SPEED CONTROLLING DEVICE FOR SINGLE-PHASE CAPACITOR MOTOR

PURPOSE:To eliminate the influence of the displacement of a center of a speed detecting generator by detecting the AC component due to the displacement of the center of the generator, adding it to the set speed voltage, and comparing it with the DC voltage obtained by rectifying and smoothing the generated voltage of the generator, thereby using it for the control of the speed of the motor. CONSTITUTION:The AC voltage generated by a speed detecting generator 2 provided at a single-phase capacitor motor 1 is full-wave rectified by a speed detector D1, is smoothed by a DC converting capacitor 5, and a negative DC voltage including AC component due to the displacement of the center of the generator 2 is obtained. Only the AC component is detected by a capacitor 6 in an AC component detector D2, and is added to a speed set voltage from a speed setting circuit S by a in-phase adder formed of resistors 7-10 and an operational amplifier 11. After the output of the adder is compared with the output of the detector D1, the output is applied through an error amplifier AM to a drive pulse generator P1 or a brake pulse generator P2, thereby controlling the speed of the motor 1.