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Inverter-less flywheel applications for voltage sags and blackouts compensation

Using a flywheel and a squirrel-cage induction motor, this paper proposes two inverter-less applications for electrical power quality improvement by compromising a little frequency fluctuations; (1) a voltage sag compensator using a capacitor self-excited induction generator without semiconductor power converters, (2) blackout delay system for industrial robots safety shutdown. In the first section, the original points are the proposal of an attractive configuration without the converters, design considerations of the stored energy in the flywheel system, and experimental validation of the design guides by a 10-kW class system. In the second section, the key point is the usefulness of the inverter-less system for industrial robots. Field tests of blackout for a real industrial robot (30 kVA) protection are reported. The flywheel system is found to work well and provides a backup for the robot.