Investigation on withstand voltage of turn insulation of high voltage motors

The authors present withstand voltage test methods and results for several kinds of turn insulation systems. It was found that the breakdown voltage level between adjacent turns is high and makes an obvious difference for different kinds of insulation systems. However, in a whole coil affected by the edge conditions of turns, the breakdown levels of several kinds of turn insulation with the same size coil are very close. This phenomenon makes it difficult to determine the test voltage value, especially in a very humid environment. The authors analyze the effect of the edge condition of turns related to the manufacturing process and humidity during test. They suggest a routine test voltage value and use it to test several hundred large high-voltage motors, which are proved to be effective