Technical GuidelinesABB LT Motors

Others

Testing 30

Motor for frequency converter drive 31

Guide and check points for motor selection

(mechanical aspects) 33

Guide and check points for motor selection

(electrical aspects) 34

Ordering Information 35

Frequently asked questions 37

Contents

Product range 3

Features of standard TEFC motors 3

Manufacturing range summary 3

Designs variants 4

Features of standard SPDP motors 4

Standards 5

Tolerances 6

Mounting arrangement 6

Degree of protection 8

Cooling methods 9

Direction of rotation 9

Insulation and insulation class 9

Effect of voltage and frequency variation 10

Permitted output in high ambient temperature

and high altitudes 10

Permitted output for voltage unbalance 10

Motors for 60 Hz operation 11

Winding connection 12

Electrical features 13

Starting method for AC motors 14

Typical motor current and torque curves 15

Comparison between starting methods 15

Starting time 16

Example of starting performance with

different load torques 17

Electrical braking 18

Duty types 20

Protection accessories 22

Guide for fuse protection 22

Voltage drop along cable 23

Negative sequence withstand characteristics 23

Power factor improvement chart 24

Mechanical Features 25

Exploded view of HX motors 26

Pulley diameter 27

Permissible radial forces 28

Permissible axial forces 29

General

Electrical

Mechanical

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

Range

Type Three phase squirrel cage induction motor

Enclosure Totally - enclosed fan cooled

Voltage ± variation 415V ± 10%

Frequency ± variation 50Hz ± 5%

Combined variation 10% (Absolute Sum)

Mounting reference As per IS 4691

Frame dimensions As per IS 1231; IS 2223

Altitude Up to 1000 M

Relative humidity Up to 100%

Degree of protection IP55

Class of insulation Class F

Ambient temperature / temperature rise 45ºC/75ºC Up to Frame 160

50ºC/70ºC Frame 180 to 400

Duty S1/Continous

Position of terminal box Top at drive end

Connection / No of leads Up to 2 HP - STAR / 3 Leads > 2 HP - DELTA / 6 Leads

Direction of rotation Bi-directional

Grease type Lithium complex grease

Greasing arrangements Online greasing arrangement for 225 and above

Cooling IC 0141 (TEFC)

Paint Polyurethane (Shade: Munsell Blue)

Output 0.18 ...500kW; 0.25 ...675hp; according to IS 325

Voltage 220 ... 660V

Frequency 25 ... 60Hz

Duty S1 ... S8 according to IS:325

Ambient Temperature -20ºC ... 65ºC

3

Design Variants

Electrical Mechanical

Non standard voltage and frequency variations Non standard mounting dimensions

AC variable speed drives Special shaft extension

High torque motors Double shaft extension

High slip motors Separately ventilated motors

Motors for frequent start / stops / reversals Low vibration and noise level

Frequency 25 to 60 Hz Brake motors

Special performance requirements Special bearings and lubrications

Class H insulation Tacho mounting / SPM mounting

Voltage 220V to 550V 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 Three phase squirrel cage induction motor

Enclosure Screen protected drip proof

Voltage ± variation 415V ± 10%

Frequency ± variation 50Hz ± 5%

Combined variation 10% (Absolute Sum)

Mounting reference As per IS 4691

Frame dimensions As per IS 1231; IS 2223

Altitude Up to 1000 M above MSL

Relative humidity Low / indoor applications

Degree of protection IP 23

Class of insulation F, Temperature rise limited to CL.B

Ambient temperature 40ºC

Duty S1

Position of terminal box Top

Connection / No of leads DELTA / 6 Leads

Direction of rotation Bi-directional

Grease type Li-complex grease

Cooling IC 01

Paint Polyurethane (Shade: Munsell Blue)

4

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

Item Tolerance

Efficiency (h)

By summation of losses Motors up to 50kW -15 percent of (1 - h) Motors above 50kW -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 ±20 percent of the guaranteed starting currentstarting method (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 ±10 per cent of the guaranteed valuemotors above 315 frame

* Upon agreement between manufacturer and purchaser

Tolerances (as per IS:325-1996)

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.

Mounting arrangements

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

Foot-mounted motor, IM B 3 IM V 5 IM V 6 IM B 6 IM B 7 IM B 8 IM 1001 IM 1011 IM 1031 IM 1051 IM 1061 IM 1071

Flange -mounted motor, IM B 5 IM V 1 IM V 3 Large flange IM 3001 IM 3011 IM 3031 IM 3051 IM 3061 IM 3071

Flange -mounted motor , IM B 14 IM V 18 IM V 19 Small flange IM 3601 IM 3611 IM 3631 IM 3651 IM 3661 IM 3671

Foot and flange-mounted, IM B 35 IM V 15 IM V 36Motor with feet, IM 2001 IM 2011 IM 2031 IM 2051 IM 2061 IM 2071Large flange

Foot and flange-mounted, IM B 34Motor with feet, IM 2101 IM 2111 IM 2131 IM 2151 IM 2161 IM 2171Small flange

Foot-mounted motor, IM 1002 IM 1012 IM 1032 IM 1052 IM 1062 IM 1072Shaft with free extensions

CodeI/CodeII

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

0 IP 3 Protected against spraying water, sprayed up to angle of 60 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

No protection

Protected against solid objects greater that 50mm(e.g. hand)

Protected against solid objects greater that 12mm(e.g. fingers)

Protected against solid objects greater that 2.5mm(e.g. tools, wires)

Protected against solid objects greater that 1mm(e.g. wire orstrips)

Ingress of dust is not totally protected, but does not enter in sufficient quantities to harm equipment

No ingress of dust

0

1

2

3

4

5

6

0

1

2

3

4

5

6

No protection

Dripping water shall have no harmful effect.

Protected against dripping water when enclosure is

0titled 15

Protected against spraying water up

0to 60

Water splashed from any direction shall have no harmful effect

Water hosed against the enclosure shall have no harmful effect (water jets)

Water from powerful jets of heavy seas shall have no harmful effects

1st Numeric 1st Numeric

8

Cooling Methods

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 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.

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.

Insulation and insulation classes

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.

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.

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%.

D-end and N-end

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.

Direction of rotation

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.

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.

180

130

155

120

4545

B130

0C

F155

H180

10Hotspot temperature margin

Permissible temperaturerise

Maximum ambienttemperature

Insulation classMaximum winding temperature

75

45

15

95

45

15

120

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%

Starting & maximum

SpeedSynchronous No change No change Increase 5% Decrease 5%Full load Increase 1% Decrease 1.5% Increase 5% Decrease 5%Slip Decrease 17% Increase 23% Little change Little change

CurrentRated Decrease 7% Increase 1% Slight decrease Slight increaseStarting Increase 10-12% Decrease 10-12% Decrease 5-6% Increase 5-6%No load Increase 10-15% Decrease 10-15% Decrease 5-6% Increase 5-6%Overload capability Increase 21% Decrease 19% Slight decrease Slight increase

Temperature rise Decrease 3-4% Increase 6-7% Slight decrease Slight increase

Magnetic noise Slight increase Slight Decrease Slight decrease Slight increase

Efficiency, full load Increase 0.5-1.0% Decrease 2% Slight increase Slight decrease

Power factor, full load Decrease 3% Increase 1% Slight increase Slight decrease

*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:

% voltage imbalance = 100 x

If this unbalance is known before the motor is purchased it is advisable to apply derating as per following table.

Unbalance 1% 2% 3% 4% 5%Derating 100 95 90 83 76

Rerating S1 duty motors to S2 and S3 duty motorsStandard 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 S3

60 min 30min 10min 60% CDF 40%CDF 25% CDF

100% 115% 120% 100% 105% 120%

maximum difference in voltage compared to average voltage value_____________________________________________________average voltage value

10

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 Connected Data at 60 Hz in percentage of values at 50Hz wound for to 60 Hz

1) 50 Hz and and Output rpm I I /I T T /T T /TN S N N S N max N

220 V 220 v 100 120 98 83 83 70 85 225 v 115 120 100 100 96 95 98

380 V 380 V 100 120 98 83 83 70 85415 V 110 120 98 95 91 85 93440 V 115 120 100 100 96 95 98460 V 120 120 100 105 100 100 103

400 V 380 V 100 120 100 80 83 66 80400 V 100 120 98 83 83 70 85415 V 105 120 100 88 86 78 88440 V 110 120 100 95 91 85 93460 V 115 120 100 100 96 95 98480 V 120 120 100 105 100 100 100

415 V 415 V 100 120 98 83 83 70 85 460 V 110 120 98 95 91 85 94

480 V 115 120 100 100 96 95 98

500 V 500 V 100 120 98 83 83 70 85550 V 110 120 98 95 91 85 94575 V 115 120 100 100 96 95 98600 V 120 120 100 105 100 100 103

Efficiency, power factor and temperature rise will be approximately the same as at 50 Hz.

1) I = rated currentN

I /I = starting current/rated currentS N

T = rated torqueN

T /T = maximum torque/rated torquemax N

T /T = starting torque/rated torqueS N

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. Two separatewindings Y/Y

Low speed High speed Low speed High speed

2. Two separatewindings D/D

Low speed High speed Low speed High speed

3. Dahlander-connection D/YY

Low speed High speed Low speed High speed

4. Dahlander-connection Y/YY

Low speed High speed Low speed High speed

12

1. VoltageRated 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.

2. FrequencyRated 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 variationMotors can be operated continuously at rated output, with a long term voltage variation of

4. Number of polesNumber 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. PowerRated 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, slipRated 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,

±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.

h = x 60(rpm)s

where h = synchronous speed (rpm)s

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, h and rotor s

speed, n; referred to the synchronous speed, is called slip. This slip, s, is expressed as a percentage;

s = x 100 (%)

When the motor is partly loaded the slip varies almost linearly with the load.

7. Rated currentIt 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:

Ix =

Where Ux = new voltageIx = new currentI = 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 currentUsually, 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

10. Moment of inertia2The moment of inertia J is given in Kgm . The moment of

2inertia is numerically equal to 1/4 GD . The moment of inertia J

11. OverloadsIn 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.

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 T is the torque developed N'

by the motor at rated speed, n while delivering rated power P. The relationship between the torque T the power P, and N'

the speed n is

T = 9550 x [Nm]N

Where P = power (kW)n = motor speed (rpm)

alternatively, torque T, in kgm can be given as

T = 974 x [kgm]N

Starting torque of the motor T is the torque developed by S'

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 T .N

Pull out torque of the motor T is the maximum torque that max'

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 T .N

of the driven machine at n rpm when referred to L L

motor speed n rpm is given by

2J = J [n /n]L L

Electrical features

f

415.I

415.I

P

p

Ux

Ux

n

h - hs

hs

13

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.

Star-Delta (Y/D) starting:

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-on-line 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.

Soft starters

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.

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

UN

Ist

UN = Rated net voltage

st I = Start current at full voltage

UN

stI

UN = Rated net voltage

st I = Start current at full voltage

Starting methods for AC motors

UN

IstR

UN = Rated net voltage

stR I = Start current at red. voltageMU

MU = Motor voltage

NU

IstR

UN = Rated net voltage

stRI = Start current at red. voltageUM

UM = Motor voltage

14

Typical motor current and torque curves

Comparison between starting methods

T = Motor torqueM

T = Motor torque with direct-on-line startingMD

T = Motor torque with start-delta startingMY

T = Load torqueL

T = Load breakaway torqueL0

T = Rated motor torqueN

T = Breakaway torque or locked rotor torqueS

T = Pull-up torquemin

T = Breakdown torque or pull-out torquemax

T = Acceleration torqueacc

I = CurrentI = Rated currentN

I = Current in D-connectionD

I = Current in Y-connectionY

n = Speedn = Synchronous speedS

Current Torque

1 = Direct-On-Line starter2 = Y/D-starter3 = 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 the torque curves for the motor and the load are known, the starting time can be calculated by integrating the equation:

T - T = (J + J ) L M L

where T = Motor torque, NmT = Load torque, NmL

2J = Moment of inertia of motor, kgmM2J = Moment of inertia of load, kgmL

W = Motor angular velocity

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:

T = (J + J ) st M L

where T = starting timest

T = acceleration torque as per diagrams, Nmacc

K = as per table below1

Speed Poles FrequencyConstant 2 4 6 8 10 Hz

n 3000 1500 1000 750 600M

K 345 157 104 78 621

n 3600 1800 1200 900 720M

K 415 188 125 94 751

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:

T ' =L

where T ' = Recalculated load torque, NmL

n = Motor speed, rpmM

n = Load speed, rpmL

The moment of inertia must also be recalculated.

2J '=J ' (n /n )L L L M

2where J '= Recalculated moment of inertia, kgmL

¶w

¶t

K1

T nL L

nM

Tacc

50

50

x

x

x

x

16

Example of starting performance with different load torques

4-pole motor, 160 kW, 1475krpm

Torque of motor:T = 1040 Nm,N

T = 1,7 x 1040 = 1768 NmS

T = 2,8 x 1040 - 2912 Nmmax

2Moment of inertia of motor: J = 2,5 kgmM

The load is geared down in a ration of 1:2

Torque of load:

T = 1600 Nm at n = rpmL L

Example 1:

Lift motion

Speed

T = 1600 Nm T' = 800 NmL L

Constant during acceleration

T = 0,45 x (T + T ) - T'acc S max L

T = 0,45 x (1768 + 2912) - 800 = 1306 Nmacc

t = (J + J' ) xst M L

t = 22,5 x = 2,7 sst

Example 2:

Piston pump

Speed

T = 1600 Nm T' = 800 NmL L

Linear increase during acceleration

T = 0,45 x (T + T ) - T'acc S max L

T = 0,45 x (1768 + 2912) - €800 = 1706 Nmacc

t = (J + J' ) xst M L

t = 22,5 x = 2,1 sst

T = 1600 x = 800 Nm at n rpmL M

Moment of inertia of load:

2J = 80 kgm at n = rpmL L

2 2J = 80 x ( ) = 20 kgm at n rpmL M

Total moment of inertia:

J + J at n r/minM L M

22,5 + 20 = 22,5 kgm

Example 3:

Fan

Speed

T = 1600 Nm T' = 800 NmL L

Square-law increase during acceleration

T = 0,45 x (T + T ) - x T'acc S max L

T = 0,45 x (1768 + 2912) - x 800 = 1839 Nmacc

t = (J + J' ) xst M L

t = 22,5 x = 1,9 sst

Example 4:

Fly wheel

Speed

T = 0L

T = 0,45 x (T + T )acc S max

T = 0,45 x (1768 + 2912) = 2106 Nmacc

t = (J + J' ) xst M L

t = 22,5 x = 1,7 sst

nM

nM

K1 K1

1

1

K1

K1

1

1

157 157

157

157

2

2

Tacc Tacc

3

3

Tacc

Tacc

2

2

1360 1839

1706

2106

Torque Torque

Torque Torque

TLTL

TL TL

1

2

1

2

17

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.

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.

The permitted number of counter current braking can be calculated approximately with the formula:

3600x

X = T xb

where x = Permitted number of brakings per hourP = Output taken from motor, kW2

P = Rated output of motor in continuous duty, kW1

t = Braking time, sb

I /I = Starting current / full load currentst

For squirrel cage motors the braking time can be calculated approximately with the formula:

t =b

where t = Braking time, sb

K = Constant depending on number of poles, see 1

table2J = Moment of inertia of motor, kgmm

J = Moment of inertia of load, referred to speed of b2motor, kgm

M = Maximum torque of motor, Nmmax

M = Starting torque of motor, Nmstart

Frequency Constant K for different number of poles1

Hz 2 4 6 8 10

50 345 157 104 78 6260 415 188 125 94 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.

For slip-ring motors the starting and braking times are both determined by the dimensioning of the rheostatic starter.

Figure 1

(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.)

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.

Electrical braking

K x (J + J )1 m b

0.45 x (M + M )max start

Torque

Torque

Torque

Torque

Braking torque

Braking torque

Acceleration torque

Acceleration torque

Mb

Speed

Speed

Countercurrent braking

Countercurrent braking

Starting

Starting

P2

2

IstP2

22

I P1

P1

4 x -

18

Direct-current 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.

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.

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.

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.)

Figure 4

(Example of braking torque with d.c. braking and different excitation currents.I = rated current of motor.)n

Regenerative braking

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.

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 startOne DC injection braking = Two startOne plug stop = Three startOne regenerative braking = One start

TorqueTorque

Time

Braking torqueAcceleration torque Mb

Torque

Direct-current braking Starting

19

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.

S1Continuous running duty

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

S2Short-time duty

Operation at constant load during a given time, less than required to reach thermal equilibrium, followed by a rest and de-energised 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.

S3Intermittent duty

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%

S4Intermittent 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, J , of the motor rotor; and the permissible M

average moment of resistance, T , during the change of the V

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.

2Designation e.g. S4 - 25% - 129 c/h - FI.2 - J = 0,1 kgm - T = M V

0,5 T .V

Duty types

N RP

N

P

Time

NP

Time

Time

Period of one cycle

P

D N RTime

Period of one cycle

P = Output powerD = StartingN = Operation under rated conditionF = Electrical braking

V = Operation of no loadR = At rest and de-energised

20

S5Intermittent duty with starting and electrical braking

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 de-energised 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 J , of the motor, and the M

permissible moment of resistance T (see duty type S4.)V

2Designation e.g. S5-40% -120 c/h- FI.3 - J = 1,3 kgm - T = 0,3 T .M V N

S6Continuous-operation periodic duty 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.

Recommended values for the cyclic duration factor are 15, 25, 40 and 60%. The duration of the duty cycles is 10 min.

Designation e.g. S6 40%

P

N

V

Time

P

D

N R

F

Time

Period of one cycle

Period of one cycle

S7Continuous-operation periodic duty with 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 J of the motor, and the permissible moment of M

resistance T ( See duty type S4)V

2Designation e.g. S7 40% - 500 c/h - FI.2 - J = 0.08 kgm - T = M V

0,5 T .N

S8Continuous-operation periodic duty with related load speed changes

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 T (see duty type S4); V

the cyclic duration factor for each speed of rotation and the moment of inertia J of the motor.M

Designation e.g.

S8 - 30 c/h - FI.30 - T = 24 kW - 740 rpm - 30%V

30 c/h - FI.30 - T = 0.5 T = 60 kW - 1460 rpm - 30%V N

30 c/h - FI.30 - T = 0.5 T = 45 kW - 980 rpm - 40% V N2J = 2,2 kgmM

The combinations of the load and speed of rotation are designed in the order they occur in use.

S9Duty with non-periodic load and speed variations A duty in which, generally, load and speed are varying non-periodically 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.

21

P = Output powerD = StartingN = Operation under rated conditionF = Electrical braking

V = Operation of no loadR = At rest and de-energised

Space heaters

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.

For motors not having the provision of space heaters, 24 V dc supply can be applied between any two terminals.

The leads of space heaters for frame 160 to 400 are terminated in a separate auxiliary terminal box

Guide for fuse protection

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

Protection accessories

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

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

10

16

16

16

25

25

25

50

50

63

63

80

100

125

160

200

200

250

300

350

500

kW Full loadcurrent, A

Fuse rating, A

DOL start Y/D start

Characteristic of a thermistor

ohms

4000

1330

550

100

Typical value _Shaded area = tolerance limits

Thermistors

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.

Thermistors generally provided are rated for 130°C (PTC 130) for class B rise and 155°C (PTC 155) for class F rise.

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.

Like space heaters, the leads of thermistors for frame 160 to 400 are terminated in a separate auxiliary terminal box.

22

Voltage drop along the cable

Determination of withstand capability

Since the negative sequence currents result in overloading, theamount of negative sequence current carried by the winding asa percentage of rated current can be used as a measure ofoverloading due to unbalance. The thermal withstandcharacteristics of the machine available for different overloadconditions can be used to represent the capacity of the machineto withstand negative sequence voltage and current. Thenegative sequence withstand characteristics are design specificand 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° VV = 410 L120° VV = 425 L 240° V

Average voltage = = 407V

Unbalance voltage = x 100 = 4.42%

Negative sequence voltage

V = =11.66Ð158° VN

% negative sequence voltage = 11.66 / 407 = 2.86% (appx. 3%)

Now if the parameters of the machine are as given below:R1 = 0.052R2 = 0.071X1 = 0.51X2 = 0.53s = 0.0123

then s1 = 2. 0.0123 = 1.9877

From the equivalent circuit diagramVN

(R1+ R2 1s1)+ j(X1 + X2)

11.66L158° (0.052 + 0.071/1.9877) + j (0.51+ 0.53)

= 11.17 L -243.4°

This corresponds to 18.6% (approx. 20%) of the rated currentfor the case considered here. This condition can be equated toan overload of 20%. Now the thermal withstand characteristicsof the motor can be used to obtain the thermal withstand timefor this particular motor. Similarly, thermal withstand time fordifferent negative sequence voltage of voltage unbalance canbe calculated.

The following table gives the thermal withstand time of thissample motor for different negative sequence voltage.

% negative % negative withstand time, sec sequence sequence voltage current Cold Hot

1 6 continuous continuous

2 10 continuous continuous

3 20 3500 1800

6 40 1600 600

9 60 1100 400

385 + 410 + 425

3425 - 407

407

2385Ð0° + a 410Ð120° + a425Ð240°3

Induction motors draw heavy currents during starting, resultingin considerable voltage drop along the cable, If other loads areconnected in parallel to the motors, the voltage drop along thecommon feeder causes operational problems to theseassociated loads. Larger the starting current and longer thecommon feeder, larger will be the voltage drop. In view of thiswhile specifying motors or cables, it is required to estimate the right combination of starting current and cable size, alternatively, itis important to know voltage drop for an installation whenstarting / locking of motors occurs such that the maximumvoltage drop is less than 3%. The relative voltage drop, D u isestimated as

where, U is the rated voltage of the motoru is the voltage drop given as

u = b Is

where u = Voltage dropb = Factor equal to 1 for three-phase circuits and

equal to 2 for single phase circuitsr = Resistivity of conductors in normal duty

taken as being equal to the resistivity at the normal duty temperature, i.e. 1.25 times theresistivity at 20°C, giving 0.02250 mm2/m forcopper and 0.0360mm2/m for aluminium

L = Length of cabling in metersS = Cross section of conductors in mm2cosf = Power factor, if exact figure is not available it

is equal to 0.8 and sin~ = 0.6l = Linear reactance of conductors, taken as

being equal to 0.08mQ/m if the exact figureis not available

l = Current in useS

Negative sequence withstand characteristics

Negative sequence withstand characteristics are used to obtaincapability of the motor to withstand the overloading caused bynegative sequence currents that occur due to unbalance insupply voltage.

While % unbalance in voltage is given by the ratio

Max. deviation (phase value) from average value x 100Average value

The negative sequence voltage, V for any degree of unbalanceN

can be calculated by

2V = 1/3 (V + (a V + a V )N a b c2where a = 1 L120° and a = 1 L240º

Estimation of negative sequence current

Once negative sequence voltage is known amount of negativesequence current that is ultimately responsible for overloadingcan be estimated from the following equivalent circuit of themotor. The value of circuit parameters can be obtained fromdesign or from test results.

rx cosf + lLsinf LS(

Du = - *100uU

R1X1 X2R /S2 1

23

The power factor compensating capacitors are specified in terms of kVAR.The input kW of the motor is multiplied by the readingto obtain the necessary improvement in the power factor.

Example - If the initial power factor = COSf1 =0.76Input active power = 100 kWCorrected power factor = COSf2 =0.90

From the chart: capacitor kVAR required per kW load = 0.37hence

Total capacitor kVAR required = 0.37 x 100 = 37 kVAR

Present Desired power factor, COSf2

powerfactor

COSf10.7 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

0.80 0.05 0.10 0.16 0.21 0.27 0.33 0.39 0.46

0.82 0.05 0.10 0.16 0.22 0.27 0.33 0.40

0.84 0.05 0.11 0.16 0.22 0.28 0.35

0.86 0.06 0.11 0.17 0.23 0.30

0.88 0.06 0.11 0.17 0.25

0.90 0.06 0.12 0.19

0.92 0.06 0.13

0.94 0.07

Power factor improvement chart

24

Enclosure

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.

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 anti-corrosion 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 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

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.

Terminal box

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

0rotatable in the steps of 90 and are made of die cast aluminum alloy. For frames 225 and 400 the terminal boxes are rotatable

0in steps of 90 and are made from cast iron. For all the terminal boxes protection of enclosure of IP 55.

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.

Mechanical

Open

Closed

25

A

RV

M C

DA

RV

M C

D

1

2

3

4

6

8

14

31

51

16

17

91

5

12

18

7

11

01

9

20

21

22

23

1 Bearing Cover DS Outer2 Endshield DS3 Bearing DS4 Bearing cover DS inner5 Shaft extension key6 Rotor assembly 7 Fan key 8 Wound stator 9 Terminal box

10 Terminal plate 11 Terminal box cover 12 Eye bolt

17 Fan18 Circlip19 Fan Cowling

13 Bearing NDS14 Bearing Cover NDS Inner15 Endshield NDS.16 Bearing Cover NDS Outer

20212223

Grease Outlet PlugRegreasing HoleDrain Hole PlugEarthing Bolt

Exploded view of HX motors

26

Pulley diameter

When the desired bearing life has been determined, the minimum permissible pulley diameter can be calculated using F as follows:R'

D=

where:D = Diameter of pulley, mmP = Power requirement, kWn = Motor speed, r/minK = Belt tension factor, dependent on belt type and type of duty. A common value for V-belts is 2.5.F = Permissible radial forceR

Permissible loadings on shaft

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.

Motors are foot-mounted 1MB3 version with force directed sideways. In some cases the strength of the shaft affects the permissible forces.

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 X and X the 0 max'

permissible force F can be calculated from the following formula :R

F =F - (F - F )R X0 X0 Xmax

E = length of shaft extension in basic version

71.9 x 10 x K x P n x FR

FRX

X0Xmax

Permissible radial forcesMotor sizes 71 to 132

Length of Ball bearingsshaft

Motor extension 20,000 hourssize Poles E (mm) X (N) X (N)0 max

71 2 30 415 3354 30 415 3356 30 415 340

80 M 2 40 670 5454 40 890 7256 40 970 830

90 SL 2 50 795 6254 50 995 7806 50 1135 880

100 2 60 1090 8754 60 1360 10956 60 1560 1250

112 2 60 1410 11204 60 1735 14006 60 2000 1620

132 SM 2 80 1700 13304 80 2130 16606 80 2495 1935

27

Permissible radial forces

Motor sizes 160 to 400

Length of Ball bearings Roller bearingsshaft

Motor extension 20,000 hours 40,000 hours 20,000 hours 40,000 hourssize Poles E (mm) X (N) X (N) X (N) X (N) X (N) X (N) X (N) X (N)0 max 0 max 0 max 0 max

160 2 110 2980 2310 2350 1810 5530 4260 4370 33604 110 3760 2900 2970 2290 6980 5380 5520 42506 110 4290 3300 3390 2750 7980 6150 6310 48608 110 4730 3660 3740 2880 8800 6780 6960 5360

180 2 110 3540 2880 2790 2260 6260 5080 4940 40104 110 4390 3560 3440 2790 7830 6350 6160 50006 110 5060 4110 3970 3220 9000 7300 7100 57508 110 5590 4540 4390 3560 9940 8060 7830 6350

200 ML 2 110 4510 3700 3530 2900 8520 7000 6710 55104 110 5660 4650 4430 3640 10710 8800 8440 69306 110 6470 5310 5050 4150 12250 10060 9640 79208 110 7160 5880 5600 5880 13520 11100 10650 8750

225 SM 2 110 4750 4010 3710 3130 9720 8200 7650 64504 140 6310 5040 4920 3840 12900 10310 10150 81206 140 7200 5760 5620 4500 14740 11800 11600 92808 140 7970 6375 6230 4980 16270 13010 12820 10250

250 SM 2 140 6100 4910 4750 3830 13600 10960 10710 86404 140 7650 6170 5960 5450 17100 13800 13470 108706 140 8700 7010 6760 5450 19520 15740 15360 124008 140 9630 7760 7505 6050 21550 17380 16970 13690

280 SM 2 140 7300 6200 5800 4900 20200 6600 16500 66004 140 9200 7800 7300 6200 25000 12000 20300 120006 140 10600 8900 8400 7100 28000 12000 23000 120008 140 11600 9800 9200 7800 30700 12000 25000 12000

315 SML 2 140 7300 6000 5800 4950 20200 6350 16500 63504 170 11300 9400 9000 7500 32500 10700 26500 107006 170 13000 10600 10300 8500 37000 10600 30000 106008 170 14300 10400 11300 9400 40000 10400 32700 10400

355 SM 2 140 9000 7900 6100 5300 26700 8900 21800 89004 210 15200 12500 12000 9850 45000 21400 36700 213006 210 17300 14300 13700 11300 51000 21100 41500 211008 210 19000 15700 15200 12400 55500 21700 45200 21700

355 ML 2 140 9100 7100 6100 5400 26900 7100 21800 71004 210 15200 12800 12000 10100 45500 19500 36700 195006 210 17300 14600 13700 11500 51000 19000 41500 190008 210 19300 16200 15200 12700 55500 19500 45200 19500

400 L 2 140 8900 3000 5700 3000 27000 3000 22000 30004 210 15000 13000 11700 10100 46000 15000 37000 150006 210 17200 13700 13600 11700 52000 13700 42000 137008 210 19200 15000 15000 12900 55500 15000 46000 15000

28

Permissible axial forces

The following tables give the permissible axial forces in newton,assuming zero radial force. The values are based on normalconditions at 50Hz with standard bearings and calculatedbearing lives of 20,000 and 40,000 hours.

At 60 Hz the values are to be reduced by 10%.

For two-speed motors, the values are to be based on the higherspeed. The permissible loads of simultaneous radial and axialforces will be supplied on request.

Given axial forces F assumes D-bearing locked by means ofAD'

locking ring.

Mounting arrangement 1M83

20,000 hours 40,000 hours

2-pole 4-pole 6-pole 8-pole 2-pole 4-pole 6-pole 8-poleMotor F F F F F F F F F F F F F F F FAD AZ AD AZ AD AZ AD AZ AD AZ AD AZ AD AZ AD AZ

size N N N N N N N N N N N N N N N N

71 270 270 350 350 440 440 - - 1) 1) 1) 1) 1) 1) - -80 400 400 510 510 590 590 - - 1) 1) 1) 1) 1) 1) - -90 450 450 560 560 640 640 - - 1) 1) 1) 1) 1) 1) - -

100 620 620 780 780 890 890 - - 1) 1) 1) 1) 1) 1) - -112 810 810 1020 1020 1170 1170 - - 1) 1) 1) 1) 1) 1) - -132 980 980 1220 1220 1400 1400 - - 1) 1) 1) I) I) 1) - -

160 2120 2120 2660 2660 3040 3040 3360 3360 1670 1670 2100 2100 2400 2400 2640 2640180 2480 2480 3070 3070 3540 3540 3910 3910 1950 1950 2430 2430 2780 2780 3070 3070200 3050 3050 3850 3850 4400 4400 4850 4850 2430 2430 3050 3050 3500 3500 3850 3850225 3440 3440 4340 4340 4960 4960 5460 5460 2730 2730 3440 3440 3940 3940 4340 4340250 4180 4180 5260 5260 6020 6020 6630 6630 3320 3320 4180 4180 4780 4780 5260 5260

280 7300 5300 8000 6000 9000 7000 10000 8000 5750 3750 6200 4200 6900 4900 7700 5700315 7000 5000 9000 7000 10600 8600 11600 9600 5600 3600 6900 4900 7900 5900 8900 6900355 10500 3500 13500 6500 15300 8300 16800 9800 8750 1750 10800 3800 12000 5000 13300 6300400L 10100 32001 3000 6000 15000 8000 16500 9500 8350 1350 10200 3250 11800 4800 13000 6000

Mounting arrangement 1MV1

20,000 hours 40,000 hours

2-pole 4-pole 6-pole 8-pole 2-pole 4-pole 6-pole 8-poleMotor F F F F F F F F F F F F F F F FAD AZ AD AZ AD AZ AD AZ AD AZ AD AZ AD AZ AD AZ

size N N N N N N N N N N N N N N N N

71 290 260 380 330 460 420 - - 1) 1) 1) 1) 1) 1) - -80 430 390 540 490 620 560 - - 1) 1) 1) 1) 1) 1) - -90 480 420 610 520 700 600 - - 1) 1) 1) 1) 1) 1) - -

100 680 580 880 740 990 840 - - 1) 1) 1) 1) 1) 1) - -112 890 760 1140 950 1280 1100 - - 1) 1) 1) 1) 1) 1) - -132 1100 919 1390 1120 1580 1300 - - 1) 1) 1) 1) 1) 1) - -

160 2420 1820 3040 2280 3480 2600 3810 2920 1970 1370 2480 1720 2840 1960 3090 2200180 2860 2100 3690 2450 4160 2920 4530 3290 2300 1570 3050 1810 3400 2160 3690 2450200 3600 2500 4580 3120 5280 3530 5720 3980 2970 1870 3780 2320 4370 2620 4720 2980225 4140 2740 5230 3440 6030 3900 6530 4400 3430 2030 4330 2550 5010 2870 5400 3270250 5020 3330 6380 4150 7440 4610 8050 5210 4160 2470 5290 3060 6200 3360 6680 3840

280 8500 4300 9500 4600 11000 5500 12200 6600 6950 2700 7700 2800 8900 3350 9750 4200315 SML 9000 3700 11600 5400 13500 6200 14500 7500 7450 2100 9450 3200 10900 3650 11900 4650355 SM 14900 800 19200 3100 22200 4100 24000 5800 13000 1) 16400 1) 18900 850 20300 2100 355 ML 15000 1) 19800 1700 23100 2500 25000 4300 13100 1) 17000 1) 19800 1) 21300 1)400 L 17300 1) 21800 1) 24300 1000 26200 2500 15400 1) 18900 1) 21100 1) 22500 1)

1) On request

FAD FAZ

FAD

FAZ

29

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. Insulation resistance test2. Measurement of resistance of the stator3. Locked rotor test4. No load test5. Reduced voltage running test6. High voltage test

Type test

1. Dimensions2. Measurement of resistance of stator3. Locked rotor test4. Temperature rise test5. Full load test6. No load test at rated voltage7. Reduced voltage running test8. Momentary overload test9. Insulation resistance test10. High voltage test

Optional tests

1. Vibration severity test2. Sound level measurement3. Degree of protection test4. Temperature rise test at limiting values of voltage and

frequency variation5. Over speed test6. Test on insulation system

Special tests

1. Acceleration constant test (B value test, for roller table motors)

2. t time test (for increased safety motors)E

3. Suitability to PWM supply

Testing

30

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.

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:

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.

2. Speed range

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).

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

Permissible maximum speeds for standard motors are describedin figure 1.

Figure 1.Maximum permissible speeds for basic motors

Frame size Speed r/min2-pole 4 -pole

71 - 200 4000 3600225 - 280 3600 2600315 3600 2300355 3600 2200400 3600 1800

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.

3. Lubrication

The effectiveness of the motor lubrication should be checked bymeasuring 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.

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.

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.

5. Bearing currents

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

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 EMC-glands). 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)

Motors for frequency converter drive

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

dU/dt filter

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.

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 cableLight Common Mode Filter = 1 toroidal core per each 3-phase motor cable

Figure 3. Motor loadability with ACS 600, Field weakening point 50Hz.

UN

< 500 V

UN

< 690 V

UN

< 600 V Standard motor+ dU/dt-filterORReinforced insulation

Reinforced insulation+ dU/dt-filter

Standard motor Standard motor+ Insulated N-bearing

Standard motor+ dU/dt-filterORReinforced insulation+ Insulated N-bearing

Reinforced insulation+ dU/dt-filter

Standard motor+ Insulated N-bearing+ Common mode filter

Standard motor+ Insulated N-bearing+ dU/dt-filterORReinforced insulation+ Insulated N-bearing+ Common mode filter

Reinforced insulation+ Insulated N-bearing+ dU/dt-filter+ Light Common mode filter

Motor nominal power P or frame sizeN

NP < 100 kW NP 100 kW or IEC 3153< NP 350kW<

Motor loadability with ACS 600

The loadability curve in figure 3 below is a guide line curve, for exact values please contact ABB.

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. .

32

Guide and check points for motor selection(mechanical aspects)

1000m or less AltitudeAbove 1000m Environment Corrosion45°/50°C or less Ambient Dust, carbon, EtcLow Temperature Humidity

Housing Protection Drip proof, IP23Totally enclosed, IP55Special, IP56

Totally enclosedfan cooled VentilationSeparately cooledNatural cooled

StandardDouble shaft Shaft end Power Transmission DirectTapered BeltSpecial Gear box

Mounting FootHorizontal Installation FlangeVertical Face

Dimension IS/IECUser specific

Epoxy Terminal Plate Terminal Box Position TOP/LHS/RHSBakelite Material Cast iron

Aluminum

Single armour TypeDouble armour Cable Entry BottomWithout armour TopOne or two Numbers side

size

Noise Standard Low

Standard Vibration

Precision

Bearings BallRoller

Special paint shade ThermistorSpecial name plate Others Space heaterDirection of rotation Brake

Tacho

33

Drive torque Characteristics TorqueOperating speed of the load characteristicsTransfer efficiency

2Load GD Operating Continuous operationLoad torque characteristics Intermittent duty & CDF

Equivalent startsper hour

Rated output Single speedand speed Dual speed

VVVF application

Single voltage with variations voltage110V - 660VDual voltage - l / D D / DD

Frequency 50 Hz

Any other frequency

Type of starting DOL startStar-Delta startAuto-transformer start % tappingSoft start

Mechanical BrakingPluggingDC injectionRegenerative

TorqueCharacteristics Normal starting

High torque Soft starting (Low pull out torque)

B/F TemperatureF/F rise / insulationF/H

Determination of motor

specification

Guide and check points for motor selection(electrical aspects)

34

Customer Name_____________________________________

Date______________________________________________

Application_________________________________________

01 Output_______________kW (___________________hp)

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

• 45°C

• 50°C0• Special (Specify)_____________________________ C

09 Temperature rise by resistance method

• 70°C

• 75°C

• 100°C0• Special (Specify)_____________________________ C

10 Altitude

• Standard (Sea level upto 1,000m)

• Special (Specify)

11 Insulation • B • F • H

12 Duty • Continuous (S1)

• Other(Specify)______________________

13 Environment

• High humidity • Dusty • Tropical

• Corrosive gas, vapour

• Area classification class

• Temp. Class______________• Division__________

14 Enclosure

• Open drip proof (IP23)

• TEFC(IP44)

• TEFC(IP55)

• Type 'n' (Non sparking)

• Type 'e' (Increased safety)

• Type 'd' (Flame proof)

• Special (Specify)

15 Construction

• Horizontal • Vertical • Special

16 Mounting

• B3 • V1 • Other(Specify)

17 Applicable codes and standards

• IS 325

• IS 6381 (Increased safety motors)

• IS 9628 (Non sparking motors)

• IS 3682 (Flame proof motors)

• IPSS:1-03-007-85 (A.C. roller table motors)

• IS 2972 (Textile application)

• IS7538 (Agriculture application)

• Other_______________________________________

18 Starting current

• 600% subject to IS tolerance

• 600%maximum

• Other_________________% full load current

19 Starting method

• Direct-on-line (full voltage)

• Star-Delta

• Auto-Transfer___________%taping____________secs

• Frequency converter

• Frequency range____________Hz to____________Hz

• Fieldweakning point____________________________

• Load torque speed curve________________________

20 Braking details

• No braking

• Electromechanical braking

• Countercurrent(Plugging)_________________no./hour

• D.C. injection___________________________no./hour

• Reversal by plugging_____________________no./hour

• Other (specify)________________________________

21 Winding connection

• Star • Delta • Special________________________

22 Starting duty

• 1 Hot, 2 Cold, 3 Equally spread

• Special (Specify)

23 Load inertia with respect to motor shaft

2 2• Actual GD ___________kgm at ___________rev./min

24 Load torque curve

• Enclosed

• Not enclosed

25 Method of coupling

• Flexible • Belt • Gear box

• Fluid • Other ____________________________

26 Belting data

• Motor pulley dia. and wt.____________mm________kg

• Load pulley dia. and wt._____________mm________kg

• Centre distance between pulleys_______________mm

• Type of belt___________________________________

• No. of belts___________________________________

27 Direction of rotation

• Bi-directional

• Clockwise from driving end

• Anti-clockwise from driving end

Ordering Information

35

28 Terminal Box

• Without

• With

Location

• Top on driving end

• Right side from driving end

• Left side from driving end

• Special (specify)______________________

29 Terminal box construction

• Stud type 3 terminals

• Stud type 6 terminals

• Other_______________________________________

• External power cable

Type________________________________________

No. of cable____________No. of core______________2 Conductor sectional area_____________________mm

Diameter : Overall ___________________________mm

Inner sheath_______________________mm

Conduit size____________________________________

•Special (specify)_______________________________

30 Anti-condensation heater

• Not required

•________________Volt

• Special (specify)_______________________________

31 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

• Cable lugs

• Special (specify)_______________________________

35 Mounting base

• Not required

• Slide rails

• Special(specify)_______________________________

36 Thrust for vertical motor

• Design thrust • Up__________kg • Down _______kg

• Momentary thrust

• Up__________kg • Down _______kg

37 Rotor end float

• ABB standard as per IS

• Special(specify)____________________________mm

38 Test

• ABB standard (Non-witnessed)

Routine test as per IS 325

• Witness routine test as per IS 325

• Witness type test as per IS 325

• Special (specify)_______________________________

39 Any special requirement __________________________

_____________________________________________

_____________________________________________

_____________________________________________

_____________________________________________

_____________________________________________

_____________________________________________

Prepared by ___________

Dated ___________

36

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 behigher 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 no-load 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 no- load 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 PFBD EBD motor motor

Efficiency, % 90 92.5

Power factor 0,89 0.83

Ampere= Rated kw/(sqrt(3)xVxEffxPower factor) 52 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

Frequency asked questions

37

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