Efficiency analysis of induction motors for ammonia compressors considering stray load losses caused by stator and rotor slot ripple

In this paper, we investigate the losses and the efficiency of induction motors for ammonia compressors, which have a metallic can inserted in the air-gap to prevent ammonia from entering the stator and damaging the primary windings. The finite element analysis is applied to calculate the torque, primary and secondary copper losses, stator and rotor core losses and eddy current losses of the can considering the magnetic saturation and the slot ripples. The calculated primary current, torque and efficiency agree well with the experimental results. It is clarified that both the losses of the can and the core increase due to the load, which can be regarded as the main part of the stray load losses.