Japanese Patent JPS3821910

B1

944,403. Semi-conductor devices, circuits for ; bi-stable valve circuits. ENGLISH ELECTRIC CO. Ltd. March 21, 1961 [March 22, 1960], No. 10093/60. Headings H3P and H3T. [Also in Divisions G1 and H2] A circuit arrangement for controlling the firing of a converting element MV in a converting system (see Division H2) comprises a bistable circuit including a pair of silicon controlled rectifiers SCR1, SCR2 (or mercury valves) whose gate circuits alternately receive timing pulses. A " start " pulse fires SCR2 and so applies a grid voltage to the valve MV. A subsequent " stop " pulse fires SCR1 causing SCR2 to stop conducting by means of a commutating circuit C1, R1, R2, R3. To protect the trigger circuit against excess voltage derived from the main valve under fault conditions a spark gap SG and a non-linear silicon carbide R5 resistor are connected across the grid circuit, and a capacitor C2 protects against spurious voltages. A common transformer may provide the "stop" and "start" pulses (Fig. 3, not shown). Fig. 4 shows an arrangement supplementary to Fig. 2 to prevent both SCR's firing simultaneously causing " fire-through." A relay RL adopts a voltage corresponding to the lowest cathode voltage (normally zero volts). On a fault occurring when both SCRs conduct the relay RL operates. An alternative circuit using mercury arc valves is disclosed (Fig. 8, not shown). Remote control is effected by firing the trigger circuits from the output of photocells, a light beam on the photo-cells being provided by a remote lamp and being modulated to give firing signals (Fig. 9, not shown).

JPS5666175

PROTECTIVE SYSTEM FOR CONTROL RECTIFIER

JP933661A

October 18, 1963

March 20, 1961

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H02H7/127; H02M1/04; H02M7/15; H03K17/723

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