A comparison between insulation systems available for PWM inverter fed motors

This paper establishes the need for two levels of motor insulation systems depending upon the available voltage waveform. An analysis of the various winding stresses is presented. The different requirements for the two insulation systems is discussed (MG1-Parts 30 and 31 for General Purpose and Definite Purpose Inverter Fed Motors), and test results show the need for higher dielectric insulations when the voltage levels of Part 30 are exceeded. The differences between existing, rebuilt and new motors is also explored.