Design of an electrical motor with wide speed range for the in-wheel drive in a heavy duty off-road vehicle

The electrification of the mobile machinery is often discussed. For agricultural tractors an electric drive can be an alternative to commonly used hydrostatic-mechanical power split drives. When compared to the hydrostatic drive, the electric motor with an efficiency above 90% offers advantages. For a meaningful comparison the complete drive train (generator, gearbox, power supply, electric motor) has to be considered. Generally, a particularly limited space is available for the integration of an electric drive. This requires a compact design of the electric motor. Therefore, a permanent magnet synchronous motor is the best candidate, due to its high power density and high efficiency. A particular challenge when designing an electric motor is a special requirement on the driving cycle of the agricultural tractor. The electric motor has to provide a high torque for the working operation off-road and a high maximal motor speed for the transportation operation to move the vehicle on road. For this research a shiftable transmission gear is omitted. The design process of the electric motor with special characteristics is described. The challenge of the motor design for a wide speed range is the main subject of this paper.