Design of a Rectangular Wave High Voltage Generator for the Evaluation of Inverter-Fed Motor Insulation

The urgent need for the safer operation of inverter-fed motors is leading research to the qualification tests under high frequency rectangular wave voltages. Consequently, the generation of rectangular wave voltages with adjustable parameters has become a major concern for manufacturers and researchers. This article presents a design of high frequency and high voltage pulse generator able to provide unipolar or bipolar pulses up to 20 kV peak-to-peak with variable rise and fall time that can be tuned down to 40 ns. Such a generator is performant enough for testing a large part of motors following standards and with more stressful conditions for research of new winding technologies. Resorting to high voltage push-pull solid-state switches and dielectrics liquid and air-cooling technique, the tested capacitance load can reach up to 3000 pF. Also, the overcurrent protection circuit is carefully designed and verified by using real-time logic control hardware. The proposed generator has been successfully used for endurance tests and partial discharge inception voltage (PDIV) detection at repetitive impulsive voltages for capacitive, inductive insulation structures, and windings during the qualification evaluation of inverter-fed motors.