The invention relates to a
motor speed adjusting device. A
control circuit of the
motor speed controller mainly comprises a PWM (pulse-width modulation) unit, a main
control unit and a
load unit, wherein the PWM unit outputs a
pulse wave with an adjustable duty ratio to the main
control unit, the main
control unit is connected with two ends of a
capacitor of the
load unit in parallel so as to be used for controlling the
capacitor to charge or
discharge, the
capacitor of the
load unit is in serial connection on a motor needing of speed adjustment, the PWM unit outputs the
pulse wave to the main control unit, the main control unit taken as a switch is connected at the two ends of the capacitor of the load unit in parallel, the load unit and the capacitor are connected on the motor in series, the
pulse wave controls the connection and the disconnection of the switch to carrying out
charge and discharge on the capacitor, when the duty ratio of the pulse wave is adjusted, and changed pulse signals are converted into the change of
charge and discharge time of the capacitor by the main control unit, so that the
reactance value of a reactor can change along with the change of the
charge and discharge time, so as to realize stepless speed adjustment. Compared with the prior art, the
motor speed adjusting device is easy in circuit, easy to realize, low in manufacturing cost, simultaneously can not generate high-frequency interference and can realize the stepless speed adjustment on the motor.