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Commutator Issues

Richard Miller

Last Subscription Date
Need advice on a commutator that is arcing between two copper segments. This is on a Crocker Wheeler shunt wound two pole dynamo 115 volts dc with 8 amps output, id plate calls out a 1891 patent date. Checked adjacent bar to bar all the way around and get the same ohm readings, no grounds from bar to ground, and 180 degree resistance bar to bar also check good. Also turned commutator, undercut mica and ballanced IMG_3006.JPGarmature. Any help on this matter would be greatly appreciated. ThanksIMG_3006.JPG


Last Subscription Date
I believe that may indicate a shorted coil. Since the resistance of each armature coil is so low, and there are always two parallel paths, finding it with an ohmmeter alone is not reliable. You really need to use a growler. Alternatively, it is possible that some carbon dust is conducting between the two segments, but it actually looks really clean.