High-Frequency Pulse Generator for Medium Voltage Motor Insulation Testing

With the new fast-switching SiC inverters, winding insulation stresses in electric machines are expected to increase dramatically compared to excitation with silicon-based devices. To verify the capacity of a motor-drive insulation to withstand pulsed waveform excitations, the motor winding system must be tested with similar waveforms encountered during operation. A high-frequency, high-voltage pulse generator is presented to generate high-voltage repetitive pulses for testing medium voltage form wound coil insulation subjected to SiC inverter operation. The implemented system comprises a high-frequency transformer and two SiC MOSFET full bridges, generating different pulse-voltage waveforms. It is a versatile system designed to create two-level, three-level, five-level, and seven-level pulse voltage waveforms at different voltage levels, frequencies, and slew rates without additional system cost and control complexity.