Improvements in permanent magnet synchronous machines with delta-connected winding

Compared with wye-connected winding machine, the delta-connected shows merits in wider constant power speed range (CPSR) and higher efficiency because of the full utilization of terminal voltage, which is promising for electric vehicles (EVs), industries and domestic appliances, etc. However, circulating loss caused by triple-order harmonics impedes the application of delta-connected winding in permanent magnet synchronous machines (PMSMs). This paper discusses the advantages of delta-connected winding, and proposes an optimal design methodology on interior permanent magnet (IPM) rotors to minimize the triple-order harmonics, aiming to arouse the awareness of adopting delta connection in PMSMs for higher performance. A 22kW IPMSM prototype with delta-connected winding is manufactured, and the minimized triple order harmonics and super premium efficiency (IE4) are verified by experiments.