Compound Permanent Magnet Machine: Opportunity and Challenge to be Next-generation Powerful Electric Drive

Permanent magnet (PM) machine designs need to be upgraded for higher electric drive output requirements. Recent vigorous development of motor technology has suggested some novel compound PM machine (CPMM) topologies, which have become alternative solutions in these applications. Not only do these CPMMs increase the power density and torque density, but also possess flexibility and adjustability in performance. According to most recent publication records, the research on CPMM targets various electric drive applications like electric propulsion, robot actuation, heavy machinery, etc., and is dedicated to suitable, feasible CPMM designs addressing pragmatic issues. This review article aims to expound the emerging CPMMs in view of topology, performance feature, relevant technology, and application potential. This article recategorizes the technical routes of achieving CPMMs into four patterns, namely by adding parts, sharing parts, additional field sources, and complementarity. The following discussion will contain quantitative and comparative survey in operational principles and performance features. Therefore, this article tends to fill in the blank of current and future comprehensive research on CPMMs in order to make a milestone and reference value.