| 摘要 |
PROBLEM TO BE SOLVED: To control rotational speed by one switch by changing a duty ratio of a switching signal for turning ON, OFF a switch connected between an AC motor and an AC power source. SOLUTION: A fan 2 is driven by an AC motor 1 connected at its one input terminal to one output terminal of an AC power source 3. A control unit 5 controls ON, OFF of a switch 4 connected between an H tap of the other input terminal of the motor 1 and the other output terminal of an AC power source 3. In the case of alternately repeating ON and OFF of the switch 4 according to a switching signal output from the unit 5, a rotational speed of the fan 2 is controlled at high or low level according to a large or small duty ratio of the signal output from the unit 5 to the switch 4. When the duty ratio of the signal is set to 100%, the fan 2 is rotated at a predetermined rotational speed. When the duty ratio of the signal is set to zero, the fan 2 is stopped. |
