Performance of series hybrid excitation synchronous machine in comparison with wound field synchronous machine

This paper explores some of the characteristics and limitations of the series configuration of hybrid excitation synchronous machine (HESM) compared to the wound field synchronous machine (WFSM). It also explores the influence of magnet excitation to field excitation ratio on their performances. The WFSM is a conventional salient pole synchronous motor, and the HESM consists of conventional salient pole synchronous motor with additional surface mounted permanent magnets. The performances of the motors are investigated using finite element analysis (FEA). All machines share a similar stator, power rating and operate at unity power factor. All simulations are performed at 120°C, which is the highest allowable machine operating temperature. This is to demonstrate HESM better performance, compared to the WFSM, even at high temperatures. An increase of magnet excitation to field excitation ratio is shown to reduce air-gap flux distortion, copper losses, and active mass of the machine. However, these improvements come at a significant increase in costs due to the use of permanent magnet material. Design challenges of the considered HESMs are discussed.