Optimization design of stator harmonic windings in brushless synchronous machine excited with double-harmonic-windings

Harmonic brushless excitation synchronous machine does not rely on permanent magnetic material, which also can be excited without brush and slip rings. The air-gap magnetic fields are easy to be adjusted. However, the tooth harmonics in 12-slots machine are relatively big. In order to reduce the tooth harmonics content, and improve the excitation performance and efficiency of this kind of machine, a dual-harmonic-winding brushless excitation synchronous machine is presented in this paper. Five different stator harmonic winding distributions are analyzed and the corresponding harmonic potentials are calculated, respectively. Results of the calculations show that in the machine with 18-slots, the rotor harmonic potential produced by the stator harmonic windings with same-sequence arrangement is largest. These structures are suitable for this kind of machine. The results of Finite Element Analysis verified the correctness and effectiveness of the structure optimization and magnetic fields calculations of the machine.