A Computationally Efficient Semi-Analytical Method for Circulating Current Loss of High Speed Permanent Magnet Machines

This article proposes a computationally efficient (CE) semi-analytical method for winding power loss calculation of high speed permanent magnet machines induced by circulating current. It combines a CE magnetostatic finite element method (FEM) for rapid slot leakage field extraction and an analytical circuit model for circulating current calculation. Time-space transformation based CE FEM is applied for efficient slot leakage field extraction considering the polyphase windings. Besides, a conductor model with an automatic and practical turn splitting strategy is proposed to consider the effect of conductor positions and bundle shapes on the circulating current loss. The results on circulating current waveforms and corresponding losses show that the proposed method has high accuracy and can significantly reduce the simulation time, with an error less than 2% and the simulation time only 1/400 for the studied machine compared with the commercial FEM. Using the proposed method, the influence of some factors, including the turn number, the transposition effect and the bundle shape on the circulating current loss are investigated. Finally, the proposed method is further verified by experimental measurements implemented on two stator specimens.