Synchronous generator is a conversion equipment that converts mechanical energy into AC electrical energy. In the past, the excitation of the synchronous generator of the oil engine generator set in the self-provided power station is widely used to provide excitation current by the DC generator. This excitation method, due to the application of DC generator, exists that the AC power is changed into DC power through the commutator, and the excitation current is supplied to the excitation winding through the copper ring and solid brush of the synchronous generator. Therefore, it brings many problems to the maintenance and safe operation. In order to improve this excitation mode. In the 1960s, the self-excited constant voltage synchronous generator with static silicon rectifier was mainly developed. This kind of generator still has carbon brush and slip ring, which still needs frequent maintenance and generates radio electromagnetic interference. In order to fundamentally solve the existing problems, modern synchronous generators, through improvement and development, widely use coaxial AC brushless exciter and rotary rectifier brushless synchronous generator.