Basic Design Method for SPMSM Based on Air-gap Magnetic Flux Density Distribution Focusing on Image Magnetic Pole

Abstract

This paper presents a basic design method for the surface-mounted permanent magnet synchronous motor (SPMSM) for both distributed and concentrated windings. The design is based on the air-gap magnetic flux density distribution focusing on the image magnetic pole. The calculus equation of the air-gap magnetic flux density distribution is analytically derived by supposing the magnetic pole is located on the magnet surface and image planes. In this study, a three-phase and double-layer stator winding SPMSM that has a linear demagnetizing characteristic magnet, such as a ferrite or rare-earth magnet is considered. From the required specifications and design conditions, the design target values of the parameters that appear in the voltages equations of the d-q axis coordinate system are calculated. Then, the relational equations for the torque constant, d-axis inductance, copper loss, and the maximum current density are presented as a function of three design parameters under i_d=0 control. They are the stator stack length, the number of coil turns in series in a phase, and the slot bottom length. Hence, this approach reduces the SPMSM basic design to the problem with these design parameters has to be solved. The proposed method makes it possible to address the concentrated winding as a special case of the distributed winding. The FEA results confirm the validity of the proposed basic design method for both distributed and concentrated windings.