| 摘要 |
An optimum arrangement of position detectors which is inexpensive but hardly affected by intrinsic mechanical deflection or radial displacement on a rotary structure or motor and by a secondary artifact or variation i the magnetic coupling resulting from the mechanical deflection or radial displacement. A brushless DC motor with N phases (N>=2) according to the present invention is provided having position detectors of which signal outputs are indicative of the location of magnetic poles of a rotor and used for controlling the rotation for a constant speed. More particularly, it includes any two adjacent position detectors being spaced from each other by a spatial angle thetai (rad) about the center of the rotor, (1/n)*(thetai/2pi)<KM is established where i=1 to N-1, 0<thetai<2pi/N, KM is the mechanical time constant of the motor (sec), and n is the number of revolutions (rps). Since the position detectors of different phases are spatially gathered in a small region, the magnetic imbalance resulting from mechanical deflection or radial displacement is attenuated. As the result, a variation of the Hall voltage output of each position detector due to the magnetic unbalance will be minimized.
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