Identification of Thermally Safe Load Cycles for an Induction Motor Position Servo

Advances in the available performance of induction motor-inverter systems permit these drive systems to meet progressively more demanding performance criteria. High performance servos require the induction motor to produce high torque and power. The severe repetitive load cycles stress the motor's insulation with high operating temperatures. The traditional rating of the induction motor based on ac line operation is not useful under these circumstances. In spite of the complexity of the thermal problem, an approximate thermal calculation procedure will allow servo designers and users alike to predetermine thermally safe load cycles for induction motor servo drives.