| 摘要 |
<p>1,207,765. Automatic current control. WESTINGHOUSE ELECTRIC CORP. Feb.20, 1969 [March 6, 1968], No.9252/69. Heading G3R. [Also in Division H2] Two pairs of traction motors are supplied through a thyristor which becomes conductive or non-conductive when a current-responsive signal is less or greater than a reference signal. For braking two loop circuits are formed, each containing two armatures and the field windings of the other two motors with a common braking resistor. The thyristor is connected across a portion of the braking resistance and is controlled, as in power operations, to maintain the braking current at a desired average value. A signal current on line 31 is modified by jerk limit and load weight circuits, and is applied to a capacitor 39. The signal representing the motor current is derived from a transistor and is applied across Zener diode 37 and resistor 38. Conductors 40, 41, provide triggering signal to an "on" pulse generator 29 and an "off" pulse generator 28 respectively. The voltage-drop across the diode 37 determines the difference between maximum and minimum valves of the motor current. In the pulse generator 28, capacitors 48, 56, are charged initially, a positive signal at the base of transistor 42 turning-off the transistor 46 whereby capacitor 48 discharges through diode 50. An output pulse on conductor 27 turns-on the transistor 51 for a short period, so causing transistor 55 to turn-off whereby capacitor 56 discharges through diode 50 to provide an output pulse for quenching the main thyristor. The capacitors 48, 56 are recharged when transistor 51 is again turned-off. In the amplifier 29, the transistor 42<SP>1</SP> is turned-off to produce an output pulse which is applied to the main thyristor and a commulating thyristor.</p> |
