| 摘要 |
PROBLEM TO BE SOLVED: To suppress deterioration in motor characteristics due to iron loss by providing air gaps between a permanent magnet and a nonmagnetic shaft and between the permanent magnet and adjacent laminated iron plate and nonmagnetic shaft and fixing a short circuit piece in the gap through a spring thereby increasing the current capacity in the constant torque region. SOLUTION: A nonmagnetic shaft is provided with a protrusion 1a which is secured, at the forward end thereof, with a laminated iron plate 2 split in the circumferential direction into four. A permanent magnet 3 is secured between the laminated iron plates 2 serving as poles such that the flux passes through adjacent poles. An air gap is provided on the inside (shaft 1 side) of permanent magnet 3 and a short circuit piece 4 is set in the air gap while being supported by a spring 5 movably in the radial direction. When the r.p.m. is low, the spring 5 is left in extended state and thereby the leakage fluxϕ2 is low and the main fluxϕ1 is relatively high. When the r.p.m. increases, a centrifugal force acts while resisting against the spring 5 and the short circuit piece 4 approaches the laminated iron plate 2 to increase the leakage fluxϕ2 thus decreasing the main fluxϕ1 .
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