In normal circumstance, the voltage wave is sine wave. When there is lighting strike ,or inappropriate operation, even the system setting may cause some part of the system has the voltage over the durability.The rate voltage and the environment have to be considered before design the insulation structure. The product has to test the withstanding voltage to make sure the insulation structure is strong enough. A HI POT Tester checks for “goodisolation”and makes surety of no current will flow from one point to another point.
When short happened on coil, it may change the parameter of inductance , capacitance, and resistance. The insulation ability reduce. Usually, the problem will be discover under high voltage. Without the high voltage, the defection point is hard to be penetrated. About The Impulse Tester. “Pulse voltage and waveform comparison” is the way we detect layer short. The pulse voltage is non-destructive/instant voltage that apply on both side of winding and detect the DUT without damage it. By compare the wave with the golden sample, we can judge the DUT.