Overview of Stator Slot-Opening Permanent Magnet Machines

In the past few decades, the stator permanent magnet (PM) machines have attracted much research attention because of their reliable rotor structure, high power density, wide speed range, and strong fault-tolerant ability. Among the recently proposed stator PM machine topologies, the stator slot-opening PM (SS-PM) machines are becoming increasingly popular because of their higher stator space utilization and robust rotor structure. According to the SS-PM magnetization direction, the SS-PM machines can be classified into three categories, namely, the tangentially magnetized stator slot-opening PM (TMSS-PM) machines, the radially magnetized stator slot-opening PM (RMSS-PM) machines, and the compound magnetized stator slot-opening PM (CMSS-PM) machines. The associated working principle and electromagnetic performance of different SS-PM machines can be diverse. Therefore, this article gives an overview of SS-PM machines in terms of machine design, working principle, and machine performance. A qualitative performance evaluation and comparative study of SS-PM machines are presented, and the future challenges and potential opportunities in the SS-PM machine design are discussed.