New insulation system for traction motors

A new heat resistant impregnating resin has been developed for two kinds of traction motors: dc motor and variable-voltage, variable-frequency (VVVF) inverter-type induction motor. Motorette test of dc motor under more severe conditions than IEEE No. 304 indicates that the insulation system satisfies the thermal class 220°. Motorette test on mica insulation for the induction motor according to IEEE No. 275 also demonstrated conformance with thermal class 220. The insulation system has been successfully applied to the VVVF inverter-type induction motors.