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In this paper, taking a high-speed permanent magnet generator (HSPMG) as an example, the unbalanced load limit of HSPMG is studied based on the analysis of the electromagnetic and temperature fields of the generator. The influences of different degrees of unbalance currents on the losses of the generator are studied, and the influence mechanisms of unbalance currents on the losses of the rotor sleeve and permanent magnet are revealed. Based on the theory of fluid dynamics and heat transfer, the temperature field distribution of HSPMG under the unbalanced load condition is studied, and the non-linear relation between the current unbalance and the temperature field of HSPMG is determined. Finally, the load unbalance resistant limit of HSPMG is determined. These conclusions can provide a reference for determining the unbalanced load limit of HSPMG. It is also helpful for improving the reliability of HSPMG under abnormal working conditions.

A new approach has been proposed to evaluate the influence of the transverse edge effect of high-temperature superconducting (HTS) linear induction motor (LIM) in this paper. Taking a 3.5 kW single-sided HTS LIM for an example, the cross-flux density distributions were analyzed by analytical method. Based on results mentioned above, a new transverse coefficient was proposed to evaluate the influence of the transverse edge effect on the cross-flux density distribution. The influences of the motor configurations and parameters on the transverse coefficient were also investigated. The 3-D finite-element method was adopted to verify the accuracy of the presented analytical method.

In a high-speed permanent-magnet generator (HSPMG), an alloy sleeve is often used to prevent damage to rotor magnets caused by the large rotational centrifugal forces. However, eddy-current losses appearing in the sleeve increase the generator working temperature, which may reduce the generator performance and even cause thermal demagnetization of the magnets. Thus, a sleeve scheme designed with low eddy current losses is necessary, and a rotor structure with copper plating is presented in this paper. The two-dimensional mathematical model of a 117 kW, 60 000 rpm HSPMG is established, and the electromagnetic field in the generator is calculated using the finite element method. The results show the effectiveness of the copper plating in reducing the eddy current losses in the rotor, and the influences of the sleeve thickness and the copper layer thickness on rotor eddy current losses are analyzed. Using the fluid-thermal coupling method, the temperature distribution of the generator with different copper layer thicknesses is comparatively analyzed based on the theories of fluid mechanics and heat transfer. The relationship between the temperature and the copper layer thickness is obtained, and finally the temperature of the permanent magnets, which is the part most seriously affected by the temperature, is given with different copper layer thicknesses. The obtained conclusions may provide useful reference for the design and research of HSPMG.