This paper presents an improved circuit model for predicting additional copper loss caused by circulating current effect. Based on basic circuit equations and winding topology, this model takes account of both slot and
end leakage inductance which are separately extracted by 2-D and 3-D finite element method. Several simplified windings are wounded in a stator to validate the accuracy of the proposed model. The results shows that
this model has high accuracy and the maximum error of loss factor is about 1.5 %. In addition, it is found that the circulating current loss factor will decrease as the end winding length grows up or winding temperature
increases.