IS 996: Single-phase a.c. industrial motors for general purpose

2009·15.1 MB·English

by  Bureau of Indian Standards

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IS 996 (2009): Single-phase a.c. industrial motors for
general purpose [ETD 15: Rotating Machinery]
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IS 996 : 2009
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Indian Standard
SINGLE PHASE a.c. INDUCTION MOTORS FOR
. GENERAL PURPOSE
(Third Revision)
ICS 29.160.30
© BIS 2009
BUREAU OF INDIAN srrANDARDS
MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002
February 2009 Price Group 8
Rotating Machinery Sectional Committee, ETD 15
FOREWORD
This Indian Standard (Third Revision) was adopted by the Bureau ofIndian Standards, after the draft finalized by
.the Rotating Machinery Sectional Committee had been approved by the Electrotechnical Division Council.
This standard was first published in 1959. The first revision was broughtout in 1964 and the second revision was
brought out in 1979. This revision has been undertaken to align it with the latest developments in the field of
rotating machinery and also to include the following changes:
a) The universal motors are excluded as these motors have very little common application with single
phase ac induction motors covered under this standard;
b) Performance requirement of various types ofmotors including for fans, pumps etc, are included except
for shaded pole and split phase motors; and
c) Guidelines for selection of fan duty motors are included (seeAnnex F).
This standard recommended the important dimensions for frame ofmotors with foot or resilient mounting either
with sleeve or ball bearings which are necessary to ensure mechanical interchangeability.
,
,
This standard covers the requirements and tests for general purpose motors.The motors used in specific applications
may have special requirements and these special requirements are subject to agreement between the user and the
manufacturer. The special requirements for single-phaseelectric motors for domestic laundry machine are covered
in IS 9582 (Part 1) : 1980 'Single-phase electric motors for definite purposes: Part 1Domestic laundry machine
motors'. The special requirements and the guidelines for selection of fan duty motors are given in Annex F.
Guidance for testing single-phase a.c. is given in IS 7572 : 1972 'Specification for guide for testing single-phase
a.c. and universal motors'.
To ensure satisfactory installation and maintenance of induction motors, it is urged that the recommendations
contained in IS 900 : 1965 'Code ofpracticefor installation and maintenance ofinduction motors (revised)'should
be carefully followed.
Ifso desired, the thermistors may be used in the windings ofthe motors. The details and specifications of thermistors
would be as agreed between the purchaser and the manufacturer.
In the formulation of this standard, assistance has been derived from the following publications:
IEC 34-1 (1969) Rotating electrical machines - Part 1: Rating and performance, issued by the
International Electrotechnical Commission.
IEC 34-2 (1972) Rotating electrical machines - Part 2: Methods ofdetermining losses and efficiency of
. rotating electrical machinery from tests (excluding machines for traction vehicles), issued
by the International Electrotechnical Commission.
IEC 72 (1971) Dimensions and outputratings forrotatingelectricalmachines- Framenumbers 56 to400
and flange numbersF55 toFI080, issued by the InternationalElectrotechnical Commission.
JIS 4203-1973 Single phase induction motors (for general purpose), issued by the Japanese Standard
Association.
BS 170: 1962 Specification for the electrical performance of fractional horsepower electric motors
and generators, issued by the British Standards Institution.
BS 1608 : 1966 Electrically-driven refrigerant condensing units, issued by the British Standards
Institution.
Publication MG-I-1967 Motors and generators, issued by National Electrical ManufacturersAssociation, USA.

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 or analysis, shall be rounded off in accordance with
IS 2 : 1960 'Rules for rounding off numerical values (revised)'. The number ofsignificant places retained in the
rounded off value should be the same as that of the specified value in this standard.
IS 996: 2009
Indian Standard
SINGLE PHASE a.c. INDUCTION MOTORS FOR
GENERAL PURPOSE
( Third Revision)
1 SCOPE 3.1.7 Thermally ProtectedMotor-A motor provided
with thermal protector.
1.1Thisstandardcovers single phase acinduction motors
of the capacitor types for voltages upto and including 3.1.8 Thermal Protector - A protective device for
250V and having windings with Class A, Class E, Class assembly as an integral part of the motor and which
B, Class F or Class H insulation (see IS 1271 : 1985 when properly applied, protects the motor against
Thermal evaluation and classification of electrical 'dangerous overheating due to overload and failure to
insulation) and output upto and including 2200 W). start.
1.2 Motors for use on systems complying to voltages 3.1.9 General Purpose Motor-A motor designed in
and frequencies other than preferred (see 4) shall be standard ratings withstandard operating characteristics
considered as complying with this standard provided and mechanical construction for use underusual service
they comply in all other respects. The voltages and conditions withoutrestrictions to a specific application
frequency for which they are designed shall be stated or type of application.
on the rating plate.
3.1.10 Breakaway (Starting) Torque - The lowest
torque developed by the motor in the stand-still
2 REFERENCES
condition when the motor is supplied at the rated
The list of standards given in Annex A are necessary
voltage and rated frequency.
adjunct to this standard.
3.1.11 Pull- Up Torque - The smallest torque
3 TERMINOLOGY developed by the motor between zero speed and the
speed which corresponds to the pull-out torque when
3.1 For the purpose of this standard, the following
the motor is supplied at the rated voltage and rated
\
definitions in addition to those covered in IS 1885
frequency.
(Part 35) shall apply.
3.1.12 Pull-Out Torque- The highest torque that the
3.1.1 Overload - Any load in excess of the rated
motor can develop while running at rated voltage and
output expressed as a percentage of rated output.
rated frequency.
3.1.2 Momentary Overload - Any overload the
3.1.13 Wide Voltage Motor - A motor rated for the
duration ofwhich isso short as not to affect appreciably
voltage range of 190-240 V (or any other band
the temperature of the motor.
specified on the nameplate). This motor shall meet all
3.1.3 Refrigeration Duty Motor - A special purpose performance specifications at the mean of the voltage
ventilated motor suitable for driving open type band. At the extreme voltage conditions the motor shall
be capable of delivering the rated output. The motors
compressor in condensing unit refrigeration.
may not necessarily have their other performance in
3.1.4 Fan-DutyMotors -A special purpose motor for
accordance with Tables 1 to 11. In case ofcontinuous
driving shaft mounted fan or blower. The motor may be
operation underextreme voltage limit, the temperature
with single speed winding or multi speed windings
rise specified in Table 1 of IS 1280~ shall not exceed
which give more than one distinct fanlblower speeds,
by 10°C. No further tolerance (as given in 5.1.4) on
wherein the cooling of motor winding is provided by
voltage isapplicable on motors with this type ofmotor.
theair handled by the shaftmounted fanes)or blower(s)
4 P.ATED CONDITIONS OF VOLTAGE,
3.1.5 Reversible Motor - A motor which is capable
FREQUENCY, .OUTPUT AND SPEED OF
of being started from rest and operated in either
MOTORS
direction ofrotation.
4.1 Rated Voltage
3.1.6 Reversing Motor - A motor capable of being
reversed even while running at normal speed by
For the purpose of this standard, the preferred rated
changing electrical connections.
voltage shall be in accordance with IS 12360 be 230V.
1
IS 996: 2009
4.2 Rated Frequency motors shall .be as in IS 1231 and IS 2223 (NEMA
frame dimensions addition in this standard suggested
The rated frequency shall be 50 Hz.
in view of its popularity).
4.3 Rated Output
NOTES
1 Whenever the motor construction requires deviation from
The preferred output ratings shall be 2.5, 4, 7, 12, 18,
the recommended dimensions, the dimensional requirements
25, 40, 60, 90, 120, 180, 250, 370, 550, 750, 1 100,
shall be a matter ofagreement between the manufacturer and
1500 and 2 200 Watt. the user.
2 Dimensional requirements of motors smaller than those
4.4 Rated Speeds
corresponding to frame 56 shall be subject to an agreement
between the manufacturer and the user.
Preferred rated speeds shall be corresponding to two
3Toleranceoncentre height shall notbe applicableforresilient
poles, four poles and six poles.
basemounted motors. Centre height for agiven framesize may
.notbeasinIS1231 andthetolerance ontheagreedcentreheight
5 SITE CONDITIONS between the manufacturerand the user shall be-1.5 mm.
4 Oblong holes may be used making it convenientfor sliding
5.1 The following shall constitute the normal site
the motors. However, the width of the oblong holes shall be
conditions. equal to the diameterspecified for the frame size.Open ended
slots are not permissible.
5.1.1 Altitude and Temperature
7.2 Non-standard Dimensions
Motors shall be designed for the following site
conditions unless otherwise agreed between the Considering the wide variety ofusage and application
manufacturer and the purchaser. of motors covered by this standard, motors may be
manufactured in frame sizes and dimensions otherthan
5.1.2 Altitude
those in 7.1. Unless otherwise specified, the
Altitude not exceeding 1000 m. dimensional tolerances (on the declared dimensions)
shall be corresponding to the nearest frame size.
5.1.3 Temperature
8 DUTY AND RATING
The cooling air temperature not exceeding 40°C.
5.1.4 Voltage and Frequency Variation 8.1 Continuous Rating
Motors covered by this standard shall be capable of For the purpose of this standard, unless otherwise
delivering rated output with, specified, the general purpose motors shall be
continuously rated.
a) terminal voltage differing from its rated value
by not more than ± 6 percent, or 8.2 Short Time Rating
b) frequency differing from its rated value by
Ifthe motors are short time rated, the preferred periods
not more than ± 3 percent, or
shall be 5, 15, 30 or 60 min.
c) any combination of (a) and (b).
NOTE- Formoredetails onselectionandapplicationofthese
In case of continuous operation at extreme voltage motors (see Annex E).
limits, the temperature rise specified inTable 1 of
9 GENERAL CONSTRUCTION
IS 12802 shall not exceed by more than 10°C. Motors
when operated under the extremeconditions ofvoltage
9.1 Mounting.
and frequency variations may not necessarily havetheir
The following types of mounting shall be used (see
performance in accordance with Tables 1 to 11.
also IS 2253).
5.2 Variation from Rated Speed
9.1.1 Foot-Mounted Motor
This shall be in accordance with Table 12.
A motor with feet, the feet being used for fixing it in
position.
6 ENVIRONMENT
9.1.2 Flange-Mounted Motor
It shall be assumed that the location and moisture or
fumes shall not seriously interfere with the operation
A motor with flange, the flange being used infor fixing
of the motor.
it in position.

7 DIMENSIONS 9.1.3 Foot-cum-Flange Mounted Motor
7.1 The recommended dimensions for rigid base A motor with flange and feet, the feet being used for
mounted, resilient base mounted and flange mounted fixing it in position.
2
IS 996: 2009
9.1.4 Resilient-Ring Mounted Motor metallic, the material of such enclosure or main
structure shall be non flame supporting or self
A motor provided with resilient mounting so that it is
extinguishing.
supported between two resilient rings affixed to itsend
shields, the rings being used for mounting by the user. 9.4.2 Thermal Protector
9.1.5 Resilient-Base Mounted Motor When motors are provided with thermal protectors it
shall bear a warning label stating 'THERMAL
A resilient-ring mounted motor provided with
PROTECTOR FITTED' or 'THERMALLY
mounting base, the base being used for fixing it in
PROTECTED' and shall be conspicuous.
position.
9.4.3 Manual Resetting Protector
9.1.6 Stator-Pad Mounted Motor
When such protectors are ofmanual resetting type the
A motor provided with three or four pads on stator
resetting arrangement shall be readily accecsible and
body, equispaced in angular position, duly tapped, the
identifiable through clear marking.
pads being used for fixing motor in position.
9.4.4 Lubrication
9.1~7 End Shield Pad Mounting
Readily accessible lubricatingpoints shall be provided,
A motor provided with three or four pads onend shield
wherever necessary.
equispaced in angular position in same plane, duly
I
tapped, thepads being used for fixing motor inposition.
9.4.5 Lubricant Temperature
9.1.8 Foot-cum-End Shield-Pad Mounting
The lubricant of the motor bearings shall be suitable
for bearing temperatures which can result from
An end shield pad mounted motor with feet, the feet
operating conditions covered by this standard.
being used for fixing motor in position.
9.4.6 Centrifugal Switch
9.1.9 Extended Bolt Mounting
Toensure satisfactory operation the centrifugal switch
A motor where extended threaded studs or motor bolts
where fitted shall be so disposed that it shall not be
are provided to be used for fixing motor in position.
exposed to lubricating grease or oil which may be
9.1.10 Frame-Mounted Motor
discharged from over lubricated bearings.
A motor withoutdriving end shield, the frame or stator
9.4.6.1 Each motor shall be subjected to the minimum
body being used for fixing it in position.
of 5 cycles of switch operation at no load for motor
fitted with centrifugal switch to ensure its proper
NOTE- Dimensionsforfixing the motor inposition ofmotors
in 9.1.4,9.1.6, 9.1.7,9.1.8,9.1.9, and 9.1.10, shall be a matter operation.
ofagreement between the manufacturer and the user.
NOTE-Astype test the numberofcycles ofswitchoperation
9.2 Terminal Box shall beconductedfor 1in 250 numbers ofeach type ofswitch.
The position ofterminal box, when provided, shall be 9.4.7 Resilient Mounting Material
a matter of agreement between the manufacturer and
When resilient mountings are an integral part of the
the user.
motor the mounting shall be oil resistant and resistant
9.3 Mounting Constructions to heat which is produced by the motor.
Various mounting constructions are possible with shaft 9.4.8 Resilient Mounting Test
horizontal, vertically upwards or vertically downwards
The resilient base mounted motor shall withstand
and the mountings covered in 9.1 which should form a
without slippage between the frame and base an applied
subjectmatter ofagreement between the manufacturer
torque of 1.5 times the maximum value ofany torque
and the user.
that can be developed by the motor at rated voltage.
9.4 Constructional Features
9.4.9 Insulating Material
Motors shall be processed in a careful and workman
Insulating materials used shall be in accordance with
like manner. The manufacturer shall use good
measurement and production techniques to ensure the IS 1271 as far as insulation class is concerned.

highest degree of productreliability and uniformity
NOTE- Materials used shall be inaccordance with the class
practicable with the materials used in the product. ofinsulation, stated in the rating plate or superior.
9.4.1 Non-metallic Material Enclosure 9.4.10 Insulation ofLeads
Ifthe enclosure or main structure ofthe motor is non- The insulation material of connection/external leads
3
IS 996: 2009
supplied with the motor shall be suitable for the 10.1.1 Open Ventilated Motor
maximum temperature ofthe part ofmotor coming in
A motor having no protective enclosure.
contact with these leads.
NOTE- Incaseofnon-protectedmotors additional protection
9.4.11 Capacitors
shall be provided by the user,
Capacitors where used shall comply to IS 2993. 10.1.2 Ventilated Motor
NOTES A motorhaving an enclosure so constructed as to give
1 For capacitor-start or capacitor-start capacitor-run motors, protection while ventilation is not materially impeded.
the voltage ofthe electrolytic capacitorduring locked rotor at
The protection provided by enclosure shall meet
rated voltage shall not exceed 90 percent of the rms surge
requirements of IP20 in accordance with IS 4691.
voltage ofcapacitor.
2 For two value capacitor/permanent split capacitor motor,
10.1.3 Drip ProofMotor
during no load run at rated voltage ofthe motorthe voltage of
thepaper dielectriccapacitorshall notexceedthe rated voltage A ventilated motor so constructed as to exclude
of the paper dielectric capacitor excepting directly loaded
vertically falling water ordirt. The protection provided
appliances such as monobloc pumps, mono-compressors and
by enclosure shall meet requirements of IP2l in
fans which always are run at or near full load. Insuch uses the
voltage ofthecapacitorshall not exceed95percentofitsrated accordance with IS 4691.
voltage when theapplianceisrun atrated load atrated voltage.
10.1.4 WaterProtected Motor
9.4.12 Construction Material
A drip proofmotor so constructed that drops of water
All materials and components'used in the manufacture
falling at an angle up to 150 from the vertical shall
of the motor shall conform to the relevant Indian
have no harmful effect, the protection provided by
Standard, wherever they exist. In case ofany difficulty
enclosure shall meet requirements of IP22 in
in complying with this requirement, it shall be subject
accordance with IS 4691.
to agreement between the manufacturer and the
10.1.5 Totally Enclosed Motor
purchaser.
A motor soconstructed as to prevent the free exchange
9.4.13 Finishing
of air between inside and outside of enclosing case.
All surfaces exposed to atmosphere which are not
The protection"provided by enclosure shall meet
adequately protected by metal deposition shall be
requirements of IP44 in accordance with IS 4691.
protected against corrosion by painting, enamelling,
10.1.6 Totally Enclosed Fan Cooled Motor
oxidizing or phosphatizing.
A totally enclosed motor with augmented cooling by
9.5 Earthing
means of a fan driven by the motor itself blowing .air
9.5.1 Earthing Terminal over motor body or cooling passages" if any. The
protection provided by enclosure shall meet
At least one separate earthing terminal of adequate
requirements of IP44 in accordance with IS 4691.
current carrying capacity conveniently located-and
visible shall be provided on the motor. The earthing 10.1.7 Environment ProofMotor
terminal shall be of suitable material adequately
A motor soconstructed that itcan work without further
protected against corrosion and shall have 'J,' or 'E'
protection from,the weather conditions specified by
on or adjacent to it.
theuser.The enclosure shall be designated by the letter,
9.5.2 Lead Earthing 'E' example IPE44 or IPE55.
If resilient mounted motor is supplied with externall 10.1~8 Weather ProofMotor
loose leads to the motor windings, a separate earthing
A motor is weather proof when its design reduces the
cord or lead shall be supplied.
ingress of rain, snow and airborne particles to an
amount consistent with a correct operation. The
9.5.3 Plug Earthing
enclosure shall be designated by the letter 'W' (placed
If any type of motor is supplied with externallloose
between IP and the numerals for example IPW44).
lead and plug the motor frame shall be connected to
10.1.9 Hose ProofMotors
the earth pin of the plug.
A motor having enclosure which provides type of
10 TYPES OF ENCLOSURES
protection IP55 in accordance with IS 4691.

10.1 Motors covered by this standard shall have one
10.1.10 Motors for Appliances
of the enclosures stated below. The enclosures shall
meet the requirements of IS 4691. Motors w.hich are intended ultimately to be
4
IS 996: 2009
incorporated in appliances may have enclosures not 12.1.2 Motors conforming to this standard are not
providing aspecific degree ofprotection. Such motors expected to.carry sustained overloads. However (unless
also shall be considered conforming to this standard agreed to between the manufacturer and the user)
so long as they comply with all the requirements of motors rated in accordance with this standard shall be
this standard except that relating to enclosures. capable ofwithstanding on test (undergradual increase
of torque) without injury, the overloads in torque for
10.1.11 Besides enclosures defined in 10.1 this
15 s is given in Table 2, after having their rated load.
standard also recognizes the enclosures arising out of
various degrees of protection stated in IS 4691. All the torque values shall be measured in accordance
with IS 7572.
11 METHODS OF COOLING
Table 2 Momentary Overload for Motors
11.1 The method of cooling of motors and their
(Clauses 3.1.13, 5.1.4 and 12.1.2)
designations shall be as given in IS 6362. Cooling
methods shall be anyone of the following types:
81 Type ofMotor Excess Torque as
No. Percentage ofRated
a) According to origin ofcooling:
Torque
(I) (2) (3)
1) Natural cooling - The motor is cooled
without the use ofa fan by the movement i) Capacitor-start Induction-run 50
of air and radiation. ii) Capacitor start-and-run 25
I
iii) Capacitor-start Capacitor-run 50
2) Self cooling - The motor is cooled by
cooling air driven by a fan mounted on
12.2 Temperature Rise
the rotor or one driven by it.
Temperature rise ofmotors for all types ofenclosures,
3) Separate cooling - The motor is cooled
when tested under the rated conditions and in
by a fan not driven by its shaft.
accordance with the requirements ofthis standard shall
b) According to manner ofcooling:
not exceed the limits given in Table 1 of IS 12802.
I) Open circuit ventilation - The heat is Motors shall, however, be capable ofoperating without
given up directly to the cooling air injurious heating at extreme voltage limits stated
flowing through the motor which isbeing in 5.1.4 (that is ± 6 percent of rated voltage) or the
replaced continuously. extremes of the voltage range specified on the rating
2) Surface ventilation - The heat is given plate. The temperature rise ofmotors to be incorporated
up to the cooling air from the external in appliances shall be tested when the motor is installed
in the appliance.
surface of a totally enclosed motor.
12 GENERAL CHARACTERISTICS
12.3 Short Time Rating
12.1Torques For motors having shorttime rating, the limits specified
in Table 1ofIS 12802 may by agreement be increased
12.1.1 With rated voltage and frequency applied to
by 1DoC. Where such an agreement is made to increase
terminals, the breakaway (starting), pull-up·and pull
the limits, the increased limits shall be indicated on
out torques shall comply with the requirements given
the rating plate.
in Table 1.
12.4 Method ofTesting
Table 1 Torques of Single-Phase a.c. Motors
The measurement of temperature rise shall be done
(Clauses 3.1.13,5.1.4,12.1.1 and,I2.3)
according to the methods given in IS 7572.
81 Type ofMotor Minimum Minimum Minimum
NOTE - In many appliances the cooling of the motor is
No. Pull Out Pull Up Break-away
affected by aircirculation throughshaftmountedfans/ blowers
Torque Torque Torque
and the enclosure and as such temperature rise test cannot be
Percent of
conductedon the motorby itself. Insuchcasesthe manufacturer
F.I.T.
and the user shall arrive at a suitable rating ofload and time
(I) (2) (3) (4) (5)
for motor temperature rise test purposes. This rating shall be
i) Capacitor-start 200 150 200 marked on the name plate and temperature rise tests may be
Induction-run conducted for this rating in the laboratory and shall be judged
ii) Capacitor start and 150 20 30 for compliance to the requirements ofthis standard.
run
iii) Capacitor-start and 200 150 200 12.5 Performance Values
capacitor-run
12.5.1 The values of minimum full load speed,
5