A Resolver is a rotating transformer, located on the motor shaft. Resolvers may be excited at operating frequency; the sine and cosine outputs may be looked at on an oscilloscope or other testing device for proper levels and change rotation. Resolvers are electromechanical devices, the resistance of the windings and the insulation of the winding to the ground should be checked. We rewind Resolvers as necessary and then test with full speed at any frequency. Testing here applies to systems that do not include bearings and are typically used in dirty, oily applications.