Patent GB-569511-A (GB)
Title: Improvements in electrical controlling apparatus employing a grid-controlled gas-filled electronic relay
IPC: G05B11/01
Filed: 1943-06-28
Abstract: 569,511. Control systems for consumption apparatus; automatic control systems for electric furnaces. ELECTRIC FURNACE CO., Ltd., and KING, S. G. June 28, 1943, No. 10409. [Class 38 (iv)] Temperature; arcs ; thermionic control.-A grid-controlled gas-filled electronic relay forming part of control apparatus has its anode and grid circuits supplied through separate phase-shifting means with A.C. voltages normally substantially in quadrature and arranged so that a controlling quantity effects a relative shift of phase whereas other variations, e.g. in the voltage of a grid bias or supply source, which cause like changes of phase in anode and grid volts will not affect the control. Fig. 2 shows phase-shifting bridges consisting of resistances A3, H3 and saturable inductances A4, H4 supplied from windings A2, H2 maintained in quadrature relation by the interconnecting phase-displacing circuit J1, J2 ; the windings A2, H2 may be supplied from a two-phase source instead. The anode circuit of the relay valve D comprises a contactor or mechanical relay K1 K2, the bridge H and the cathode of the valve ; the grid circuit comprises a peaking transformer winding F2 fed from the bridge A and a grid bias from a D.C. source G. The device K1, K2 controls a furnace heating element K. A resistance A6 responsive to furnace temperature controls the saturating current in the reactor A5, whereby the phase of the grid voltage is varied in relation to the phase of the anode voltage. The phase relationship is restored to effect intermittent action of the device K1, K2 by a temperature-sensitive resistance H6 heated in proportion to furnace current. In this arrangement the valve is rendered intermittently conducting, but the normal phase relation of anode and grid volts may be arranged to produce progressive change in valve conductivity with change of phase relation and the resulting variable anode current may operate a saturating winding in a further bridge to control the phase of the grid volts of a mercury valve in series with the furnace heater, Fig. 3 (not shown). Two full wave mercury rectifiers N, Fig. 4, may be similarly grid controlled to determine the direction of current in the armature of a D.C. motor adjusting the electrodes of an arc furnace in accordance with want of balance in the voltage and current of the arc. One saturating winding H5 is energized in proportion to arc volts and the other A5 in accordance with arc current. Two relay valves are used and their anode and grid circuits cross-connected as shown. Their anode circuits include saturating windings L5 in phase shifting bridges controlling the rectifiers, which are connected in reverse parallel to the armature S of the electrode adjusting motor. Hunting may be prevented by negative feedback resulting from the vector readjustment of anode volts resulting from the assumption of load by the relay valves or additional saturating windings A10, H10, L10 may be fed with the voltage or current of the adjusting motor. The invention is applicable to manual as well as automatic control.