ABSTRACT
A flywheel system is generally composed of an electric machine coupled to a rotating mass. With the help of a power electronic converter, the driving torque of the variable-speed machine (positive for charging and negative for discharging) can be imposed precisely and allows controlling the exchanged power level. Flywheels have been based for a long time on normal steel and reduced speed, but modern equipment benefit from advanced materials like carbon composites and fast-running permanent magnet motors that can rotate at several hundred thousand revolutions per minute. Partially evacuated encapsulations reduce the aerodynamic losses of the flywheel and motor. A schematic representation of a flywheel system is given in Figure 8.1.
