Bill, well I think its working ok at 20vac and 8 amps. Its a huge electromagnet and you cant separate the two while running. Interesting I saw a guy on youtube running a growler with rubber gloves. Was he thinking he was going to get shocked? Meter on brushes would be testing it in the shell. I think I will connect a light bulb up in series with the secandaries to use as a continuity checker (I think thats how real growners work). Thanks for your input, it was helpful.
Growler theory:
The windings in an armature typically take two or more paths between the brushes and are shorted to form a loop. The alternating magnetic field induces a voltage in both paths. If one path has a short or open, the currents will no longer be equal in both paths. The unequal currents will produce unequal magnetic field around both windings. These fields will no longer cancel and the armature under test will develop a magnetic pole on the surface of the armature. This may be detected with a hacksaw blade.
The voltages developed in both current paths will be equal. If there is a damaged coil this will cause a net difference in voltage to be developed at the brushes. This voltage will drop to zero when the damaged pole passes under the brush.
The growler is typically used for small automotive type armatures in generators that will probably be disassembled for cleaning and bearing replacement.
The AC test is typically used for larger DC motors, generators and exciters for trouble shooting. If a rotor is good, it need not be disassembled, and the rotor may well be too large for a growler in any event.
Bill
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"Why not the best?"
Jimmy Carter
Pics of my homebrew. Does it matter if a/c or d/c is applied to the field coils? I saw an article in a 1921 popular mechanics where they cut a starter motor in half to use the field coils then applied 32vdc to the coils.
