Design and Analysis of a Static Excitation Part of a Brushless Wound Rotor Excitation Synchronous Machine without an Exciter

The static excitation part of a brushless wound rotor hybrid excitation generator without an exciter (brushless WRHEG) is analyzed in this paper. The DC stator excitation windings and rotor harmonic coils are placed in the iron core as the excitation part, so that the brushless excitation for a wound rotor hybrid excitation generator (WRHEG) can be realized. In this study, the selection of stator excitation windings and rotor harmonic coils, which are essential for achieving of the brushless excitation, is providing. The effect of the static magnetic field on the air-gap magnetic field is studied theoretically. The harmonic content of the air-gap magnetic field is analyzed by Fourier series form and the effect of harmonics on the output voltage is also investigated. The influence of the static excitation field on the iron loss is also considered. A 1.5 kVA prototype is fabricated to verify the validity of the theoretical and Finite Element (FE) analysis. The output voltage under the no-load and the rated load conditions are measured. The field regulation capacity and the efficiency of the brushless WRHEG are tested. It shows that the brushless excitation is achieved by remaining the operating performance of WRHEG unchanged.