A novel split two-phase excitation scheme of synchronous starter generator for aircraft

Synchronous starter/generator is one of the most important technologies for the development of modern more electric aircraft. One main challenge that impedes the successful application of the starter/generator is its excitation system, as an AC excitation magnetic field has to be provided for engine starting while a DC excitation magnetic field generated for power generation for the sake of multiple engineering reasons. In this paper, a novel excitation scheme using split two-phase symmetric windings is proposed. This scheme is capable of producing required magnetic excitation field without utilization of relays or contactors; mode transfer function is accomplished smoothly through power converters at the power source's end. The scheme possesses higher reliability and the control logics are relatively simplified compared with existing schemes. Main circuits of power source converter that can provide both AC and DC excitation power as required are also presented. Main exciter model in rotating d-q coordinate is built and simulations are carried out to observe the output voltage characteristics. In order to reduce the control complexity and enhance main exciter output performance, a modified general asynchronous control technique is adopted. Simulation test results show that the presented excitation scheme is feasible and effective.