Design and analysis of a semi-symmetrical double winding with same poles number high-speed permanent magnet generator

In order to relieve the problem of bearing wear in high-speed permanent magnet generator, a semi-symmetrical double winding structure with the same number of poles is proposed in this paper. The coupling of the winding magnetic fields enables the rotor to be subjected to a radial electromagnetic force along the direction of overcome gravity, which could effectively extend the service life of the bearings. Firstly, the design principle of the semi-symmetrical double winding structure and the winding MMF are analyzed based on the AC machine winding theory, and the elliptical magnetic field characteristics of the harmonic winding are clarified. Combining the characteristics of order and frequency for harmonic magnetic field, the magnetic fields coupling mechanism of the double winding is revealed, and the analytic model of the power generation and radial electromagnetic force are determined. Secondly, based on rolling contact fatigue theory, the service life improvement of bearing by the double winding structure is certificated. In addition, the magnetic fields of double winding are decoupling calculated by using the finite element method, and the consistency of results between the theoretical analyses and the finite element calculations is determined. Finally, the calculation accuracy of the finite element analysis is demonstrated by experiments on the prototype.