Generator Operation of a Switched Reluctance Starter/Generator at Extended Speeds

Switched reluctance (SR) drive systems are a candidate technology for electric vehicle applications, particularly where a high degree of component integration is required within a thermally demanding environment-typical of engine-mounted power-assist solutions. This paper discusses the design, prototype realization, and test validation of an SR machine for a mild-hybrid power-assist starter/alternator application that has performance requirements of both high starting torque and a wide speed range at full power. While a number of papers on SR machine design for automotive starter/alternator applications have been published, a comprehensive case study discussing the design and application issues has not been published. This paper focuses on the impact of the performance requirements and volumetric and environmental constraints on the machine design. It is shown that a higher number of stator and rotor poles is more appropriate for the utilization of the available active volume. While various operation and fault scenarios have been presented for SIR drive systems, this paper also discusses test observations that suggest the potential for the transient self-excitation of the SR generator via residual magnetization of the machine rotor-a fault scenario that has only been briefly reported on.