EVALUATION OF HIGH VOLTAGE REFLECTIONS AND THEIR INFLUENCE ON VOLTAGE STRESS ON MOTOR INSULATION SYSTEMS

Other conference contribution, 2025

The presence of PWM waveforms in electric driven vehicles and within the electric power engineering industry overall is
generally increasing today. Shorter rise time increases the probability for voltage wave reflections within the motor windings due
to impedance mismatches which is known to increase the voltage stress exposure as it introduces superimposed voltage oscillations.
This work elaborates these kinds of stresses on random wound motor insulation material when applying square shaped voltages.
The impact on the resulting partial discharge (PD) distribution due to this kind of excess stimuli is investigated and a specialized
test set-up utilized to generate a controllable waveform for these tests, which enables a high level of flexibility. It is observed that
the charge polarity and magnitude of the initial overshoot pulses influence the consequent ones strongly, suggesting a strong
interaction of space charge activity. Due to this, the number of oscillations with sufficient magnitudes and width will influence the
total PD exposure and the inception voltage (PDIV). Also, observations suggest that a sufficiently thin overshoot may have less
influence on the PDIV level, which is significant when performing insulation coordination of motor winding material.