Research On Radial Magnetic-Field-Mdulated Brushless Double-Rtor Machine

In Hybrid Electric Vehicles, the electronic continuously variable transmission system is the most successful hybrid drive system at present. The radial magnetic-field-modulated brushless double-rotor machine (RMFM-BDRM) , combined with the traditional motor, can replace the continuously variable transmission system, which is based on the planetary gear power-split unit, and provide the speed and torque difference between the engine and the vehicle. Additionally, it can solve the problems of the overheated windings in the inner rotor and the low reliability as the result of brushes and slip rings in compound motors. In this thesis, the radial MFM-BDRM is deeply investigated and the main research work is as follows.Firstly, the operating principle of the RMEM-BDRM is deduced and analyzed by the analysis method because of its particularity. The relation of the pole pairs of permanent magnet (PM) in the PM rotor, the numbers of the magnetic block in the modulating ring rotor and the pole pairs of the stator armature field is deduced. The mathematical model of the speed and torque among the PM rotor, the modulating ring rotor and the stator armature is established to provide the reference for the design and control of the motor. The motor models of different structures are analyzed by the finite element method. The rightness of the operating principle and the feasibility of the scheme design is validated by the comparative analysis of the air-gap magnetic field, the back electromotive force and the torque.Secondly, the system power flow of the RMFM-BDRM is investigated. On that basis, the motor operating mode is discussed and the design principle and method are proposed, to provide the theoretical direction for the electromagnetic design of the RMFM-BDRM. The influence of the matching relation between the PM and the magnetic block on the air-gap magnetic field and the back electromotive force is researched, to provide the reference for the structural selection of the radial MFM-BDRM.Thirdly, the power factor and torque of the RMFM-BDRM is analyzed, which lays the foundation of improving the electromagnetic performance of the RMFM-BDRM. Combined with the established motor model, the reason of the low power factor of the RMFM-BDRM is analyzed, and that the method of the improvement of the power factor is proposed. On that basis, some factor effecting on the power factor is analyzed, such as the relation of the magnetic block and PMs, the span and height of the magnetic block, the air-gap length and the length-diameter ratio of the RMFM-BDRM. The influence of the span and height of the magnetic block and the slot-opening width on the torque and the torque ripple is investigated.Lastly, when the RMFM-BDRM is operating under its no load or load, the distribution of the magnetic field in the PM rotor, the PMs and the modulating ring rotor is investigated, based on the principle of the core loss, and that the distribution of the core loss in the RMFM-BDRM is analyzed, to provide the theoretical reference for the calculation of the efficiency and temperature rise. Additionally, when the soft magnetic composite is made for the stator, the stator core loss is analyzed. And when the solid iron is made for the magnetic block, the core loss of the modulating ring rotor is analyzed. Finally, the motor's indexes of the RMFM-BDRM are comprehensively evaluated.