Re: How to test a universal motor ?
Hello dineshdeshmuk,
Look for the brushes, if they have real contact.
Look for the commutator, that there are no scorch marks round around. If yes, look for the contact pressure of the brushes or change them directly.
If there are only a few scorch marks, the winding of the armature has a short circuit. It must be change or make new windings.
Now measure the resistance of the total resistor of the motor. If the windings of the field and armature is ok, you must have a low resistance. If it is open circuit, turn the armature a little bit, because the brushes can be between 2 contacts of the commutator.
Measure the isolation resistance between windings and case. It must be very high until endless.
If all is ok, you can start the motor.
The best way to test with AC is, to use a variable transformer (VARIAC). During starting control the amparage of the motor.
If you want to test with DC, it's also good to use a variable power supply. Take care that you motor has a mechanical load, because it will work as a series motor.
I hope it will help.
Regards
Rainer