Design optimization of the magnetic suspension for a flywheel energy storage application

Flywheel energy storage is one of the most suitable solutions for power-intensive applications due to its high reliability, relative immunity to environment aspects and long lifespan. On the other side, power supply of magnetic bearings, required for high-speed systems, may lead to the complete self-discharge at no-load in islanded operation within hours. The paper presents an optimized design of a hybrid suspension system for steel rotor flywheels combining permanent magnets and excitation coils, activated only in presence of displacements with respect to vertical steady-state position. Dynamic behavior is simulated by the adoption of a non-linear electromagnetic model including the influence of different parameters (for instance, temperature on magnet properties).