| 摘要 |
1,203,046. Automatic speed and current control. ALLMANNA SVENSKA ELEKTRISKA A.B. Nov.28, 1967 [Nov.29, 1966], No.54022/67. Heading G3R. A closed loop control system comprises an error signal generating means, to generate an error signal, which is a function of the difference between input and output signals of the control system, an amplifier being arranged to sense the error signal, amplify this, and add the amplified signal to the original error signal, the amplifier comprising a means for limiting its output signal. A D.C. motor 1 is supplied through converter 2 having controller 4, the motor current being detected by transformer 5 associated with rectifier 6 and pulse transformer 7. The voltage across resistor 9 is supplied to amplifier 11 having a feedback network comprising resistors 111, 113, and capacitors 112, 114. The speed of the motor is detected by tachometer generator 12 which supplies a signal to an amplifier 14 which also receives a reference signal through resistor 15. The output voltage of the amplifier 14 represents a reference signal for the motor current and is applied to the input of the amplifier 11 whose output is connected to the controller 4. The voltage developed across the secondary winding 72 of the transformer 7 is proportional to the A. C. component of the motor current, a capacitor 17 being tuned to block the oscillations due to converter commulation, and to pass the signals representing the self-oscillation of the motor current. These signals are rectified, smoothed, and applied across a resistor 21. A Zener diode 24 breaks down when the voltage across the resistor 21 reaches a given value, so that current passes through bridge 22 having its A.C. terminals in the feedback network of the amplifier 11. The effective feedback impedance and gain of the amplifier 11 is thus reduced, so restricting the amplitude of self-oscillation to an acceptable level. A network comprising resistor 115, capacitor 116, and diodes 117 limits the rate-of-change of the converter direct voltage. In a further embodiment, the amplitude of selfoscillation is sensed directly across the resistor 111, two opposed Zener diodes in series with a capacitor being connected in parallel with a feedback resistor of the auxiliary amplifier. With increasing amplitude of self-oscillation, the impedance of the diodes decrease together with the gain of the amplifier 11. In this embodiment, the bridge 22 and associated components are dispensed with Fig.2 (not shown). |
