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. The paper discusses the design, prototype realisation and test validation of a switched reluctance (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. Whilst a number of papers have published on SR machine design for automotive starter/alternator applications, a comprehensive case study discussing the design and application issues has not been published. The paper focuses on the impact of performance requirements and volumetric and environmental constraints on the machine design. It is shown that a higher number of stator and rotor poles are more appropriate for utilisation of the available active volume. Whilst various operation and fault scenarios have been presented for SR drive-systems, the paper also discusses test observations that suggest the potential for transient self-excitation of the SR generator via residual magnetisation of the machine rotor, a fault scenario that has only been briefly reported upon.