This paper presents an experimental and simulation study of the speed control of a universal motor using the ON/OFF method for the input DC voltage. A microcomputer-based system is proposed which requires minimum hardware compared to conventional analog controllers. Fast-switching semiconductor devices such as MOSFETs can be used for this method of speed control. The controller is based on continuous adaptation for the DC chopper duty ratio in order to re-adjust the motor speed. Transient and steady state behaviors of ON/OFF speed control of the universal motor performance are presented. The proposed study incorporates the effect of load torque disturbances. The results show that the proposed control method is both simple and useful for industrial applications which need variable speeds with good motor performance.
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