Flux-weakening strategies for a five-phase PM synchronous machine

In order to get a low cost mild hybrid system, a global objective is to keep the actual thermal engine architecture as in Figure 1. As consequence, the current clawpole synchronous automotive generator must be replaced by a new more powerful electrical machine but with the same large speed range [0-18000 rpm]. In the project, a power of 15 kW and a DC bus voltage of 60V have been chosen to provide a regenerative breaking at minimum cost. With this payload (250A for the DC bus current), a five-phase machine appears to be interesting because MOSFET transistors of the voltage source inverter (VSI) have not to be used in parallel configuration (only two rated 150A transistors per leg for the VSI). As the speed range is large, a flux weakening must be applied. As the five-phase drives have more degrees of freedom than three-phase ones, different flux weakening strategies can be considered. The aim of this paper is to compare one of them.