Do we use insulated bearings for ALL induction motors?

NOT Exactly.

The bearings in induction motors can benefit from insulated bearings where shaft currents are high and use

the bearings as a route to earth. Most induction motors do not suffer with this problem however, those fed up

withVariable Frequency Drives can and do. If you feel that your application would benefit from some form of

protection, there are other solutions can be adopted as well as insulated bearings. But for present, Insulated

bearings are no wonder the best solution for this purpose.