A high voltage repetitive square wave voltage generator used for endurance evaluation of inverter-fed motors

To ensure the reliability of insulation systems of Type-II inverter-fed motors driven by power electronics, endurance tests should be performed at sinusoidal or repetitive impulsive voltage higher than the partial discharge inception voltage (PDIV) on insulation systems/models according to the standards released by the International Electrotechnical Commission (IEC). When repetitive impulsive voltages are used for endurance tests, the setup of the repetitive impulsive generator with variable and/or required parameters such as frequency, magnitude, dv/dt (rise time and fall time) is the first and the most important consideration since the voltage parameters can affect the endurance results significantly. This paper aims to report the development of one high voltage repetitive square wave voltage generator used for the insulation lifetime tests for high voltage traction (Type II) motors fed by converters. The paper presents the principle of the generator and the influence of the conductance distribution in the circuit on the overvoltage of the repetitive impulsive waveform. Moreover, we report the hardware design for the rise time and fall time adjustment, control method for parameter setting, and short circuit protection. The maximum voltage magnitude, the shortest rise time and maximum frequency of the generator developed can reach 20 kV, 23 ns and 20 kHz, respectively.