Ultra-light-weight high torque density brushless PM machine design: Considering driving-cycle of a four-wheel drive race car

This paper explores the design of an ultra-light-weight power and torque dense motor to enhance the performance of a light-weight electric racing vehicle. Such a racing vehicle is to compete in formula student racing events. The state-of-the-art powertrain in these vehicles are axial-field machines or medium speed radial-field machines with a gear. This paper concerns a high speed traction machine radial-field design that closely considers the endurance duty-cycle and/or driving cycle of a race car and provides fast acceleration. The proposed electrical machine is designed to be ultra-light-weight. Therefore, an 18,000 rpm (single gear), 24 slot, 4 pole and 33 Nm brushless highly saturated permanent magnet machine is designed, with an active mass of around 3.0 kg (~ 10kW/kg and 10 Nm/kg). To account for the various race events, the velocity of the racing tracks is to be closely matched with the machine output characteristics. Within this paper, the design and no-load results will be presented. In the near future (Q2 of 2015), following extended tests, this machine (integrated with a specifically designed single-stage gear) will be used to drive the vehicle using torque vectoring on all four-wheels. We expect that this will result in a significant performance gain in acceleration, endurance and handling characteristics of the 2015 University Racing Eindhoven race vehicle.