Analysis on mechanical response of external rotor core of direct drive permanent magnet generator under time-varying loads

The mechanical response of external rotor direct drive generator under time-varying loads is analyzed theoretically, calculated by simulation and verified by test. Firstly, the source of magnetic pull of the rotor core of the external rotor generator and its variation with load were analyzed. The expression of magnetic pull of the rotor and the characteristics of time and space order were determined. The basic vibration model of the external rotor core was analyzed, and the basic vibration equation of the external rotor core was determined. Then the simulation model of the external rotor generator was established, and the spatiotemporal order characteristics of the magnetic pull and the typical daily variation rule with time were obtained. The magnetic pull density obtained from the electromagnetic field was used as the input load to guide the structure field. The magnetic-solid coupling simulation was carried out, and the deformation and stress distribution and noise response of the external rotor core were calculated and analyzed. Finally, a simulation example of a 13 kW external rotor direct-drive generator proved the correctness of the analysis and simulation. The results of the study determined the time-varying load on the outer rotor core and its mechanical response distribution. It is found that the time and position of the rotor core should be tested emphatically when the generator is running. Noise characteristics under time-varying loads are also analyzed. The analysis provides reference for the maintenance and design of the generator.