If an electric motor operates at too high a voltage, excess current flowing through the windings can cause them to become hot and burn out. While it is normally not practical to repair small, direct current (DC) motors that have burnt out, other motors can be repaired by rewinding.
When a motor burns out, a short circuit occurs in the windings and the motor ceases to turn. You can test for a short circuit by checking the resistance of the windings with an ohmmeter; a reading of 0 ohms (Ω) indicates a short.
The first step in rewinding a motor is to remove the old winding. Commercially, this is done by baking the stationary part of a motor in an oven at 343 degrees Celsius for several hours.
The new windings are wound on a coil winding machine, under the supervision of a technician, who controls the tension, layering and number of turns. The newly wound coil is dipped in epoxy varnish and, once again, baked in an oven to complete the process.
- Motor Diagnostics: Time Savings and Energy Efficiency through Alternate Electric Motor Rewind Methods
- Maintenance World: Maintenance and Troubleshooting of Electric Motors
- "Robot Builder's Sourcebook"; Gordon McComb; 2002