Magnetic circuit and torque analysis of a brushless transverse flux dual-rotor machine used for HEVs

The paper proposes a new compound-structure transverse flux permanent-magnet synchronous machine (CS-TFPMSM) system to fulfill power split for hybrid electric vehicles (HEVs). The key component of this system is one brushless transverse flux dual-rotor machine (TFDRM) which originates from transverse flux machines. The TFDRM can realize speed adjustment and torque transfer. The structure and operation principle are first introduced. The magnetic flux path and its characteristics are then described. The magnetic circuit model of the proposed TFDRM is also developed. Based on the magnetic circuit analysis, the expressions for d-, q-axis magnetic flux and electromagnetic torque are deduced. The 3D finite element method (FEM) is used to simulate the impact of main parameters on the torque. The methods to obtain high average torque and reduce torque ripple are finally discussed.