque
Mb
Torque Direct-current braking
Starting
Figure 4 (Example of braking torque with d.c. braking and different excitation currents. In = rated current of motor.) 19
Duty types
The duty types are indicated by the symbols S1 ... S9 according to IS:12824-1989. The outputs given in the tables are based on continuous running duty. S1 with rated output.
S1 Continuous running duty
P N
Operation at constant load of sufficient duration for thermal equilibrium to be reached. In the absence of any indication of the rated duty type, continuous running duty will be assumed. Designation: S1 Time
S2 Short-time duty
P
N
Operation at constant load during a given time, less than required to reach thermal equilibrium, followed by a rest and deenergised period of sufficient duration to re-establish motor temperatures equal to the ambient or the coolant temperature. The values 10, 30, 60 and 90 minutes are recommended for the rated duration of the duty cycle. Designation e.g. S2 60 min. Time
S3 Intermittent duty
P N
R
A sequence of identical cycles, each including a period of operation at constant load and a rest and de-energised period. The period is too short for thermal equilibrium to be obtained. The starting current does not significantly affect the temperature rise. Recommended values for the cyclic duration factor are 15, 25, 40 and 60%. The duration of the duty cycle is 10 min. Designation e.g. S3 25%
Time Period of one cycle
S4 Intermittent duty with starting A sequence of identical duty cycles, each cycle including a significant period of starting, a period of operation at constant load and rest and de-energised period. The period is too short for thermal equilibrium to be obtained. In this duty type the motor is brought to rest by the load or by mechanical braking, where the motor is not thermally loaded. After the duty type the following factors must be indicated; the cyclic duration factor; the number of duty cycles per hour (c/h); the factor of inertia FI; the moment of inertia, JM, of the motor rotor; and the permissible average moment of resistance, TV, during the change of the speed given with the rated load torque. The factor inertia FI is the ratio of the total moment of inertia, to the moment of inertia of the motor rotor. Designation e.g. S4 - 25% - 129 c/h - FI.2 - JM = 0,1 kgm2 - TV = 0,5 TV. 20
P Period of one cycle
D
N
R
Time
P = Output power V = Operation of no load D = Starting R = At rest and de-energised N = Operation under rated condition F = Electrical braking
S5 Intermittent duty with starting and electrical braking
P Period of one cycle
A sequence of identical duty cycles, each cycle consisting of a significant period of starting, a period of operation at constant load, a period of rapid electric braking and a rest and deenergised period. The period is too short for thermal equilibrium to be obtained. After the duty type the following factors must be indicated: the cyclic duration factor; the number of duty types per hour (c/h); the factor of inertia FI; the moment of inertia JM, of the motor, and the permissible moment of resistance TV (see duty type S4.)
Time
D F N
R
Designation e.g. S5-40% -120 c/h- FI.3 - JM = 1,3 kgm2 - TV = 0,3 TN. Period of one cycle
S6 Continuous-operation periodic duty P
A sequence of identical duty cycles, each cycle consisting of a period at constant load and period of operation at no load. The period is too short for thermal equilibrium to be obtained.
N V
Recommended values for the cyclic duration factor are 15, 25, 40 and 60%. The duration of the duty cycles is 10 min. Time
Designation e.g. S6 40%
P = Output power V = Operation of no load D = Starting R = At rest and de-energised N = Operation under rated condition F = Electrical braking
S8 S7 Continuous-operation periodic duty with Continuous-operation periodic duty with related load speed changes electrical braking A sequence of identical duty cycles, each cycle consisting of a period of starting, a period of operation at constant load and a period of braking. Braking method is electrical braking e.g. countercurrent braking. The period is too short for thermal equilibrium to be obtained. After the duty type the following factors must be indicated: the number of duty cycles per hour c/h, the factor of inertia FI: the moment of inertia JM of the motor, and the permissible moment of resistance TV ( See duty type S4) Designation e.g. S7 40% - 500 c/h - FI.2 - JM = 0.08 kgm2 - TV = 0,5 TN.
S9 Duty with non-periodic load and speed variations A duty in which, generally, load and speed are varying nonperiodically within the permissible operating range. This duty includes frequently applied overloads that may greatly exceed the full loads. For this duty type, suitable full load values should be taken as the basis of the overload concept.
A sequence of identical duty cycles, each cycle consisting of a period of starting, a period of operation at constant load corresponding to a predetermined speed of rotation, followed by one of more periods of operation at other constant loads corresponding to different speeds of rotation. The period is too short for thermal equilibrium to be obtained. This duty type is used for example by pole changing motors. After the duty type the following factors must be indicated; the number of duty cycles per hour c/h; the factor of inertia FI; the permissible average moment of resistance TV (see duty type S4); the cyclic duration factor for each speed of rotation and the moment of inertia JM of the motor. Designation e.g. S8 - 30 c/h - FI.30 - TV = 24 kW - 740 rpm - 30% 30 c/h - FI.30 - TV = 0.5 TN = 60 kW - 1460 rpm - 30% 30 c/h - FI.30 - TV = 0.5 TN = 45 kW - 980 rpm - 40% JM = 2,2 kgm2 The combinations of the load and speed of rotation are designed in the order they occur in use.
21
Protection accessories
Space heaters
Thermistors
Motors subjected to atmospheric condensation, either through standing idle on a damp environment or because of the wide variation in the temperature of the surroundings, may be fitted with a heater for extra precaution. The heater ensures that the temperature of the air inside the motor, is maintained a few degrees above that of the ambient to avoid any condensation. Such heaters shall not be kept ON when the motor is operating. These space heaters are generally rated for 240 V ac/dc.
PTC thermistor is the most common type of temperature detector. It is the characteristics of the thermistors that its resistance hardly varies with increasing temperature until the threshold temperature is reached, thereafter the resistance increases sharply as shown in figure below. Thermistors must be connected to a separate control unit which trips power circuit when the resistance in the thermistor circuit increases abruptly.
For motors not having the provision of space heaters, 24 V dc supply can be applied between any two terminals.
Thermistors generally provided are rated for 130°C (PTC 130) for class B rise and 155°C (PTC 155) for class F rise.
The leads of space heaters for frame 160 to 400 are terminated in a separate auxiliary terminal box
Normally three thermistors are provided in series - one thermistor in each phase. Six nos. (three nos. for tripping and three nos. for alarm.) can be provided if intimated at the time of enquiry.
Guide for fuse protection
Like space heaters, the leads of thermistors for frame 160 to 400 are terminated in a separate auxiliary terminal box.
In addition to the starters being used to protect motors from overload and under voltage, the motors are protected with fuse as per the following table kW
Full load current, A
Fuse rating, A DOL start
0.37 0.55 0.75 1.1 1.5 2.2 3.7 4.0 5.5 7.5 9.3 11 15 18.5 22 30 37 45 55 75 90 110 132 160 200 250
22
1.2 1.6 2.1 2.9 4.0 5.7 8.3 9.5 12.2 15.5 19.4 22 29.5 37 42 52 66 80 98 128 155 188 223 270 332 415
6 6 6 6 10 16 16 25 25 25 32 32 50 63 63 80 100 125 160 200 225 250 315 355 400 500
Characteristic of a thermistor
Y/D start
ohms
4000
1330
10 16 16 16 25 25 25 50 50 63 63 80 100 125 160 200 200 250 300 350 500
550
100
Typical value _ Shaded area = tolerance limits
Voltage drop along the cable
Induction motors draw heavy currents during starting, resulting in considerable voltage drop along the cable, If other loads are connected in parallel to the motors, the voltage drop along the common feeder causes operational problems to these associated loads. Larger the starting current and longer the common feeder, larger will be the voltage drop. In view of this while specifying motors or cables, it is required to estimate the right combination of starting current and cable size, alternatively, it is important to know voltage drop for an installation when starting / locking of motors occurs such that the maximum voltage drop is less than 3%. The relative voltage drop, D u is estimated as Du = u - *100 U where, U is the rated voltage of the motor u is the voltage drop given as
(
u = b rx L cosf + lLsinf Is S where u b r
L S cosf l lS
= Voltage drop = Factor equal to 1 for three-phase circuits and equal to 2 for single phase circuits = Resistivity of conductors in normal duty taken as being equal to the resistivity at the normal duty temperature, i.e. 1.25 times the resistivity at 20°C, giving 0.02250 mm2/m for copper and 0.0360mm2/m for aluminium = Length of cabling in meters = Cross section of conductors in mm2 = Power factor, if exact figure is not available it is equal to 0.8 and sin~ = 0.6 = Linear reactance of conductors, taken as being equal to 0.08mQ/m if the exact figure is not available = Current in use
Negative sequence withstand characteristics Negative sequence withstand characteristics are used to obtain capability of the motor to withstand the overloading caused by negative sequence currents that occur due to unbalance in supply voltage.
Determination of withstand capability Since the negative sequence currents result in overloading, the amount of negative sequence current carried by the winding as a percentage of rated current can be used as a measure of overloading due to unbalance. The thermal withstand characteristics of the machine available for different overload conditions can be used to represent the capacity of the machine to withstand negative sequence voltage and current. The negative sequence withstand characteristics are design specific and will vary from motor to motor. A sample method for obtaining negative sequence withstand characteristics of the motor is given hereunder. Sample calculation: Let nominal voltage be 415 V and rated current be 60A. Under unbalance condition let the voltages be V = 385 L0° V V = 410 L120° V V = 425 L 240° V 385 + 410 + 425 = 407V 3 Unbalance voltage = 425 - 407 x 100 = 4.42% 407 Negative sequence voltage Average voltage
VN =
385Ð0° + a2410Ð120° + a425Ð240° 3
Now if the parameters of the machine are as given below: R1 = 0.052 R2 = 0.071 X1 = 0.51 X2 = 0.53 s = 0.0123 then s1 = 2. 0.0123 = 1.9877 From the equivalent circuit diagram VN (R1+ R2 1s1)+ j(X1 + X2) 11.66L158° (0.052 + 0.071/1.9877) + j (0.51+ 0.53)
Max. deviation (phase value) from average value x 100 Average value The negative sequence voltage, VN for any degree of unbalance can be calculated by VN = 1/3 (Va + (a2Vb + a Vc) where a = 1 L120° and a2 = 1 L240º Estimation of negative sequence current Once negative sequence voltage is known amount of negative sequence current that is ultimately responsible for overloading can be estimated from the following equivalent circuit of the motor. The value of circuit parameters can be obtained from design or from test results.
X1
R2/S1
=11.66Ð158° V
% negative sequence voltage = 11.66 / 407 = 2.86% (appx. 3%)
While % unbalance in voltage is given by the ratio
R1
=
X2
= 11.17 L -243.4° This corresponds to 18.6% (approx. 20%) of the rated current for the case considered here. This condition can be equated to an overload of 20%. Now the thermal withstand characteristics of the motor can be used to obtain the thermal withstand time for this particular motor. Similarly, thermal withstand time for different negative sequence voltage of voltage unbalance can be calculated. The following table gives the thermal withstand time of this sample motor for different negative sequence voltage. % negative sequence voltage
% negative sequence current
withstand time, sec Cold
Hot
1
6
continuous
continuous
2
10
continuous
continuous
3
20
3500
1800
6
40
1600
600
9
60
1100
400 23
Power factor improvement chart
Present power factor
Desired power factor, COSf2
COSf1
0.7
0.75
0.8
0.82
0.84
0.86
0.88
0.9
0.92
0.94
0.96
0.30
2.16
2.30
2.42
2.48
2.53
2.59
2.65
2.70
2.76
2.82
2.89
0.35
1.66
1.80
1.93
1.98
2.03
2.08
2.14
2.19
2.25
2.31
2.38
0.40
1.27
1.41
1.54
1.60
1.65
1.70
1.76
1.81
1.87
1.93
2.00
0.45
0.97
1.11
1.24
1.29
1.34
1.40
1.45
1.50
1.56
1.62
1.69
0.50
0.71
0.85
0.98
1.04
1.09
1.14
1.20
1.25
1.31
1.37
1.44
0.52
0.62
0.76
0.89
0.95
1.00
1.05
1.11
1.16
1.22
1.28
1.35
0.54
0.54
0.68
0.81
0.86
0.92
0.97
1.02
1.08
1.14
1.20
1.27
0.56
0.46
0.60
0.73
0.78
0.84
0.89
0.94
1.00
1.05
1.12
1.19
0.58
0.39
0.52
0.66
0.71
0.76
0.81
0.87
0.92
0.98
1.04
1.11
0.60
0.31
0.45
0.58
0.64
0.69
0.74
0.80
0.85
0.91
0.97
1.04
0.62
0.25
0.39
0.52
0.57
0.62
0.67
0.73
0.78
0.84
0.90
0.97
0.64
0.18
0.32
0.45
0.51
0.56
0.61
0.67
0.72
0.78
0.84
0.91
0.66
0.12
0.26
0.39
0.45
0.49
0.55
0.60
0.66
0.71
0.78
0.85
0.68
0.06
0.20
0.33
0.38
0.43
0.49
0.54
0.60
0.65
0.72
0.79
0.70
0.14
0.27
0.33
0.38
0.43
0.49
0.54
0.60
0.66
0.73
0.72
0.08
0.22
0.27
0.32
0.37
0.43
0.48
0.54
0.60
0.67
0.74
0.03
0.16
0.21
0.26
0.32
0.37
0.43
0.48
0.55
0.62
0.76
0.11
0.16
0.21
0.26
0.32
0.37
0.43
0.50
0.56
0.78
0.05
0.11
0.16
0.21
0.27
0.32
0.38
0.44
0.51
0.05
0.10
0.16
0.21
0.27
0.33
0.39
0.46
0.05
0.10
0.16
0.22
0.27
0.33
0.40
0.05
0.11
0.16
0.22
0.28
0.35
0.06
0.11
0.17
0.23
0.30
0.06
0.11
0.17
0.25
0.06
0.12
0.19
0.06
0.13
0.80 0.82 0.84 0.86 0.88 0.90 0.92
0.07
0.94
The power factor compensating capacitors are specified in terms of kVAR. The input kW of the motor is multiplied by the reading to obtain the necessary improvement in the power factor. Example -
If the initial power factor Input active power Corrected power factor
= COSf1 =0.76 = 100 kW = COSf2 =0.90
From the chart: capacitor kVAR required per kW load = 0.37 hence Total capacitor kVAR required = 0.37 x 100 = 37 kVAR 24
Mechanical
Enclosure
Terminal box
Motors in frame 71 to 315 have cast iron enclosures and larger ones have fabricated enclosures. Foot mounted motors have integrated feet. The housing and the end shields are machined to class tolerances to obtain perfect alignment and fits.
As standard practice, the terminal box is located on the top of the motor. Extended side terminal box can be offered for frame 90 to 280. The terminal boxes for frames 71 to 280 are rotatable in the steps of 900 and are made of die cast aluminum alloy. For frames 225 and 400 the terminal boxes are rotatable in steps of 900 and are made from cast iron. For all the terminal boxes protection of enclosure of IP 55.
Core The stator and rotor cores of the motor are made of high quality cold rolled non-grain oriented magnetic steel having low iron loss.
Protection against corrosion Special attention has been paid to the finish. Polyurethane paint is applied to motors. This provides an excellent finish and protection against corrosion. The color of the paint is Munsell Blue. All the hardware are zinc passivated to give reliable anticorrosion protection under most server environmental conditions.
Winding and insulation The insulation of the motors meet class F requirements (temperature limit 155°C) the normal temperature however does not exceed the values permitted by class B (temperature limit 130°C). The motors therefore have large overload margin and long winding lifetime. If the temperature rise to class F is allowed, the outputs given in the table can generally be increased by approximately 12%.
Motor upto 1.5 kW (2 hp) are provided with 3 terminal and others are provided with 6 terminals as standard practice. The terminal plates and lead ferrules are marked U1, V1 and W1, of U1, V1, W1 and U2, V2, W2. Terminal boxes have provision for fixing cable glands to support copper or aluminum cables.
Drain holes Motors for operation in very humid or wet environments, and especially under intermittent duty, should be provided with drain holes. HX Motors from frame HX 180 onwards are provided with drain holes and closeable plastic drain plugs in the drain holes. The plugs will be opened, on delivery. When mounting the motors, it should be ensured that the drain holes face downwards. In the case of vertical mountings, the upper plug must be hammered home completely. In very dusty environments, both plugs should be hammered home.
Motor stators are wound with enamel wire and the winding is then impregnated with solventless resin. The impregnation effectively fills the gaps between conductors and makes the winding mechanically strong, moisture and tropic proof. The rotor cages of the motors upto 315 frames have die cast construction whereas those of larger motors have fabricated construction.
Earthing Provision is given for earthing of motor. One earthing terminal on terminal box and two earthing terminals on motor body are provided.
Shaft and shaft extension
Open
Closed
The shaft is made of EN8/C40 steel. On special request shaft with EN24 steel can be offered. Standard motors have cylindrical shaft extension in accordance with IS:1231. Non standard shaft extensions on drive end are also available on request. Orders should be accompanied by a sketch of the shaft extension and if need be, a clear text description. A second shaft extension has to be ordered as a special design. All shaft extension of frame sizes have a drilled and tapped shaft according to IS:1231. All standard flange motors comply with tolerances N (normal) according to IS:2223 with respect to shaft extension runout, concentricity and perpendicularity of the extension in relation to the flange face.
25
Exploded view of HX motors
19 18 17
16 15 13
11 14
10 9 12
8 7
RV M
CD A
6
5 4 23
3
2
1
21
22 20
1 2 3 4 5 6 7 8 9 10 11 12
26
Bearing Cover DS Outer Endshield DS Bearing DS Bearing cover DS inner Shaft extension key Rotor assembly Fan key Wound stator Terminal box Terminal plate Terminal box cover Eye bolt
13 14 15 16 17 18 19 20 21 22 23
Bearing NDS Bearing Cover NDS Inner Endshield NDS. Bearing Cover NDS Outer Fan Circlip Fan Cowling Grease Outlet Plug Regreasing Hole Drain Hole Plug Earthing Bolt
Pulley diameter
When the desired bearing life has been determined, the minimum permissible pulley diameter can be calculated using FR' as follows:
Permissible radial forces Motor sizes 71 to 132
7
D= 1.9 x 10 x K x P n x FR where: D = Diameter of pulley, mm P = Power requirement, kW n = Motor speed, r/min K = Belt tension factor, dependent on belt type and type of duty. A common value for V-belts is 2.5. FR= Permissible radial force
Poles
Length of shaft extension E (mm)
20,000 hours X0(N) Xmax(N)
71
2 4 6
30 30 30
415 415 415
335 335 340
80 M
2 4 6
40 40 40
670 890 970
545 725 830
Motor size
Permissible loadings on shaft
Ball bearings
The tables below give the permissible radial force in newtons, assuming zero axial force. The values are based on normal conditions at 50Hz and calculated bearing lives for motor sizes 71 to 132 of 20000 hours and for motor sizes 160 to 400 of 20,000 and 40,000 hours.
90 SL
2 4 6
50 50 50
795 995 1135
625 780 880
100
Motors are foot-mounted 1MB3 version with force directed sideways. In some cases the strength of the shaft affects the permissible forces.
2 4 6
60 60 60
1090 1360 1560
875 1095 1250
112
2 4 6
60 60 60
1410 1735 2000
1120 1400 1620
132 SM
2 4 6
80 80 80
1700 2130 2495
1330 1660 1935
At 60Hz the values must be reduced by 10%. For two - speed motors, the values must be based on the higher speed. Permissible loads of simultaneous radial and axial forces will be supplied on request. If the radial force is applied between points X0 and Xmax' the permissible force FR can be calculated from the following formula : FR=FX0 - (FX0 - FXmax) E = length of shaft extension in basic version FR
Xmax
X
X0
27
Permissible radial forces
Motor sizes 160 to 400
Poles
Length of shaft extension E (mm)
20,000 hours X0(N) Xmax(N)
40,000 hours X0(N) Xmax(N)
20,000 hours X0(N) Xmax(N)
40,000 hours X0(N) Xmax(N)
160
2 4 6 8
110 110 110 110
2980 3760 4290 4730
2310 2900 3300 3660
2350 2970 3390 3740
1810 2290 2750 2880
5530 6980 7980 8800
4260 5380 6150 6780
4370 5520 6310 6960
3360 4250 4860 5360
180
2 4 6 8
110 110 110 110
3540 4390 5060 5590
2880 3560 4110 4540
2790 3440 3970 4390
2260 2790 3220 3560
6260 7830 9000 9940
5080 6350 7300 8060
4940 6160 7100 7830
4010 5000 5750 6350
200 ML
2 4 6 8
110 110 110 110
4510 5660 6470 7160
3700 4650 5310 5880
3530 4430 5050 5600
2900 3640 4150 5880
8520 10710 12250 13520
7000 8800 10060 11100
6710 8440 9640 10650
5510 6930 7920 8750
225 SM
2 4 6 8
110 140 140 140
4750 6310 7200 7970
4010 5040 5760 6375
3710 4920 5620 6230
3130 3840 4500 4980
9720 12900 14740 16270
8200 10310 11800 13010
7650 10150 11600 12820
6450 8120 9280 10250
250 SM
2 4 6 8
140 140 140 140
6100 7650 8700 9630
4910 6170 7010 7760
4750 5960 6760 7505
3830 5450 5450 6050
13600 17100 19520 21550
10960 13800 15740 17380
10710 13470 15360 16970
8640 10870 12400 13690
280 SM
2 4 6 8
140 140 140 140
7300 9200 10600 11600
6200 7800 8900 9800
5800 7300 8400 9200
4900 6200 7100 7800
20200 25000 28000 30700
6600 12000 12000 12000
16500 20300 23000 25000
6600 12000 12000 12000
315 SML
2 4 6 8
140 170 170 170
7300 11300 13000 14300
6000 9400 10600 10400
5800 9000 10300 11300
4950 7500 8500 9400
20200 32500 37000 40000
6350 10700 10600 10400
16500 26500 30000 32700
6350 10700 10600 10400
355 SM
2 4 6 8
140 210 210 210
9000 15200 17300 19000
7900 12500 14300 15700
6100 12000 13700 15200
5300 9850 11300 12400
26700 45000 51000 55500
8900 21400 21100 21700
21800 36700 41500 45200
8900 21300 21100 21700
355 ML
2 4 6 8
140 210 210 210
9100 7100 15200 12800 17300 14600 19300 16200
6100 12000 13700 15200
5400 10100 11500 12700
26900 45500 51000 55500
7100 19500 19000 19500
21800 36700 41500 45200
7100 19500 19000 19500
400 L
2 4 6 8
140 210 210 210
8900 15000 17200 19200
5700 11700 13600 15000
3000 10100 11700 12900
27000 46000 52000 55500
3000 15000 13700 15000
22000 37000 42000 46000
3000 15000 13700 15000
Motor size
28
Ball bearings
3000 13000 13700 15000
Roller bearings
Permissible axial forces
The following tables give the permissible axial forces in newton, assuming zero radial force. The values are based on normal conditions at 50Hz with standard bearings and calculated bearing lives of 20,000 and 40,000 hours.
For two-speed motors, the values are to be based on the higher speed. The permissible loads of simultaneous radial and axial forces will be supplied on request. Given axial forces FAD' assumes D-bearing locked by means of locking ring.
At 60 Hz the values are to be reduced by 10%.
FAD
Mounting arrangement 1M83
FAZ
20,000 hours
40,000 hours
Motor size
2-pole FAD N
71 80 90
270 400 450
270 400 450
350 510 560
350 510 560
100 112 132
620 810 980
620 810 980
780 1020 1220
160 180 200 225 250
2120 2480 3050 3440 4180
2120 2480 3050 3440 4180
2660 3070 3850 4340 5260
280 315 355 400L
4-pole FAZ FAD N N
7300 5300 8000 7000 5000 9000 10500 3500 13500 10100 32001 3000
6-pole FAZ FAD N N
8-pole FAZ N
2-pole FAD FAZ N N
4-pole FAD FAZ N N
6-pole FAD FAZ N N
-
1) 1) 1)
1) 1) 1)
1) 1) 1)
1) 1) 1)
1) 1) 1)
1) 1) 1)
-
-
-
-
1) 1) 1)
1) 1) 1)
1) 1) 1)
1) 1) I)
1) 1) I)
1) 1) 1)
-
-
3360 3910 4850 5460 6630
3360 3910 4850 5460 6630
1670 1950 2430 2730 3320
1670 1950 2430 2730 3320
2100 2430 3050 3440 4180
2100 2430 3050 3440 4180
2400 2780 3500 3940 4780
2400 2780 3500 3940 4780
2640 3070 3850 4340 5260
2640 3070 3850 4340 5260
6000 9000 7000 10000 7000 10600 8600 11600 6500 15300 8300 16800 6000 15000 8000 16500
8000 9600 9800 9500
5750 5600 8750 8350
3750 6200 3600 6900 1750 10800 1350 10200
4900 7700 5900 8900 5000 13300 4800 13000
5700 6900 6300 6000
FAD N
FAZ N
440 590 640
-
780 1020 1220
890 890 1170 1170 1400 1400
2660 3070 3850 4340 5260
3040 3540 4400 4960 6020
440 590 640
3040 3540 4400 4960 6020
4200 6900 4900 7900 3800 12000 3250 11800
8-pole FAD FAZ N N
FAZ Mounting arrangement 1MV1
FAD
20,000 hours Motor size
40,000 hours
2-pole 4-pole FAD FAZ FAD N N N
71 80 90
290 430 480
260 390 420
100 112 132
680 890 1100
580 760 919
160 180 200 225 250
2420 2860 3600 4140 5020
1820 2100 2500 2740 3330
6-pole FAZ FAD N N 380 540 610
330 490 520
2-pole FAD FAZ N N
FAZ N
4-pole FAD FAZ N N
6-pole FAD FAZ N N
8-pole FAD FAZ N N
420 560 600
-
-
1) 1) 1)
1) 1) 1)
1) 1) 1)
1) 1) 1)
1) 1) 1)
1) 1) 1)
-
-
880 740 1140 950 1390 1120
990 840 1280 1100 1580 1300
-
-
1) 1) 1)
1) 1) 1)
1) 1) 1)
1) 1) 1)
1) 1) 1)
1) 1) 1)
-
-
3040 3690 4580 5230 6380
3480 4160 5280 6030 7440
2600 2920 3530 3900 4610
3810 4530 5720 6530 8050
2920 3290 3980 4400 5210
1970 2300 2970 3430 4160
1370 1570 1870 2030 2470
2480 3050 3780 4330 5290
1720 1810 2320 2550 3060
2840 3400 4370 5010 6200
1960 2160 2620 2870 3360
3090 3690 4720 5400 6680
2200 2450 2980 3270 3840
280 8500 4300 9500 4600 11000 5500 315 SML 9000 3700 11600 5400 13500 6200 355 SM 14900 800 19200 3100 22200 4100 355 ML 15000 1) 19800 1700 23100 2500 400 L 17300 1) 21800 1) 24300 1000
12200 14500 24000 25000 26200
6600 7500 5800 4300 2500
6950 7450 13000 13100 15400
2280 2450 3120 3440 4150
460 620 700
8-pole FAZ FAD N N
2700 7700 2800 8900 3350 9750 4200 2100 9450 3200 10900 3650 11900 4650 1) 16400 1) 18900 850 20300 2100 1) 17000 1) 19800 1) 21300 1) 1) 18900 1) 21100 1) 22500 1)
1) On request 29
Testing
The standard test programmes are dividing into four parts: routine tests, type tests, optional tests and special tests. The routine test program is done to every machine. Type test is performed in addition to routine tests normally to one of the machines of a series of similar machines or by a request of the customer. Optional tests are additional type tests subject to mutual agreement between purchases and the manufacturer. Special tests are needed if the machine has to run in special conditions e.g. roller table, hazardous areas, cranes applications. The special test program is specified by the customer/consultant/standards bureaus. If the motor will be fed by a frequency converter it is most often tested together with the frequency converter. Unless otherwise specified all the tests are performed according to standard IS:325-1996.
Contents of test programmes: Routine tests 1. 2. 3. 4. 5. 6.
Insulation resistance test Measurement of resistance of the stator Locked rotor test No load test Reduced voltage running test High voltage test
Type test 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
Optional tests 1. 2. 3. 4. 5. 6.
Vibration severity test Sound level measurement Degree of protection test Temperature rise test at limiting values of voltage and frequency variation Over speed test Test on insulation system
Special tests 1. 2. 3.
30
Dimensions Measurement of resistance of stator Locked rotor test Temperature rise test Full load test No load test at rated voltage Reduced voltage running test Momentary overload test Insulation resistance test High voltage test
Acceleration constant test (B value test, for roller table motors) tE time test (for increased safety motors) Suitability to PWM supply
Motors for frequency converter drive
Squirrel cage induction motors offer excellent availability, reliability and efficiency. In addition to that, a motor with a frequency converter - variable speed drive (VSD) - has even more excellent properties. A variable speed drive motor can be started softly with low starting current, and the speed can be controlled and adjusted to suit the application demand without steps over a wide range. Also the use of a frequency converter together with a squirrel cage motor usually leads to remarkable energy savings.
At low speed operation the motor's ventilation fan loses its cooling capacity, which causes a higher temperature rise in the motor and bearings. A separate constant speed fan can be used to increase cooling capacity and loadability at low speed. It also important to check the performance of the grease at low speeds.
Most of the squirrel cage motors manufactured by ABB are suitable for variable speed use, but in addition to the general selection criteria, the following points must be taken into account:
The effectiveness of the motor lubrication should be checked by measuring the bearing temperature under normal operating conditions. If the measured temperature is higher than + 80°C, the relubrication intervals specified in ABB' s standard instruction manuals must be shortened; i.e. the relubrication interval should be halved for every 15K increase in bearing temperature. If this is not possible ABB recommends the use of lubricants suitable for high operating temperature conditions. These lubricants allow normal relubrication interval and a 15K increase in bearing temperature conditions.
1. Dimensioning The voltage (or current) fed by the frequency converter is not purely sinusoidal. This may increase the losses, vibration, and noise of the motor. Furthermore, a change in the distribution of the losses may affect the motor temperature balance and lead to an increase in the temperature of the bearings. In every case, the motor must be correctly sized according to the instructions supplied with the selected frequency converter. When using ABB converters use the Drive Size dimensioning program or "ISOTHERM GUIDE-LINES" of the corresponding converter type for sizing the motors. The loadability curve of a standard motor used with a ACS 600-frequency converter can be found from figure 3.
3. Lubrication
4. Insulation protection If the frequency converter has IGBT power components with very rapid switching, practically all cables between the converter and the motor will be long. In that case, steep voltage pulses and reflections at the cables increase voltage stresses at the winding of the motor and therefore, the precautions described in figure 2 below must betaken to avoid risks of insulation damage.
2. Speed range
For GTO converters, consideration must be given to the information about cable length, pulse rise time and the voltage overshoot using the voltage/ cable length guideline.
In a frequency converter drive, the actual operating speed of the motor may deviate considerably from its nominal speed (i.e. the speed stamped on the rating plate).
5. Bearing currents
For higher speeds, ensure that the highest permissible rotational speed of the motor or the critical speed of the entire equipment is not exceeded. When high speed operation exceeds the nominal speed of the motor, the following points should be checked: • Maximum torque of the motor • Bearing construction • Lubrication • Balancing • Critical speeds • Shaft seals • Ventilation • Fan noise
Bearing voltages and currents must be avoided in all motors. When using an IGBT frequency converter insulated bearings and/or a properly dimensioned filter at the converter output must be used according to instructions in figure 2 below. (For other alternatives and converter types, please contact ABB.) When ordering clearly state which alternative will be used. For more information about bearing currents and voltages, please contact ABB.
6. Cabling, grounding and EMC
Permissible maximum speeds for standard motors are described in figure 1. Figure 1. Maximum permissible speeds for basic motors Frame size
Speed r/min 2-pole 4 -pole
71 - 200 225 - 280 315 355 400
4000 3600 3600 3600 3600
3600 2600 2300 2200 1800
The use of a frequency converter causes some extra requirements on the cabling and grounding of the drive system. The motor must be cabled by using shielded symmetrical cables and cable glands providing a 360º bonding (also called EMCglands). For motors up to 30 kW unsymmetrical cables can be used, but shielded cables are always recommended. For motor frame size 280 and upward, additional potential equalisation between the motor frame and the machinery is needed, unless they are installed on a common steel fundament. When a steel fundament is used for the potential equalisation, the high frequency conductivity of this connection should be checked. More information about grounding and cabling of a variable speed drive can be found from the manual "Grounding and cabling of the drive system" (Code: 3AFY 61201998RO125REVA)
31
For fulfilling the EMC requirements, special EMC cable(s) must be used in addition to the correct cable gland mounting, with special, extra earthing pieces. Please refer to the manuals of the frequency converter. Figure 2. Selection rule for insulation and filtering in variable speed drives Motor nominal power PN or frame size PN < 100 kW U
U
U
N
N
N
PN < 100 kW or 3IEC 315
PN < 350kW
< 500 V
Standard motor
Standard motor + Insulated N-bearing
Standard motor + Insulated N-bearing + Common mode filter
< 600 V
Standard motor + dU/dt-filter OR Reinforced insulation
Standard motor + dU/dt-filter OR Reinforced insulation + Insulated N-bearing
Standard motor + Insulated N-bearing + dU/dt-filter OR Reinforced insulation + Insulated N-bearing + Common mode filter
< 690 V
Reinforced insulation + dU/dt-filter
Reinforced insulation + dU/dt-filter
Reinforced insulation + Insulated N-bearing + dU/dt-filter + Light Common mode filter
dU/dt filter
Motor loadability with ACS 600
Series reactor. dU/dt filters decrease the changing rate of the phase and main voltages and thus reduce voltage stresses in the windings. dU/dt filters also decrease so called common mode currents and bearing currents.
The loadability curve in figure 3 below is a guide line curve, for exact values please contact ABB.
Common mode and light common mode filters Common mode filters are made of toroidal cores installed around motor cables. These filters reduce so called common mode currents in VSD applications and thus decrease the risk of bearing currents. Common mode filters do not significantly affect the phase or main voltages on the motor terminals. For the exact type of the core, please contact ABB. Common Mode Filter = 3 toroidal cores per each 3-phase motor cable Light Common Mode Filter = 1 toroidal core per each 3-phase motor cable
These guidelines present the maximum continuous load torque of a motor as a function of frequency (speed) to give the same temperature rise as with rated sinusoidal supply at nominal frequency and full rated load. The temperature rise of squirrel cage motors manufactured by ABB is normally class B. If the ABB catalogue indicates that class F temperature rise is utilised on a sinusoidal supply, the dimensioning of the motor at frequency converter supply should be done according to the temperature rise class B loadability curve For further information, please contact ABB. .
Figure 3. Motor loadability with ACS 600, Field weakening point 50Hz.
32
Guide and check points for motor selection (mechanical aspects)
1000m or less Above 1000m 45°/50°C or less Low Temperature
Altitude Environment
Corrosion Dust, carbon, Etc Humidity
Ambient
Housing Protection
Totally enclosed fan cooled Separately cooled Natural cooled Standard Double shaft Tapered Special
Ventilation
Shaft end
Horizontal Vertical
Epoxy Bakelite
Single armour Double armour Without armour One or two
Drip proof, IP23 Totally enclosed, IP55 Special, IP56
Power Transmission
Direct Belt Gear box Mounting
Foot Flange Face
Dimension
IS/IEC User specific
Position Material
TOP/LHS/RHS Cast iron Aluminum
Cable
Entry
Bottom Top side
Noise
Standard Low
Installation
Terminal Plate
Terminal Box
Type Numbers size
Standard
Vibration
Precision Bearings
Special paint shade Special name plate Direction of rotation
Others
Ball Roller
Thermistor Space heater Brake Tacho
33
Guide and check points for motor selection (electrical aspects)
Drive torque Operating speed Transfer efficiency Load GD2 Load torque
Characteristics of the load
Torque characteristics Operating characteristics
Continuous operation Intermittent duty & CDF Equivalent starts per hour
Rated output and speed
Single voltage with variations 110V - 660V Dual voltage - l / D D / DD
Single speed Dual speed VVVF application
voltage
Frequency
50 Hz Any other frequency
Type of starting
Mechanical Plugging DC injection Regenerative
Braking
Torque Characteristics
B/F F/F F/H
Temperature rise / insulation
Determination of motor specification
34
DOL start Star-Delta start Auto-transformer start % tapping Soft start
Normal starting High torque Soft starting (Low pull out torque)
Ordering Information
Customer Name_____________________________________
18
Starting current
Date______________________________________________
• 600% subject to IS tolerance
Application_________________________________________
• 600%maximum
01
Output_______________kW (___________________hp)
• Other_________________% full load current
02
Frame size____________________________________
03
Volatge______________________________________V
04
Voltage variation_______________________________%
05
Frequency Hz • 50 • 60, Other___________________Hz
06
Frequency variation____________________________%
07
Number of poles
08
Ambient temperature
• Frequency range____________Hz to____________Hz
• 45°C
• Fieldweakning point____________________________
• 50°C
• Load torque speed curve________________________
• Special (Specify)_____________________________0C 09
19
• Direct-on-line (full voltage) • Star-Delta • Auto-Transfer___________%taping____________secs • Frequency converter
20
Temperature rise by resistance method
• Electromechanical braking
• 75°C
• Countercurrent(Plugging)_________________no./hour
• 100°C • Special (Specify)_____________________________0C
• D.C. injection___________________________no./hour
Altitude
• Reversal by plugging_____________________no./hour
• Standard (Sea level upto 1,000m)
• Other (specify)________________________________
• Special (Specify) 11
Insulation • B • F • H
12
Duty
• Continuous (S1) • Other(Specify)______________________
13
21
22
• Special (Specify) 23
• Area classification class • Temp. Class______________• Division__________
24
• Not enclosed
• TEFC(IP44) 25
• Flexible
• Belt
• Type 'e' (Increased safety)
• Fluid
• Other ____________________________
26
• Special (Specify)
Belting data
• Load pulley dia. and wt._____________mm________kg • Centre distance between pulleys_______________mm
Mounting
• Type of belt___________________________________
• B3 • V1 • Other(Specify)
• No. of belts___________________________________
Applicable codes and standards • IS 325
• Gear box
• Motor pulley dia. and wt.____________mm________kg
Construction • Horizontal • Vertical • Special
17
Method of coupling
• Type 'n' (Non sparking) • Type 'd' (Flame proof)
16
Load torque curve • Enclosed
• Open drip proof (IP23)
15
Load inertia with respect to motor shaft • Actual GD2___________kgm2 at ___________rev./min
Enclosure
• TEFC(IP55)
Starting duty • 1 Hot, 2 Cold, 3 Equally spread
Environment • Corrosive gas, vapour
Winding connection • Star • Delta • Special________________________
• High humidity • Dusty • Tropical
14
Braking details • No braking
• 70°C
10
Starting method
27
Direction of rotation
• IS 6381 (Increased safety motors)
• Bi-directional
• IS 9628 (Non sparking motors)
• Clockwise from driving end
• IS 3682 (Flame proof motors)
• Anti-clockwise from driving end
• IPSS:1-03-007-85 (A.C. roller table motors) • IS 2972 (Textile application) • IS7538 (Agriculture application) • Other_______________________________________
35
28
Terminal Box
35
• Without
Mounting base • Not required
• With
• Slide rails Location
• Special(specify)_______________________________
• Top on driving end
36
Thrust for vertical motor
• Right side from driving end
• Design thrust • Up__________kg • Down _______kg
• Left side from driving end
• Momentary thrust
• Special (specify)______________________ 29
Terminal box construction
• Up__________kg • Down _______kg 37
• Stud type 3 terminals
• ABB standard as per IS
• Stud type 6 terminals
• Special(specify)____________________________mm
• Other_______________________________________
38
• External power cable
Routine test as per IS 325
No. of cable____________No. of core______________
• Witness routine test as per IS 325 2
• Witness type test as per IS 325 • Special (specify)_______________________________
Diameter : Overall ___________________________mm Inner sheath_______________________mm
30
31
Test • ABB standard (Non-witnessed)
Type________________________________________ Conductor sectional area_____________________mm
Rotor end float
39
Any special requirement __________________________
Conduit size____________________________________
_____________________________________________
•Special (specify)_______________________________
_____________________________________________
Anti-condensation heater
_____________________________________________
• Not required
_____________________________________________
•________________Volt
_____________________________________________
• Special (specify)_______________________________
_____________________________________________
PTC Thermistors • Class B 130°C • Class F 155°C • Special (specify)_______________________________
32
Paint • Standard Munsel Blue • Epoxy shade 631 of IS 5 • Any other__________________________shade of IS 5
33
Balancing • Half key (ABB standard) • full key
33
Special features • Export packing • Tropical protection • Foundation bolts • Jacking facility • Jacking bolts • Grounding lug • Cable gland
36
• Cable lugs
Prepared by ___________
• Special (specify)_______________________________
Dated
___________
Frequency asked questions
Q. What are the general performance concerns of motor? Rated current, speed, starting current, starting torque, efficiency, power factor, noise and vibration. Above all is the temperature rise of the motor in accordance with operating environment and class of insulation.
Q. Why is the consideration for efficiency growing ? Higher efficiency means lower kW power drawn from electric supply and hence, lower electricity bills. Further, energy efficient operation has been a top social obligation from an environmental and global viewpoint.
Q. How are efficiency and power factor correlated? Due to continuous innovations made in the designs of motors, over the years, values of efficiency and power factor in standard motors have reached an optimum level. Thus here onwards, unless an entirely new series of motors are made, improvement in one adversely affects other. That is, in standard motors, an attempt to improve efficiency normally results in lower power factor and vice-versa.
Q. What is efficiency based design (EBD) and what is power factor based design (PFBD) ? Around the world, in standard series motors, there are two design philosophies. One is called "Efficiency Based Design (EBD)" and the other is called "Power Factor Based Design (PFBD)". In the former case, the basic design including stamping designs are optimised for maximising efficiency, while retaining power factor to reasonably acceptable level. Where as in the latter case, it is otherwise.
Q. What is the difference in electromagnetic parameters in case of the above two designs? EBDs are based on lower losses and hence lower resistances. Lower resistance in the circuit could lead to lower power factor. Where as PFBDs have higher rotor resistances.
Q. How EBDs and PFBDs compare on other performance parameters? Since EBDs have lower rotor resistances, the starting torque could be lower. To compensate this, flux level might go up leading to higher magnetic current.
Q. How about starting current? Starting current is dependent on stator and rotor leakage reactances and resistances. Since leakage reactances and resistances are lower for EBDs, the starting current is likely to be higher as compared to the case of PFBDs.
Q. What is no-load current and why is one concerned about it? No-load current is a quality control parameter used to check health of motor as per design and manufacturing practice. It is a normal practice to provide this data to the customer for each motor, so that the motor could be subjected to routine test, as and when required.
Q. What is the normal value of no-load current? There is no standard value of no-load current. It depends on the design philosophies and manufacturing practices. This parameter is in-fact manufacturer specific and its value varies widely from manufacturer to manufacturer. Further, pole number and size of motor greatly influence values of no-load current. Value of no-load current can vary from 20% of full load current for 4 pole motors to 80% for 8 pole motor. Similarly, in smaller motors the value of noload current as a percentage of full load current is much higher as compared to larger motors. In smaller motors of higher pole numbers, there are cases where no-load current is higher than full load current.
Q. How is no-load current related to the design philosophy? Since EBDs use magnetic circuit more optimally than electric circuit, the magnetising current could be higher as compared to PFBDs. This could lead to higher no-load current in EBD designs.
Q. Is there any adverse effect of higher no-load current on the motor? No, if the motor is designed for higher no-load current, it would have no effect on its declared performance and life.
Q. Does higher no-load current design affect other performance parameters? Only in a few cases, the rated current of EBD motors could be slightly higher than that of PFBD motors. Since the motor is designed for the rated current, declared performance is guaranteed. But in terms of input kW, EBD motors would result in lower electricity bills. After all it must be understood that noload current is a quality control parameter and not a performance parameter.
Q. Why EBDs are more popular than PFBDs ? Both efficiency and power factor can be built into the motor. But once the motor is built, efficiency can not be improved by external measures, though, power factor can be improved by using capacitors. Hence, the usual practice is to maximise the motor efficiency at design stage and improve power factor at operational stage i.e. by capacitors. A case study of benefits in energy saving by employing EBD motor is illustrated below for 3 number 30kW /4pole motors in a pump application. Parameter Efficiency, % Power factor Ampere= Rated kw/(sqrt(3)xVxEffxPower factor)
PFBD EBD motor motor 90 0,89 52
92.5 0.83 54
Input power=Rated Power*100/Eff, kW 33,333 32.432 Pdiff=Difference in Input Power, kW 0.901 Energy saved/year, kWh=Pdiff x No. of hours/yr when each pump runs 8 hr/day 7081 kWh = Pdiff x 7860 Saving in Rs., @ Rs.3.50/- per kWh 24784
37
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