Indian Standard
ROTATING ELECTRICAL
MACHINES — SPECIFICATION
(
Second Revision)
ICS 621,313-13 0 BIS 2001BUREAU
OF
IN DIAN
STANDARDS
MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARC NEW DELHI 110002
August 2001 Price Group 8
I /
FOREWORD
This Indian Standard (Second Revision) was adopted by the Bureau of Indian Standards, after the draft finalized by the Rotating Machinery Sectional Committee had been approved by the Electrotechnical Division Council.
In the first revision of this standard following contents have been brought out in separate independent standards: a) Type of duty and classes of ratings assigned to rotating electrical machines covered in IS 12824:1989,
and
b) Temperature-rise measurements of rotating electrical machines covered in IS 12802:1989.
In this revision, a number of editorial corrections have been incorporated and in addition, some changes have also been incorporated based on experience for operation of this standard.
The requirements of rotating electrical machines covered in this standard have been updated in line with current international practices.
While revising this standard, assistance has been derived from the IEC Pub 34(1983) now designated as IEC 60034 ‘Rotating electrical machines’, issued by the International Electrotechnical Commission (IEC).
For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated, expressing the result of a test, shall be rounded off in accordance with IS 2:1960 ‘Rules for rounding off numercial values (revised)’. The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard.
IS 4722:2001
Indian
ROTATING
MACHINES —
Standard
ELECTRICAL
SPECIFICATION
(Second Revision)
1 SCOPE1.1 This standard covers requirements for rotating electrical machines without distinction of output and voltage but excluding:
a) Traction equipment, and
b) Motors covered by IS 996:1979 ‘Single phase small ac and universal electric motors (second
revision)’.
1.1.1 Attention is drawn to certain other standards listed below which may apply when machines are required for particular applications. The rating plate of machines built to comply with these standards indicate the number of the Indian Standards invoked:
IS No. Title
325:1996 Three-phase induction motors
~ourth revision)
2635:1975 DC electric welding generators (second revision)
2972 Textile motors:
(Part 1): 1979 Loom motors (/irst revision) (Part 2): 1979 Card motors (@f revision)
(Part 3): 1979 Spinning frame motors (@ revision)
3682:1966 Flameproof ac motors for use in mines
5422:1996 Turbine type generators (/h?
revision)
7538:1996 Three-phase squirrel cage induction motors for centrifugal pumps for agricultural application
8151:1976 Single-speed three-phase induction motors for driving lifts
9283:1995 Motors for submersible pumpsets 9628:1980 Three-phase induction motors with
type of protection ‘n’ 2 REFERENCES
The Indian Standards listed in Annex A are necessary adjuncts to this standard.
3 TERMINOLOGY
3.0 For the purpose of this standard, the following definitiofis shall apply. The definitions of general terms used in this standard are given in IS 1885 (Part 35).
3.1 Rating
The whole of the numerical values of the electrical and mechanical quantities with their durations. and sequence assigned to the machine by the manufacturer and stated on the rating plate, the machine complying with the specified conditions.
3.2 Rated Value
The numerical value of a quantity included in the rating.
3.3 Rated Output
The numerical value of the output included in the rating.
3.4 Load
All the numerical values of the electrical and mechanical quantities that signify the demand to be made on a rotating machine by an electrical circuit or a mechanism at a given instant.
3.5 No-Load (Operation)
The state of a machine rotating with zero output power (but under otherwise normal operating conditions). 3.6 Full Load
The highest value of load specified for a machine operating at rated output.
3.7 Full Load Power
The highest. value of power specified for machine operating at rated output.
NOTE — This concept also applies to torque, current, speed, ete.
3.8 Rest and De-energized
The complete absence of all movements and of all electrical supply or mechanical drive.
IS 4722:2001
3.9 Duty 3.18 Cooling
.
The statement of the load(s) to which the machine is A method by means of which heat resulting from subjected, including, if applicable, starting, electric Iossesoccurnng in a machine is given up first to a braking, no-load and rest andde-energized periods, primary cocdant by increasing its temperature. The and including their durations and sequence in time. heated primary coolant may be replaced by a new 3.10 Duty Type coolant at a lower temperature or may be cooled by a
secondary coolant in some form of heat exchanger. A continuous short time or periodic duty, comprising
one or more loads remaining constant for the duration specified, or a non-periodic duty in which generally load and speed vary within the permissible operating range.
3.11 Thermal Equilibrium
The state reached when the temperature rises of the several parts of the machine do not vary by more than 2 K over a period of 1 h.
3.12 Cyclic Duration Factor
The ratio between the period of loading, including starting and electric braking, and the duration of duty cycle, expressed as a percentage.
3.13 Locked Rotor Torque
The minimum measured torque which the motor develops with the rotor locked and rated voltage applied at rated frequency.
3.14 Locked Rotor Current
The measured steady-state root-mean-square current taken from the line with the rotor locked with rated voltage and frequency applied.
3.15 Pull-up Torque (of an ac Motor)
The smallest torque which the motor develops between zero speed and the speed which corresponds to the breakdown torque when the motor is supplied at the rated voltage and frequency.
NOTES
1 This definition does not apply to those asynchronous motors of which the torque continually decreases with increase in speed. 2 This valueapplies to the usual mean torque characteristic which excludes transient effects.
3.16, Breakdown Torque (of an ac Motor)
3.19 Coolant
A medium (liquid or gas) by means of which heat is transferred.
3.20 Primary Coolant
A medium (liquid or gas) which, by being at a lower temperature than a part of the machine and in contact with it, removes heat from that part.
3.21 Secondary Coolant
A medium (liquid or gas) which, by being at a lower temperature than the primary coolant, removes the heat given up by this primary coolant by means of a heat exchanger.
3.22 Direct Cooled (Inner Cooled) Winding A winding in which the coolant flows through hollow conductors, tubes or channels which form an integral part of the winding inside the main insulation. 3.23 Indirect Cooled Winding
A winding cooled by any other method than that of 3.22.
NOTE— In all cases when ‘indirect’ or ‘direct’ is not stated, an indirect cooled winding is implied.
3.24 Supplementary Insulation
An independent insulation applied in addition to the basic insulation in order to ensure protection against electric shock in the event of faihtre of the basic insulation.
3.25 Moment of Inertia
The (dynamic) moment of inertia of a body about an axis is the sum (integral) of the products of its mass element and the square of their distances (radii) from the axis.
The maximum torque which the motor develops with
NOTE — This quantity is designated by the letter symbol J and rated voltage and frequency applied at operating is exrmased in K~m2
temperature without an abrupt drop in speed. .
NOTES 3.26 Thermal Equivalent Time Constant
1The definition does not apply to those asynchronous motors The thermal equivalent time constant is the time of which the torque continually decreases with increase in speed.
2 This valueapplies to the usual mean torque characteristic constant replacing several individual time constants, which excludes transienteffects. which determines approximately the temperature 3.17 Pull-out Torque (of a Synchronous Motor)
course in a winding after step-wise current change. 3.27 Encapsulated Winding
The maximum torque which the synchronous motor
develops at operating temperature and at synchronous A winding which is completely enclosed or sealed by speed with rated voltage, frequency and field current. moulded insulation.
3.28 Routine Tests
Tests carried out on each machine to check the essential requirements which are likely to vary during production.
3.29 Type Tests
Tests carried out to prove conformity with the requirements of this standard. These are intended to prove the general quality and design of a given type of machine.
4 OPERATING CONDITIONS
4.1 Altitude, Temperature and Coolant
Machines shall be designed for the following operating site conditions, unless other conditions are specified by the purchaser.
4.1.1 Altitude
Height above sea level not exceeding 1000 m. For machines intended for operation on a site where the altitude is in excess of 1000 m (see 6.3 of IS 12802).
4.1.2 Ambient Temperature and Temperature of the Coolant
4.1.2.1 Maximum ambient and coolant temperature
The temperature of the air at operating site (which may be the primary or the secondary coolant, depending on the ventilation system of the machine) is subject to seasonal variation, but does not exceed 40°C. For machines intended for operation on a site where the coolant temperature is low, by reason of high altitude, see 6.3 of IS 12802.
Machines intended for operation with a maximum ambient temperature other than 40°C are covered by 5.3 of IS 12802.
For machines having water-cooled heat exchangers, the temperature of the water at the intake to the heat exchangers shall not exceed 25°C (see 6.1.4 of IS 12802).
4.1.2.2 Minimum ambient and coolant temperatures
The minimum temperature of the air at the operating site (which may be the primary or the secondary coolant, depending on the ventilation system of the machine) is–15°C, the machine being installed and in operation or at rest and de-energized.
This applies to all machines except the following: a) ac machines with rated outputs exceeding
3300 kW (or lcVA) per 1000 r/rein, machines with rated outputs less than 600 W (or VA) and all machines having a commutator or sleeve
b)
bearings. For these machines the minimum ambient temperature is +5”C; and
Machines having water as a primary or secon-dary coolant. The minimum ~emperature of the water and the ambient air is +5”C.
NOTE — If temperatures below those given in this standard are to be expected the manufacturer should be informed of the minimum ambient temperature and it should be specified whether this applies only during transport and storage or also after installation. Temperatures below those given shall be the subject of an agreement between the manufacturer and the purchaser.
4.1.2.3 Characteristics of gas used as coolant in hydrogen-cooled machines.
Hydrogen-cooled machines shall be capable of operating at a rated output underrated conditions with a coolant containing not less than 95 percent hydrogen by vohtme.
NOTE — For safety reason, the hydrogen content should at all times be maintained at 90 percent or more, it being assumed that the other gas in the mixture is air.
For calculating efficiency in accordance with IS 4889 from tests (excluding machines for traction vehicles), the standard composition of the gaseous mixture shall be 98 percent hydrogen and 2 percent air by volume, at the specified values of pressure and re-cooled temperature, unless otherwise agreed between the manufacturer and the purchaser. Windage losses shall be calculated at the corresponding density.
4.2 Electrical Conditions 4.2.1 Electrical Supply
ac machines within the scope of this standard shall be suitable for three-phase 50 Hz, with voltage derived from the nominal voltages given in IS 12360. In deriving rated voltages for machines, it is necessary to take into consideration the differences between distribution and utilization system voltages.
NOTE — For large high-voltage ac generators, the voltage may be selected for optimum performance.
4.2.2 Form and Symmetry of Voltage and Currents
Machines shall be so designed as to be capable of operating under the conditions detailed in 4.2.2.1, 4.2.2.2 as appropriate (see also 4.2.2.3).
4.2.2.1 In the case of an ac motor, the supply voltage is assumed to be virtually sinusoidal as defined in item (a) below. In the case of a polyphase motor, the supply voltages are also assumed to forma virtually balanced system as defined in item (b) below. Should the limits in items (a), and (b), occur simultaneously in service at the rated load, this shall not lead to any deleterious temperature in the motor and it is recommended that the excess resulting temperature rise or temperature related to the limits specified in 13.2 should be not more than 10°C.
a)
b)
The voltage is considered to be virtually sinusoidal. If, when supplying an ac motor at rated load, the waveform is such that the dif-ference between the instantaneous value and the instantaneous value of the fundamental component does not exceed 5 percent of the amplitude of the latter;
In temperature-rise testing, as specified in IS 12802 such amplitude difference shall not exceed 2.5 percent.
A polyphase voltage system is deemed to form a virtually balanced system of voltages if the negative sequence component does not exceed 1 percent of the positive-sequence component of the system of voltages over a long period, or 1.5 percent for a short period not exceeding a few minutes, and if the voltage of the zero-sequence component does not exceed 1 percent of positive-sequence component.
NOTE — Motors shall be able to operate with a negative sequence component of voltage of 2 percen~ but this may involve very severe conditions which could affect the life of motors.
In temperature-rise testing as, specified in IS 12802, negative-sequence component shall be less than 0.5 percent of the positive sequence component of the system of voltages, the influence of zero-sequence system being eliminated. By agreement between manufacturer and purchaser, the negative-sequence component of the system of currents maybe measured instead of the negative-sequence component of the voltages, and this shall not exceed 2.5 percent of the positive-sequence component of the system of currents.
NOTE — In the vicinity of large single-phase loads (for example, induction furnaces), and in rural areas particularly on mixed industrial and domestic systems, supplies may be distorted beyond the limits set out above. Special arrangements will then be necessary between the manufacturer and purchaser.
4.2.2.2 In the case of an ac generator, the circuit which it supplies is assumed to be virtually non-deforming and virtually balanced as defined in items (a) and (b) below. Should the limits defined in items (a) and (b) occur simultaneously in service at the rated load, this shall not lead to any deleterious temperature in the generator and it is recommended that the excess resulting temperature rise of temperature related to the limits specified in Table 1, Table 2 and Table 3 of IS 12802 should be not more than 10”C.
a) A circuit is considered to be virtually non-deforttiing if, when supplied by a sinusoidal, that is to say, none of the instantaneous values differ from the instantaneous value of the same phase of the fundamental wave by more than 5 percent of the amplitude of the latter.
b) A polyphase circuit is considered to be vir-tually balanced if, when supplied by a balanced system of voltage, the system of currents is virtually balanced, that is to say, neither the negative-sequence component nor the zero-sequence component exceeds 5 percent of the positive sequence component.
4.2.2.3 In the case of a dc motor supplied from a static power converter, the pulsating voltage and current affect the performance of the machine. Losses and temperature rise will increase and the communication is more difficult compared with a dc motor supplied from a pure dc power source.
Thus it is necessary for motors intended for static converter supply to be designed to operate under these conditions and it is often necessary to provide a dc motor with an external inductance for reducing the pulsation.
In order to obtain a proper combination of dc motor and static power converter, the motor manufacturer should be consulted.
4.3 Voltage and Frequency Variation During Operation
4.3.1 Generators complying with these requirements shall be capable of suppl ying their rated output at rated speed (and at rated power factor where separately controllable) at a voltage that may vary between 95 percent and 105 percent of their rated voltage. 4.3.2 Motors complying with these requirements shall be capable of providing their rated output with:
a) The terminal voltage differing from its rated value by not more than * 6 percent, or b) The frequency differing from its rated value by
not more than i 3 percent, or c) Any combination of (a) and (b).
In the case of continuous operation at the extreme voltage limits specified above, the temperature-rise limits stated in Table 1 and Table 2 of IS 12802 shall not exceed by more than:
a) 10°C for machines of outputs up to and including 1000 kW (or kVA), and
b) 5° C for machines of outputs exceeding 1000 kW ( or kVA).
Motors, when operated at the extreme conditions of voltage and frequency variation, may not necessarily have their performance specified in the relevant standard.
NOTE — Machines should not be operated in service at loads in excess of their rated load or under conditions differing from the rated conditions unless it is known that they are suitable for such use. / ,’ ,,... . . 4
Table 1 Weighting Factors
(Clauses 4.2.2.2 and 9.1,2)
Frequency Weighting Frequency Weighting
Hz Factor Hz Factor (1) 16.66 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 950 1000 1050 1100 1150 1200 1250 1300 1350 1400 1450 1500 1550 1600 1650 1700 1750 .1800 1850 1900 1950 2000 (2) (3) 0.00000117 2050 0.0000444 2100 0.00112 0.00665 0.0223 0.0556 0.111 0.165 0.242 0.327 0.414 0.505 0.585 0.691 0.790 0.895 1.000 1.10 1.21 1.32 1.40 1.46 1.47 1.49 1.50 1.53 1.55 1.57 1.58 1.60 1.61 1.63 1.65 1.66 1.68 1.70 i.71 1.72 1.74 1.75 1.77 2150 2200 2250 2300 2350 2400 — 2450 2500 2550 2600 2650 2700 2750 2800 2850 2900 2950 3000 3100 3200 33tXl 3400 3500 3600 37Mt 3800 3900 4000 4100 4200 4300 4400 4500 4600 4700 4800 4900 (4) 1.79 1.81 1.82 1.84 1.86 1.87 1.89 1.90 — 1.91 1.93 1.93 1.94 1.95 1.96 1.96 1.97 1.97 1.97 1.97 1.97 1.94 1.89 1.83 1.75 1.65 1.51 1.35 1.19 1.04 0.890 0.740 0.610 0.4% 0.396 0.316 0.232 0.199 0.138 0.125 5000 0.100
Table 2 Cross-Sectional Areas of Earth Conductor
(Clauses 4.2.2.2 and 12.1.6)
Cross-SectionalArea of t%ss-Seetional Area of the the Live Condrretor Earth of Protective
mm2 rnrr? (1) (2) 4 4 6 6 10 10 16 16 25 25 35 25 50 25 70 35 95 50 120 70 150 70 185 95 240 120 300 150 4txl 185
4.4 Machine Neutral Earthing
4.4.1 ac machine shall be suitable for continuous operation with the neutral at or near earth potential. They shall also be suitable for operation on unearthed systems with one line at earth potential for infrequent periods of short duration; for example, as required for normal fault clearance. If it is intended to run the machine continuously or for prolonged periods in this condition, a machine with a level of insulation suitable for this condition will be required and the condition shall be defined in operating instructions.
If the windings do not have the same insulation at the line and the neutral ends, this shall be defined in operating instructions.
NOTE — The earthhrg of interconnection of machine neutral points should not be undertaken without consulting the machine manufacturers because of the danger of zero-sequence components of currents of all frequencies under some operating conditions and the possible mechanical damage to the winding due to line-to-neutral fault conditions.
5 TYPES OF ENCLOSURES
Machines covered by this standard shall have one of the degree of protection as given in IS 4691.
6 METHOD OF COOLING
The methods of cooling of rotating electrical machines and their designations shall be in accordance with IS 6362.
7 ASSIGNMENT OF RATINGS
7.1 The ratings assignment to the electrical machines shall take into account the class and type of duty covered in IS 12824 and as marked on the rating plate (see 3.1).
7.2 Preferred Voltages
For the purpose of this standard, the preferred voltage shall be in accordance with IS 12360.
7.2.1 The voltages preferred for three-phase 50 Hz machines are 415 V, 3.3 kV, 6.6 kV, and 11 kV.
NOTES
1 The voltages above 11 kV are subjeet to mutual agreement between the manufacturer and the user.
2 The coordination of voltage and output ratings of ac machines is given in10.1.
7.3 Frequency and Number of Phases
For ac machines the frequency shall be the standard frequency of 50 Hz.
7.3.1 The standard number of phases for ac machines shall be three.
7.4 Preferred Rated Output
The rated output of the various types of rotating electrical machines should be assigned in accordance with IS 12824.
5
I /
Table 3 Overspeed
(Clauses 4.2.2.2 and 17.1)
Item Machine Type No.
(1) (2)
1 ac machines: —All machines except
@
b)
c)
those specifiedbeiow: Water-turbine driven genera tors, any auxiliary machines connected directly (electrically or mechanically) to the main machine Machines which may under certain circumstances be driven by the load Series and universal motors 2 dc machines: O b) c) d) Shunt-wound and separately excited motors Compound-wound motors having speed regulation of 35 percent or less
Compound-wound motors, having speed regulation greater than 35 percent and series-wound motors Permanent-magnet excited motors -e) Generators OverSpeedRequirements (3)
1.2 times the maximum rated speed
Unless otherwise specified, the runaway speed of the set but not less than 1.2 times the maximum rated speed
The specified runaway speed of the set but not less than 1.2 times the maximum rated speed
1.1 times the no-load streed at rated voltage. For motors integrally attached to loads that cannot become accidentally disconnected, the term no-load speed shall be interpreted to mean the lightest load condition possible with the load
1.2 times the highest rated speed or 1.15 times the corresponding no-load speed, whichever is greater
1.2 times the highest rated speed or 1.15 times the corresponding no-load speed, whichever is greater but not exceeding 1.5 times the highest rated speed As per mutual agreement between the manufacturer and purchaser
Overspeeds as spmitied in item 2(a), unless the motor has a series winding and, in such a case, they shall withstand the overspeeds specified in item 2(b) or 2(c) as appropriate
1.2 times the rated soeed 7.4.1 Preferred Outputs of Motors
The preferred output ratings for dc motors and ac induction motors up to and including 110 kW are:
kW kW kW 0.06 1.1 18.5 0.09 1.5 22 0.12 2.2 30 0.18 3.7 37 0.25 5.5 45 0.37 7.5 55 0.55 11 75 0.75 15 90 110
7.4.2 The output ratings above 110 kW shall follow the R20 series covered in IS 1076.
7.5 Machines with More Than One Rating 7.5.1 Ratings for Multi-speed Motors
For multi-speed motors, a definite rating shall be assigned for each speed.
7.5.2 Rating for Machines with Varying Quantities
When a rated quantity (output, voltage, speed, etc) may assume several values or vary continuously within two limits, the values shall be stated at these limits. This provision does not apply to voltage variation of N percent or to star-delta connections intended for starting.
8 MACHINES FOR NON-STANDARD
VOLTAGES, FREQUENCY AND NUMBER OF PHASES
Machines within the scope of this standard for use on systems complying voltages, frequencies and phases other thun standard shall be considered as complying with this standard provided they comply with this standard in all other respects. The voltages, frequency and number of phases for which they are designed shall be stated on the rating-plate.
9 IRREGULARITIES OF WAVEFORM
9.1 The requirements of this clause apply only to synchronous machines of 300 kW or (kVA) or above, intended for connection to power networks operating at rated frequencies of 16 2/3 Hz 100 Hz inclusive, with a view to minimizing interference between power’ lines and adjacent circuits.
9.1.1 Requirements
When tested on open circuit and at rated speed and voltage, the telephone harmonic factor (THF) of the line-to-line terminal voltage as measured according to 9.1.2 shall not exceed the following value:
Rated Output THF, percent 300 kW (or kVA) e P S 1000 kW (or kVA) 5 1f)CtOkW(orkVA)<PS5000 kW (or kVA) 3
5000 kW (or kVA) < P 1.5
NOTES
1Limiting values of individual harmonics are not specified as it is considered that machines which meet the above requirements shall be operationally satisfactory,
2 Where the synchronous machine is to be connected to the system in an unusual manner (for example, where the star point of machine is connected to earth and the machine is not linked to the system via a transformer), the waveform requirements should be agreed between the manufacturer and the purchaser.
..
9.1.2 Tests conformity with 9.1.1, shall be verified by type tests on ac generators. The range of frequencies measured shall cover all harmonics from rated frequency up to 5000 Hz. Either the THF may be measured directly by means of a meter and associated network specially designed for the purpose or each individual harmonic shall be measured and from the measured values the THF shall be computed using the following formula:
THF (percent)= 100
7{ E12klz+ Ez2~z2+Es 2ks2+ ...+E.2 kf12 where
En = rms value of nth harmonic line-to-line terminal voltage,
U = rms value of line-to-line terminal voltage of machine, and
An = weighting factor for frequency corresponding to nth harmonic.
Numerical values of the weighting factor for different frequencies shall be obtained from Table 1. The curve in Fig. 1 may be used as an aid to interpolation.
2.0 1.8 1.6 1.4 m o g 1.2 if * 1.0 ~ + x 008 g ; 1.6 0.4 0.2 0 0 FREQUENCY Iiz
FIG. 1 WEIGHING CURVE
10 CO-ORDINATION OF VOLTAGES AND
OUTPUTS
In the case of ac machines, the rated output should be greater than the limits given below in terms of the rated voltage:
Rated Voltage (UtJ Minimum Rated Output
kV kW or kVA
2< U. <3.3 100
3.3< u. <6.6 200
6.6<U. <11 1000
11 DUTY AND RATING The type of duty and class electrical machine shall be IS 12824.
of rating of rotating in accordance with
12 CONSTRUCTIONAL REQUIREMENTS
12.1 Earth Terminali
Machines shall be provided with means for connecting a protective conductor or an earth conductor, such means being identified by the appropriate symbol or legend. This requirement does not apply to machines with supplementary insulation, to machines with rated voltages up to 42 V, or to machines for assembling in supplementary insulation.
12.1.1 In the case of machines having rated voltages above 42 V, but not exceeding 1000 V ac or 1500 V dc, the terminal for the earth conductor shall be situated in the vicinity of the terminals for the line conductors, being placed in “the terminal box if provided. Machines having rated outputs in excess of 100 kW shall have, in addition, an earth terminal fitted on the frame.
12.1.2 Machines for rated voltages higher than 1000 V ac or 1500 V dc, shall have an earth terminal on the frame, for example, an iron strap and in addition a means inside the terminal box for connecting cable armour, if any.
12.1.3 The earth terminal shall be designed to ensure a good connection with the earth conductor without any damage to the conductor or terminal. Accessible conducting parts which are not part of the operating circuit shall have a good electrically conducting connection with each other and with the earth terminal. The shaft need not be electrically connected to the earth terminal unless the bearings are insulated and the accessible parts of the shaft and of these insulated bearings can be subjected to dangerous contact voltages under fault conditions.
12.1.4 When an earth terminal is provided in the terminal box, it shall be assumed that the earth conductor is made of the same metal as the live conductors.
12.1.5 When an earth terminal is provided on the frame, the earth conductor may, by agreement, be made of another metal (that is, steel). In this case, in designing the terminal, proper consideration shall be given to the conductivity of the conductor.
12.1.6 The earth terminal shall be designed to accommodate an earth conductor of crosssectional area in accordance with the Table 2. If an earth conductor larger than the size given in the Table 2 is used, it is recommended that it should correspond as nearly as possible to one of the other sizes listed.
“
,$ ,.$, ,-. : . . 712.1.7 For other cross-sectional areas of the live conductors, the earth protective conductor shall have cross-sectional areas at least equivalent to:
a) that of the live conductor for cross-sectional areas less than 25 mm2,
b) 25 mm2forcross-sectional areas between25 mm2 and 50 mm2,
c) 50 percent of that of the live conductor for cross-sectional areas exceeding 50 mm2, and d) the earth terminal shall be identified by
symbol_!_. =
12.2 Mounting Arrangements
The designation for types of construction and mounting arrangements shall be in accordance with IS 2253.
12.3 Shaft Extension Key
When the machine shaft extension is provided with keyway, it should be provided with a full key of normal shape and length.
NOTE — The use of shaft extension key for the purpose of vibration measurement is covered in IS 12075.
13 TEMPERATURE-RISE
13.1 The determination of temperature-rise of rotating electrical machine delivering rated output under the rated condition of voltage, frequency and power factor shall be in accordance with IS 12802. 13.2 The limits of temperature-rise applicable to rotating electrical machines shall be in accordance with Table 1 to Table 3 of IS 12802.
14 OCCASIONAL EXCESS CURRENT FOR ROTATING MACHINES
The excess current capability of machines is given for the purpose of co-ordinating these machines with control and protective devices. Tests to demonstrate these capabilities are not a requirement of this standard.
The heating effect in the machine windings varies approximately as the product of the time and the square of current. A current in excess of the rated current will result in increased temperattrte. Unless otherwise agreed between the manufacturer and the purchaser, it can be assumed that the machine will not be operated at the excess currents specified for more than a few short periods during the lifetime of the machine.
When an ac machine is to be used both as generator and a motor, the excess current capability should be the subject of agreement between the manufacturer and the purchaser,
14.1 Occasional Excess Current for ac Generators ac generators having rated outputs not exceeding 1200 MVA shall be capable of withstanding a current equal to 1.5 times the rated current for not less than 30s. 14.1.1 ac generators having rated outputs above 1200 MVA shall be capable of withstanding a current equal to 1.5 times the rated current for a period which shall be agreed between the manufacturer and the purchaser, but this period shall not be less than 15s. 14.2 Occasional Excess Current for dc Machines and ac Motors (Except Commutator Motors) Three-phase ac motors having outputs not exceeding 315 kW and rated voltage not exceeding 1 kV shall be capable of withstanding a current equal to 1.5 times the rated current for not less than 2 min.
NOTE — Forthree-phasemotors havingrated outputs above 315 kW and all single-phasemotors, no occasional excess currentis specified.
14.3 Occasional Excess Current for dc Machines and ac Commutator Motors
dc motors and generators and ac commutator motors shall be capable of withstanding at the highest full-field speed (rated speed of a generator) and corresponding armature voltage. Acurrent equal to 1.5 times the rated current for not less than 1 min. 14.3.1 For large machines, a shorter time may be agreed between the manufacturer and the purchaser but this shall be not less than 30s.
15 MOMENTARY EXCESS TORQUE FOR MOTORS
15.1 Polyphase Induction Motors and dc Motors (Excluding Motors in 15.2)
The motors shall, whatever their duty and construction, be capable of withstanding for 15 s, without stalling or abrupt change in speed (under gradual increase of torque), an excess torque, of 60 percent of their rated torque, the voltage and frequency (induction motors) being maintained at their rated values. For dc motors, the torque maybe expressed in terms of overload current.
15.1.1 Motors for duty Type S9 (see IS 12824) shall be capable of withstanding momentarily an excess torque determined according to the duty specified.
NOTE — For an approximate determination of the change of temperature due to the course of the current-related losses, thermal equivalent time constant, determined according to IS 12S02 maybe used. In addition in the case of commutator machine, attention, should be given to the limits of commutation capability.
15.2 Induction Motors for Specific Applications For motors intended for specific application which require high torque (for example, for hoisting), excess
torque shall be the subject of agreement between the manufacturer and the purchaser.
15.2.1 For cage-type induction motors specially designed to ensure a starting current less than 4.5 times the rated current, the excess torque can be below the figure of 60 percent given in 15.1, but not less than 50 percent.
15.2.2 In the case of special types of induction motor with special inherent starting properties, for example motors intended for use at variable frequency, the value of the excess torque shall be the subject of agreement between the manufacturer and the purchaser.
15.3 Polyphase Synchronous Motors
15.3.1 Unless otherwise agreed, a polyphase synchronous motor irrespective of the duty, shall be capable of withstanding an excess torque as specified below for 15s without falling out of synchronism, the excitation being maintained at the value corresponding to rated load. When brushless excitation is used, the limits of torque shall be the same value with the excitation equipment operating under normal conditions:
Synchronous (wound rotor) 35 percent excess induction motors torque
Synchronous (cylindrical rotor) 35 percent excess
motors torque
Synchronous (salient pole) 50 percent excess
motors torque
15.4 Other Motors
The momentary excess torque for single-phase, commutator and other motors shall be the subject of agreement between the manufacturer and the purchaser.
16 PULL-UP TORQUE
16.0 Unless otherwise specified, the pull-up torque of cage induction motors under full voltage shall be at least equal to the following values.
16.1 Sbgle Speed Three-Phase Motors
a) For output less than 100 kW: 0.5 times the rated torque, and 0.5 times the locked rotor torque.
17 OVERSPEED
17.1 Machines shall be designed to withstand the speeds specified in Table 3.
17.1.1 An overspeed test is not normally considered necessary but can be performed when this is specified and has been agreed to between the manufacturer and the purchaser (For turbine-type ac generators see
also IS 5422).
17.1.2 An overspeed test shall be considered as satisfactory if no permanent abnormal deformation is apparent subsequently, and no other deficiency is detected which would prevent the machine from operating normally, and provided the rotor windings after the test comply with the required dielectric tests. The duration of any overspeed test shall be 2 min. 17.1.3 Due to settling of laminated rotor rims, laminated poles held by wedges or by bolts, etc, a minute permanent increase in the diameter is natural, and is not to be considered as an abnormal deformation indicating that the machine is not suitable for normal operation.
17.2 During commissioning of a hydraulic turbine driven synchronous generator, the machine shall be driven at the speed it can reach with the overspeed protection operating, so as to ascertain that the balance quality is satisfactory up to that speed.
18 UNBALANCED CURRENTS OF
SYNCHRONOUS MACHINES
18.1 Unless otherwise specified, three-phase synchronous machines shall be capable of operating continuously on an unbalanced system such that, with none of the phase currents exceeding the rated current, the ratio of the negative sequence component of current (12)to the rated current(L) does not exceed the values in Table 4 and under fault conditions, shall be capable of operating with the product of (12/ln)2 and time in second (t) not exceeding the value in Table 4.
19 SHORT-CIRCUIT CURRENT
19.1 Unless otherwise specified, the peak value of the short-circuit current for synchronous machines, and turbine-type machines not covered by IS 5422. In case of short-circuit of all phases during operation at rated voltages, shall not exceed 15 times the peak value or 21 times therms value of the rated current.
b) For output equal to or greater than 100 kW: 19.1.1 For three-phase turbine-type machines, see 0.3 times the rated torque, and IS 5422.
0.5 times the locked rotor torque.
19.1.2 The check may be carried out by calculation or 16.2 Multi-Speed Three-Phase Motors by means of a test at a voltage of 50 percent of the rated 0.3 times the rated torque. voltage or above.
8
Table 4 Unbalanced Operating Conditions for Synchronous Machines
(Clause 18.1)
Item Machine Type Maxtmum (12/1.)Maximum (lz/1n)2t
No. for Continuous for Oswatfon
Operation
(1) (2) (3)
1 Salient pole machines Indirectly cooled:
motors 0.1
generators 0.08
synchronous condensers 0.1 2 Directly cooled (innercooled) stator
and/or field
motors 0.08
generators 0.05
synchronous condensers 0.08 cylindrical rotor synchronous
machines
3 Indirectly cooled rotoc
air-cooled 0.1
hydrogen-cooled
0.1
4 Directly cooled (innercooled) rotor
<350MVA 0.08
>350 <900 MVA see Note 1 >900<1250MVA see Note 1 >1250< 1600 MVA 0.05 NOTES Und& Fault Conditions (4) 20 20 20 15 15 15 15 10 8 see Note 2 5 5
1 Forthesemachines,the@ue of12/1.k calculatedasfollows:
[1
s“ -35012/1. = 0.08- —
3 x
104
2For these mach:nes, the ~alue of (12/1,,)is calculated as follows:
(12/[.)2[= (84.005 45) (S. - 350) Where
S,,is the ratedapparentpowerin MVA
20 SHORT-CIRCUIT WITHSTAND AND EXCITATION OF SYNCHRONOUS MACHINES 20.1 Short-Circuit Withstand Test for Synchronous Machines
The three-phase short-circuit test for synchronous machines shall be carried out only at the request of the purchaser. In this case, the test shall be carried out on the machine running on no load with an excitation corresponding to the rated voltage unless otherwise agreed. The test shall not be cat-tied out with an excitation greater than that corresponding to
1.05 times the rated voltage at no load.
20.1.1 The test excitation, as determined, may be reduced by agreement between the manufacturer and the purchaser, in order to take into account the impedance of the transformer which may be placed between the machines and the system. In this latter case, it may also be agreed that the test be made on the operating site with the over-excitation device in operation. The short-circuit shall be maintained for 3 s.
20.1.2 The test is considered satisfactory if no harmful deformation occurs and if the requirements of the applied voltage dielectric test (see 30 and Table 6) are met after the short-circuit test. For three-phase turbine-type-machines (see IS 5422).
20.2 Excitation
20.2.1 Generator Reserve Excitation
When running at the rated operating temperature and at rated speed, generators shall be capable of developing for a short time their rated voltage and a current eqtrat to 125 percent of the rated current (at rated power factor for ac generators). For separately excited or self excited machines, the field winding shall be designed accordingly. For machines with direct coupled exciter, the exciter shall be capable of supplying the required excitation voltage.
NOTES
1 The operating conditions stated above are only intended to
ascertain that the reserve excitation is sufficient and are not associated with any temperature-rise condhion. However, if the test is carried out after a temperature-rise test, it is recommended that its duration be limited in order to prevent winding temperatures from exceeding the limits of temperature resulting from the values specified in Tables 1 to 3 of IS 12802. 2 The above requirement shall not apply to compound generators without any voltage regulation system.
3 If the operating temperatureof field winding is not known, it shatl be considered to be 75°C for windkrg of Classes A, E and B and 115°C for Classes F and H.
The ceiling voltage shall not be less than 1.4 times the rated excitation voltage for a minimum of 10s. 20.2.2 Ceiling Voltage (Up)
The ceiling voltage of the excitation system of non-compounded synchronous condensers is the maximum voltage at which the excitation system is capable of operation, with field windings of the machine at their operating temperature.
20.2.3 Initial Excitation System Response
The initial excitation system response is the initial rate of increase in the excitation voltage expressed by its relative value in relation to the excitation voltage for the rated conditions of the main machine, the temperature being the ceiling voltage to be attained in the shortest possible time.
The conventional expression of the initial exciatioti system response is:
up – Ufn=—P–1 Ufn
x tt
tt
whereUfn = Excitation voltage for the rated conditions of the main machine;
up = Excitation ceiling voltage;
“
P = Q; ~n~
Uflr
tl = The time required for the excitation voltage U. to increase from Ufn to ( Ufn + 0.632 (UP - Ufn)).
The reciprocal of the initial excitation system response shall be less than 2s.
NOTE — If the operatingtemperatureof field windingis not known,it shallbeconsideredto be 75°Cforwindingsof Classes A, E and B and 115°Cfor ClassesF and H.
20.2.4 Excitation Response Ratio
The excitation response ratio is the initial excitation system response (see 20.2.3) as calculated by replacing the actual change in voltage by a linear variation leading to the same mean value as measured during the first half second unless otherwise agreed. In the case of a measurement made during the first halfsecond, the excitation response ratio will be expressed by:
41Ufn (0.5)– Ufn
1
Ufn
Where
Ufn = Excitation voltage for the rated condition of the main machine; and Ufn (0.5)= Mean value of the excitation voltage
during the first half-second. 21 LIMITS OF VIBRATION SEVERITY
Unless otherwise specified, the limits of vibration severity for the machine shall be within the limits specified in IS 12075.
22 COMMUTATION
Commutation of dc machines and ac Commutator Motor (Excluding those of the Brush Shifting Type)
The machine shall work with brush fixed setting from no load to the momentary overload specified in 14 and 15 without injurious sparking or injury to the commutator or brushes.
Annex B gives the details of the grades of sparking that may be used in specifying the degree of sparking. 23 EFFICIENCY
If a statement of efficiency is required, the purchaser shall specify at the time of enquiry the load and in the case of ac generators and synchronous motors, the power factor to which the statement shall apply. The method of arriving at the efficiency shall be as set out in IS 4889. Tolerances are specified in Table 5.
24 POWER FACTOR
If a statement of power factor is required for an induction motor the purchaser shall specify at the time of enquiry the loads on which the statement is to be based. Tolerances are given in Table 5.
25 TOLERANCES
Unless otherwise specified, tolerances shall be in accordance with Table 5. Where a tolerance is stated in only one direction the tolerance in thi other direction is considered unimportant.
26 TERMINAL MARKINGS
Terminal markings, when used, shall be in accordance with IS 4728.
27 RATING PLATES
27.1 Every electrical machine shall be provided with a rating plate (or rating plates), containing the following appropriate information which shall be easily legible and durable. This complete information need not be on the same plate. As far as possible, the rating plate(s) shall be fixed to the frame of the machine and, unless otherwise specified, located in such a way as to be easily legible in the position of use as determined by the type of construction of the machine. a) b) c) d) e) 0 g) h) j) k) m) n) P) q) r)
Reference to this Indian Standard, that is, IS 4722;
The manufacturer’s name;
The manufacturer’s serial number of identification mark and year of manufacture; Frame reference in accordance with IS 1231, if applicable;
Type of machine, a motor or generator, shunt, series, compound, cage, etc;
The class of rating or the duty type according to IS 12824;
The rated voltage;
The rated output in kW or kVA; The rated curren~
Type of current(dc or at);
Rated speed or speed range in revolutions per minute;
The class of insulation or the permissible temperature-rise;
For hydrogen-cooled machines, the hydrogen pressure at rated output
The maximum ambient temperature if the machine is designed for a maximum ambient temperature other than 40°C, or the maximum water temperature if the machine is designed for a maximum water temperature other than 25°C;
The altitude, if the machine is designed to be used at altitude exceeding 1000 m;
(
“‘4 ...” ...
.
Table 5 Schedule of Tolerance (Clauses 23,24 and 25) S1No. Item (1) (2) 1 Efficiency a) By summation of losses: Machines up to 50 kW Machines above 50 kW b) By input-output test
2 Total losses (see Note 1) applicable to machines above 50 kW
3 Power factor for induction machines
4 a) Speed of dc shunt and separate excitation motors (at full load and at working temperature)
b) Speedof dc seriesmotors (at full loadand at working temperature)
c) Speed of dc compound excitation motors (at full load and at working temperature)
5 a) Slip of induction motors (at full load and at working temperature): 1) machines having output 1 kW(or kVA) or more
2) machines having output less than 1 kW (or kVA)
b) Speed of ac motors with shunt characteristics (at full load and at working temperature)
6 inherent voltage regulation of dc generators, shut or separately excited at any point on the characteristic
7 Inherent voltage regulation of generatcxswith compoundexcitation (at the rated powerfactorin the case of alternating current)
8 Locked rotor current of cage induction motors with short-circuited rotor and with any specified starting apparatus
9 Peak values of short-circuit of ac generator under specified conditions 10 Steady short-circuit current of an ac generator under specified conditions
11 Variation of speed of dc shunt-wound and compound wound motors (from no-load to full load)
12 Locked rotor torque of induction motors
13 Pull-up torque of induction motors 14 Pull-out torque of induction motors
15 Moment of inertia
16 Locked rotor torqueforsynchronous motors 17 Pull-out torque for synchronous motors
18 Locked rotor currentfor synchronousmotors 19Voltage balance test at no load
Tolerance (3)
-15percentof(l -q) -lOpercentof(l -q) -15 percent of (1 - q) + 10percent of the total losses
-1/6 of (1 - cos $ ) :kfin0.02
:Max0.07
f 15 percenL if (kW/l CN30rev/rein)< 0.67 + 10 percent, if [0.67 < (kW/l 000 rev/rein)< 2.51 + 7.5 percent, if [2.5s (kW/ 1000 rev/rein)< 10] + 5.o pement, if (kW/100 rev/rein) ~ 10
&20 percent, if (kW/l COOrev/rein)< 0.67 f 15 percent, if [0.67s (kW/l 000 revlmin) <2.51 + 10 percent, if [2.5 S (kW/ 1000 rev/rein)< 101 f 7,5 percent, if (kW/100 rev/rein) 210
Tolerances as per item 4 (b) unless otherwise agreed between the manufacturerand the purchaser.
i 20 percent of the guaranteed slip i 30 percent of the guaranteed slip On the highest speed:
-3 percent of the synchronous speed On the lowest speed:
+ 3 percent of the synchronous speed
f 20 percent of the guaranteed regulation at that point
f 20 percent of the guaranteed regulation, with a minimum of +3 percent of the rated voltage (TMs tolerance appfies to the maximum deviation
at any load between the observed voltage at that load and a stmightline drawn between the points of guaranteed no-load and full-load voltage) +20 percent of the guaranteed current (no lower limit)
* 30 percent of the guaranteed value * 15 percent of guaranteed value
.+20 percent of the guaranteed variation with a minimum of i 2 percent of the rated speed -15 percent +25 percent of the guaranteed torque (+25 percent may be exceeded by agreement) +15 percent of the guaranteed torque
-10 percent of the guaranteed torque except that after allowing for this tolerance, the torque shall be not les rJran 1.6or 1.5tis the rated torque (see 15) t 10 percent of the guaranteed value
-15 percent +25 percent of the guaranteed value (+25 percent may be exceded by agreement) –10 percent of the guaranteed value except that after allowing for this tolerance, the torque shall be not less than 1.35or 1.5timesthe rated torque (see 14) +20 percent of the guranteed value (no lower limit) +1%
“
s)
t)
The mass of the machine shall be indicated, if greater than 30kg when this indication is of interest; and
Additional information required, if any see 27.2.
NOTE —The above items are numbered for convenient referencebut the order in wh]chthey appearon the ratingplate is not standardized.
27.2 Additional Information on Rating Plate 27.2.1 dc Machines
The rating plate shall carry the following particulars in addition to &ose given in 27.2:
Rated field current and voltage, if separately excited. 27.2.2 ac Generators
The rating plate shall carry the following particulars in addition to those given in 27.1:
a) b) c)
d)
e)
Rated frequency in Hz and number of phases; Power factor;
Winding connectors designated by appropriate symbols in accordance with IS 4728;
Rated field (excitation) current and voltage at rated output; and
The permissible overspeed, if applicable (for example, turbine-type generators and hydraulic-turbine driven generators).
27.2.3 Synchronous Motor or Synchronous Induction Motor or Condensers
The rating plate shall carry the following information or rating plate, in addition to those given in 27.1:
a) b) c) d) e) f) g) h) j) 27.2.4
Rated frequency in Hz and number of phases; Winding connections designated by ap-propriate symbols in accordance with IS 4728; Rated input in kVA or MVA, in case of synchronous condensers;
Rated current in amperes or rated output (for motors) and input (for condensers)
Rated field (excitation) current and voltage at rated input for separately excited machines; Power factor;
For asynchronous motor intended to be started as an induction motor, standstill voltage be-tween the sliprings (or secondary terminals) in starting condition;
Secondary current for synchronous induction motOrs; and
Permissible overspeed, if applicable.
Irrduction Motor and ac Commutator Motor
The following information, in addition to 27.1, shall be given on the rating plate:
a) b)
Frequency in Hz;
Number of phases and winding connections
c)
designated by appropriate symbols in accord-ance with IS 4728; and
For wound-rotor (slipring) machines, open circuit rotor voltage and full load rotor current. 28 INFORMATION TO BE GIVEN WITH ENQUIRY AND ORDER
The details are given in Annex C. 29 TESTS
29.1 General
The tests specified in these clauses shall normally be carried out at manufacturer’s works.
29.2 Test Certificates
29.2.1 Unless otherwise specified when inviting tenders, the purchaser if so desired by the manufacturer, shall accept manufacturer’s certificate, as evidence of the compliance of the machine with the requirements of temperature-rise test (see IS 12802),
14 and 15 on a machine identical in essential details with the one purchased, together with routine tests on each individual machine. In the case when a batch of 20 or more similar machines is supplied on one order, type tests, as specified,.- shall be made on one of these machines, if the purchaser so requires.
29.2.2 Certificates of routine tests shall show that the machine purchased has been run and has been found to be electrically and mechanically sound and in working order in all particulars.
29.2.3 If so specified, at the time of enquiry, tests shall be carried out at the manufacturer’s works in the presence of the purchaser or his representative to ensure that the machine complies in every respect with the requirements given in this draft standard and agreed to earlier at the time of agreement.
29.2.4 Certificates of all type tests together with a record of any alterations, whether essential or not, which have been made to the machine since the type tests were carried out, shall be kept available by the manufacturer for inspection.
29.3 Classification of Tests
NOTE — Impulse tests on windings of rotating electrical machines are under consideration.
29.3.1 Induction Motors and Generators
29.3.1.1 Type tests
The following shall constitute the type tests:
A IS 4722:2001 a) b) c) d) e) f-) g) h) j) k)
Measurements of stator resistance and rotor resistance of slipring motors;
No load running of motor and reading of volt-age, current, power input and speed;
Open circuit voltage ration on slipring motors:
Reduced voltage running up test at no load (for squirrel cage motors only)
To check the ability of the motor to run up to full speed on no load, the value of reduced voltage in case of motors up to 37 kW shall be I/@of the rated line voltage in each direction of rotation of motors.
For motors above 37 kW, the value of reduced voltage shall be l/~ of rated line voltage of less but only in the specified direction of rotation of motov
Locked rotor readings of voltage, current, power input and torque of squirrel cage motors;
NOTE —This test may be made at a reduced voltage. Full load values of voltage, current, power input and slip;
Temperature-rise test; Momentary excess torque;
Insulation resistance test (both before and after the high Dielectric tests); and
Dielectric tests. 29.3.1.2 Routine tests
The following shall constitute the routine tests: a) b) c) d) e) f)
Insulation resistance tests (before Dielectric test only);
Dielectric test;
No load running of motor and reading of current in the three-phase and voltage; Locked-rotor readings of voltage, current power input at a suitable reduced voltage; Reduced voltage running up test at no load to check the ability of the motor to run up to full speed on no load in each direction of rotation with l/fi of the rated line voltage applied to the stator terminals (for squirrel cage motors only); and
Open circuit voltage ratio (for slipring motors only).
29.3.2 Synchronous Motors and Generators 29.3.2.1 ;ype tests
The following shall constitute the type tests: a) Measurement of winding resistance; b) Phase sequence test;
c) Regulation test (for generators only);
d) e) f) g) h) j) k) m) n) P) @ r) s) t)
Measurement of leakage reactance and potier reactance (for generators only);
Measurement of open-circuit characteristic (for generators only);
Measurement of short-circuit characteristic (for generators only);
Efficiency test; Temperature-rise test;
Occasional excess current test; Overspeed test
Insulation resistance test (both before and after Dielectric test);
Dielectric tes~
Starting current and torque test (for synchronous motors);
Determination of deviation of voltage wage-form from sinusoidal (for generators only); Measurement of bearing current for machines above 1000 kW;
Short-circuit withstand test and measurement of reactance and time constants (for generators above 1000 kW only); and
Pressure test on coolers for closed circuit cooling.
29.3.2.2 Routine tests
The following shall constitute the routine tests: a) b) c) d) e) f) @ h) j)
Measurement of winding resistance; Insulation resistance test;
Phase sequence test;
Regulation test (for generators only); Measurement of open-circuit characteristic (for generators only);
Measurement of short-circuit characteristic (for generators only)(see Note 1);
Dielectric test;
Measurement of bearing currents for machines above 1000 kW; and
Pressure test on coolers for closed-circuit cooling.
29.3.3 de Motors and Generators 29.3.3.1 Type tests
The following shall constitute the type tests: a)
b) c)
d)
Measurement of winding resistance; Measurement of insulation resistance; Determination of open-circuit characteristics (subject to agreement between the purchaser and the supplier);
Determination of regulation characteristics (subject to agreement between the purchaser and the supplier);
-.
“
,
.“ .. 14e)
f)
.9
h) j) k) m) n)Determination of external characteristics( for generators only) this test shall be applicable for generators having output ratings above 150 kW and shall be subject to agreement between the purchaser and the supplie~ Temperature-rise test;
Commutation-rise test;
Determination of efficiency of machines; NOTE — For sliprings alternators these tests are conducted with respect to main field current and for brusbless these tests are carried out with respect to field current.
Load saturation characteristics (for exciters only);
Nominal exciter response for dc exciters (subject to agreement between the purchaser and the supplier);
Overspeed test; and Dielectric test. 29.3.3.2 Routine tests
The following shall constitute the routine tests: a) Measurement of winding resistance;
b) Measurement of insulation resistance, before and after high voltage test;
c) Commutation test; and d) Dielectric test. 30 ELECTRIC STRENGTH 30.1 Dielectric Test
30.1.1 The high voltage shall be applied between the windings under test and the frame of the machine with the core and the windings not under test connected to the frame. It shall be applied only to a new and completed machine with all its parts in place under conditions equivalent to normal working conditions and shall be carried out at the manufacturer’ works. When the temperature-rise test is carried out, the dielectric test shall be carried out immediately after this test.
30.1.2 In the case of polyphase machines with rated voltage above lkV having both ends of each phase individually accessible, the test voltage shall be applied between each phase and the frame, with the core and the other phases and windings not under test connected to the frame.
30.1.3 The test voltage shall be of power-frequency and shall be as near as possible to sine wave form.
30.1.4 The test shall be commenced at a voltage of not more than one half of the full test voltage. The voltage shall then be increased to the full value steadily or in steps of not more than 5 percent of the full value, the time allowed for the increase of the voltage from half value being not less than 10 s. The full test voltage shall then be maintained for 1 minute in accordance with the value as specified in Table 6.
30.1.5 During the routine testing of quantity produced machines, the one-minute test may be replaced:
a) for machines up to 200 kW (or kVA) and with rated voltages up to 660 V, by a test of approximately 5 s at the normal test voltage specified in Table 6; and
b) for machines up to 5 kW (or kVA) by a test of approximately 120 percent of the normal test voltage in Table 6.
The test voltage being applied by means of probe. 30.1.6 The high voltage test at full voltage made on the windings on acceptance shall not be repeated. If, however, a second test is made at the request of the purchaser after further drying if considered necessary, the voltage shall be 80 percent of the voltage specified in Table 6.
30.1.7 Completely rewound windings shall be tested at the full test voltage for new machines.
30.1.8 When a user and a repair contractor have agreed to carry out dielectric tests in cases where windings have been partially rewound or in the case of an overhauled machine, the following provisions are recommended:
a) Partially rewound windings are tested at 75 percent of the test voltage for a new machine. Before the test, the old part of the winding shall be carefully cleaned and dried; and
b) Overhauled machines after cleaning and drying are subjected to a test at a voltage equal to 1.5 times the rated voltage with a minimum of 1 000 V if the rated voltage is equal to or greater than 100 V and a minimum of 500 volt if the rated voltage is less than 100 V. 30.2 Insulation Resistance Test
30.2.1 The procedure for determination of insulation resistance of insulated parts of the machines given in IS 7816 shall be followed. The value of recommended dc voltage at which the test may be carried out are given in Table 7.
Table 6 Dielectric Tests (Clauses 30.1.4,30.1.5 and 30. 1.6)
sl Machine or Part
No.
(1) (2)
1)Insulated windings of size less than 1kW (or kVA)and of rated voltage less than 100V with the exception of those S1 No. (d) to (h)
2) Insulated windings of rotating machines of size less than 10000 kW (or kVA) with the exception of those in item (a) and S1No. (d) to (h) (see Note 2)
3) Insulated windings of rotating machines of size 10000 kW (or kVA) or more with the exceptionof drme in S1No. (d) to (h) (see Note 2)
Rated voltage (see Note 1): Upto24W30V
above24CMlV
4) Separately excited field windings of dc machines
5) Field windings of synchronous generators, synchronousmotors and synchronous condensers:
a) Rated field voltage Up to 500 V Above 500 V
b) When a machine is intended to be started with field winding short-circuited or connected across a resistance of the value less than ten times the resistance of the winding
c) When the machine is intended to be started either with the field winding connected across a resistance of value equal to or more than ten times the resistance of the winding or with the field windings on open circuit with or without a field dividing switch
6) Secondary (usually rotor) windings of induction motors or synchronousinductionmotors is not permanentlyshort-circuited (for example, if intended for rheostatic starting):
a) For non-reversing motor or motor reversible from standstill only; and
b) For motors to be reversed or braked by reversing the primary sLIpplywhile the motor is running
7) Exciters (except as below)
Exception 1 — Exciters of synchronous motors (Including synchronous induction motors) if connected to earth or disconnected from the field windings during starting. Exception 2 — Separately excited field windings of exciters Isee S1 No. (4)]
8) Assembled group machines and apparatus
NOTES
Test Voltage (rms)
(3)
500 V + twice the rated voltage
1000 V+ twice the rated voltage with a minimum of 1500 V (see Note 1)
1000V+2U,where U is the rated voltage
Subject to agreement between the manufacturer and the purchaser 1000 V+ twice the maximum rated circuit voltage with a minimum of1500v
Ten times the rated field voltage with a minimum of 4000 V+ twice the rated field voltage
Ten times the rated field voltage with a minimum of maximum of 3500 V
500v
500 V and
1 000V + twice the maximum value of the rms voltage which can occur under the specified starting conditions between the terminals of the field winding or in the case of a sectional field winding between the terminals of any section with a minimum of 1500 V (see Note 3)
.’
1 000V+ twice the open-circuit standstill voltage as measure between siiprings of secondary terminals with rated voltage applied to the primary windings
1000V+four times the open-circuit standstill secondary voltage as defined in S1No. 6(a)
As per the windhrgs to which they are connected
1000 V + twice the rated exciter voltage with at minimum of
1500V
A repetition of the test in S1No. 1 to6above should be avoided, if possible, but if a test on an assembled group of several pieces of new apparatus each one of which has previously passed its high voltage test, is made the test voltage to be applied to such assembled group shall be 80 percent of the lowest test voltage appropriate for any part of the group (see Note 4)
1 For two-phase windings having one terminal in common, the voltage in the formula shafl be the highest rms voltage arising between
any two terminals during operations.
2 High-voltage tests on machines having graded insulation should be the subject of an agreement between the manufacturer and the purchaser.
3 The voltage occuring between the terminals of the field windings, or sections thereof under the specified starting conditions maybe measured at any convenient reduced supply voltage and the voltage so measured shall be increased in the ratio of specified starting voltage to the test supply voltage.
4 For windings of one or more machines connected together elcctnca\Iy the voltage to be considered is the maximum vohage that occurs in relation to earth.
--- -.. . ..
Table 7 Test Voltages for Insulation Resistance (Clause 30.2.1)
Rated Voltage Test Voltagefor Insulation
ac Resistance, dc
(1) (2)
Up to 660 5MIv
Above 660 up to and 1000 V or higher value as agreed includhrg I 100 between the manufacturer and the
mer
30.2.2 The minimum values of insulation resistance shall be determined by the following empirical relationship:
Where
R. =
kv =
Rm=kV+l
Minimum insulation resistance in megaohms at 40°C of entire machine windings; and
Rated voltage of the motor, in kilovolts. NOTE —Rmat 40° C is ineffectone megaohmper 1000 volts plus one megaohm.
30.2.3 ac machines rated above 3.3 kV and having output more than 1 000 kW may also be tested for polarization index (PI) of insulated windings. The method for measurement of polarization index shall be in accordance with IS 7816. The minimum values of PI (lRlornin/lRl rein) shall be 1.5 for Class A, 2.0 for
Class B and 1.75 for Class E insulation systems. NOTE — The recommended minimum value of PI (!~=vhq~~)shall be 1.3 for all classes of insulations of the windings.
31 COMMUTATION TEST
31.1 The commutation test shall be made to verify the machine meets the requirements specified in 22 of this
IS No. 1076:1985 1231:1974 1885 (Part 35) : 1993 2253:1974 1s 47LL :Z(JU1
standard. In case of type test, this is to be carried out at the conclusion of the temperature-rise test of the machine.
32 OVERSPEED TEST
The test, if agreed, shall be made, to verify the requirements of 17 of this standard.
33 UNBALANCED CURRENTS OF
SYNCHRONOUS MACHINES
The test, if agreed, shall be carried out to verify the provisions of 18 of this standard.
34 SHORT-CIRCUIT CURRENT TEST
The test, if agreed, shall be carried out to verify the provisions of 19 and 20 of this standard.
35 OCCASIONAL EXCESS CURRENT
This test shall be carried out to verify the provisions of 14 of this standard.
36 MOMENTARY EXCESS TORQUE
This test shall be earned out to verify the provisions of 15 of this standard.
37 PULL UP TORQUE FOR MOTORS
This test shall be carried out to verify the provisions of 16 of this standard.
38 LIMITS OF VIBRATION
If agreed between the user and the manufacturer, this test may be arranged to verify the specified limits of vibration according to IS 12075.
ANNEX
A
(Clause 2)
LIST OF REFERRED INDIAN STANDARDS
Title IS No.
Preferred number (second revision) 4691:1985
Dimensions of three-phase foot-mounted induction motors (third
revision) 4728:1975
Electrotechnical vacabulaty: Part 35 Rotating machinery (first revision)
4889:1968
Designation for types of construction and mounting arrangement of
rotat-ing electrical machines (tirst 5422:1996
revision)
17
Title
Degrees of protection provided by enclosures for rotating electrical machines (tlrst revision)
Terminal marking and direction of rotation for rotating electrical machinery (first revision)
Method of determination of ef-ficiency of rotating electrical machines
