Compact permanent-magnet generator for hybrid vehicle applications

In hybrid electric vehicle (HEV) drive-trains an electrical generator is coupled onto the shaft of an internal-combustion engine (ICE) in order to process either the entire or a given fraction of the traction power required by the vehicle wheels. As such an ICE-driven generator is being confined within the vehicle hood and is exposed to heating resulting from ICE operation, high compactness, totally-enclosed construction and suitable machine cooling arrangement become challenging targets the generator design must deal with. Due to unique characteristics such as higher torque per volume and higher efficiency compared to other machine topologies, the axial-field permanent magnet machine (AFPM) topology was selected for the development of a 15 kW @ 4500 rev/min rated generator prototype that would be utilized in a demonstrator of HEV drive train. This paper describes the original solutions adopted for the design of such a HEV generator and reports experimental results taken from the prototype machine.