大型永磁直驱发电机磁固耦合特性研究

The magnetic-structural coupling characteristics of large permanent magnet direct drive generator are studied in this paper. Using the conformal mapping method, the scalar magnetic potential of air gap magnetic field considering cogging effect is calculated. Based on the discrete current element and magnetic equivalent circuit model, the local magnetic saturation effect of generator stator and rotor is quantitatively simulated, and the air gap magnetic field intensity distribution is obtained by numerical iteration. A series of uniformly distributed magnetic equivalent springs are introduced to simulate the coupling between the stator and rotor, and the magnetic-structural coupling finite element analysis model of the permanent magnet direct drive generator is established. Taking the megawatt permanent magnet direct drive generator in service as the object, the proposed air gap magnetic field analysis method is verified by the electromagnetic finite element calculation results. Based on the test platform of Goldwind megawatt permanent magnet generators, the modal test of rotor/stator coupling system is carried out and compared with the natural frequencies and modal shapes obtained from the theoretical model. On this basis, the effects of air gap length and rotor speed on the natural frequencies of the coupling system are analyzed. The results can provide important reference for accurate evaluation of generator vibration energy, avoiding dangerous resonance points and guiding unit design.