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है”ह”ह

IS 14569 (1999): Commutators for Electrical Machines [ETD15: Rotating Machinery]

IS 14569:1999

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Indian Standard

COMMUTATORS FOR ELECTRICALMACHINES — SPECIFICATION

ICS 29.160.10

0 BIS 1999

February 1999

BUREAU OF IN DIAN STANDARDSMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

Price Group 4

Rotating Machkery Sectional Committee, ET 15

FOREWORD

This Indian Standard was adopted by the Bureau of Indian Standards, after the draft finalized by the RotatingMachinery Sectional Committee had been approved by the Electrotechnical Division Council.

The Commutator is an essential part of direct current or alternating current commutating electrical machines.The function of the commutator is to facilitate the collection or supply of current in the armature conductorsand, to convert the alternating current induced in the armature conductors into a direct current (in case ofgenerator). The present standard would help in streamlining the quality and production of such a part.

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 “IS2:1960 ‘Rulesfor rounding off numerical values (revised)’. The number of significant places retained in the rounded off valueshould be the same as that of the specified value in this standard.

IS 14569:1999

Indian Standard

COMMUTATORS FOR ELECTRICALMACHINES — SPECIFICATION

1 SCOPE

This standard covers requirements, dimensions,tolerances and tests for commutators used in directcurrentlalternating current motors or generators ofvarious applications.

2 REFERENCES

The Indian Standards listed below are necessaryadjuncts to this standard:

1S No.

1885 (Part 35) :1993

2464:1963

5885:1977

13586:1993

Title

Electrotechnical vocabulary: Part35 Rotating machinery

Built-up mica for electricalpurposes

Copper commutator bar (jlrstrevision)

Definitions and nomenclature forcarbon brushes, brush holders, com-mutators and slip rings for rotatingelectrical machinery

3 TERMINOLOGY

The definitions given in IS 13586 and 1S 1885 (Part35) shall apply.

4 TYPES OF COMMUTATORS

Commutators may be classified according to type of-construction. The basic types are:

a) Moulded type,

b) Revetted type, and

c) Built-up industrial type.

NOTE — Generally the type of construction of a commutatorfor a~articular electric machine is selected based on the designtype specified by the user (manufacturer of electric machine).Construction types other than those mentioned above may alsobe used, if required by the user,

5 CONSTRUCTION

The commutator is an assembly of wedge shapedconducting members called segments insulated fromeach other by mica separators. Wedge shapedsegments and mica separation form a circularassembly. The type of commutator assemblydetermines how this is held together as shown inFig. 1 to 3.

5.1 Commutator segments and mica separatorsassembly is heId by insulating moulding compoundwith or without inner metal bush.

5.2 Commutator assembly is held by steel spidersknown as shell and cap. The shell and cap are heldtogether by forming rivet and insulated from thesegment assembly.

5.3 Commutator should be ‘Arch-bound’ segmentand Mica separator assembly is held together byinsulated steel spiders known as shell and cap.Insulated steel spiders are held together by threadedfasteners.

6 MATERIAL

6.1 Segments

The commutator segments shall conform to IS 5885.The choice of the copper material between ETP,FRHC, silver bearing, oxygen free and cadmiumcopper shall be subject to agreement between themanufacturer and the user.

6.2 Commutator Segment Insulation

The insulation material, if based on built-up mica shallconform to IS 2464.

Use of other alternative materials like mica paper,insulation paper or any other material shall be subjectto agreement between the manufacturer and the user.

6.3 Steel Parts (Spiders)

These parts shall be machined from steel bars, steelcastings, plates or forgings. The type and grade of thematerial shall be decided between the manufacturerand the user. In the case of moulded construction withinner brush, the material of the brush shall be steel orbrass or as agreed between the manufacturer and theuser.

7 DIMENSIONS AND TOLERANCES

7.1 Dimensions

Unless otherwise specified, the various dimensions ofthe commutator assembly shall conform to themanufacturer’s drawings approved by the user.

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IS 14569:1999

7.2 Tolerances

The following limits of tolerances shall be applicable for all types of constructions:

a)

b)

c)

d)

. . . . . ,.Internal diameter : H7 or H8 [seeIS919 (Part i )J as per users’ requirement ror

all types of.construction

Outside diameter of brush seating : h9 [see IS 919 (Part 1)] for moulded and rivetted types +1.0mm for built-up types

Total length Range Tolerance

: lf3t050mm * f).3 mm

for commutator Type A and B: 5.1 to ioomm +0.5 mm

for all type commutators: 101 to400mm *1.5mm

: 401 to 800 mm * 2,0 mm

: 801 and above * 3.f) mm

Maximum allowable axial skew Range of Length Tolerance

on the commutator segment length 10t050mm 0.3 x Mica separator thickness0.3 mm, Max

51 to 100mm 0.4 x Mica separator thickness0.8 mm, Max

101 to400mm 0.5 x Mica separator thickness1.0 mm, Max

401 to 800 mm 0.6 x Mica separator thickness1.2 mm, Max

801 mm and above 0~8 x Mica separator thickness1.5 mm, Max

e) Radial skew : 0.5x Mica separator thickness for all types of commutators

f) Slot depth : * 5% of the depth for A and B Type commutators~ 2% mm for slot depth up to 40 mm for Type C* 3% for slot depth above 40 mm for Type C

g) Slot width : +0.05 mm

h) Concentricity between ID and Brush OD : 0.1 mm TIR for Type A and B commutators0.5 mm TIR for Type C commutators

j) Slot pitch error : M.2 mm cumulative.

NOTES

1 Method of measurement of slot pitch error-This is to be measured with isvernier for wider slot widths, For smafler slot width, pinsare to be inserted in two slots (pin diameter should be equal to the slot width) and the distance between pins to be measured with avernier,

2 Tolerance for industrial commutator segment pitch error should be 0.5 mm for eve[y quadrant of the commutator and 0.2 mm formoulded and rivetted commutators.

8 PACKING the Rules and Regulations made thereunder. The

Commutator should be packed in a suitable containerdetails of conditions under which the Iicence for use

to avoid damage to any part or surface of theof Standard Mark may be granted to manufacturers or

commutators due to shocks. The container should beproducers may be obtained from the Bureau of IndianStandards.

water proof and moisture proof.

9 MARKING10 TESTS

9.1 The manufacturers’ identification marks shall be10A Type Tests

placed on the commutators. The following shall constitute the type tests:a)

9.1.1 The commutators may also be marked with the b,Standard Mark. c)

9.1.2 The use of the Standard Mark is governed by theprovisions of Bureau of lndian StandardAct, 1986 and d)

Inters;gment short circuit test (see 11.1),High voltage test (see 11.2),Humidity test (for moulded type commutatorsonly) (see 12), andSpin test (see 13).

2

IS 14569:1999

10.2 Routine Tests

The following shall constitute the routine tests:a) Bar to bar short circuit test (see 11.1),b) Flash test (see 11.2), andc) Insulation resistance test (see 11.3).

11 ELECTRICAL TESTS

11.1 Intersegment Short Circuit Test

All the segments shall be checked for intersegmentshort circuit by applying AC voltage the value shouldbe as per the user’s requirement, based onintersegments insulation thickness) through probes ofa high voltage breakdown tester to adjacent segmentsfor two seconds. The leakage current shall not exceed5 mA.

11.2 High Voltage Test

This test shall be carried out between the commutatorsegments shorted by wrapping with a metallic foil orbraid, and the bush. The test voltage shall be appliedfor 60 s and its value shall be subject to agreementbetween the manufacturer and the user. Generally,this test is carried out at 1000 V + two times the ratedvoltage of the electrical machine on which thecommutator will be used, with leakage current notexceeding 100 mA.

11.3 Insulation Resistance Test

11.3.1 [n.sulation Resistance Test for Moulded

Commutators

The above test shall be conducted with a 500 V meggerbetween shorted segments and the bore of thecommutator. The IR value shall be more than 50NK2 at 130”C.

11.3.2 lrrsulation Resistance Test for Built-up ConE

mutators

Insulation resistance shall be more than 10 IWQbetween shorted segment and the bore when checkedwith a 500 V megger at room temperature.

12 HUMIDITY TEST

This test is conducted only for moulded typecommutators. The commutator shall be subjected tohumidity treatment as under:

Temperature 25°CRelative Humidity Not less thm95 percentDuration 24 h.

Immediately after taking out from the humiditychamber and wiping the condensate with dry cloth orblotting paper, the insulation resistance of thecommutator when checked in limit with 11.3.1 shallnot be less than 10 MQ at ambient temperature.

13 SPIN TEST

The spin test is conducted (See Annex A) to ascertainthe mechanical stability of the commutator underworking conditions. The commutator shall bemounted on a mandrel and a cut made on the brushsurface to reduce the TIR to as little as possible. Thecommutator shall then be heated to 140°C and run atan RPM of 1.2 times the maximum rated speed for aduration of 1 minute. The test result shall be as follows:

Segment to segment deflection:– 0.004 mm, Max for moulded commutators– 0.010 mm, Max for rivetted commutators– 0.005 mm, Max for built-up commutators

Change in TIR– 0.006 mm, Max for moulded commutators– 0.020 mm, Max for rivetted commutators– 0.040 mm, Max for built-up commutators

IS 14569:1999

ANNEX A

(Clause 13)

TEST METHOD FOR SPIN TEST AND CHECKING TIR

A and B Type Commutators:

Mount the commutator on the Spin Test mandrel andcut the brush surface to reduce TIR to the minimum.Measure and record TIR between centres. Makemarking on the mandrel and the commutator to ensurerelocation of the commutator while Spin Testing.Remove the commutator, heat it in an oven to getcommutator temperature to 140°C. Mount thecommutator in hot condition on the mandrel as peroriginal position marked. Mount the mandrel and runat a rev/rein of 1.2 times the maximum rated speed ofthe machine for a duration of 1 minute. Check thecommutator for cracks, mica separators flaking andother changes.

Change in TIR will be the difference between thereadings before and after spin test. Bar deflection shallbe measured between adjacent copper bars. Testresult should”be asfollows.

C Type Commntators:

Mount the Commutator on spin test mandrel. Cut thebrush surface to reduce TIR to the minimum possible.

Measure TIR between centres and record the readings.Mount the mandrel with commutator on the spin testmachine. Put a band heater around brush surfaceleaving a gap to permit rotation of the commutator.Run at the slowest rev/rein possible to heat thecommutator to a temperature of 155”C. Afterchecking the commutator temperature and arsuring itis 155°C * 5°C, the commutator is to be run to arev/rein of 1.2 times the maximum rated speed for aduration of 5 minutes. Speed is then slowly reducedto stop rotation and the commutator allowed to coolto room temperature without removing thecommutator from the mandrel.

Mount the mandrel between centres and measure TIRand bar deflection.

Change in TIR will be the difference between thereadings taken before and after the spin test. Bardeflecticm will be the reading taken between adjacentcopper bars.

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IS14569:1999

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IS14569:1999

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Bureau of Indian Standards

BIS is a statutory institution established under the Bureau o~ Indian Standards Act, 1986 to promoteharmonious developmetrt of the activities of standardization, marking and quality certification of goods andattending to connected matters in the emm~.

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without the prior permission in writing of BIS. This does not preclude the free use, in the counse of

implementing the standard, of necessary details, such as sy-mbols and sizes, type or grade designations.Enquiries relating to copyright be addressed to the Director (Publication), BIS.

Review of Indian Standards

Amendments are issued to standards as the need arises on the basis of comments. Standards are also reviewedperiodically; a standard along with amendments is reaffirmed when such review indicates that no changes areneeded; if the review indicates that changes are needed, it is taken up for revision. Users of Indian Standardsshould ascertain that they are in possession of the latest amendments or edition by referring to the latest issueof ‘BR3Handbook’ and ‘Standards Monthly Additions%’

This Indian Standard has been developed from DOC:No! ET 15 ( 2951 )./

Amendments Issued Since Publication

Amend No. Date of Issue Text Affected—

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