High efficiency permanent magnet drive systems for electric vehicles

This paper discusses the history of the development of electric vehicles (EVs), and the range of traction systems in use. A case is made for permanent magnet machines (PMs), particularly those using axial flux geometry. The speed limitation of PMs is addressed, and two simple methods of surmounting this limitation are presented. Issues in axial flux machine design relevant to the pursuit of very high efficiency are presented. The development of a very high efficiency hard switched controller is discussed, where the specific requirements of the drive system allow substantial reduction of switching rates, thus allowing stringent control of switching losses