Abstract: A flywheel energy storage system incorporates various embodiments in design and processing to achieve a very high ratio of energy stored per unit cost. The system uses a high-strength steel rotor rotating in a vacuum envelope. The rotor has a geometry that ensures high yield strength throughout its cross-section using various low-cost quenched and tempered alloy steels. Low-cost is also achieved by forging the rotor in a single piece with integral shafts. A high energy density is achieved with adequate safety margins through a pre-conditioning treatment. The bearing and suspension system utilizes an electromagnet that off-loads the rotor allowing for the use of low-cost, conventional rolling contact bearings over an operating lifetime of several years.

Abstract: A claw-pole-type stepping motor includes a stator annularly disposed therein and having a coil, a rotor rotatably disposed inside the stator and having a multiply magnetized permanent magnet and a shaft, an outer yoke provided in the stator and having a cup shape opening toward an axially outside direction an outer circumferential portion provided in the outer yoke and having a cylindrical shape and an inner circumferential portion including first pole teeth, an inner yoke provided in the stator and having second pole teeth provided in an inner circumference thereof and an outer circumferential portion fixed to an inner circumferential surface of the outer circumferential portion of the outer yoke, in which the first pole teeth and the second pole teeth are engaging with each other via a gap in an axial direction and are disposed with respect to the permanent magnet of the rotor via a gap, a fixed portion of the inner yoke and the outer yoke is positioned at the axial inside of an opening end of the cup shape