Reliability of the adjustable speed drives in power electronic waveform environment

Industrial controls have experienced dramatic changes in the past twenty years. Especially advances in adjustable speed drive technology are very well observable. However, this technology is an advantage for drive control; the voltage waveforms generated by power frequency converters may affect significantly the reliability of electric motor insulation system. It has been observed over voltage phenomenon, bearing currents, charge accumulation, partial discharges activity increasing due to the high frequency square waveform voltage generated by power converters. Any of above could case the electrical motor reliability decreasing. The result of this work shows how the life time of the electrical insulation material is significantly decreasing in high frequency square waveform voltage environment.