The design method to realize magnetic decoupling for a radial-radial flux compound-structure permanent-magnet synchronous machine

A radial-radial flux compound-structure permanent-magnet synchronous machine (CS-PMSM) is an electromagnetic transmission which is integrated by two concentrically arranged electric machines. As the two electric machines share a rotor as structural and magnetic common part, their magnetic paths are coupled. The magnetic-path coupling may cause the magnetic-field interference of the two machines, which will increase the control complexity. In this paper, the design principle to realize magnetic decoupling is proposed, and the design method to ensure magnetic decoupling as well as to minimize the yoke thickness of the common rotor for improving power density is further investigated. A prototype machine is designed based on the proposed method, and the degree of the magnetic-field interference is evaluated by both finite-element-method calculations and experimental tests, which validate the proposed design method.