Research On The New Start Scheme For Brushless Electro-Magnetic Synchronous AC Motor

Start/generator double function system has become the tide of electric devices in advanced aircraft. Many research works and application reports have been presented. It will be a competitive scheme as start/generator system, if Brushless Electro-magnetic Synchronous Machine (BESM) can succeed in start the engine of the aircraft, because the wide application of BESM as generator hi aircrafts will definitely decrease the risk and cost of research and development. However, there still lie many difficulties in start of BESM because of some special structure, which leads to no filed current available in stand still.Little systematical research has been carried out long after the new start scheme was presented, especially lack of quantified analysis of the nature of the system and the characteristic of torque output in standstill and low speed range. In this thesis, research has been performed by the means of theoretical analysis and numerical simulation systematically. At first, a method for modeling of BESM hi the MATLAB environment is presented, which is also suitable for other mixed model system. The influence of frequency, voltage, waveform of the excitation source and other factors in the new exciting scheme are discussed, based on which an optimum excitation scheme is presented to maximum the torque output of the machine in the low speed range. After that, a modified Direct Torque Control (DTC) scheme is discussed, to overcome the control difficulties come with the characteristic of low armature inductance. The simulation results confirm the feasibility of the new start scheme.The research work in this thesis has revealed the systematical nature of the new start scheme for BESM and further research and application will be carried based on it soon.This research project is supported by The Aviation Foundation of Science, JVb.98Z52061.