Design of a Permanent-Magnet Assisted Synchronous Reluctance Machine for a Plug-In Hybrid Electric Vehicle

In this thesis, a permanent-magnet assisted synchronous reluctance machine (PMSynRel) design is presented for a plug-in hybrid electric vehicle application. Apart from operating as a traction machine to propel the vehicle, the machine is also used when the vehicle’s battery is charged from the grid. This additional functionality puts restraints (that are discussed in the thesis) on the final machine design. The PMSynRel is designed following a classical approach in which initially the machine geometry is designed to maximize the reluctance torque. Magnets are then introduced to increase the torque further. Rotor dimensions are calculated alongside the resulting magnetic model of the machine. A finite-element method (FEM) based parametric study is then performed to maximize the developed torque. The effect of different design parameters such as, the insulation ratio and the number of flux barriers, on the machine performance is investigated with and without the magnets in the rotor. For a given magnet volume, the performance of the machine is investigated with different magnet placements in the rotor. A prototype has been built based on the resulting machine design to verify the simulation results. A torque map of the prototype machine has been measured for id<0 and iq>0 at constant speed (1500 rpm). The torque, efficiency and power factor of the machine are measured at 1500 rpm and rated current. The experimentally obtained results have been compared, with good agreement, with corresponding FEM simulations. Finally, the performance of the prototype machine in terms of developed torque and maximum speed is compared to alternative designs utilizing surface-mounted or interiormounted permanent magnets in the rotor.