Topologies for future automotive generators - Part II: Optimization

This paper compares the relative suitability of four different alternator topologies for use in an advanced automobile electrical system. The four candidate topologies are: the salient-and non-salient-pole wound-field synchronous alternators, the Lundell alternator, and the homopolar inductor alternator. In part I, each of the four alternators was modeled. Relative power and efficiency were evaluated based on hand calculations. Part II involves a more accurate optimization of each of these alternators for cost, subject to constraints on output and efficiency. The performance of each machine is determined both with a conventional diode rectifier bridge and also with a switched-mode boost rectifier. Mechanical finite element analyses are performed to evaluate stresses. The most cost effective machines are compared based on size, weight, and inertia. The results reveal that the Lundell and salient-pole wound-field synchronous alternators are the most cost effective. Most surprising is the finding that the Lundell is capable of meeting the challenging next-generation requirements of power and efficiency while meeting the mechanical constraints set on the machines. Also noteworthy is the fact that the switched-mode boost rectifier gives a decrease in cost of more than 10% for each of the least expensive machines.