| 摘要 |
PROBLEM TO BE SOLVED: To prevent generation of a torque impulse resulting from a through- hole even when such through-hole is provided. SOLUTION: A rotor iron core 22 forming a rotor of induction motor is provided with many through-holes 29, 30 in order to ventilate the cooling air. The through-hole 29 is provided through the area between an upper aperture 29a of the rotor yoke 22 and a lower aperture 29b and is given a skew to form a sloping surface in the axial direction of the rotor yoke 22. Narnely, the through-hole 29 is formed through the area between the k-th upper aperture 29a-k and the (k+1)-th lower aperture 29b-(k+1) by deviating the lower aperture as much as one pitch, just like the through-hole 30. According to this induction motor 10, even when the through-holes 29, 39 are provided, the magnetic flux between gaps in the axial section S does not almost change due to the rotation of the rotor. Therefore, a torque impulse or the like resulting from variation of magnetic flux is not generated.
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