Study on Winding Design of Dual Three-Phase Electrical Machines for Circulating Current Harmonics and Vibration Suppression

The dual three-phase electrical machines (DTP-EMs) have significant advantages and application potential in large-power and high reliability electromagnetic drive system. Nevertheless, one of the main operating challenges of DTP-EMs is the significant high-frequency circulating current harmonics when supplied with voltage-source inverters (VSIs), which will bring unexpected vibration and loss. This article provides a thorough study on the mutual magnetic coupling effect and design criterion of dual three-phase winding. First, the mathematical model of DTP-EMs is established. Then, the internal mechanism of mutual magnetic coupling and the relationship among the mutual leakage inductance in x-y subspace, alpha-ss subspace, and stator leakage inductance is revealed. Furthermore, the winding design criterion for DTP-EMs considering high-frequency circulating current harmonics and vibration suppression is proposed. It is drawn that full pitch is required for DTP-EMs to minimize the high-frequency current harmonics and vibration. Finally, two prototypes of the DTP-EM are built and tested to validate the theoretical analysis. This article provides an effective winding design guide of DTP-EMs for the high-frequency current harmonics suppression and can also be expand to other multiphase machines.