Cogging Torque Minimization in Novel Direct-Drive PMSM with Toroidal Windings

This paper focuses on the cogging torque minimization of novel direct-drive PMSM with toroidal windings (NTWDDPMSM). First, the motor structure is described and its parameters are reported. And the influence of cogging torque on the rated torque is analyzed. Second, the method of different combinations of polar arc coefficients (PAC) is introduced. After that, the cogging torque expression is derived. Then, the finite-element models of NTWDDPMSM with different combinations of PAC are established. The cogging torque and rated torque are calculated and compared. Besides, the static and dynamic performances of motors with different permanent magnets are studied, such as no-load back electromotive force (EMF), air-gap flux density and efficiency. Finally, it is confirmed that the cogging torque of NTWDDPMSM can be effectively minimized using different combinations of PAC. Moreover, the rated output torque is also improved.