Investigations into the Improvement of a Single Phase Permanent Magnet Brushless DC Motor

The work presented in this thesis is aimed at improving single phase permanent magnet brushless DC motors; including their operation, design, efficiency and smoothness. Three main areas were identified and researched for further improvement. As a precursor to this work, a detailed literature study related to each area is also presented. The first of these areas concentrates on the improvement of the open circuit torque for a single phase BLDC motor. The open circuit torque is not only due to the slot openings, but is also contributed by the uneven airgap which is conventionally used to solve starting problem. The aim is to enhance the starting torque at alignment positions and attenuate the torque ripple between null points where the back EMF is non-zero. The improvement of the open circuit torque was investigated in two stages. In the first stage the open circuit torque due to the slot openings was reduced, and in the second stage the focus was on enhancing the open circuit torque contributed from the uneven air gap topology with minimum ripple. The second area of investigation was to devise a new encoderless control method for a single phase BLDC motor. A detailed analysis on the derivation of the method is presented. The method has been validated both analytically and numerically. The third area of investigation was the creation of a new non-complex phase advance control method. The details of the analytical simulation and practical implementation are presented. The method has been validated experimentally and it was shown that the experimental results agree well with the analytical predictions.