Influence of sleeve conductivity on starting performance of high-speed permanent magnet synchronous starter generator for micro-gas turbine

High-speed permanent magnet synchronous machine is often used as a starter generator for a single-shaft micro-gas turbine due to its high efficiency and high-power density. However, when the machine works in the starting mode, it usually needs a complex control system to start since the machine cannot realise self-starting. Therefore, here, a dual-purpose rotor sleeve is proposed for the machine to have the starting ability. Furthermore, the dynamic response speed of the machine also can be improved by optimising the electromagnetic characteristics of the sleeve. Taking a 40 kW, 20,000 r/min surface-mounted permanent magnet machine as an example, the two-dimensional finite element model of the machine is established. The start-up time and locked rotor parameters under different sleeve conductivities are studied by the finite element method. In order to find out the reason for the change of starting performance, the rotor eddy current distribution is studied. Furthermore, the starting torque of the machine is decoupling analyzed, and the influence of sleeve conductivity on various kinds of torques are found to reveal the influence mechanism of sleeve conductivity on starting performance. Finally, the correctness of the model is verified by experiments.