Tom Bishop, P.E.
EASA Technical Support Specialist
A frequent question that arises during repair or maintenance is how much voltage to apply when performing a high potential test. The test voltage for a new winding will be higher than that of a winding that has been in service, but what is the appropriate test voltage? Seeking answers to this question can sometimes lead to confusion. Our goal in this article is to clarify high potential testing and test voltages.
What is meant by high potential (hipot) testing is not always clear. The term “high potential testing” is defined by NEMA (MG1-1.57) and IEEE (IEEE Standard 858) as a test that “consists of the application of a voltage higher than the rated voltage for a specified time for the purpose of determining the adequacy against breakdown of insulating materials and spacings under normal conditions.” For example, a 5000-volt hipot test on a motor rated 4000 volts would be considered a high potential test.
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