Importance

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Abstract

A flywheel uninterruptible power supply includes a solid steel cylindrical flywheel levitated for rotation about a vertical axis at tip speeds greater than 250 m/s on magnetic bearings in a low pressure housing. The cylindrical flywheel has a length L and a diameter D, wherein L/D.gtoreq.1.0. A motor/generator attached to said flywheel accelerates the flywheel and maintains it at operating speed for storage of energy; and decelerates the flywheel for retrieval of the stored energy. The flywheel inertia section operates with a maximum stress of greater than 60% and less than 80% of the material yield stress when spinning at fully charged operating speed. The flywheel is constructed from steel with an ultimate strength greater 150 ksi and a toughness greater than 100 ksi (in)^1/2. The flywheel is a solid steel cylinder that is hardened to centerline structure throughout the axial thickness of the large diameter portion that is greater than 40% martensite. The flywheel is a solid steel cylinder that, in normal, fully charged operation, spins at a speed that would cause a fracture failure no sooner than one hundred thousand cycles between the fully charged normal operating speed and ten percent of that normal operating speed. The flywheel is free of flaws with length greater than 1/8th inch at a diameter less than 20% of the outer diameter of the flywheel.

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First Claim