Electric Motors and Generators in Hybrid-Electric Powertrains

Hybrid-Electric vehicle powertrains combine conventional power sources and energy storage with electric machines, in either motoring operation, generating operation or combined operation. The specifications for operation in minimal- or fully-hybrid powertrains lead some electric machine candidates to be more attractive than others. Starter motor and alternator suppliers now offer the next generation product: an Integrated Motor-Generator, with initial application in 42V systems. The characteristic strengths of the Lundell alternator, the commutated dc motor, the brushless dc motor-generator, the wound rotor generator, the induction motor, and the switched reluctance motor-generator are discussed, and compared. A selection is offered based on operation, while considering unit cost. The brushless dc motor-generator stands out as the most attractive candidate for applications either generating or in combined operation.