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The excitation control strategy of the three-stage synchronous machine in the start mode

In order to overcome the excitation problem of three-stage synchronous machine(TSM) used as starter for the engine cranking, this paper presented a novel three-phase open-winding structure of the exciter for the proposed machine with the dual-inverter for supplying the integrated AC and DC excitation power. The operation principle of the dual-inverter and the control method of the three-phase AC excitation and DC excitation were analyzed in detail and the selection basis of the AC excitation frequency and the switching point were derived by the characteristics of the main exciter. Then, the simulation and experiment results verify that the integrated AC and DC excitation control strategies could supply steady excitation current and the smooth switching process from AC to DC excitation for the proposed machine in the start process.