An accurate stray loss calculation method of squirrel-cage induction motors for efficiency optimization

An accurate stray loss calculation method of squirrel-cage induction motors is presented in this paper. The stray losses are divided into the stray rotor copper losses and the stray core losses, which are determined by the air gap magnetic field. The field is supposed to be completely radial and calculated by the product of stator magnetomotive forces and air gap permeance coefficient. The effect of magnetic wedges is reflected in the equivalent stator slot width. A correction factor is added to the field considering the rotor reaction. On the basis of the new stray loss model, the complex method algorithm is used to optimize the motor efficiency. Based on the 1250kW prototype, the detailed optimizing process is illustrated and the validity of the proposed method is proved.