Analysis of thermal stresses in medium-voltage motor coils under repetitive fast pulse and high-frequency voltages

The paper provides an analysis of the thermal stresses in medium-voltage form-wound motor coils that arise from pulsed width modulated, repetitive square-wave, and impulse voltages. The effects of the shape, repetition rate, and rise and fall time of the pulses are studied through experimental and computational work. Based on the frequency spectra of the pulse trains and their corresponding signal powers, it is shown that a set of sinusoidal high-frequency voltages of predetermined amplitudes can effectively produce consistent thermal stresses, and both the experimental and simulation results confirm the validity of the proposed scheme.