Form wound stator insulation system under different voltage waveform stresses

The paper presents the experimental results under power frequency, exponential decay pulse, square and sinusoidal pulse width modulated (SPWM) voltage waveforms, with the same peak values, applied to the insulation system of a form wound stator coil. Both the infrared images and the maximum temperature rise of the coil under different electrical stresses were recorded. Results show that the temperature rise of the coil surface under square wave or SPWM wave stress are much higher than the temperature rise observed under the stress of power frequency sinusoidal voltage or exponential decay pulses. FFT analysis shows that both the square and SPWM waveforms used in this study contain significantly higher harmonic components, similar to a real drive output voltage; hence resulted in a higher temperature rise compared to the other voltage waveforms used. Thus, neither the power frequency sinusoidal voltage nor the fast repetitive exponential decay type pulsed voltage can fully represent the transients caused by a voltage waveform of a real drive; voltage source converter.