is 12824 (1989): types of duty and classes of rating

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IS 12824 (1989): Types of Duty and Classes of RatingAssigned to Rotating Electrical Machines [ETD 15: RotatingMachinery]

Indian Standard

IS 12824 : 1969 ( RedKrmd 1993 1

TYPES OF DUTY AND CLASSES OF RATING ASSIGNED TO ROTATING ELECTRICAL

MACHINES

UDC 621’313 - 13 : 621’3’02

0 BIS 1990

BUREAU OF INDIAN STANDARDS MANAK BH.I\VAN, 9 BAHADUR SHAlI ZAFAR MARG

NEW DELHI 11OOW

June 1990 Price Croup 4

Rotating Machinery Sectional Committee, ETDC 15

FOREWORD

This Indian Standard was adopted by the Bureau of Indian Standards on 24 July 1989, after the draft finalized by the Rotating Machinery Sectional Committee had been approved by the Elec- trotechnical Division Council.

This standard defines the types of duty, classes of rating along with the designations and the criteria for.assigning these parameters to the rotating electrical machines. It also includes the guidelines for declaration of duty type and selection of a class of rating to such machines.

IS 4722 : 1968 ‘Rotating electrical machines’ which specified the duty and class of ratings is under revision.

While preparing this sfandard assistance has been taken from IEC Pub 34-l(1983) ‘Rotating electrical rn: chines - Part 1 Rating and performance’, issued by the International Electrotechnical

Commission ( IEC ).

Indian Standard

TYPES OF DUTY AND CLASSES OF RATING ASSIGNED TO ROTATING ELECTRICAL

MACHINES 1 SCOPE

1.1 This standard covers types of duty and classes of rating applicable to rotating electrical machines.

1.1.1 This standard also gives the designation of duty types and guidelines for declaration of duty and for selection of a class of rating of rotating electrical machines.

4.2 Short-Time Daty - Duty Type S2

Operation at constant load during a given time, less than that required to reach thermal equilibrium, followed by a rest and de-energized period of sufficient duration to re-establish machine temperatures within 2°C of the collant ( see Fig. 2 ).

The recommended values for the short-time dnty are 10, 30,60 and 90 minutes.

2 REFERENCES

2.1 The following Indian Standards are necessary adjuncts to this standard:

IS No.

IS 1076 : 1967

Title

Specification for preferred numbers ( first revision )

IS 1885 Electrotechaical vocabulary: ( Part 35 ) : 1973 Part 35 Rotating machinery

IS 4722:1968 Specification for rotating electrical machines (under revi- sioon )

4.3 Intermittent Periodic Duty - Doty Type $43

A sequence of identical duty cycles, each including a period of operation at constant load and a rest and de-energized period. These periods being too short to attain thermal equilibrium during one duty cycle ( see Fig. 3 ). In this duty, the cycle is such that the starting current does not significantly affect the temperature rise for this duty cycle.

Unless otherwise specified the periodic duty type rating given in 5.4 shall be applied.

3 TERMINOLOGY 4.4 Intermittent Periodic Duty with Stutiag - Duty Type S4

3.1 For the purpose of this standard, the defini- tions given in IS 1885 ( Part 35 ) : 1973 and the following shall apply.

3.2 Duty The statement of the load(s) to which the machine is subjected, including, if applicable, starting, electric braking, no-load and rest and de-energized periods, and including their dura- tions and sequence in time.

A sequence of identical duty cycles, each cycle including a significant period of starting, a period of operation at constant load and a rest and de-energized period. These periods being too short to attain thermal equilibrium during one duty cycie ( see Fig. 4 ).


3.3 Duty Type

A continuous, short time or periodic duty, com- prising 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.

4 DUTY TYPES

4.0 The duty types are given in 4.1 io 4.9. Whilst the nine duty types are intended to apply primarily to motors, certain of them may also be used to define generator duties (for example, the duty types Sl, S2).

4.5 Intermittent Periodic Duty with Electric Braking - Day Type S5

A sequence of identical duty cycles, each cycle consisting of a period of starting, a period of operation at constant load, a period of rapid electric braking and rest and de-energized period. The operating and rest and de-eaargized periods being too short to attain thermal equilibrium during one duty cycle ( see Fig. 5 ).


4.6 Continuous-Operation Periodic Doty - DptJ Type S6

4.1 Continuous Ronning Duty - Daty Type Sl

Operation at constant load of sufficient duration A sequence of identical duty cycles, each cycle

for thermal equilibrium to be reached ( see c;onsisting of a period of operating. at constant load and a period of operation at no-load_

Fig. 1 ). There is no rest and de-energized period. The

1

ELECTRIC I LOSSES .

TEW I I

I I

I

I- I

TIME -

A’ - 3peration at constant load f3 mSI = Maximum temperature attained

Fla. 1 CONTINUOUS RUNNING DUTY, DUTY TYPE Sl

LOAO

ELECTRIC LOSSES

TEMP

-N-

TIME

N - Operation at conrtaot load _ Maximum temperature attained during the duty cycle

e m.r =

FIG. 2 SHORT TIME DUTY, DUTY TYPE S2

. / .

t-

_ PERIOD OF ONE CYCLE

LOAD

ELECTRIC LOSSES

TEMP

TIME

N = Operation at constant load R = At rest and de-energized

e lDAX = Maximum temperature attained during the duty cycle.

Cyclic duration factor N

- KR. 100%

FIG. 3 INTERMITTENT PERIODIC DUTY, DUTY TYPE 53

-PERIOD OF

LOAO

I

t I

I

TEMP

I I

/

TIME .

D = Startiog N = Operation at constant load R - At rest and de-energized

0 ID** = Maximum temperature attained during the duty cycle 8

Cyclic duration factor - b D-I-N +N+R’lwh-

Fro. 4 INTERMITTENT PERIODIC DUTY WITH STARTING, DUTY TYPS S4

“’ I

OF ONE CXLP

D = Starting N - Operation at constaot load F - Electric braking R = At rest and de-energized

e 1.X PI Maximum temperature attained during the duty cycle.

Cyclic duration factor = u ,” i T >+FR . 100%

FIG. 5 INTERMITTENT PERIODIC DUTY WITH ELECTRIC BRAKINQ, DUTY TYPE S5

operation and no load periods being too short to attain thermal equilibrium during one duty cycle. ( see Fig. 6 ).


4.7 Continoons-Operation Periodic Duty with Electric Braking - Duty Type S7

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 electric braking. There is no rest and de-energized period, these periods being too short to attain thermal equilibrium during one duty cycle ( see Fig. 7 >.

Unless otherwise specified the periodic duty type rating given m 5.4 shall be applied.

4.8 Continuous-Operation Periodic Duly with Related Load/Speed Changes - Duty Type SX

A sequence of identical duty cycles, each cycle consisting of a period of operation at constant load corresponding to a predetermined speed of rotation, followed by one or more periods of

4

operation at other constant loads corresponding to different speeds of rotation ( carried out for example, by means of a change of the number of poles in the case of induction motors ). There is no rest and de-energized period. These periods being too short to attain thermal equilibrium during one duty cycle ( see Fig. 8 ).


4.9 Duty with Non-periodic Load and Speed Variations - Duty Type S9

A Duty in which generally load and speed are varying non-periodically within the permissible operating range ( see 5.5 ). This duty includes frequently applied overloads that may greatiy exceed the full loads ( SY~ Fig. 9 ).

NOTE - For this duty type sutablc full Ioad values should be taker] as the basis of the overload concept.

5 CLASSES OF RATING

5.0 In assigning the rating, the manufacturer shall select one 01’ the classes of rating defined in 5.1 to 5.5.

COAO

ELECTRIC LOSSES

1lHE

0 MAY

N = Operation at coostant load Y = Operation on no load

e maz ==_ Maximum temperature attained durinl the duty cycle.

Cyclic duration factor = -$$. 100%

FIG 6 CONTINUOUS-OPERATION PERIODIC DUTY, DUTY TYPE S6

LOAD

ELECTRIC LOSSES

TEMP err*

. TIME

D = Starting N = Operation at constant load

e F - Electric braking

ma= - Maximum temperature attained during the duty cycle.

cyclrc aurarloo tactor = 1 Fro. 7 CONTINUOUS-OPERATION PERIODIC DUTY x

WITH ELECTRE BRAKING, DUTY TYPE S7 ii 52

;;

g

. I .

ELECTRIC LMSES

m TEMP

SPEED

FjF2 = Electric braking D = Acceleration

N,J~zIV, = Operation at constant load . _ 0 mar = Maximum temperature attained during the

duty c! cle. Cvclic duration factors

D + N, D t N, + F, + NP + F;+

100%.

FL + Np

=~NltF,+A'a$F,+Ns loox -- _.

F;G :J CONTINUOUS-OPERATION PERIODIC DUTY WITH RELATED/LOAD SPEED CHANGES,

SPEEO

ELECTRIC LOSSES

TEMP

FIG. 9

D - Starting

TIME

F I Electric braking S - Operation under overload

e m,X = Maximum temperature attained L = Operation under various loads R = At rest and de-energized

Cp - Full load DUTY WITH NON-PERIODIC LOAD AND SPEED VARIATIONS,

DUTY TYPE S9

DUTY TYPE S8

. / .

5.1 MaxImom Contimoo~ Bating

The statement of the load and conditions, assigned to the machine by the manufacturer, at which the machine may be operated for an unlimited period while complying with the requirements of this standard.

5.2 Short-Time Rating

For the duty type S2, the abbreviation 52 is followed by an indication of the duration of the duty. For duty types S3 and S6, the abbreviations S3 and S6 are followed by the cyclic duration factor.

Examples: ig 60 minutes 25 percent

S6 40 percent

The statement of the load, time and conditions, For the duty type S4 and SS, the abbreviations assigned to tbe machine by the manufacturer, at S4 and S5 are followed by the indication of the which the machine may be operated for a cyclic duration factor and the moment of limited period, starting at the ambient tempera- inertia of the motor ( JIU ) and the moment of ture, while complying with the requirements of inertia of the load ( Jest ), both referred to the this standard. motor shaft.

5.3 Equivalent Contioooos Rating

The statement of the load and conditions, assigned to the machine for test purposes by the manufacturer, at which the machine may be operated until thermal equilibrium is reached, and which is considered to be equivalent to one of the periodic duty types defined in 4.3 to 4.8 or to the duty type S9, as defined in 4.9, while complying with the requjrements of this standard.

5.4 Periodic Duty Type Rating

The statement of the loads and conditions, assigned to the machine by the manufacturer, at which the machine may be operated on duty cycles while complying with the requirements of this standard.

This class of rating if applied shall correspond to the periodic duty S3 and S6 types defined in 4.3 and 4.6.

The time for a duty cycle shall be 10 minutes and the cyclic duration factor shall be one of the following values:

15, 25,40 and 60 percent

5.5 Non-Periodic Duty Type Ratiog

The statement of the varying loads over varying speed and conditions, including overloads, assigned to the machine by the manufacturer, at which the machine may be operated non- periodically while complying with the requirements of this standard.

This class of rating if applied shall correspond to the non-periodic duty with non-periodic load and speed variations, as defined in 4.9.

Example: S4 25 percent JM=0’15 kg m* J ext = 0’7 kg ma

For the duty type S7, the abbreviation S7 is followed by the moment of inertia of the motor ( JM ) and the moment of iuertia of the load ( Jelt ), both referred to the motor shaft.

Example: S7 JM = 0’4 kg m* J rst = 7’5 kg ma

For the duty type SS, the abbreviation SS is followed by the moment of inertia of the motor ( JM ) and the moment of inertia of the load ( Jaxt ), both referred to the motor shaft, toge- ther with tee load, speed and cyclic duration factor for each speed condition.

Example: S8 JM = 0’5 kg ma Jsxt = 6 kg ma 16 kW 740 r/min 30 percent 40 kW 1 460 r/min 30 percent 25 kW 980 r/min 40 percent

6.3 Classes of Rating

~o~“oe~gnations of the classes of rating are as :

a) Maximum continuous rating - ‘cant’ or ‘Sl’;

b) Short time rating - duration of the opera- t,i;$mp;$ci, for example, ‘60 min’ or

,

c) Equivalent continuous rating - equ; and

d) Periodic and non-periodic duty type ratings - as for the duty types. See above, for example, S3 25 percent.

7 ASSIGNMENT OF RATINGS

6 DESIGNATION OF DUTY TYPES AND 7.1 The ratings shall be assigned in accordance CLASS OF RATINGS with the requirements of this standard and be

6.1 The designations specified in 6.1 and 6.2 marked on the rating plate of the machine.

follow the value of the rated output. If no 7.1.1 For machines with more than one rating,

designation follows the rated output, maximum the machine shall comply with relevant Indian

continuous rating applies. Standard in all respects at each rating.

6.2 Duty Types 7.1.2 Where reactors are connected between

A duty type may be designated by an abbrevia- machme terminals and the supply and are re-

tion of the terms given in 4, for example. duty garded as an integral part of the machine, the rated values shall refer to the terminals of the

types Sl and S9 by Sl and S9. reactor on the supply side.

7

.

IS 12824 : 1989

NOTE - Thir doa not apply to power transfor- mers connected between the machines end the ruPPlY.

7.1.3 For all machines the preferred rated output values expressed in watts shall be taken from the %O series of preferred numbers, rounded off in accordance with IS 1076 : 1967.

7.1.4 When a specific Indian Standard exists for machines of a particular type, the rated output values shall be in accordance with any series specified in the standard.

8 GUIDELINES FOR DECLARATION OF DUTY AND FOR SELECTION OF A CLASS OF RATING

8.1 hty

The duty, as defined in 3.2 may be described by one of the duty types defined in 4, or by the specification of another duty by the purchaser.

8.2 Declaration of Dnty

It is the responsibility of the purchaser to declare -the duty as accurately as possible.

8.2.1 In certain cases, where the load does not vary or where it varies in a known manner, the duty may be declared numerically ( see 4 ) or with the aid of a time sequence graph (see Fig. 1 to 9 ) of the variable quantities.

8.2.2 If the time sequence is indeterminate, a fictitious time sequence ( duty types S2 to SS ) not less onerous than the true one. shall be selected or the duty type S9 shall be applied.

8.2.3 If the duty is not stated, duty type Sl ( continuous running duty ) applies.

8.3 Rating

8.3.1 The whole of the numerical values of the electrical and mechanical quantities with their duration ‘and sequences, assigned to the machine by the manufacturer and stated on the rating plate, the machine complying with the specified conditions.

The rating is assigned by the manufacturer by selection of one of the classes of rating defined in 5. The class of rating selected shall normally be maximum continuous rating based on duty type Sl ( continuous running duty ) or short- time-rating based on duty type 52 (short-time duty).

8.3.2 If this is not possible, a periodic duty typo rating based on one of the duty types S3 to S8 ( periodic duty ) or the non-periodic duty type rating based on the duty type S9 ( non-periodic duty ) shall be selected.

8.4 Selection of a Class of Rating

8.4.1 Where a machine is manufactured for general purposes, it shall have maximum continuous rating and be capable of performing duty type Sl.

8.4.2 If the duty has not .been specified by the purchaser, duty type Sl applies and the class of rating assigned shall be maximum continuous rating.

8.4.3 When a machine is intended to have a short-time rating, the rating shall be based on t;t~ type S2 as defined in 4.2 and as designated

.

8.4.4 When a machine is intended to supply varying load or loads including a period of no- load or periods where the machine will be in a state of rest and de-energized, the class of rating shall be a periodic duty type rating based on a duty type selected from duty types S3 to S8 as defied in 4.3 to 4.8 and as designated in 6.

8.4.5 When a machine is intended non-periodically to supply variable loads at a variable speeds, including overloads, the non-periodic duty type rating. shall be based on duty type S9 as defined in 4.9 and as designated in 6.

8.4.6 A class of rating having been assigned to a machine on the basis of a duty selected from duty types S3 to S9, where a test is specified, it is normally suflicient to test the machine at an equivalent continuous rating as defined in 5.3.

8.4.7 In some cases, a test at the actual or estimated duty may be arranged by agreement between the manufacturer and the purchaser but such a procedure is not generally practical.

In the determination of the rating:

a)

b)

for duty types Sl to S8, the specified value(s) of the constant load(s) is taken to be the rated output and is expressed in watts for motors and volt-amperes for generators ( see 4.1 to 4.8 ) and period(n) N in Fig. 1 to 8; and

for duty type S9. a suitable full load value(s) is taken as the rated output ( see 4.9 and CP in Fig. 9 1.

8

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This Indian Standard has been developed from Dot: No. ETD 15 ( 2960 )

Amendments Issued Since Publication

Amend No. Date of Issue Text Affected

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is 12824 (1989): types of duty and classes of rating

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