Patent GB-410880-A (GB)
Title: Improvements in and relating to control systems for vapour electric discharge devices
IPC: H02M1/04
Filed: 1932-12-05
Abstract: 410,880. Converting; changing phase. SOC. ANON. HEWITTIC, and DEMONTVIGNIER, M., 11, Rue du Pont, Suresnes, Seine, France. Dec. 5, 1932, No. 34468. Convention date, Dec. 5, 1931. [Class 38 (ii).] In an arrangement for controlling the periodic starting of the discharge in a vapour electric discharge device by the periodic sudden variation of the voltage applied between a control electrode and a main electrode of the device, an auxiliary valve, rectifier or spark-gap, supplied from an alternating current source through a circuit containing resistance and reactance, is so connected to the control and main electrodes as to apply between them the sudden voltage increase produced at the terminals of the auxiliary valve, rectifier or spark-gap upon extinction of the current therethrough. Fig. 1 shows an auxiliary rectifier 2 and a resistance 4 connected across an inductance 3 and the secondary winding of a transformer 1 of which the primary winding is supplied with alternating current, and Fig. 2 indicates in the curves 10, 11, the varying potential difference across the terminals 5, 6, Fig. 1, during the cycle. the sudden voltage increase being at the moment to when no current passes through the rectifier 2. Fig. 3 shows the application of sudden voltage increases so obtained to the regulation of the voltage supplied by a three-phase mercury vapour rectifier 25. The three-phase supply 15 is connected to the primary windings 16, 17, 18 of a three-phase transformer and the anodes 22, 23, 24 of the rectifier 25 are supplied from main secondary windings 19, 20, 21 respectively. Auxiliary secondary windings 27, 28, 29 supply the auxiliary rectifiers 36, 37, 38, e.g. of the cuprous oxide type, through inductances 30, 31, 32 and resistances 33, 34, 35 respectively, and the control electrodes 39, 40, 41 of the rectifier 25 are connected through resistances 42, 43, 44 so as to be subjected to negative direct voltages, derived from part of a resistance 45 and filtered by a condenser 46, superposed upon the voltages at the terminals of the aggregates 33+36, 34+37, 35+38 respectively. A single resistance may replace the resistances 33, 34 and 35. If it is desired to compensate the drop of potential in the rectifier 25 under load to produce compounding or over compounding, the centre core of each inductance 30, 31, 32 is provided with a winding in series with the rectifier supply circuit. If it is desired that the rectifier current shall vary as little as possible within certain limits of the rectified voltages, there are provided on the centre core of each inductance 30, 31, 32, two windings, one of fine wire traversed by a constant direct current and the other of heavy wire traversed by the rectified current or a fraction thereof ; these windings are so arranged that their ampereturns are in opposition and the numbers of turns are such that a relatively small variation of the rectified current produces a relatively large variation in the desired direction in the resultant ampere-turns. If it is desired that the rectifier 25 shall give a substantially constant voltage, the centre core of each inductance 30, 31, 32 is provided with a single core of fine wire traversed by a current resulting from the application to a small fixed resister of the difference between the rectified voltage and a constant voltage which is somewhat greater than the desired value. Fig. 6 shows a modified arrangement in which the auxiliary rectifier is incorporated in the main rectifiers by the provision therein of a supplementary anode 62 supplied from an alternating current source 64 through a transformer 63, an inductance 65 and a resistance 66. Upon extinction of the discharge from the anode 62, the difference of potential between the point 67 and the cathode increases suddenly and this increase is applied in correct polarity to the control electrode 16 through a transformer of which the primary winding 68 is connected between the point 67 and the cathode and the secondary winding 69 is connected between the grid resistance 70 and the cathode advantageously with the interposition as shown of a direct current source 71. In a modification the direct current voltage is derived from the auxiliary rectifier and filtered by a suitable arrangement of inductance and capacity. Alternatively, with a number of rectifiers to be controlled the supplementary anode of one rectifier tube may be employed to control the grid of another ; also the direct current voltage derived from the auxiliary rectifier of one tube may be supplied to the grid of another tube. Fig. 8 shows the application to the control of the discharge in vapour electric discharge tubes 75, 76, 77 of a three-phase inversed rectifier arranged to permit the recuperation of energy in a traction sub-station, e.g. as described in Specification 391,792. A threephase source 74 supplies the three cathodes and the three main anodes 111, 112, 113 are connected together and also through an inductance 78 to the positive pole of the direct current source, the neutral point 79 of the three-phase supply being connected to the negative pole of such source. The three-phase source 74 supplies also the star-connected primary windings 80, 81, 82 of a transformer of which the corresponding secondary windings 83, 84, 85 feed the supplementary anodes 92, 93, 94 through inductances 86, 87, 88 and resistances 89, 90, 91 respectively. The voltages superposed upon the control electrodes 114, 115, 116 are derived from the secondary windings 99, 100, 98 of single phase transformers of which the primary windings 96, 97, 95 are supplied from the terminals of the aggregates 84+87, 85 + 88, 83 + 86 respectively.