Hi, 1st post on this forum I hope someone can help. I have a 230v single phase capacitor start induction motor. It drives an earth vibrating compactor plate. The field coil is burnt out and the rotor is a squirrel cage. What I need to know is should the rotor shaft be insulated from the cage. If I do an insulation test between what I assume to be the cage solder fixing on the rotor end ring and the rotor shaft there is a short circuit there. I don't know if this is ok as I don't work on induced voltage rotors. I mainly work on DC Armature motors. Any help would be appreciated. Thanks

 

No it is not insulated.
That is a very old motor it it has a copper cage!
Max.

 

No it is not insulated.
That is a very old motor it it has a copper cage!
Max.

I can’t actually see what the cage is made of. Could the rotor cause the field coil to burn out?

 

No the cage represents shorted turn windings as it is.
Modern rotors have the aluminum cage cast in then turned usually, prior to about 4 to 5 decades ago they used copper with soldered end plates.
Max.

 

Copper has become more expensive, and therefore most if not all manufacturers have switched to aluminum.
Higher losses, though.

 

I have not seen copper cage in a motor since the '50's - 60's.
Max.