Theoretical and experimental analyses of a hybrid excitation synchronous generator with integrated brushless excitation

This paper proposes a novel integrated brushless excitation method (IBEM) for a rotor-excited generator. IBEM is applied to a rotor-excited hybrid excitation synchronous generator (HESG) to realise brushless excitation while the key features of the rotor-excited generator are maintained. The new generator is referred as IBE HESG here. The stator excitation windings are buried in the stator slots. The static excitation field is established in the air gap when there is dc excitation current in the stator excitation windings. The three-phase armature coils of the rotor induce the static excitation field and provide the dc excitation current for the rotor excitation windings via a rotating rectifier. The operating principles are discussed theoretically. The magnetic field distribution and the operating characteristics are studied by finite-element analysis. The no-load, external, regulation and excitation characteristics are analysed. Compared with the brush excitation HESG, the rotor excitation current is able to meet the requirement and the output voltage is conveniently regulated by the stator excitation current. Finally, a 1.5 kVA prototype is fabricated to test the operating characteristics of IBE HESG. It demonstrates that the brushless excitation is realised and the output voltage is regulated by the stator excitation current.