IS 13584: Brush Materials for Electrical Machinery

39 Pages·1993·3.1 MB·English

by  Bureau of Indian Standards

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timely dissemination of this information in an accurate manner to the public.
“जान1 का अ+धकार, जी1 का अ+धकार” “प0रा1 को छोड न’ 5 तरफ”
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“The Right to Information, The Right to Live” “Step Out From the Old to the New”
IS 13584 (1993): Brush Materials for Electrical Machinery
[ETD 15: Rotating Machinery]
“!ान $ एक न’ भारत का +नम-ण”
Satyanarayan Gangaram Pitroda
““IInnvveenntt aa NNeeww IInnddiiaa UUssiinngg KKnnoowwlleeddggee””
“!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता हहहहै””ै”
Bhartṛhari—Nītiśatakam
“Knowledge is such a treasure which cannot be stolen”

IS 13584:1993
C Superseding IS 3003 ( Part 2 ) : 1977 I

Indian Standard
BRUSH MATERIALS FOR ELECTRICAL
MACHINERY- SPECIFICATION
UDC 621’3 13’047’4

0 BlS 1993
BUREAU OF INDIAN STANDARDS
MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG
NEW DELHI 110002

March 1993 Price Group 11
Rotating Machinery Sectional Committee, ETD 15
CONTENTS
PAGE
SCOPE . . . . . . . . . . . 1
:: REFERENCES . . . . . . . . . 1
3. TERMINOLOGY . . . . . . . . . . . . 1
4. TOLERANCES . . . . . . . . .
TEST SPECIMEN . . . . . . . . . . . . :
6: DENSITYA ND POROSITY . . . . . . . . . . . . 2
7. HARDNESS . . . . . . . .
RESISTIVITY . . . . . . . . . . . . ::
;: TRANSVERSES TRENGTH . . . . . . . . . . . 9
10. ASH CONTENT . . . . . . . . . . . . 11
11. MEASUREMENTO F OPERATIONALC HARACTERISTICOSF BRUSHES . . . 12
11.1 CONTACT DROP VOLTAGE . . . . . . . . . . . 15
11.2 MEASUREMENTO F COEFFICIENOTF FRICTION . . . . . 16
11.3 MEASUREMENTO F BRUSH WEAR . . . . . . . . . 18
12. MARKING . . . . . . . . . . . 19
13. PACKAGING . . . . . . 19
14. INFORMATIONT O BE GIVEN ON ENQUIRYO R ORDER . . . . . . 19
TABLE 1 TOLERANCES . . . . . . . .
TABLE 2 PREFERREDV ALUESO F SPECIMENA ND TESTINGC ONDITIONS . ;
TABLE 3 RECOMMENDEDSP ACING( Is ) FOR TEST LOADS . . . . . . :‘:
TABLE 4 PRESSURET EST CONDITIONS . . . . . . .
.. .
ANNEX A . . . . . . . . 20
ANNEX B . . . . . . . . . . .
ANNEX C . . . . . . . . . . . 2’:
ANNEX D . . . . . . . . . . 9. 28
ANNEX E . . . . . . . . . . . .
ANNEX F . . . . . . . . . . . :;
FIG. 1 RELATIONB ETWEENT HICKNESSp, w AND 1 OF TEST SPECIMEN 1
AND DIRECTIONO F PRESSINGP RESSURE . . . . . .
FIG. 2 RELATIONB ETWEEND IMENSIONSP,w AND I OF TEST SPECIMEN 2
AND DJRECTIONO F -EXTRUSION . . . . . . . . .
FIG. 3 HARDNESST EST: INDEKTATIONM ETHOD . . . . . . 6
Fr;. 4 TEST SPECIMENF OR RESISTIVITYM EASUREMENT .., . . . 8
FIG. 5 THREEK NIFE EDGESF OR TRANSVERSES TRENGTH . . . . . . IO
FIG. 6 IJPPERA ND LOWER~LIMITSO F TRUE ASH CON~NT FOR DIFFERENTV ALUES SPECIFIED 12
FIG. 7 TOTAL VOLTAGED ROP FROMT HE BRUSHT ERMINALT O SLIP-RING OR COMMUTATOR 15
FIG. 8 ANODIC AND CATHODIC BRUSHES . . . . . . . . . 15
FIG. 9 LOCATIONO F CONTACTP ROBE . . . . . . . . . 16
FIG. 10 ILLUSTRATIONO F COMPONENTSIF -FRICTIONALF ORCE . . . . . . 17

FIG. 11 SKETCHS HOWING METHOD OF MEASUREMENTO F COEFFICIENOT F FRICTION 18

FIG. 12 MEASUREMENOT F B RUSHW EAR . . . . . . . . 19
FIG. 13 TEST RING . . . . . . . . . . . .
FIG. 14 SEGMENTO F TEST RING . . . . . . . . . z:
FIG. 15 SEGMENT“ DOMIMG” . . . . . . . . . . . .
# FIG. 16 DEGREEO F ROUGHNESSR a . . . . . . . . . if
FIG. 17 SPACINGO F BRUSHESR OUND TEST RING .I. . . . 23
FIG. 18 PRESSUREO N BRUSHES . . . . . . . . .
FIG. 19 TEST SLIP RINGS ( GROOVED) . . . . . . . . . ;:
FIG. 20 RIPPLEF ACTOR . . . . . . . . . . . .
FIG. 21 BRUSH WEAR . . . . . . . . . . . . z”s”
FIG. 22 BRUSHT EST MACHINE ( DYNAMOMETER) . . . . . . 29
FIG. 23 POSITIONINGO F THERMOCOUPLES . . . . . . . . .
FIG. 24 TEMPERATUREG RADIENTO F BRUSH . . . . . . . . . 33:
FIG. 25 TYPICAL DESIGN OF THERMOCOUPLE . . . . . . . . .
FIG. 26 RELATIONSHIOP F RELATIVEH UMIDITYA ND TEMPERATURE . . . ::.
FOREWORD
This Indian Standard was adopted by the Bureau of Indian Standards, after the draft finalized by
the Rotating Machinery Sectional Committee had been approved by the Electrotechnical Division
Council.
( Continued on third cover )
IS 13584 : 1993
Indian Standard
BRUSH MATERIALS FOR ELECTRICAL
MACHINERY - SPECIFICATION
1 SCOPE brush block material, it is necessary (iu order to
obtain a correct value when measuring the hardness
1.1 This standard covers the test methods and the and the transverse strength) that the thickness p,
tolerances applicable for determination of the width w and length’ I (see Fig. 1 and 2) have a
properties which are inherent in the brush materials definite relation to the direction of pressing pressure
for electrical machinery. or axis of extrusion. The length L shall be
perpendicular to the direction of compression for
1.2 The performance characteristics of the carbon pressed blocks and shall be along the axis of extrusiou
brushes in operation on electrical equipment will be for extruded blocks. On brush material of laminated
covered later. structure, the thickness p shall be perpendicular to
the lamination (parallel to the direction of
2 RJZFERXNCE STANI)ARDS compression).
The Indian Standard8 listed in Amlex A are necessary 5.2 The dimensions p x w x 1 of the standard test
adjuncts to this standard. specimen should be:
3 TERMINOLOGY 10 mm x 10 mm x 64 mm
or
For the purpose of this standard, the definitions given
in IS 13586 : 1992 shall apply. 4 mm x 8 mm x 32 mm
4 TOLERANCES NOTE - See 5.4 for tolerance on dimensions.
4.1 Values of physical properties published is 5.2.1 Where practicable, a +est specimen may bc
catalogues of the manufacturers of brush material cut from a manufactured brush provided it meets
shall be based upon test methods given in this standard the requirements of 4.1 and ~for which a cutting plan
and shall be subject to the tolerances specified in may be obtained from the carbon brush
Table 1. It may be noted that the values of tolerances manufacturers.
specified are the maximum values and those may
be reduced suitably for a particular application, if
considered necessary and agreed to between the
DIRECTION OF
user and the supplier.
PRESSING PRESSURE

Table 1 Tolerances
I
(Clnuses 4.1, 6.2.5, 7.4, 8.4, 9.4,
10.4 and 11.3.3)
Characteristics Tolerance on Declard Values
Density Not exceeding f 5 percent
Porosity Under consideration
Hardness NOI exceeding ? 15 percent
Resistivity Not exceeding + 25 percent BLOCK
Transverse strength Not exceeding fr 20 percent
Ash content See Note in 10.4 and Fig. 6 FIG;. 1 RELATION BETWEEN DIMENSIONS p, w
AND I OF TEST SPECIMEN AND DIRECTION OF PRESSING
Brush wear Sea Note in 11.3.3 PRESSURE
5.2.2 In caseswhere it is not possible to cut a standard
5 TEST SPECIMEN size test specimen from a manufactured brush, the
size should be a matter of agreement between the
5.1 Some of the properties are to be determined on user and the supplier. Caution should be used iu
a standard test specimen (sample) with dimensions testing smaller size pieces as the deviation may be
as given in 8.2. When ~the test specimen is cut from great, due to difficulty in handling.
1
IS 13584 : 1993
5.3 All adjacent surfaces shall be at right angles. The apparent porosity is defined by the formula:
The specimen should be carefully machined to the
surface finish normally used for carbon brushes. All V
traces of any die skin or extrusion skin should be P, = 0 x 100 percent
removed. vb
6.2 Methods for Determining the Bulk Density and
DIRECTION OF Porosity
EXTRUSION
The bulk density may be determined by one of
following standard methods:
a) Measurements-and-weight method (6.2.2),
b) Immersion method (6.23) a~nd
c) Oil-absorption method (6.2.4).
The porosity Ps may be determined by the oil-
abs-orption method.
EXTRUDED BLOCK 6.2.1 The measurements-and-weight method is
suitable for production quality control and should
FIG. 2 RELATION BETWEEN DIMENSIQNS p, w preferably be used. The immersion method is
ANY 1 OF TEST SPECIMEN AND DIRECTION OF considered to be an alternative and may be used
EXTRIJSION in cases where the measurements-and-weight method
cannot be applied or is unsuitable. The oil-absorption
5.4 The tolerance on the dimensions p and w is method is suitable for laboratory use. All these
kO.04 mm and the tolerance on the dimension s is methods are considered accurate to three significant
20.8 mm. figures, which is sufficiently accurate for checking
these properties.
When a large number of test specimens are concerned
and density is one of the properties measured, it
NOTE - The oil-absorptionm ethod may give unreliable
is more convenient to apply the tolerance of -C 0.04 values for material with a porosity higher than 30 percent.
mm to dimension 1 is well as to dimensions p and
W. 6.2.2 Measurements-and-Weight Method
In order to ensure squareness of p x w section, 6.2.2.1 Equipment and test specimen
the telerance for the angles shall be 215. The
parallelism defined by the difference between the
The following shall be required:
dimensions of the two opposite sides at any cross
section perpendicular to the dimension 1 should be
a) Micrometer with an accuracy of ~~0.01 mm
within 0.04 mm.
suitable for measuring the test specimen;

6 DENSITY AND POROSITY
9 A scale of single fan balance to determined
mass (m) in grams. The sensitivity of
6.1 Letter Symbols
measurement shall be O.Fpercent or better.
The following letter symbols are used for The balance of capacity 100 g and sensitivity
quantities: 1-0.005 g may be found suitable for normal
samples;
m = mass of test specimen (dry), in g;
cl Saw or other device for cutting the sample
Vb = bulk (apparent) volume of material
to a required size;
(including accessible and closed pores), in
cm3;
d) Grinding wheel or other device for machining
v, = volume of the accessible pores of the the test specimen so that all adjacent surfaces
specimen, in cm3; are at right angles; and
6, = bulk density, in glcm3; The specimen in accordance with 5.4 or any
rectangular or cylindrical sample of a suitable
Ps = apparent porosity, in percentage; and
size the ends of which are plane at an right
d = diameter, in mm. angles to the sides.
The bulk density is then defined by the 6.2.2.2 Procedure
equation:
The measurements necessary for calculating the
6, = + volume of the test sample shall be ~made using the
micrometer. This requires measuring the thickness,
b

2
IS 13584 : 1993
width and length of rectangular pieces or the diameter 6.2.3.3 Calculations
and length of cylindrical pieces. These measure-
ments shall be taken to the nearest hundredth of a When weighed in air, the force on the sample (due
millimetre. to gravity) is Go, when the sample is immersed in
water, the force on it (due to gravity) is also Go,
The sample shall be weighed in grams to three but, according to Archimedes’ principle another force
significant decimal places. y, x Vb (where y, is the specific gravity of water
and Vb is the volume of the sample) is also acting
6.2.2.3 Calculations on the sample so that the weight measured in water
is:
The volume V, of the sample expressed in cm3 shall
be calculated as follows: G, = Ga - Y, ‘,
v,=pxw x 1 for rectangular pieces However,
or
G
VbZ * = _--L_-
3rdJ
= - x I for cylindrical pieces b g . ‘b
4
and Y, = g x aw
The bulk density 6, shall be calculated as follows:
where g is the acceleration due to gravity and y,
m is the density of the water.
6b= v
b Thus: % x Gil
G, = Go -
6.2.3 Immersion Method
‘b
or
6.2.3.1 Equipment and ‘test specimen
6, (GO - G,) = aw x GD
The following shall be required:
or
4 Container of water large enough to immerse
G
the test sample; 6, = aw x n
Ga- G,
b) Weighing scale or balance in accordance
with 6.2.2.1(b);
The value of aw is very close to 1.
cl Grease or other waterproof masking material
for coating the sample to prevent the 6.2.4 Oil-Absorption Method
absorption of water;
6.2.4.1 Equipment and test specimen
4 Thread to suspend sample while it is being
weighed during immersion . The diameter of
The following shall be required:
the thread shaH not exceed 0.08 mm; and
a) A weighing scale or balance in accordance
4 Test specimen.
with -6.2.2.1(b);
As this method may be used for irregularly-shaped b) Hydrometer having a specific gravity range
samples, no preparation is necessary beyond making of 0.800~to 0.900 at 20°C and graduated to
sure that the sample is clean, dry and free from 0.001;
extraneous metal or foreign material.
Cl Hydrometer cylinder;
6.2.3.2 Procedure 4 Thermometer having a range of -1OOC to
+ 100°C, accuracy 0. l°C;
The sample shall be weighed in air. All surface of
the sample shall be coated as thinly aspossible with e) Banker of wide mouth and a capacity of
grease or other waterproof masking material. The 1 000 cm3;
sample shall be weighed in air again. The increase
f) Vacuum desiccator or bell jar;
due to the coating should not exceed one part in
200. The result shall be expressed in grams to three t3)V acuum pump capable of developing an
significant figures. absolute pressure of 20 mm Hg (about 25
mbar);
The sample shall be suspended by a piece of thread
h) Water-bath maintained at a temperature below
from the balance. It shall be immersed completely
2ooc;
in water, taking.care to remove all air bubbles, and
it shall be weighed while it is thus immersed. The j> Petroleum oil grade SAE-10 (24-32 CSt at
minimum possible length of thread shall be used. 5OOC) or kerosene;

3
IS 13584 : 1993
k) Saw or other device for cutting the sample analogy with the calculations in 6.2.3.2, the bulk
to a required size; density b can be obtained as:
4 Grinding wheel or other device for
GO
smoothing off rough edges; and 6, = aw x
G2- G3
4 A test specimen with a mass of 2.5 to 100
g. If the sample is taken from a piece which and the porosity
originally had metal fittings, plating, etc, all
such foreign material shall be removed. All V
surfaces shall be ground to reasonable p, = 0 x 100 percent
smoothness so that there are no burrs or v,
sharp edges to chip off during the test. In
6.2.5 The values of bulk density as obtained from
general, metal-graphite grades and very
any of the test method specified in 6.2.2 to 6.2.4
dense materials should be tested in samples
shall comply with the declared value subject to a
larger than those taken from other brush
tolerance given in Table 1.
materials.
6.2.6 The value of porosity as obtained from 6.2.4
6.2.4.2 Procedure
shall comply with value declared by the
manufacturer. The tolerance on porosity is under
The sample shall be weighed in air to three significant
consideration. If required, the tolerance shall be a
figures.
subject of agreement between the user and the
manufacturer.
The sample and a thermometer shall be placed in
the beaker and the pump connected to the beaker.
7 -HARDNESS
The pressure shall be reduced gradually to 20 to
60 mm Hg (about 2580 mbar).
7.1 General
Without breaking the vacuum preheated to 70°C,
There are two methods in general use for determining
the oil or kerosene <hall be gradually introduced into
the hardness of brush materials, namely:
the beaker so that the sample is covered completely
with oil. a) Rebound method (7.2), and
b) Indentation method (7.3).
The pressure shall be maintained at 20 to 60 mm
Hg (about 25-80 mbar) for 5 hours or until the sample
7.1.1 It should be kept in mind that there is no
stops emitting bubbles, whichever is reached earlier.
general relation between the hardness of a brush
material and the abrasiveness of the same material.
NOTE -To judge that sample has stopped emitting bubbles,
it would be seen that no bubble is evolved during a period
of half an hour. 7.12 It is recognized that results obtained for a
particular test method can be checked only against
The beaker and its contents shall be cooled to below results obtained by the same method and standardized
20°C in the waterbath. The be aker shall be removed against equivalent standards. The rebound method
from the bath and the temperature shall be allowed of hardness measurement reflects the property of
to rise lo 20°C. elasticity of material whereas the indentation method
indicates the plasticity of material. The user may
At this point, ~the sample shall be removed from the specify the method to be used for determining the
oil and wiped dry. hardness of brush material. In case method (b) is
being followed shore hardness value +hall also be
The oil-impregnated sample shall be weighed in air indicated by the manufacturer.
to three significant figures. This mass G,, shall be
recorded. 7.1.3 The value of hardness measured on individual
brushes may not be comparable to those taken on
The oil from the beaker shall be pured into the other brushes, or cm brush blocks, unless the direction
hydrometer cylinder, bring its temperature up to 20°C of pressing or of extrusion is the same.
and its specific gravity shall be read. This value
shall be recorded as 6,. 7.2 Rebound Method
The oil-impregnated sample submerged in water shall This test method is suitable for production, quality
be weighed as described in 6.2.3.2. This mass, G,, control, especially if the material to be tested is not
shall be recorded. very soft.
6.2.4.3 Calculation 7.2.1 Equipment and Test Specimen
The mass of the oil-absorbed is G, = G, - Ga. Thus
The following shall be required:
G0
the volume of oil-absorbed is Vo = y-. In a) Scleroscope, Shore model C* or equivalent,
0

4
IS 13584 : 1993
equipped with a special hammer for testing 7.2.3 Procedure
brush material.
The piece shall be placed on the appropriate anvil
NOTE - The hammer and its components should be so that the hammer impact is applied in the direction
as follows: of the pressing pressure in the case of brush block
materials and perpendicular to the axis of extrusion
i) Mass : 2.2 g ?r 5 percent; for extruded materials.
: .j 94 +0.013 mm
ii) Outside diameter . -0
The tube shall be lowered against the test piece and
iii) Overall length : 20.7 to 21.4 mm;
held firmly while the test is being made.
iv) Clearance between
hammer and tube - The hammer shall be released and the height of the
at the top of tuba : 0.19 to 0.31 mm; rebound shall be read.
at the bottom of the tube : 0.04 to 0.08 mm;
If possible, the hardness shall be measured at five
v) Height from which : 251.21 $:i mm; points on each side of the test specimen.
and hammer falls
To avoid random low readings giving a false result,
vi) The tip of the hammer should be a diamond, oval
in shape and driven into a tapered hole in the the lowest readings in each of the two groups of
hammer body. The body should be of water five readings shall be disregarded. The average of
hardening drill-rod containing approximately 1.2 the eight remaining readings is taken as being
percent of carbon and should be hardened and representative of the hardness of the specimen.
tempered after insertion of the diamond. Measured
at the contact surface, the diamond should have a
curvature of 1.32 mm +5 percent, measured over a 7.3 Indentation Method
0.61 mm long arc.
The test consists in forcing a ball into the surface
b) The test specimen may be of a size indicated of a test piece in two operations and measuring the
in 5.2 or any other convenient size. The piece permanent increase of the depth of indentation of
to be tested should have the skin removed, this ball under specified conditions (see Fig. 3).
and the surface should be machined smooth
and free from defects, dirt, grit or other The hardness may be measured directly on
foreign material. A rectangular piece should manufactured brushes if:
have at least two parallel surfaces. A circular
piece should have a uniform diameter, a) the brush is not coppered and t, a and r [see
otherwise the hammer will strike the piece Dot : ETDC 15(3100)] are at least 10 mm;
a glancing blow and false readings will result. or
Preferably, and if permissible, when testing
circular pieces two parallel flat surfaces b) the brush is coppered and a to t are at least
should be machined to facilitate accurate 10 mm and at the same time the part of
testing. r that is not coppered is at least 10 mm.

7.2.2 Setting-Up the Instrument Measurements taken on ~a smaller specimen may be
subject to error due to possible effects of cracking,
The instruments shall be placed on a firm support
crushing and deformation.
and levelled up.
It shall be checked that the ‘plumb bob’ on the front For all other brushes, the measurement of the
of the instrument can swing freely in the ring. hardness should be made on the brush block material
before the brushes are cut to size.
The calibration of the instrument shall be checked
using previously prepared reference samples.
7.3.1 Equipment and Test Specimen
The anvil for the test piece shall be prepared.
The following shall be required:
If the test piece is circular in cross section and suitable
parallel flat surfaces cannot be machined, the vee- a) Rockwell hardness test apparatus
block anvil shall be used. If the test piece is rectangular
(Ponetrometer) with equipment for different
in cross section, the basic flat anvil (which is part loads F,, F and F (see Fig. 3). A device
of the instrument proper) shall be used. (such as a d ashpot) should be incorporated
NOTE - Keep the anvils clean. Wipe dust and dirt particles to prevent the load from being applied
off the anvil with a soft lintless cloth. When a vee-block anvil suddenly, it should be adjusted so that,
is used, wipe the flat anvil and the mating surface of the vee- during the hardness test, the load increases
block anvil, clean before placing them together. Dirt particles from F, to F = F, + F, within 2 to 8 second;
between the two anvils would cause false readings.