Bürstenlose Motoren

摘要

In a brushless motor of the kind not including a sensor for detecting the rotor position, a rotational reference position of the rotor is detected based on the voltage induced in the stator excitation coil (La,Lb), and an energisation switching point of the stator excitation coil (La,Lb) is determined so as to occur a delayed time from the reference position. The time delay set by a delay circuit (5) is increased or decreased in response to the rotational speed of the motor, so that energisation switching of the excitation coil (La,Lb) is performed by a switching circuit (1) at the optimum position in accordance with corresponding changes in the rotational speed of the motor. Signal masking is performed by a masking circuit (8) so that noise generated by the excitation coil switching does not interfere with the detection of the rotor reference position.