DC motor failure -maybe due to balancing putty ?

Thread Starter


Joined Dec 14, 2018
I have a faulty DC brushed motor (PWM controlled / duty cycle is S6 / insulation class is B / fitted to a woodturning lathe) , I am keen to see why it may of failed and have the following thoughts.

I could see a couple of slightly burned areas on the commutator bars , I carried out a bar to bar resistance test and this highlighted that 1 of the bars in the burned area was open circuit. ( this would confirm the occasional intermittent starting of the motor)

I then noticed that both of the problem areas were directly inline with the blue balancing putty. (see pictures below)
Picture A shows a break where the windings are connected to the commutator bar ,

I wonder if the blue balancing putty is restricting the movement of the windings during expansion and contraction , and when motor gets hot and cools ,over time the windings could break away from the commutator bars ?

I would very welcome any thoughts or Ideas ?

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