| 摘要 |
PURPOSE:To rotate a ring very quietly at the number of revolution which is determined by a ratio of the length of its circumference to an interval between magnetic poles by generating an AC magnetic field between two sets of magnetic poles which are opposite to each other across a space between magnetic cores formed by laminating magnetic sheet plates. CONSTITUTION:When an exiting coil 7 is electrified by an AC power source 16, an AC magnetic field in a space between the magnetic pole 16b of a magnetic core 6a and the magnetic pole 17b of a magnetic core 6b, and an AC magnetic field between the magnetic pole 16a of the magnetic core 6a and the magnetic pole 17a of the magnetic core 6b generate a phase difference due to short rings 12, 15. Thereby, on the same principle as a shading-coil type induction motor, a ring 4 inserted in said space becomes a motor-driven fan which rotates by receiving a one-way driving torque. The number of revolution at this time is determined by the ratio of the length of the circumference part of the ring 4 to an interval between the magnetic poles 16a, 16b. Since the diameter of the ring 4 is about 15cm, a fan of several number of revolutions per second can be provided. Accordingly, a fan thus obtained has a small air flow, and will not give an unpleasant feeling to a person, while without causing any danger even if one might touch it.
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