Importance

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Abstract

Electric power is stored in a flywheel assembly, from a dc power buss, and supplied to the buss, through electronics associated with a motor/generator, its rotor integral with a flywheel supported by magnetic bearings. The power is reciprocally converted by the motor/generator, controlled by current in its polyphase stator windings, between electricity and kinetic energy. The flywheel and rotor assembly spins around a vertical axis. The rotor contains radial-field permanent magnets attached to supporting outer annular high-permeability steel, attached to inner annular steel. This completes a path for the magnets' field, which interacts with current in the stator windings, to produce torque between the rotor and the stator. Polyphase sinusoidal currents in the stator windings are controlled by the associated electronics, responsive to respective rotation angle sensors and the dc power buss voltage, with override control responsive to flywheel rotation speed, axial and radial position sensors, and operator settings. During normal operation, the flywheel assembly is levitated by axial attraction of its annular high-permeability poles near its top, to a fixed annular permanent magnet and high-permeability poles above it. The stator windings and non-rotating parts are affixed to a sealed and evacuated stationary flywheel enclosure. The flywheel assembly is released by mechanical backup bearings at startup, which then normally remain disengaged until shutdown. During normal operation, the flywheel assembly is levitated by the axial magnetic field, which also provides inherently stable centering. Axial position stability, and continuous axial position adjustment to seek and maintain axial position where force due to the permanent magnet is equal to levitated weight, is provided by a cooperative annular concentric coil whose current is controlled by an axial servo responsive to an axial position sensor. The coil adjusts strength of the magnetic field between the fixed and rotating poles, and thereby dynamically adjusts and stabilizes lift force. A coil current time-integral is combined with axial position feedback, so that average current is continuously adjusted to zero, by axial position adjustment. Radial electromagnets damp flywheel swirling at resonant vibration frequencies, stabilize its spin axis attitude at spin speeds too low for effective gyro stabilization, and constrain radial position during possible earth tremors. At normal spin rates, with the spin-axis at the rotor assembly center of mass, spin-axis verticality is stabilized by gyroscopics and leveled by gravity.

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First Claim