Due to high efficiency, high power density and low cost, single-phase permanent magnet brushless DC motor has increasingly been used in industrial and domestic applications. This thesis focuses on the design and analysis of high-speed, single-phase, conventional and flux-switching permanent magnet brush less DC motors.
This thesis presents a comparative study of conventional three-phase and single-phase permanent magnet brush less DC motors, which operate at 45,OOOrpm with I.lkW output power for the pump application, in terms of their machine design, drive system and electromagnetic performance. It is found that the single-phase permanent magnet brush less DC motor has a relatively lower drive system cost without significantly compromising the electromagnetic performance. Further, significant rotor eddy current loss exists in both motors. Hence, the analytical models are developed to predict the rotor eddy current loss which is resulted from the armature reaction field. By comparing with the 2D finite element method (FEM) predicted results, good agreement is obtained over the full speed range if the eddy current reaction field is taken into account. FEM is further employed to investigate open-circuit, armature and on-load rotor eddy current losses of the permanent magnet brushless DC motors. Particular emphasis is placed on the single-phase motor having an eccentric airgap with consideration for degree of airgap eccentricity, excitation current waveform, magnet segmentation, thickness and electrical conductivity of the retaining sleeve.
The single-phase flux switching permanent magnet motor, which operates at 100,000rpm with 1.2kW output power for the automotive electrical turbo-charger application, is also investigated. Its operational principle is introduced and winding topologies are investigated. In addition, the chamfered rotor pole is optimised to improve the starting capability. In order to investigate the influence of significant end leakage-flux, a 3D lumped circuit magnetic model is developed to predict the back-EMF and the inductance and validated through experiment. This model is also employed to optimise the rotor pole width for increasing the motor power density and to investigate the relationship between the magnet dimensions and the motor end effect.
Finally, the dynamic simulation models are developed to predict the dynamic electromagnetic performance and experimentally validated for a three-phase and a single-phase permanent magnet brush less DC motor, and a single-phase flux switching permanent magnet motor.