Partial discharge inception voltage for two insulating materials (PVC and PE) under inverter surge voltage

Rise time of pulse voltages in inverter systems has decreased due to improvements in efficiency, ranging from several microseconds to several tens of nanoseconds, depending on the type of switching device (MOSFET, IGBT, GTO) used in motor drive systems. Although partial discharge (PD) can occur at any parts of the whole inverter drive systems (motor, load cable, switching devices, inverter), the behavior of PD under such steep pulses has not been clearly understood. We report PD inception voltage for two different insulating materials (PVC and PE) using an optical method to avoid electrical noise caused by applied surge voltage itself. We measured the effect of frequency on PD inception voltage (AC, mono-polar pulse), finding that the PD inception voltage showed a tendency to increase with an increase in the frequency, and we present the effect of pulse polarity. These experimental results are discussed with respect to the dielectric properties (dielectric constant, charge decay characteristics) of the materials.