The effect of mechanical deformation and wire size on the ozone erosion resistance of inverter-duty magnet wires

Abstract

The use of variable frequency PWM drives with long inverter-to-motor cable lengths produces ringing transmission line behavior and high voltage transients at the motor. In response to this, the major magnet wire manufacturers have introduced a number of different inverter-duty insulations. These new insulation systems incorporate oxide-filled polymer layers in different configurations in an effort to resist the erosive effects of ozone produced during corona discharge resulting from these voltage spikes. A large amount of accelerated life testing has been done on as-manufactured wire, but little testing done with inverter-duty wire that has been subjected to the rigors of actual motor winding processes. The purpose of this study is to evaluate the effects of mechanical deformation (i.e. wire stretch) upon the coronal erosion resistance of commercially available inverter-duty magnet wires incorporating oxide-filled corona shielding layers in their insulation systems. The effects of wire size were also investigated to determine the impact of wire size substitution during motor manufacture upon the ultimate coronal erosion resistance of the insulation system.