Patent GB-476331-A (GB)
Title: Improvements in and relating to magnetic amplifiers for controlling gas or vapour electric discharge gaps
IPC: H02M1/04
Filed: 1936-04-02
Abstract: 476,331. Electricity supply; converting; non-contact-making relays; automatic control systems. SIEMENSSCHUCKERTWERKE AKT.-GES. April 2, 1936, No. 9792. Convention date, April 18, 1935. [Classes 38 (ii) and 38 (iv)] [Also in Group XXXIX] Transformer arrangements ; temperature.-A magnetic amplifier for providing control potentials for grid-controlled gas or vapour discharge valves in accordance with very small regulating potentials comprises a number of transformers or auto-transformers arranged in two groups 20, 21 and 22, 23 of at least two transformers each. The transformers are all excited by sets of windings b, d, a, the windings of each set being connected in series and energized from A.C. supply, from a source of contact D.C., and from the source of small regulating potential respectively so that the output potentials appearing across output windings c in the group 20, 21 oppose those in the group 22, 23 and produce a resultant A.C. potential which reproduces in amplitude and phase the magnitude and sign of the input regulating potential. With a given sign of the input regulating potential, the windings a and d are wound and connected so that the fluxes produced by these windings assist each other in opposite phases in the upper pair of transformers 20, 21 whilst they oppose each other in opposite phases in the lower pair 22, 23 and vice versa. The result is that a change in the regulating potential produces changes in opposite senses in the windings c of the upper pair of transformers and the windings c of the lower pair thereby enhancing the amplifying action. The amplifier may be applied to control a rectifier 2 in response to temperature in a furnace 1 supplied with heating current through the valve 2. A thermo-electric element 8 has its voltage opposed by a battery 11 in the input control circuit of the amplifier so as to reverse the phase of peaked potentials from the amplifier applied to the valve 2 in dependence on whether the furnace temperature is above or below the desired value. This provides an " on and off " control. A small part of the output potential from the rectifier may be taken from a resistance 25 and applied in the control circuit. A continuous or graded control may be effected by using the output potential from the amplifier to vary the instant of ignition of the valve 1 in accordance with its amplitude. In a modification, Fig. 3, two valves 33 acting as a full wave rectifier may be used to supply the furnace 31. In this case, an additional set of secondary or output windings c<1> is provided on the transformers 20-23, the two sets c, c<1> being used to control the two valves and their common point being at cathode potential. The windings b are supplied with A.C. from a transformer secondary 38 through a phase shifting network 48, 49. The windings d are supplied with constant D.C. through a rectifier 39 from a part of the winding 38. The windings a are connected across a resistance 55a which is in circuit with the thermo-electric element 41 and a resistance 46 supplied with constant E.M.F. from a rectifier 45 and a constant current resistance 43. Voltage dependent upon the output of the rectifier is applied across part of the resistance 55a. The grid circuits of the valves 33, 34 include a condenser 50, rectifiers 51, 52, 56 and leak resistances for providing D.C. bias potential whilst preventing flow of current through the windings due to conductivity between the grids and cathodes of the valves. The Specification as open to inspection under Sect. 91 discloses an arrangement in which a magnetic amplifier for grid control of a valve rectifier supplying a furnace is composed of two transformers having the primary windings on each connected in series to A.C. supply, the secondary windings on each oppositely connected in series to the grid of the valve and a single control winding on each connected oppositely in series with each other to the thermo-electric element through a bias battery and choke. This subject-matter does not appear in the Specification as accepted.