Implementation of Permanent Magnet Motors in Electric Vehicles

Abstract

This thesis has studied permanent magnet motors in electric vehicles (EVs) under the assumption that they are tractable due to a low weight and high compactness. The implementation has been investigated through a case study, which resulted in an EV simulation model. The model contains a maximal torque per ampere and a closed-loop field weakening controller. Abstract Faults are a special concern in permanent magnet motors. Fault sources and faulted behavior are addressed separately. The EV model was used to simulate faulted behavior. Abstract Two passive fault measures are suggested as the most attractive for propulsion purpose motors; these are shutting down the inverter and imposing a balanced short to the machine terminals. The balanced three phase short circuit showed a considerable transient behavior not seen during inverter shutdown. This results in an increased requirement to the inverter rating using the balanced short. Also, demagnetization risk of rotor magnets is higher under the balanced short. Abstract The maximal braking torque during inverter shutdown was high for the simulation model, and exceeded the braking torque of any fault. This concern led to a mathematical examination of the inverter shutdown, resulting in two equations that may be of use during design. The resulting equations are based on simplifications done in the literature, and show the relationship of the balanced short to the inverter shutdown.