MOTOR SPEED CONTROL ARRANGEMENT

摘要

A variable motor speed control arrangement of the tachogenerator feedback loop type comprises a triac (5) connected in series with the motor (M). The triac is fired in each half cycle of the AC mains supply. The firing angle of the triac is varied to provide the required control. The arrangement employs a single cycling counter (CT) to time the interval between two output pulses of the tachogenerator (T) in order to determine the current motor speed and also to provide a count-down from the beginning of each half cycle to the required firing instant. The control processes are carried out in periods beginning at each counter overflow instant. This breaking up of the processing, together with the use of the single counter allows a microcomputer (1), which is running other programs to provide the speed control in addition.