Design of a novel electromagnetic planetary gear used for hybrid electric vehicles

A new electromagnetic planetary gear (EPG), which is the key part of compound-structure permanent-magnet synchronous machine (CS-PMSM) for hybrid electric vehicles (HEVs), is designed in this paper. To obtain the optimal electromagnetic performance of the EPG, the distribution law of permanent-magnet (PM) magnetic field and armature field are investigated, respectively. Furthermore, the influence of some key parameters, like span and thickness of magnetic block, and PM pole-arc coefficient on the PM magnetic field and armature field are investigated. On that basis, the electromagnetic performances of no-load and load working conditions are analyzed. The influence of magnetic blocks and PMs on fundamental back EMF, voltage distortion rate, electromagnetic torque and torque ripple are further investigated. Finally, a optimal scheme of EPG with a high torque and a low torque ripple is designed.