Dual Third-Harmonic-Current Excitation Principle of a Brushless Synchronous Machine Based on Double Three-Phase Armature Windings

Traditional harmonic excitation synchronous machine can only be used for generator. One of the main reasons why the harmonic excitation synchronous machine can not be used as a motor is that the field current of the harmonic excitation synchronous machine can not be generated when the rotor is at a stationary state. A double three-phase brushless synchronous machine employing double third-harmonic-current excitation method is proposed in this paper. A rotating harmonic magnetic field can be generated in the air-gap by the double three-phase orthogonal harmonic currents. Therefore, the brushless excitation can still be realized when the rotor is stationary or at a low speed. The stator harmonic magnetic fields are theoretically analyzed. The FEA results verify the correctness of the theoretical analyses.