Test apparatus, procedures, and results are given for dc-motor brushes operating in dry argon. Minimum concentrations of argon impurities are also determined

Bernstein, G. J.

Coleman, L. F.

Slawecki, M. A.

English

NASA Technical Reports Server

January l70
	 -
Brief 70-10045 
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Commutating Brushes Tested in DC Motors

in Dry Argon Atmospheres 
The test apparatus and procedures for testing of 
dc-motor brushes operating in a dry argon atmosphere 
have been described (see Reference). Operation of dc 
motors in a dry, low-oxygen atmosphere can cause 
rapid wear of the commutating brushes. Operation of 
manipulators, driven by direct current, has presented 
commutation problems requiring extensive tests of 
brush materials. 
These tests were performed by o1eration of dc 
motors, of the type used in the manipulators, in an 
enclosure containing an atmosphere of high-purity 
argon; a gas-purification system was used to control 
the moisture and oxygen contents of the enclosure. 
Brushes were supplied by three vendors on the basis 
of their brushTgrade recommendations for use in dry 
atmospheres. 
The initial purpose of the tests was to determine as 
quickly as possible the best grade of brush for such 
use, since brush failures were' seriously hampering 
operation of the manipulators. As testing progressed, 
the possibility of determination of minimum concen-
trations of impurities in argon (primarily moisture, 
with some emphasis on oxygen), conducive to good 
brush wear, became apparent. 
One grade of brush was tested by variation of the 
moisture concentration between less than 5 and 100 
ppm; the results are summarized in the Reference. 
Data scatter in the test results is discussed as a func-
tion of both oxygen and nitrogen concentrations and 
other variables pertinent to brush wear on a sliding 
surface. Specific applications of the most promising 
brush materials tested are cited, aside from the use 
for which the tests were originally performed.
The tests resulted in selection of a brush • material 
(Stackpole grade-660) that is being used successfully 
in manipulator-drive motors. Similar brushes have 
also been installed in other dc motors used in process-
ing equipment undergoing test in argon atmospheres. 
The same material has been employed in universal 
motors used in vacuum cleaners and hand-drill units 
working in argon atmospheres; here the material has 
greatly increased the life of motors whose commutator 
peripheral speeds approach 5000 ft/mm. 
One such vacuum-cleaner motor ran for only about 
15 min in a dry argon atmosphere. on the brushes pro-
vided with the unit; the brushes had then worn com-
pletely down and caused short-circuiting of the com-
mutator of the armature. An identical motor has now 
been in heavy use for about 1 year in a similar 
atmosphere after substitution ' of Stackpole grade-
660 in the brushes. The new brushesstill wear faster 
than in normal-humidity atmospheres, but at a reason-
able rate that can be tolerated. Limited tests show 
promise for other grades of brushes in low-impurity 
atmospheres. 
Reference: 
Slawecki, M. A.; Bernstein, G. J.; Coleman, L. F.: 
Tests of Commutating Brushes for Use in DC Motors 
Operating in a Dry Argon Atmosphere. ANL-7262. 
Argonne National Laboratory. 
Notes: 
1. Designers or users of electric motors in dry, low-
oxygen environments may be interested.
(continued overleaf( 
Alm
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2. Inquiries concerning this information may be di-
rected to:
Office of Industrial Cooperation 
Argonne National Laboratory 
9700 South Cass Avenue 
Argonne, Illinois 60439 
Reference: B70-10045 
Source: M. A. Slawecki, G. J. Bernstein, 
and L. F. Coleman
Chemical Engineering Division
(A RG- 10243)
Patent status: 
Inquiries concerning rights for commercial use of 
this innovation may be made to: 
Mr. George H. Lee, Chief 
Chicago Patent Group 
U.S. Atomic Energy Commission 
Chicago Operations Office 
9800 South Cass Avenue 
Argonne, Illinois 60439 
p 
Brief 7010045	 Category 01


Commutating brushes tested in dc motors in dry argon atmospheres

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