| 摘要 |
<p>715,660. Rectifying: automatic current control systems. STANDARD TELEPHONES & CABLES, Ltd. May 1, 1953 [May 9, 1952], No. 11790/52. Classes 38(2) and 38(4) D.C. is supplied from an A.C. source to a load such as a repeater station in controlled stages of operation, through a rectifying circuit comprising a thyratron V2 and another, e.g. a selenium, rectifier MR3 permanently connected to the load, the thyratron being disabled during the first stage while the rectifier MR3 supplies half wave current to heat the repeaters and the thyratron warms up while during a subsequent stage the thyratron and rectifier act together as a voltage doubling pair to supply full power to the load under control of the thyratron. The rectifiers are energized from selected ones of tappings 9-13 of a secondary winding of mains transformer TR1, and supply output terminals 1, 2 through a smoothing network of capacitors and inductors, through relay windings A/4 and JC, and through resistances RV2, R12. The thyratron grid is energized by a standard voltage developed across a gas tube V 1 through rectifier MR 1 , balanced against the voltage drop developed across resistor RV2 by the load current, so that the time of firing of the thyratron varies with the load current to keep it constant. Also added to the thyratron grid are a saw tooth voltage developed in network MR2, R8, R19, C3 C4, a small direct voltage across RV1 which varies with and compensates for, changes in the supply voltage, and a small A.C. voltage from R6, C2, R7, in antiphase to the thyratron anode voltage. For starting, main switch SW1 is closed, contacts MC1, MC2 of relay MC/4 in the control circuit, Fig. 2 close, and rectifier MC3 supplies half wave current of a value determined by resistor RV3 to the load to heat the repeater valves. The thyratron V2 fires after a time delay lasting while the disabling negative voltage applied to the grid by the saw tooth wave, is gradually overcome by a positive voltage developed across a gas tube V1 through rectifier MR1 Relay A/4 operates, opens contacts A-2 and the thyratron and rectifier are connected to the load in conjunction with capacitors C10, C11 as a voltage doubling pair. The control circuit, Fig. 2 energized from transformer TR2 controls appropriately the sequence of operations under the following conditions, (1), (2) normal working into a resistive and a repeater load respectively, (3), (4) short circuit and open circuit respectively while working normally, (5)-(8) abnormal conditions of low current, high current, low voltage, high voltage while working normally. The control circuit is regulated by the current relays A/4 and JC and the voltage relay JV in the main supply circuit. This circuit includes buzzer BZ1 and signal lamps LS1-4 which operate during the starting periods to indicate correct operation, and under fault conditions. A relay DR/2 operating with a delay period gives time for further heating of the valves when supplying a repeater load. The control circuit also incorporates other relays X/4, P/6, LV/4, HV/4, LC/4, HC/4 to regulate its own working. A chart is given, Fig. 3 (not shown) of the sequence of operations for the various conditions mentioned..</p> |
