| 摘要 |
PROBLEM TO BE SOLVED: To ensure satisfactory operation of a motor for any operating state by switching a commutation circuit at a frequency significantly higher than the operating frequency of the motor among a plurality of modes for generating different commutation angles. SOLUTION: A DC motor 1 has a permanent magnet rotor 6 and the rotational position thereof is detected by a position detector 7 delivering a position signal to a control circuit 8 which receives a voltage Ug and controls the switching state of a commutation circuit 5. The commutation circuit 5 is switched at a frequency significantly higher than the operating frequency of the motor among a plurality of modes for generating different commutation angles. A mode switching frequency is derived from a pulse width modulation frequency of for controlling time variation in the amplitude of phase voltage. A control signal of desired frequency corresponding to the mode switching frequency can be derived easily by dividing or multiplying the pulse width modulation frequency being produced regularly. |
