Rotor, Bearing and Dynamic Equations in Energy Storage Flywheels for Vehicles

Energy storage systems for vehicles present significant challenges for rotor and bearing design. This paper discusses rotor and bearing design technology in energy storage flywheels for vehicles, with particular emphasis on orientation of flywheel rotors, rotor geometry and magnetic bearings. Material, rotational speed and geometry are mainly factors of flywheel rotor design. In order to achieve an attractive specific energy, the rotor speed should be as high as possible. The bearings must be capable of extremely high speed, have very low friction, and be stiff to adequately constrain the rotor, have long life, and have high load capacity. These requirements frequently lead to choosing magnetic bearings for Flywheel Energy Storage System applications. A flywheel energy storage system prototype with active magnetic bearings was designed. The flywheel was suspended by the permanent magnetic bearings and stabilized by the active magnetic bearing. Finally, we deduce differential equations of the magnetic suspended flywheel for the design of control system.