Harmonic loss analysis and air-gap optimization of high speed induction motors

The Air-gap width of high speed induction motors is optimized in order to improve the efficiency. First, the loss and torque of the conventional motor are calculated by the finite element method in order to separately estimate the harmonic components. It is revealed that the largest loss component at high speed conditions is the harmonic core losses by the stator and rotor slots. It is also revealed that these harmonics also cause considerable decrease in the torque of the motor at the high speed conditions. Next, the air-gap width of the motor is optimized by the finite element method. The optimized motor is manufactured and measured in order to verify the characteristics. It is clarified that the efficiency of the optimized motor is significantly improved by the decrease in the loss as well as the increase in the torque.