Formula SAE electric competition: Electrical motor design

Abstract

Electric mobility is becoming a growing reality due to increase of the demand and cost of oil and the environmental impact of conventional internal combustion engines. To follow this trend, national student competitions belonging to Formula SAE (Society of Automotive Engineers) series have been introduced for purely electric vehicles, in addition to those traditionally associated with internal combustion engine vehicles. On the other hand, the most promising and known electric motor candidates for traction application, represented by permanent magnet synchronous machines, are highly affected by the remarkable increase of the cost of rare earth magnet. For these reasons the research of rare-earth free alternatives, such as ferrite permanent magnet assisted synchronous reluctance motor, has potentially interesting implications especially in the perspective of industrial mass production. This paper shows the design criteria of ferrite permanent magnet assisted synchronous reluctance motors for a Formula SAE electric vehicle. The electromechanical performance have been evaluated and compared, in terms of torque and power. The most promising candidate has been finally compared with two equivalent size surface mounted permanent magnet machines: one is equipped with the same stator, while the second is characterized by a fractional slot concentrated winding. Finally, this research provides a brief description of the electric supply system in order to accurately and efficiently manage the motors for achieving the requested performance.