Influence of Phase Shift Angle on Performance of Permanent-Magnet Machine With Multiple Star-Delta Windings for Electric Vehicle Drive

The different phase shift angles among subwindings of machine with multiple star-delta connection (MSDC) can result in varied winding connections, thereby introducing different output performance and reliability. The influence of phase shift angle on performance of MSDC machine with any number of subwindings is systematically investigated in this article. First, the possible phase shift angle laws of different pole-slot combinations and any number of subwindings is given, and the mechanism of its influence on performance is analyzed. Then, the corresponding rules for eliminating armature magnetomotive force (AMMF) harmonics with different number of subwindings and phase shift angles are presented. Moreover, the performance of different number of subwindings machines with different phase shift angles are analyzed, including the harmonics of AMMF, output torque, torque ripple, loss, fault tolerance, vibration, etc. It is found that MSDC windings with a phase shift angle of 30/i (i is the number of independent sets of subwindings) electrical degrees can maximize the output torque, minimize the torque ripple, and eddy current loss of permanent magnet (PM). Finally, a 24-slot/10-pole MSDC-PMSM prototype with a phase shift angle of 15 and 60 electrical degrees is tested, which verifies the reasonableness of the theoretical and simulation analyses.