Quote:
Originally Posted by Bill_B
That's a big help in telling whether a motor is repairable. My armature coils measured much less than 20 ohms. That is further support for my presumption that there is invisible damage to my coils internally.
I'm confused about your 6 ohm measure though. Why would shorting the inductor cause less than the coil winding resistance?
So, my advice now about trying to repair a motor is to measure your coils first, across all three pairs of commutator contacts. If you find a coil pair that is significantly less than 20 (or 6?) ohms, don't bother trying to replace the inductor. Even if you were to get an operating motor going, its work and power characteristics will be different than a stock motor. That would make the repaired motor questionable to use for prototyping. It might still be useful as an arm mover on an FTC robot though.
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Thats a good idea... I was wondering about the possible failure modes of the choke. If it fails open, the motor should be a brick which I suspect most people see that can revive the motor by replacing that. If the choke can have a partial failure mode and still allow current to flow then we should see a partial power motor... like all three of the ones we smoked. But if the choke can typically only fail open, then likely the windings are shorted and should be tested like you propose.
What confuses me is the motor R should be 12v/Imax = 12/7.5 = 8/5 ohm.
So I suspect that the shunt capacitor may be interacting with the ohm meters to corrupt the reading.