Electromagnetic Modeling and Analysis of 3-DOF Permanent Magnet Spherical Motor Using Magnetic Equivalent Circuit Method

This paper studies the magnetic field distribution and torque of permanent magnet spherical motor (PMSM) adopting the magnetic equivalent circuit (MEC) method. Taking into account the unsaturation of the magnetic field, the stator coils and permanent magnet (PM) poles are meshed in the cylindrical coordinates, respectively. The expressions of reluctances and magneto motive force (MMF) are deduced. The radial magnetic flux density in air gap under spherical coordinates is obtained by transforming the coordinate systems. The overall air-gap magnetic field is obtained by adding the magnetic field of stator and rotor. Based on this, the torque model is built in the Maxwell stress tensor (MST) method. The proposed method is verified by comparing with the finite element analysis (FEA) method and helpful for the PMSM parameter optimization.