Influence of Power Factor on High Temperature Demagnetization of High-Speed Permanent Magnet Generator

As an emergency power supply, the reliability of high-speed permanent magnet generator (HSPMG) must be guaranteed. However, affected by armature reaction, the variation of power factor will cause the changes of the loss and temperature field, which leads to the risk of permanent magnet (PM) demagnetization. In addition, regulating power factor is also the most effective way to improve the utilization of power resources. It is particularly important to select a reasonable power factor. In this paper, the influences of power factor on losses, especially on sleeve and PM eddy current loss, are determined by field-circuit coupling method. The variation mechanism of the loss is revealed. Furthermore, based on the losses study, a 3D model for calculating temperature field is established by applying hydrodynamics and heat transfer theory. The temperature distributions under different power factors are studied, and the sensitivity of temperature to power factor is determined. The power factor at the PM working temperature limit is found. The research not only assists generator designers to select power factor, but also provides early warning for PM high temperature demagnetization to improve HSPMG reliability.