DIRECT CURRENT MOTOR OPERATED BY SELECTING AUTOMATICALLY ITS EFFICIENCY AT NEAR MAXIMUM VALUE

摘要

PURPOSE:To operate the DC motor and improve the efficiency of operation selecting the efficiency near the miximum value automatically at all times, by a method wherein the shunt field currents of the DC motor are computed in response to output from a load detector, and the shunt field currents are controlled at the optimum value. CONSTITUTION:An adding and subtracting circuit 14 multiplies the angular velocity omega of the DC shunt motor 2 detected by means of an angular velocity detector 11 by a constant C1, and addes a value obtained by multiplication and a constant (Ra.Rf)1/2 (Ra: the resistance of an armature, Rf: shunt field resistance). A dividing circuit 15 divides a value of the voltage VA of the armature by an output value of the adding and subtracting circuit 14. A differential amplification circuit 16 sets the upper limit value and lower limit value of a Schmidt-trigger circuit 10 in response to deviation between an output value of the dividing circuit 15 and a value of mean shunt field currents If. The Schmidt-trigger circuit 10 interrupts or conducts a transistor 7 at a point of time when the shunt field currents If reach the same value as the upper limit value or the lower limit value set, and controls the shunt field currents.