A high torque density, direct drive in-wheel motor for electric vehicles

The use of in-wheel motors as a source of propulsion for electric vehicles is particularly attractive because they offer new levels of controllability in the vehicle, whilst also freeing up space within the main body of the car. The in-wheel motor is housed in the rim, alongside existing mechanical brakes and suspension systems. This produces tight space constraints, so that the motor and drive electronics must both be power dense and compact. The motor must also offer high efficiency, low cogging torque and be intrinsically fail safe. This paper examines the design options for a direct drive in-wheel motor for use in passenger and light commercial vehicles. The study focuses on achieving high torque density whilst considering magnetic, mechanical, electrical and physical limitations posed on the motor.