| 摘要 |
PROBLEM TO BE SOLVED: To impart driving force, proportional to the current command value, to a rotor and make each electromagnet as small as possible. SOLUTION: Electromagnets 21a, 22a are opposedly arranged with a rotor 10 placed in between. A current control part 30a feeds a bias current I10' and a currentΔI1 for driving the rotor 10 to the electromagnet 21a and feeds a bias current I20 and a current -ΔI2 for driving the rotor 10 to the electromagnet 22a. The cross-sectional area AG2 of the electromagnet 22a is smaller than the cross-sectional area AG1 of the electromagnet 21a. The respective cross-sectional areas AG1, AG2 and the change portionsΔB1,ΔB2 of magnetic flux density of the respective electromagnets corresponding to the currentsΔI1,ΔI2 satisfy the relation of AG1.ΔB1<2> =AG2.ΔB2<2> .
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