Research on a Transverse-Flux Brushless Double-Rotor Machine for Hybrid Electric Vehicles

With the advantages of good driving performance, high fuel economy, and low emission, the series-parallel hybrid electric vehicles (HEVs) are widely developed. Power-split device, which is a kernel part of HEV, can be based on planetary gear or compound-structure machine (CSM). A transverse-flux brushless double-rotor machine (TF-BDRM), which can form a CSM by being connected with a traditional permanent-magnet synchronous machine (PMSM), is investigated in this paper. The equivalent magnetic circuits are established, and the equivalent reluctances, and d- and q-axis armature-reaction reactance are deducted. It is found that the armature-reaction reactances are in direct proportion to pole-pair number. The reluctances of stator core, inner, and outer air gaps, transverse-flux (TF) tooth and leakage reluctance are analyzed, and it is found that the improvement of reluctances may affect other performances of the machine. Flux-concentration structure is investigated to increase the main flux of the machine. Flux-concentration factor ξFC is used to illustrate the effect of flux-concentration structure, which can be increased by the increase of the radial and circumferential thickness of permanent-magnet. The flux-density distributions of two typical situations are simulated, and the flux-density distribution laws in inner and outer air gaps are given. With manufacturing technology investigated, the TF-BDRM prototype is made, and experiments are carried out. The tested waveforms of the back electromotive force are approximately sinusoidal, and the tested torque ripple is obvious.