AC Loss Calculation of Integral Transposed Winding in PM Motor for Electric Vehicles

The flat wire winding has the characteristics of a high filling coefficient and strong heat dissipation ability. Applying it to a permanent magnet synchronous motor (PMSM) can further improve efficiency and power density. However, its relatively significant eddy current effect has become the key to limiting motor speed and power level improvement. Based on the analytical calculation of flat wire winding eddy current loss, according to the characteristics of PMSM with multiple turns and few strands, a newly integral transposed winding (ITW) structure is proposed, which adopts 288 degrees incomplete transposition structure in the overall length of the winding, and the ends do not need to be connected by the welding process. Then, taking a 15-kW PMSM for electric vehicles as an example, based on the 3-D time-stepping finite-element analysis (TSFEA), the strand current distribution and ac additional copper loss of the winding under rated working condition and high-speed working condition are calculated, and by comparing the losses of different windings, the results show that the ITW structure can greatly suppress the eddy current loss while introducing circulating current loss is negligible. Finally, the PMSM prototype is manufactured and the correctness of different winding designs is verified by a no-load back electromotive force (EMF) experiment.