Design and Analysis of the Multi-layer Sleeve Structure for the Rotor Eddy Current Loss Reduction of a High-speed Permanent Magnet Motor for Flywheel Energy Storage System

The flywheel energy storage system (FESS) has been widely applied in transportation and industry fields due to its desirable performance in efficient energy conservation and conversion. Normally, High-speed permanent magnet motor (HSPMM) is regarded as the core component in FESS. However, the rotor mechanical strength and temperature rise are always the critical problems for HSPMMs in high-speed operation. Therefore, the rotor structure with multiple sleeve layers structure for HSPMM is researched in detail to reduce the rotor eddy current loss and temperature rise. The design parameters regarding the multi-layer sleeve rotor structure are studied and investigated. Moreover, the multi-physics fields iterative analysis design for the multi-layer sleeve rotor structure is proposed in this paper to further reduce the rotor operating temperature with the rotor mechanical strength maintained. The analytical calculation method for the rotor with multiple layers is proposed in this paper, with its accuracy verified by Finite element method (FEM). The 30 kW, 30,000 r/min HSPMM for FESS application is also manufactured and tested to verify the analysis results.