Rotating electrical machines - Test methods and apparatus for the measurement of the operational characteristics of brushes

IEC 60773:2021 applies to test methods for the measurement of the operational characteristics of brushes designed to operate on commutating and slip ring machines under specified test conditions. By extension some tests may be relevant for other kinds of sliding electrical contacts for electrical appliances.
This second edition cancels and replaces the first edition published in 1983. This edition includes the following significant technical changes with respect to the previous edition:
- the clause structure has been modified on the view point of a laboratory testing procedure. The new sequence is as follows: test rig specification, general testing procedure, and specific procedure for each operational characteristic
- a new clause has been added to introduce the black-band test for the characterisation of the brush grades for DC machines.

Machines électriques tournantes - Méthodes d'essai et appareils pour le mesurage des caractéristiques opérationnelles des balais

IEC 60773:2021 s'applique aux méthodes d'essai pour le mesurage des caractéristiques opérationnelles des balais conçus pour fonctionner sur des machines avec commutation et sur des machines à bagues, dans des conditions d'essai spécifiées. Par extension, certains essais peuvent être pertinents pour d’autres types de contacts électriques glissants pour appareils électriques.
Cette deuxième édition annule et remplace la première édition parue en 1983. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
- La structure des articles a été modifiée du point de vue d’une procédure d’essai en laboratoire. La nouvelle séquence est la suivante: spécification du banc d’essai , procédure générale d’essai, et procédure spécifique relative à chaque caractéristique opérationnelle.
- Un nouvel article a été ajouté pour présenter l’essai de bande noire pour la caractérisation des nuances de balais pour machines à courant continu.

General Information

Status
Published
Publication Date
06-Apr-2021
Technical Committee
Current Stage
PPUB - Publication issued
Completion Date
07-Apr-2021
Ref Project

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IEC 60773
Edition 2.0 2021-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Rotating electrical machines – Test methods and apparatus for the
measurement of the operational characteristics of brushes
Machines électriques tournantes – Méthodes d'essai et appareils pour le
mesurage des caractéristiques opérationnelles des balais
IEC 60773:2021-04(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 60773
Edition 2.0 2021-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Rotating electrical machines – Test methods and apparatus for the
measurement of the operational characteristics of brushes
Machines électriques tournantes – Méthodes d'essai et appareils pour le
mesurage des caractéristiques opérationnelles des balais
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.160.10 ISBN 978-2-8322-9656-1

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 60773:2021 © IEC 2021
CONTENTS

FOREWORD ........................................................................................................................... 6

1 Scope .............................................................................................................................. 8

2 Normative references ...................................................................................................... 8

3 Terms, definitions, symbols and abbreviated terms .......................................................... 8

3.1 Terms and definitions .............................................................................................. 9

3.2 Symbols ................................................................................................................ 15

3.2.1 Symbols and units ......................................................................................... 15

3.2.2 Subscripts ..................................................................................................... 16

3.3 Abbreviated terms ................................................................................................. 17

4 Test rig specification...................................................................................................... 18

4.1 Common specification ........................................................................................... 18

4.1.1 General ......................................................................................................... 18

4.1.2 Rings ............................................................................................................. 18

4.1.3 Brushes ......................................................................................................... 19

4.1.4 Brush holders ................................................................................................ 19

4.1.5 Power supply ................................................................................................. 21

4.1.6 Instrumentation .............................................................................................. 21

4.2 Test rig specification for commutators ................................................................... 31

4.2.1 General ......................................................................................................... 31

4.2.2 Test rings ...................................................................................................... 31

4.2.3 Brushes arrangement .................................................................................... 34

4.2.4 Special brush for voltage drop measurement ................................................. 35

4.3 Test rig specification for slip rings ......................................................................... 36

4.3.1 General ......................................................................................................... 36

4.3.2 Ring............................................................................................................... 36

4.3.3 Brushes ......................................................................................................... 38

4.3.4 Configuration for DC and AC operation .......................................................... 38

5 Test schedule and operating conditions ......................................................................... 40

5.1 General ................................................................................................................. 40

5.2 Environmental conditions ...................................................................................... 41

5.2.1 Laboratory environment ................................................................................. 41

5.2.2 Ambient air temperature and ring surface temperature ................................... 41

5.2.3 Ambient humidity ........................................................................................... 41

5.3 Operating conditions ............................................................................................. 41

5.4 Test preparation and inspection ............................................................................ 42

5.4.1 General ......................................................................................................... 42

5.4.2 Test rig .......................................................................................................... 42

5.4.3 Brush-holders ................................................................................................ 42

5.4.4 Test brushes .................................................................................................. 42

5.4.5 Ring roughness ............................................................................................. 42

5.4.6 Brush bedding ............................................................................................... 43

5.4.7 Brushes measurement ................................................................................... 43

5.5 Test sequence ...................................................................................................... 43

5.5.1 Test starting .................................................................................................. 43

5.5.2 Test duration ................................................................................................. 43

5.6 Measurements and observations ........................................................................... 43

5.6.1 General ......................................................................................................... 43

---------------------- Page: 4 ----------------------
IEC 60773:2021 © IEC 2021 – 3 –

5.6.2 Interval between measurements .................................................................... 44

5.6.3 Before starting a test sequence ..................................................................... 44

5.6.4 Measurements during a test sequence ........................................................... 45

5.6.5 Measurements after a test sequence ............................................................. 45

6 Determination of friction coefficient ................................................................................ 45

6.1 General ................................................................................................................. 45

6.2 Test conditions ..................................................................................................... 46

6.3 Measurements ...................................................................................................... 46

6.3.1 General ......................................................................................................... 46

6.3.2 Test rig arrangement of Method a) ................................................................. 46

6.3.3 Test rig arrangement of Method b) ................................................................. 46

6.4 Calculation of friction coefficient ........................................................................... 46

6.4.1 Test rig arrangement of Method a) ................................................................. 46

6.4.2 Test rig arrangement of Method b) ................................................................. 47

6.5 Report................................................................................................................... 47

7 Determination of voltage drop ........................................................................................ 48

7.1 General ................................................................................................................. 48

7.2 Test conditions ..................................................................................................... 49

7.3 Measurements ...................................................................................................... 49

7.3.1 General ......................................................................................................... 49

7.3.2 Brush total voltage drop U ........................................................................... 49

7.3.3 Brush contact voltage drop U ....................................................................... 49

7.4 Calculation ............................................................................................................ 50

7.4.1 Brush total voltage drop U ........................................................................... 50

7.4.2 Brush contact voltage drop U ....................................................................... 50

7.5 Report................................................................................................................... 51

8 Determination of brush wear .......................................................................................... 52

8.1 General ................................................................................................................. 52

8.2 Test conditions ..................................................................................................... 52

8.3 Measurements ...................................................................................................... 52

8.4 Calculation of brush wear...................................................................................... 53

8.5 Report................................................................................................................... 54

9 Determination of commutation ability of brush grades by a specific black-band test

on a DC machine ........................................................................................................... 54

9.1 General ................................................................................................................. 54

9.2 Set-up ................................................................................................................... 55

9.3 Test procedure ...................................................................................................... 58

9.3.1 Preparation of the test ................................................................................... 58

9.3.2 Operating conditions and test sequence ........................................................ 58

9.4 Black-band graph .................................................................................................. 59

9.5 Interpretation ........................................................................................................ 60

9.5.1 General ......................................................................................................... 60

9.5.2 Influence of commutator skin thickness on the black-band zone .................... 61

9.5.3 Influence of brush contact resistance ............................................................. 62

9.5.4 Estimation of mechanical contact stability deviation by comparing the

black-band figures before and after longtime critical operation ....................... 64

Annex A (informative) Additional information for friction coefficient measurement ................ 67

A.1 Details of calculation of friction coefficient by using method a) of 4.1.6.1.2 ........... 67

---------------------- Page: 5 ----------------------
– 4 – IEC 60773:2021 © IEC 2021
A.2 Adjustment of strain sensor for calculation of friction coefficient by using

method b) of 4.1.6.1.3 ........................................................................................... 68

A.2.1 General ......................................................................................................... 68

A.2.2 Correlation between output voltage and load ................................................. 68

A.2.3 Correlation between friction coefficient and load ............................................ 68

Annex B (informative) Black-band zone deviation cases ...................................................... 71

B.1 Black-band zone in case of limited contact area .................................................... 71

B.2 Influence of brush mechanical contact instability of brush chattering on the

black-band zone ................................................................................................... 72

B.3 Black-band zone hysteresis between increased I and decreased I .................... 73

a a

Annex C (informative) Test report example .......................................................................... 75

Bibliography .......................................................................................................................... 77

Figure 1 – Profile and determination of height of profile elements ........................................... 9

Figure 2 – Forces acting on a brush ...................................................................................... 12

Figure 3 – Voltage drops in a brush when in operation .......................................................... 12

Figure 4 – Brush holder configuration ................................................................................... 20

Figure 5 – Measurement of the mechanical torque by Method a) ........................................... 22

Figure 6 – Brush test machine for Method b) ......................................................................... 23

Figure 7 – Test rig arrangement with a load cell .................................................................... 24

Figure 8 – Brush contact probe application point for U ........................................................ 27

Figure 9 – Thermocouples insertion position ......................................................................... 28

Figure 10 – Evaluation of contact temperature θ by interpolation ......................................... 29

Figure 11 – Illustration of bar grooves dimensions and preparation ....................................... 32

Figure 12 – Brush covering ................................................................................................... 34

Figure 13 – Brushes configuration ........................................................................................ 35

Figure 14 – Control brush arrangement ................................................................................. 36

Figure 15 – Characteristics of grooves .................................................................................. 37

Figure 16 – Test rig arrangement for DC operation with 2 brushes per polarity ..................... 39

Figure 17 – Test rig arrangement for AC operation with 2 brushes ........................................ 40

Figure 18 – Example of friction coefficient µ graph as a function of peripheral speed ν ....... 48

Figure 19 – Example of brush total voltage drop U graph as a function of

current density J ................................................................................................................. 52

Figure 20 – Example of brush wear rate WR of brushes during the test for a test rig

with 4 brushes ...................................................................................................................... 53

Figure 21 – Black-band test circuit configuration using DC generator and resistance

load 56

Figure 22 – Black-band test circuit configuration for Brondell’s loading-back method ............ 57

Figure 23 – Determination of black-band zone for a specified constant speed of

rotation ................................................................................................................................. 60

Figure 24 – Influence of commutator film thickness on the black-band zone .......................... 62

Figure 25 – Comparison of black-bands for a high contact resistance brush and a low

contact resistance brush in case of a motor .......................................................................... 63

Figure 26 – Comparison of black-bands for a high contact resistance brush and a low

contact resistance brush in case of a generator .................................................................... 64

---------------------- Page: 6 ----------------------
IEC 60773:2021 © IEC 2021 – 5 –

Figure 27 – Black-band figure deviation of before and after the critical operation of

repetitive peak load application of 225 %, for a "strong" grade .............................................. 65

Figure 28 – Black-band figure deviation of before and after the critical operation of

repetitive peak load application of 225 %, for a "weak" grade ............................................... 66

Figure A.1 – Correlation of load cell output voltage U with mass m ..................................... 68

Figure A.2 – Example of correlation between load and friction coefficient µ .......................... 69

Figure B.1 – Limited contact area and reduction of tangential dimension at contact .............. 71

Figure B.2 – Black-band zone in case of a limited contact area ............................................. 72

Figure B.3 – Influence of brush mechanical contact instability of brush chattering on

the black-band zone.............................................................................................................. 73

Figure B.4 – Black-band zone hysteresis between increasing I and decreasing I ....... 74

arm arm

Table 1 – Dimensions of test brushes ................................................................................... 19

Table 2 – Test conditions ...................................................................................................... 42

---------------------- Page: 7 ----------------------
– 6 – IEC 60773:2021 © IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
ROTATING ELECTRICAL MACHINES –
TEST METHODS AND APPARATUS FOR THE MEASUREMENT
OF THE OPERATIONAL CHARACTERISTICS OF BRUSHES
FOREWORD

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International standard IEC 60773 has been prepared by IEC technical committee 2: Rotating

machinery.

This second edition cancels and replaces the first edition published in 1983. It constitutes a

technical revision.

This edition includes the following significant technical changes with respect to the previous

edition:

– The clause structure has been modified on the view point of a laboratory testing procedure.

The new sequence is as follows: test rig specification (Clause 4), general testing procedure

(Clause 5), and specific procedure for each operational characteristic (Clauses 6 to 8).

– A new Clause 9 has been added to introduce the black-band test for the characterisation of

the brush grades for DC machines.
---------------------- Page: 8 ----------------------
IEC 60773:2021 © IEC 2021 – 7 –
The text of this International Standard is based on the following documents:
FDIS Report on voting
2/2045/FDIS 2/2050/RVD

Full information on the voting for the approval of this International Standard can be found in the

report on voting indicated in the above table.

This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to

the specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
---------------------- Page: 9 ----------------------
– 8 – IEC 60773:2021 © IEC 2021
ROTATING ELECTRICAL MACHINES –
TEST METHODS AND APPARATUS FOR THE MEASUREMENT
OF THE OPERATIONAL CHARACTERISTICS OF BRUSHES
1 Scope

This document applies to test methods for the measurement of the operational characteristics

of brushes designed to operate on commutating and slip ring machines under specified test

conditions.

By extension some tests may be relevant for other kinds of sliding electrical contacts for

electrical appliances.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies.

For undated references, the latest edition of the referenced document (including any

amendments) applies.
IEC 60034-19:2014, Rotating electrical machines – Part 19: Specific test methods
...

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