Excitation method in starting process for three-stage brushless synchronous machine

Considering the excitation switch problems in the starting process of three-stage brushless synchronous machine, characteristics of the excitation current of the main generator vs speed were analyzed when AC excitation mode and DC excitation mode applied in the exciter respectively. Based on the Matlab simulation results and the experiment data, an exciter control strategy in the starting process of motor was given. In order to realize the AC and DC switching method in this control strategy, the switch-status of the inverter circuit and the resultant method of output voltage vectors were analyzed. An integrated single phase AC/DC excitation modulation algorithm was proposed to realize the smooth switch between AC excitation mode and DC excitation mode. Experiment results verify the validity of the proposed excitation control strategy and modulation algorithm.