Research On A Transverse-Flux Dual Rotor Machine Used For Hybrid Electric Vehicles

To increase the fuel economy and reduce the exhuast emission pollusion, hybrid electrical vehicles(HEVs) are widely researched. Within the HEVs, the power-split component is reponsible for adjusting the output power from the battery and the inernal combust engine(ICE) to face different road conditions, and becomes an important direction for the research of the HEVs. The compound-structure machines can fulfill the power-split function for the HEVs, and have a compact structure which is convenient to control and maintain. Recently, the compound-structure machines with brushes have been studied deeply and widely, which proves the advantages and feasibility of the machine. But the researches also indicate that the brushes and rings will reduce the stability and reliability of the system. A novel transverse-flux dual rotor machine(TFDRM) is proposed in this paper which can cooperate with another common permanent-magnet synchronous machine to form the compound-structure transverse-flux permanent-magnet synchronous machine(CS-TFPMSM). The CS-TFPMSM is able to take full control on the speed and torque from the ICE without using any brushes. The research of this paper is mainly about the structure, principle, and performances of the TFDRM, and consists of several parts:First of all, the structure scheme of the TFDRM is proposed, the operation principle of the TFDRM is analyzed, and the equivalent magnetic circuit model is established. The speed adjustment and torque transferring function of the TFDRM is analyzed. The equation of flux linkage and voltage, torque equation, and mechanical motion balance equation are given. According to different road conditions faced by the HEVs, the operation modes of the TFDRM are analyzed; and the design demands for the speed and torque of the TFDRM are discussed. The complicated three-dimension magnetic flux path of the TFDRM is analyzed, and the distributions of main magnetic flux and leakage magnetic flux are investigated in detail. Based on the magnetic flux path of the TFDRM, the equivalent magnetic circuit model is set up.Secondly, the analytical expressions for magnetic flux density through inner air gap and magnetic reluctances are deduced; and the armature reaction reactance, electromagnetic torque, and power factor are researched. The ability of the flux-concentration mode to increase the magnetic flux density through the inner air gap, and the influences of dimension parameters on the magnetic reluctances are analyzed in detail. According to the equivalent magnetic circuit model, the expression for the electromagnetic torque is deduced. Afterwards, according to the structure characteristics of the TFDRM, the electric load and magnetic load are both redefined. The analytical expression for the torque density is deduced, and the methods to obtain higher torque density are analyzed. The phase diagram for the TFDRM is established according to the voltage and current equation. The expression for the power factor of the TFDRM is obtained, and the main reasons for the low power factor are investigated; and the methods to improve power factor in the design and control of the TFDRM are given.Thirdly, the 3D FEM model of the TFDRM is set up and simplified, and the parameters and characteristics of the TFDRM are investigated utilizing the 3D FEM simulation. For the complicated 3D magnetic flux path of the TFDRM, the 3D FEM model is established. Considering the huge volume of the 3D FEM model and the high time consumption of the 3D FEM calculation, the 3D FEM model is simplified to be the part of one pole pair in one phase. Adopting the 3D FEM method, the magnetic flux distribution and no-load flux leakage coefficient are simulated and analyzed. The influences of the parameters on the no-load BEMF, output torque, torque ripple, and power factor are researched. Based on simulation and former analytical results, the output torque and power factor are optimized. And the selection ranges for the pole-pair number, the length of the inner/outer air gap, the sizes of transverse-flux teeth, and the sizes of the PMs are given.Finally, according to the special structure of the TFDRM, the structure and manufacturing process are designed; and a prototype of the TFDRM is manufactured and tested. In order to simplify the manufacturing process and obtain high slot fill factor, the yoke and endings of stator core are designed to be manufactured separately and assembled together. Moreover, the material epoxy phenol aldehyde glass cloth laminated board is adopted to manufacture the holder of the transverse-flux rotor, in order to cut down the eddy loss and maintain the mechanical strength of the holder. Afterwards, the experiment platform of the TFDRM is set up, and the parameters and characteristics, including no-load BEMF, average torque, torque ripple, power factor, efficiency, and so on, are measured. Furthermore, in a series of operation modes, the curves of velocity, torque, and power are tested and obtained to validate the speed adjustment and torque transferring function of the TFDRM.