| 摘要 |
1,180,500. Control of D.C. motors. SIEMENS A.G. 7 June, 1968 [9 June, 1967], No. 27331/68. Heading H2J. [Also in Division G3] A shaft A is driven at a variable speed in either direction by oppositely-rotating D.C. motors M1, M2 which are coupled to the shaft through a differential gear D and are alternately and periodically connected to a D.C. source U by respective switching transistors p2, p3 whose conductive periods are controlled by a pulse-width modulator G in accordance with a D.C. voltage el. This voltage is applied to the input of a differential amplifier p1 whose output is fed to the modulator G together with a voltage of triangular waveform from a generator Dr, these two input voltages being compared in the modulator which produces output voltages at terminals a2, a3 dependent on the comparison. As the voltage e1 is varied from a maximum positive to a maximum negative value, the modulator output correspondingly varies from a condition in which there is a steady voltage at terminal a2 and no voltage at terminal a3 to the reverse of this condition, the corresponding motor operating conditions being transistor switch p2 continuously conducting, motor M1 running at maximum speed, motor M2 stationary and transistor switch p3 continuously conducting, motor M2 running at maximum speed, motor M1 stationary. For values of e1 intermediate these extreme conditions corresponding pulse trains appear at terminals a2, a3, which trains additively represent a substantially constant voltage and individually determine the speed of the motor controlled thereby. When the value of e1 is zero the motor speeds are equal and shaft A is stationary. Constant speed of the shaft is provided by a feedback circuit comprising tacho-generators T1, T2 respectively responsive to the speeds of the motors M1, M2 and providing outputs which are connected in opposition to produce a second input signal e2 to the amplifier p1.
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