Design of a 43kW switched reluctance machine for a high performance hybrid electric vehicle

A switched reluctance machine (SRM) is very robust and capable to perform well under harsh conditions. It is simple in construction and avoids the use of magnets so it is cheap to manufacture. The powertrain of a hybrid vehicle presents challenging conditions for an electric machine. A SRM is a potentially strong contender for such applications. In this paper, a 43kW SRM is designed for a hybrid traction application. Three topologies: three-phase 6/4, three-phase 12/8 and 4-phase 8/6 machines are considered as possible design choices. The main design objectives are to satisfy the torque and efficiency requirements and a secondary objective is to minimise the torque ripple. A base design is developed for each topology under consideration. The base designs are improved by carefully focusing on the impact of all important machine geometrical parameters such as rotor diameter, pole arcs and stator back-iron thickness on torque and efficiency. One design topology is selected and a detailed design optimization is carried out to maximize the efficiency. Results show that SRM can meet torque and efficiency requirements. The efficiency increases with the speed so SRM is better suited to high speed traction application especially where the high field weakening is required with low back EMF