Patent GB-414746-A (GB)
Title: Improvements in the control of electric discharge vessels
IPC: H02M1/04
Filed: 1933-01-11
Abstract: 414,746. Converting. SIEMENSSCHUCKERTWERKE AKT.-GES., Siemensstadt, Berlin. Jan. 11, 1933, No. 991. Convention date, Jan. 20, 1932. [Class 38 (ii).] In the control of electric circuits by gridcontrolled ion-discharge vessels, the moment of initiating the arc in the vessels is varied by supplying to the grids a potential which is converted from an initial negative value into a positive value at a rate which may be regulated as desired, but the wave form of which is not a sine curve. The grid potential is restored to its negative value before the commencement of the next positive anode half-wave. A straight curve of grid potential S1, Fig. 1, may be obtained by a condenser charged from an A.C. source through an auxiliary discharge vessel with constant current, the source being of the same frequency as the anode supply to the vessel controlled, and a grid battery being used also. The condenser is discharged through a second auxiliary discharge vessel. The steepness of the curve may be varied by varying the internal resistance of the auxiliary vessels as by varying the heating of their cathodes. High vacuum vessels may be used or other means for passing constant current. Two electric circuits of this arrangement are illustrated by a drawing in the Specification as open to inspection under Sect. 91. Fig. 2 shows an arrangement wherein the grid voltage curve is given an exponential component. The variable condenser 6 is charged at the end of each negative half-wave by a peaked wave impulse from a super-saturated-iron circuit. A rectifier 11 and transformer 13 supplied through a saturated choke 12, applies to the grid 4 of the controlled vessel 1 a negative potential. A constant direct current source supplies a positive potential to reverse the charge of the grid condenser at a rate determined by the capacity of the condenser and the value of an adjustable resistance R. According to the arrangement shown in Fig.4, an oscillating circuit consisting of a condenser 6 and inductance L is fed by a unidirectional peaked impulse to apply the negative potential to the grid 4 and the ensuing oscillation changes the grid potential to a positive value at a rate determined by the adjustment of the condenser and inductance. According to a further arrangement, Fig. 6, the anode current supply to the controlled vessel 1 charges the grid condenser 6 during the negative half wave through a rectifier 11 and reverses the grid potential during the positive half-wave by current passing into the condenser through a resistance R ; this resistance and the condenser 6 are adjustable to vary the slope of the grid potential curve. In all cases the auxiliary rectifier may be arranged within the controlled discharge vessel. The grid condenser may be charged from a direct or alternating voltage at the commencement of each positive anode half-wave by a switching member working synchronously with the working current ; this switching member may be a mechanical switch or a valve controlled by the working alternating voltage. The positive charge on the grid may be applied through an ohmic resistance an inductance or a discharge vessel. The rate of change of grid potential may be varied by varying the E.M.F. in series with the grid condenser. The invention may be applied in the control of the mean current of any power-consuming device and the control may be effected automatically. In remote-control installations the grid potential may be regulated by varying the resistances in series with a conductor connected to the grid controlling arrangement. Mercury or glowing cathodes may be used.