PM-Assisted Synchronous Reluctance Machine Drive System for Micro-Hybrid Application

The demand for increased power and improved fuel economy are driving changes in alternator technology for automotive applications. To meet these demands requires a drive system with capabilities of torque assist, regenerative braking and power generation to supply vehicle loads while keeping the battery charged. Furthermore, to minimize add-on cost, the system must be air-cooled with minimal changes to the vehicle hardware and operate at 12 V with the same or smaller packaging footprint of the current alternator. In this paper, a low cost 12 V, 4 kW air-cooled permanent magnet-assisted synchronous reluctance machine drive system for a micro-hybrid vehicle is presented. The design and analysis in terms of machine, inverter, controller, and control algorithm are discussed in detail. Thermal performance of the system under different operating conditions, which is another key aspect for the harsh environment application, is also studied. Fuel economy analysis of the proposed low-cost micro-hybrid system for a Segment B vehicle shows significant reduction in fuel consumption resulting in a direct benefit to the customer. Finally, a prototype drive system was built and tested and found to meet the cost, performance, and packaging requirements.