Analysis of a light permanent magnet in-wheel motor for an electric vehicle with autonomous corner modules

Abstract: The use of in-wheel motors is an attractive alternative in small passenger vehicles aimed for transportation in urban areas. The improved control possibilities and the removal of certain components such as the transmission systemare some of its advantages. Therefore, this thesis deals with the analysis of an permanent magnet synchronous outer rotor motor aimed for an in-wheel application with the autonomous corner module concept. First, some basic concepts about permanent magnet motors are reviewed and an analytical model of a permanent magnet outer rotor motor is presented. As a result from this analytical model, three motor configurations are obtained including both distributed and concentrated windings. Next, finite element method simulations are conducted on the previously obtained motor configurations. Torque-speed curves, voltage-speed curves and losses are computed. Differences with the results obtained using the analytical model are observed due to its simplicity. Both sinusoidal and pulse width modulation currents are used as an input to the motors obtaining considerably different results, especially in terms of losses. Stator skew is introduced for torque ripple reduction and an analytical magnet segmentation model is applied to reduce the magnet losses. Finally, a thermal analysis is carried out to confirm the thermal viability of the motors under two different driving cycles. The material properties are contrasted with the obtained temperatures to a discard possible magnet demagnetization or insulation failure. It is concluded that the current density in the motors can be increased.