Influence of the Electromagnetic Characteristics in Air Region on High‐Speed Permanent Magnet Generator Based on Multi‐Physical Field.

The cooling performance of the machine with the closed liquid cooling system is excellent. However, the electromagnetic characteristics of the oil separator which sealing the cooling oil in the stator side can have a significant impact on the performance of the machine. In this paper, a liquid cooling structure with the magnetic oil separator is proposed. Taking the 20 000 rpm high‐speed permanent magnet generator as an example, the influence of the electromagnetic parameters of the magnetic oil separator on the generator output performance is studied by the analytical calculation and the finite element method, and the mechanism of the nonlinear variation of the generator output performance with the permeability of the oil separator is obtained. The influence of the oil separator on the air‐gap magnetic field and electromagnetic force is analyzed, and the reduction mechanism of the different permeability of the oil separator on the harmonic magnetic field and radial force is revealed. The vibration acceleration response of the generator stator is obtained through the modal and harmonic response analysis, it is confirmed that the magnetic oil separator has the effect of reducing vibration. In addition, the 3‐D temperature field calculation model of the generator is established, the influence of the thermal parameters of the oil separator on the internal heat exchange of the generator is studied, and the temperature distribution is obtained. Finally, experiments on the electromagnetic performance and temperature rise of the prototype are carried out to verify the correctness of the theoretical analysis. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]