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BS EN IEC 60773:2021

BS EN IEC 60773:2021

$215.11

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

Published By Publication Date Number of Pages
BSI 2021 84
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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.

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PDF Pages PDF Title
2 undefined
5 Annex ZA(normative)Normative references to international publicationswith their corresponding European publications
7 English
CONTENTS
11 FOREWORD
13 1 Scope
2 Normative references
3 Terms, definitions, symbols and abbreviated terms
14 3.1 Terms and definitions
Figures
Figure 1 ā€“ Profile and determination of height of profile elements
17 Figure 2 ā€“ Forces acting on a brush
Figure 3 ā€“ Voltage drops in a brush when in operation
20 3.2 Symbols
3.2.1 Symbols and units
21 3.2.2 Subscripts
22 3.3 Abbreviated terms
23 4 Test rig specification
4.1 Common specification
4.1.1 General
4.1.2 Rings
24 4.1.3 Brushes
4.1.4 Brush holders
Table 1 ā€“ Dimensions of test brushes
25 Figure 4 ā€“ Brush holder configuration
26 4.1.5 Power supply
4.1.6 Instrumentation
27 Figure 5 ā€“ Measurement of the mechanical torque by Method a)
28 Figure 6 ā€“ Brush test machine for Method b)
29 Figure 7 ā€“ Test rig arrangement with a load cell
32 Figure 8 ā€“ Brush contact probe application point for Uc
33 Figure 9 ā€“ Thermocouples insertion position
34 Figure 10 ā€“ Evaluation of contact temperature (c by interpolation
36 4.2 Test rig specification for commutators
4.2.1 General
4.2.2 Test rings
37 Figure 11 ā€“ Illustration of bar grooves dimensions and preparation
39 4.2.3 Brushes arrangement
Figure 12 ā€“ Brush covering
40 4.2.4 Special brush for voltage drop measurement
Figure 13 ā€“ Brushes configuration
41 4.3 Test rig specification for slip rings
4.3.1 General
4.3.2 Ring
Figure 14 ā€“ Control brush arrangement
42 Figure 15 ā€“ Characteristics of grooves
43 4.3.3 Brushes
4.3.4 Configuration for DC and AC operation
44 Figure 16 ā€“ Test rig arrangement for DC operation with 2 brushes per polarity
45 5 Test schedule and operating conditions
5.1 General
Figure 17 ā€“ Test rig arrangement for AC operation with 2 brushes
46 5.2 Environmental conditions
5.2.1 Laboratory environment
5.2.2 Ambient air temperature and ring surface temperature
5.2.3 Ambient humidity
5.3 Operating conditions
47 5.4 Test preparation and inspection
5.4.1 General
5.4.2 Test rig
5.4.3 Brush-holders
5.4.4 Test brushes
5.4.5 Ring roughness
Table 2 ā€“ Test conditions
48 5.4.6 Brush bedding
5.4.7 Brushes measurement
5.5 Test sequence
5.5.1 Test starting
5.5.2 Test duration
5.6 Measurements and observations
5.6.1 General
49 5.6.2 Interval between measurements
5.6.3 Before starting a test sequence
50 5.6.4 Measurements during a test sequence
5.6.5 Measurements after a test sequence
6 Determination of friction coefficient
6.1 General
51 6.2 Test conditions
6.3 Measurements
6.3.1 General
6.3.2 Test rig arrangement of Method a)
6.3.3 Test rig arrangement of Method b)
6.4 Calculation of friction coefficient
6.4.1 Test rig arrangement of Method a)
52 6.4.2 Test rig arrangement of Method b)
6.5 Report
53 7 Determination of voltage drop
7.1 General
Figure 18 ā€“ Example of friction coefficient Āµ graph as a function of peripheral speed Ī½p
54 7.2 Test conditions
7.3 Measurements
7.3.1 General
7.3.2 Brush total voltage drop UB
7.3.3 Brush contact voltage drop Uc
55 7.4 Calculation
7.4.1 Brush total voltage drop UB
7.4.2 Brush contact voltage drop Uc
56 7.5 Report
57 8 Determination of brush wear
8.1 General
8.2 Test conditions
8.3 Measurements
Figure 19 ā€“ Example of brush total voltage drop UB graphas a function of current density JB
58 8.4 Calculation of brush wear
Figure 20 ā€“ Example of brush wear rate WRi of brushesduring the test for a test rig with 4 brushes
59 8.5 Report
9 Determination of commutation ability of brush grades by a specific blackband test on a DC machine
9.1 General
60 9.2 Set-up
61 Figure 21 ā€“ Black-band test circuit configuration using DC generator and resistance load
62 Figure 22 ā€“ Black-band test circuit configuration for Brondellā€™s loading-back method
63 9.3 Test procedure
9.3.1 Preparation of the test
9.3.2 Operating conditions and test sequence
64 9.4 Black-band graph
65 9.5 Interpretation
9.5.1 General
Figure 23 ā€“ Determination of black-band zone for a specified constant speed of rotation
66 9.5.2 Influence of commutator skin thickness on the black-band zone
67 9.5.3 Influence of brush contact resistance
Figure 24 ā€“ Influence of commutator film thickness on the black-band zone
68 Figure 25 ā€“ Comparison of black-bands for a high contact resistance brushand a low contact resistance brush in case of a motor
69 9.5.4 Estimation of mechanical contact stability deviation by comparing the black-band figures before and after longtime critical operation
Figure 26 ā€“ Comparison of black-bands for a high contact resistance brushand a low contact resistance brush in case of a generator
70 Figure 27 ā€“ Black-band figure deviation of before and after the critical operationof repetitive peak load application of 225 %, for a “strong” grade
71 Figure 28 ā€“ Black-band figure deviation of before and after the critical operation of repetitive peak load application of 225 %, for a “weak” grade
72 Annex A (informative)Additional information for friction coefficient measurement
A.1 Details of calculation of friction coefficient by using method a) of 4.1.6.1.2
73 A.2 Adjustment of strain sensor for calculation of friction coefficient by using method b) of 4.1.6.1.3
A.2.1 General
A.2.2 Correlation between output voltage and load
A.2.3 Correlation between friction coefficient and load
Figure A.1 ā€“ Correlation of load cell output voltage Ulc with mass m
74 Figure A.2 ā€“ Example of correlation between load and friction coefficient Āµ
76 Annex B (informative)Black-band zone deviation cases
B.1 Black-band zone in case of limited contact area
Figure B.1 ā€“ Limited contact area and reduction of tangential dimension at contact
77 B.2 Influence of brush mechanical contact instability of brush chattering on the black-band zone
Figure B.2 ā€“ Black-band zone in case of a limited contact area
78 B.3 Black-band zone hysteresis between increased Ia and decreased Ia
Figure B.3 ā€“ Influence of brush mechanical contact instabilityof brush chattering on the black-band zone
79 Figure B.4 ā€“ Black-band zone hysteresis between increasing Iarm and decreasing Iarm
80 Annex C (informative)Test report example
82 Bibliography

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BS EN IEC 60773:2021
$215.11