Aiming at the technical challenge of limited motor heat dissipation under vacuum conditions in high-power flywheel energy storage systems

this paper proposes a novel structure with separated motor and flywheel rotors. In this configuration

the flywheel rotor is placed inside the vacuum chamber while the motor rotor is arranged in an atmospheric environment outside the chamber

and contactless torque transmission is realized via a tubular magnetic coupling. Based on the Newton-Euler equations

a dual-rotor dynamic model is established

which comprehensively considers the gyroscopic moment

stiffness and damping of magnetic bearings

as well as the radial coupling stiffness of the magnetic coupling. Electromagnetic field simulations show that the ultimate torque of the magnetic coupling is 11.26 kN·m

and its equivalent radial stiffness ranges from -416.40 to -445.58 N/mm within the operating torque range of 0~10 kN·m. Dynamic analyses reveal that the critical speeds of the first seven rigid-body modes of the system are 371.21~1988.10 r/min

and the first bending critical speed is 13707 r/min

indicating sufficient safety margin within the operating speed range. Unbalance excitation induces synchronous resonance on both the flywheel and motor sides

with maximum vibration displacements of 65.19 μm and 30.23 μm

respectively. Parameter sensitivity results demonstrate that the magnetic bearing stiffness dominates the low-order critical speeds of the system

damping can reduce the resonance amplitude by more than 70%

whereas the coupling stiffness has a minor effect on the system dynamic performance. A 1.2 MW-125 kWh prototype is constructed and full-speed vibration tests are carried out. The experimental results agree well with the simulation trends

providing a theoretical reference for the design of such dual-rotor flywheel energy storage systems.