Switched Reluctance Turbo-Generator for Exhaust Gas Energy Recovery

The paper describes a comparative study of low voltage and high voltage SR machines for use in an automotive turbo-generator exhaust gas energy recovery system. Their relative merits, in terms of the total machine loss and the loss distribution, are quantified. It is shown that the requirement for an integer number of turns imposes severe restrictions on the design of the low voltage system, whereas the flexibility to employ various winding designs in the high voltage system can be exploited to advantage. A comprehensive analysis of both the winding design and the operating control angles is presented. While the magnitude of the total machine loss is relatively insensitive to the operating voltage, the copper loss at full load is significantly lower in the high voltage system. The merits of operating the system at high voltage, in terms of the thermal rating of the electric machine, are also discussed.