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Cutting out damaged coils from large, low-speed machines

Publication date: 
June 2010
Chuck Yung, EASA Senior Technical Support Specialist

Historically, one emergency repair used for large, low-speed machines (motors as well as generators) was to remove the damaged/failed coils from the circuit. Cutting out a single damaged coil permitted the machine to be quickly returned to service with minimal disruption. As long as some basic principles are followed, this method can be safely used. It is still popular with operators of large, low-speed synchronous machines. One common application for such machines is hydro power stations. There are many old hydro generators operating with a dozen or more coils bypassed. The underlying goal when cutting out coils is to minimize the negative side effects and keep coil groups intact for future removal. WARNING: This procedure is not recommended for 2-pole machines. The odds of success are slim.

AC motors