Wound rotor (WR) motors represent only a small fraction of all electric motors in service. Reviewing the Technical Support call logs, one might conclude that the proportion of wound rotor motors in service is far greater. Because many of us do not work on wound rotor motors very often, it is understandable that not everyone has a clear understanding of how they differ from a squirrel cage motor. The purpose of this article is to dispel some misconceptions about how they work, and to offer valuable tips for failure analysis, repair and testing.

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