Instead of using separate machines for cold cranking and battery charging, the concept of integrated starter generator (ISG) is becoming attractive for modern automobiles and mild hybrid electric vehicles (HEVs)[1]-[6]. Because of the requirements of very high starting torque (up to 4 times the rated torque) for cranking, as well as constant output voltage over a very wide speed range (25% to 4 times the based need) for charging, the design of this ISG is challenging. Recently, the PM synchronous machine has been utilized for ISG application, since it inherently offers high torque density and high efficiency[6]-[10]. However, because of uncontrollable PM flux, it cannot maintain high efficiency or constant output voltage over the wide speed range. To enable flux control, the idea of stator doubly fed doubly salient PM (SDF-DSPM) machine has been proposed[11]. However, it involves a bulky structure to accommodate two kinds of excitations, leading to difficulty in manufacturing.
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