If it’s of sufficient size to justify the cost, rewinding a motor usually makes sense. But sometimes, the rewinding process introduces problems. If your replacement motor is a rewind and its no-load current is high, the motor shop probably didn’t follow best practices.
Make sure your rewind agreement specifies that before it rewinds the motor, the motor shop will:
- Test the magnetic-flux densities, performing any necessary adjustments.
- Check the stator core laminations. This involves looking at several things, such as the condition of the varnish and whether the steel has warped.
- Test the rotor for axial runout. It’s possible the rotor is bent or has some other defect (so also inspect for pitting). While this can be done after rewinding the motor, you may waste a rewind if you wait until then.
Good motor shops conduct a battery of quality control tests on the motor after it’s assembled. But always perform your own battery of acceptance tests upon delivery, in case of shipping damage.
