Electromagnetic design and analysis of a salient-pole synchronous machine with tooth-coil windings for use as a wheel hub motor in an electric vehicle

This paper presents the electromagnetic design and analysis of a salient-pole synchronous machine for use as a wheel hub drive in an electric vehicle. To achieve high efficiency and torque density, recently patented cast coils are considered in a tooth-coil stator winding topology that allow slot fill factors of up to 90%. The selection of the number of stator slots and the number of poles is discussed to meet the requirements for a highly integrated wheel hub drive. For this entirely innovative design, a rotating transformer is used for field voltage supply. Three different machines are compared using finite element methods (FEM) for electromagnetic analysis along with lumped thermal networks to simulate transient and stationary temperature distribution for continuous load and with respect to driving cycles. The most promising machine configuration is electromagnetically optimized, and simulations of real-life driving cycles show its technical capability for automotive applications.