Energy Efficient Motor for Shell Eco-Marathon: Ironless axial flux permanent magnet synchronous machine for the Shell Eco-Marathon competition

Abstract

A new electric motor was designed for the DNV FuelFighter electric vehicle in co-operation with the Trondheim based company Smart Motor and NTNU. The machine is an ironless axial flux permanent magnet synchronous motor designed and built specifically for the Shell Eco-Marathon competition. This paper presents the theory, design and construction of an ironless AFPM machine with calculations and measurements. Two motors were designed with different winding topologies. Only one was built before the race due to delivery delays of the parts and the time schedule. The completed motor is an in-wheel, direct driven ironless AFPM with an improved efficiency compared to the existing motor. Measurenents show over 5% increase in the motor drive efficiency at nominal load and speed. The motor still has room for improvement by reduceing the motor weight with the use of Halbach arrays, reducing the eddy-current losses and increase the fill factor with litz wire. Also the air-gap could be further reduced to increase efficiency. Other observations and experiences during the machine construction are also discussed in this paper along with the suggestions for improvements on both the electromagnetic and mechanical design of the machine. It is recommended that the next NTNU-team further develop the ironless AFPM as it has great potential as an in-wheel motor for electrical vehicles.