PURPOSE: To always control the rotating speed of a motor at constant speed irrespective of a motor load by controlling the phase angle of a supply source to the motor.
CONSTITUTION: The rotating speed setter 29 of rotating speed setting means 26 outputs an output voltage Va in response to set rotating speed, and the voltage is input to a comparator 34 of a feedback circuit 25. The rotating speed of a motor 10 is detected by rotating speed detecting means 23, an output voltage Vb in response to the real speed is output through a counter 31 and a ladder circuit 32, and the output is input to the comparator 34. When a motor load is large, the pulse width of the output Q2 of a comparator 39 of phase angle controller 22 is increased so that the ON time of a bidirectional control unit 17 is increased to enhance the motor speed. If a load is small, the pulse width of the output Q2 of the comparator 39 of the controller 22 is narrowed to decelerate the speed of the motor 10.
UESUGI NAOYOSHI
MUKAIKUBO JUNICHI
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