Patent GB-407014-A (GB)
Title: Improvements in or relating to electric control systems, particularly for electric theatre and like lighting, motor and other loads
IPC: G05F1/32
Filed: 1932-07-01
Abstract: 407,014. Controlling two or more motors. BARON, H., 231, Strand, London.- (FitzGerald, A. S.; 433, Warwick Road, Wynnewood, Pennsylvania, U.S.A.) July 1, 1932, No. 18677. [Class 38 (iii).] A number of load circuits, such as illuminating circuits in a theatre lighting system or motors driving textile machinery, paper-making or wire and rope winding equipment, are jointly controlled from a single control element 100 which varies the current in the saturating windings of saturable core devices 20, one for each load circuit, each of which determines the degree of energization of a control element 10 adapted to control one of the circuits. Fig. 1 shows a system in which a number of A.C. load circuits 1 are controlled by saturable reactors 4 the saturating windings of which are supplied from an A.C. circuit through rectifiers 7 and a further saturable reactor 8 deriving its saturating current through a rectifier 9 from a control element 10, which is preferably a single phase induction regulator with relatively movable primary and secondary windings. Switches 23 may determine whether any circuit or circuits shall be group controlled, independently controlled, or rendered inoperative. Each group of load circuits is jointly controlled by a control element (colour master) 100 through a similar catenation of rectifiers and saturable reactors and the groups are likewise controllable jointly from a control element (grand master) 1000. Any number of group stages may be employed. Reversal of the control effect in any one or more circuits is obtained by exciting an auxiliary oppositelywound saturating winding 160 on a reactor 20 associated with the desired circuit. The saturating windings of the group control reactors are connected in a circuit of constant impedance, such as the series circuit shown, rendering the control effect independent of the number of circuits set for group control. Means may be provided to preselect any one or more of the following : the load circuits to be utilized for any desired effect, those to be controlled individually, those to be group controlled, group control circuits which are to be controlled directly and inversely, and the intensities of illumination to be provided by each individual circuit. Fig. 2 shows an alternative means of obtaining inverse control in which a switch 33A may be set to place the saturable reactor either in parallel or in series with its related control element, the supply current to these passing through an impedance or choke coil 34A serving to maintain substantially constant the current in the control circuit. The arrangement is such as to apply a lower voltage to this circuit when the series connection is established to render the energization of the control element substantially the same under both conditions. This Figure also indicates the method of obtaining preselection by employing scene changing relays 28A, 28B under the control of master switches such as 32. The control elements may be operated by mechanical means to produce continued slow changes. The catenation of rectifiers and saturable reactors may comprise any desired number of stages. The effect of the current flowing in the saturating winding of a reactor such as 4, Fig. 2, when saturating current is not being applied to the reactor 8 may be neutralized by an auxiliary exciting winding 13. Specification 404,034, [Group XXXIX], is referred to.