GB413634A - Improvements in and relating to electric controlling and regulating systems - Google Patents

Abstract

413,634. Control systems for consuming devices; automatic control of A.C. voltage; protective arrangements. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Nixdorff, S. P. ; 18, Hampton Avenue, and Alexanderson, E. F. W. ; 8, Adams Road, both in Schenectady, New York, U.S.A.) Dec. 16, 1932, No. 35753. Convention date, Dec. 16, 1931. [Classes 38 (ii) and 38 (iv).] Phase changing.-In order to control or regulate an alternating current circuit a discontinuous-control, or vapour-filled, electric valve energized from the circuit has its grid circuit subjected to a potential which is modified by a saturable reactor, the reactance of which varies with the output of the valve, so that the valve oscillates between fully conducting and non-conducting conditions. The reactor may be used as a series reactance, the average value of which determines the current or voltage in the A.C. circuit. In a further modification, for maintaining a generator in phase with a network from which it has been disconnected, the reactor is used as an element in a phaseshifting circuit supplying the grid potential. Fig. 1 shows the invention applied to control the current in an A.C. circuit, in particular the starting, stopping, or speed control a commutator motor 10, in accordance with the operation of a phase-shifting transformer 25 which, with a phase-shifting circuit 21, 22 determines the phase relation between grid and anode potentials of valves 16, 17. When anode current flows the windings 14, 15 saturate the reactors 12, 13 and the voltage applied to the phase-shifting circuit dies away, so that the grid voltage vector shifts in relation to the anode voltage vector and the valves become suddenly nonconducting, whereupon the cycle recommences. The average value of the series reactance in the A.C. circuit will depend upon the setting of the phase-shifting transformer 25. Fig. 3 shows the automatic regulation of A.C. voltage of load circuit 11. This voltage is applied, through an amplifying resistance-bridge 30 and a rectifier and filter circuit, as a unidirectional voltage bias in series with the voltage applied to the grids of the valves by a phase-shifting circuit 21, 22 which, as in Fig. 1, is subject to the voltage across the series reactances 12, 13 which become saturated when the valves conduct. Fig. 5 shows saturable reactances 53 in a phase-shifting circuit energized from a supply network 41 and normally arranged to render the valves 46, 47 nonconducting. Should the circuit breaker 42 open and a phase difference occur between the generator 40 supplying the anodes and the network 41 supplying the grids of the valves, these are rendered intermittently conducting to apply by means of the resistance 44 an average load compensating for the load lost by the disconnection of the network and preventing loss of synchronism.