Study on method of eddy-current-loss suppression and power-factor enhancement of integrated magnetic-field-modulated machine

Integrated magnetic-field-modulated machine is a single-air-gap magnetic-field-modulated machine, which is highly integrated by using the magnetic gear and high-speed permanent-magnet machine. It has the advantages of compact structure, high torque density, high reliability, which has potential application prospects in aerospace area. However, this kind of machine uses the multiple modulation harmonics with small amplitude for energy conversation, resulting in the large harmonic loss and low power factor. To solve the above mentioned problems, the eddy current loss suppression and power factor enhancement methods of the integrated magnetic-field-modulated machine are studied. Firstly, the modulated magnetic-field composition of machine is analyzed to determine the contribution of permanent-magnet modulated harmonics and armature modulated harmonics to electromagnetic torque. Secondly, the loss production mechanism is studied. As the eddy current loss of permanent magnet is the main loss, the influence of the permanent magnet segmentation on the eddy current loss is studied. In order to optimize the air gap performance, two improved configurations of the modulated rotor are proposed. Thirdly, the expression of the power factor under different control strategy is deduced. The power factor enhancement method is studied in aspect of the control strategy and the machine design. Finally, a prototype of the integrated magnetic-field-modulated machine is manufactured. The test bench is built up to carry out the experiment. The experimental results verify the correctness and feasibility of the theoretical analysis. The results show that the circumferential segmentation scheme of the permanent magnet can reduce the eddy current loss by at least 75%. The sinusoidal-surface configuration of the modulated rotor can reduce the eddy current loss to 73% of the conventional configuration. By adjusting the input phase angle of the machine, the power factor can be increased by 25%, the eddy current loss can be reduced by 50%, and the efficiency can be increased by 10% without the sacrificing torque.