| 摘要 |
PROBLEM TO BE SOLVED: To reduce the variation of the rotation of a DC brushless motor caused by the chopping of the driving current by setting the chopping period of a chopping driving current so that a natural number of cycles of periods can be contained in one commutating period to the chopping driving current. SOLUTION: A chopping frequency computing section 70 makes computation by using the chopping frequency corresponding to the rotating speed command value Nt in accordance with a target speed signal TS. The section 70 sets a chopping driving current when a permanent-magnet rotor 14 is rotated at the command value Nt so that the chopping driving current can be contained by (n) (=1, 2,...) cycles in one commutating period to drive windings 11-13. For a three-layer four-pole DC brushless motor 10, therefore, the section 70 computes the value of the chopping period Tc of the motor 10 so that a relation Tc =Tr /(6×N) can be met (Tr : the specified period of rotation of the motor 10). As a result, the noise level of the motor 10 can be reduced and the efficiency of the motor 10 can be improved by effectively suppressing the variation of the rotation of the motor 10. |
