| 摘要 |
PURPOSE:To reduce the eddy current loss incurred in a magnetic yoke by providing a magnetic yoke composed of a coil, a commutator and multiple magnetically soft materials arranged with a slight clearance between a magnet and the yoke. CONSTITUTION:The rotation of a rotor 10 turns out the rotation of a fan 20 by a fan boss section 22. At this moment, a disc-type magnetic yoke 16 made up of multiple thin magnetically soft materials reduces the magnetic resistance and heightens the magnetic density of a coil 19. The eddy current is then gener ated to the disc-type magnetic yoke 16 made up of the multiple magnetically soft materials by the change of flux with the rotation of the rotor 10. However, as the magnetically soft substance is formed in a thin plate as compared with the magnetically soft substance integrated with the magnetic yoke 16, it becomes difficult to generate the eddy current by the resistance between the plates, resulting in the small eddy current flow.
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