Abstract
This paper presents a method to calculate efficiency of induction motors considering stray losses caused by stator and rotor slot ripple. The harmonic electromagnetic fields are calculated by the combined 3D-2D nonlinear time-stepping finite element analysis considering movement of the rotor to estimate the harmonic copper and iron losses. The calculated losses and efficiency is compared with the experimental results. It is clarified that the losses concentrate at the surface of the stator and the rotor core and that the consideration of the time-harmonics caused by the rotor movement is indispensable to estimate the losses and the efficiency of the motor.