Integrated AC and DC excitation method for brushless synchronous machine

In order to overcome the excitation problem of the brushless synchronous machine used as starter for engine cranking in the variable frequency starter/generator system, this paper presented a novel three phase open-winding structure of the excitation generator with double inverters for supplying the integrated AC and DC excitation power to the major machine. The control strategies of three-phase AC excitation in the initial start process and DC excitation in the high-middle speed was given, then, the switch method of AC and DC excitation was analyzed. A simulation model of the proposed excitation system is built and the simulation results verify that the proposed control strategies could supply smooth excitation current for the brushless machine and the torque in start process can be maintained.