Design and Experimental Study of a Toroidal Winding Flywheel Energy Storage Motor

Design cost and bearing stability have always been a challenge for flywheel energy storage system (FESS). In this study, a toroidal winding flywheel energy storage motor is designed for low and medium speed occasions, aiming to meet the challenges of conventional high-speed flywheel energy storage motors in terms of process cost and control difficulty. Firstly, the research motivation of this paper is introduced by analyzing the traditional high-speed flywheel energy storage motor structure and its problems. Secondly, the hybrid shaft-bearing system is established to improve the stability of shaft control and reduce maintenance costs. The magnetic equivalent circuit (MEC) of the axial magnetic bearing (AMB) is created to simplify the design and radial mechanical bearing (RMB) life is analyzed. Besides, comparing different rotor and winding structures, an interior permanent magnet motor (IPM) and toroidal winding (TW) scheme is proposed to reduce production costs and increase the critical speed of the flywheel rotor. Fourthly, the performance indexes of the TW flywheel energy storage motor, such as rotor static, losses, temperature rise and electromagnetic vibration are analyzed by the FEA. Finally, a 10 kW-3 MJ prototype is manufactured and tested. The experiment verifies the rationality of the concept and design. This article provides reference for the design and optimization of flywheel energy storage motors in low and medium speed occasions, which has certain theoretical and practical application significance.