GB527147A - Improvements in and relating to electric converter devices - Google Patents

Abstract

527,147. Converting. BRITISH THOMSONHOUSTON CO., Ltd. March 31, 1939, No. 10182. Convention date, March 31, 1938. [Class 38 (ii)] In a converting arrangement comprising polyphase discharge devices 30, 40 interconnected through an interphase transformer 7, means are provided for periodically varying the transformation ratio of the interphase transformer to increase the frequency of the D.C. nipple. In the form shown in Fig. 1 the interphase transformer is tapped and connected to the D.C. circuit through a discharge device 70. During the period a conducting anode in group 31-33 has a higher voltage than the simultaneously conducting anode in group 41-43 the anode 71 is conductive and vice-versa. By suitable adjustment of the winding ratio the sixth harmonic will be eliminated. If desired the discharge device 70 may be provided with additional anodes which are connected to the ends of the interphase transformer. In a modification shown in Fig. 5, the star points of the transformer windings 3, 4 are connected to tappings on the interphase transformer 7, the ends of which are connected to auxiliary anodes 71, 72 in the main discharge device 10. In this form, the arc transfer from a conductive anode in the group of anodes associated with the winding 3 to the anode 71 when the voltage applied to the anode 71 from the interphase transformer exceeds that applied to the main anode from the winding 3, and will transfer back to another main anode when the voltage of that anode becomes greater. A similar operation occurs between the auxiliary anode 71 and the main anodes supplied from the winding 4. In this way a stepped waveform of the current is obtained in each parallel operating circuit and by suitable adjustment of the interphase transformer ratio, the sixth harmonic can be eliminated from the output. An arrangement having three twophase groups is described, in which the interphase transformer has three windings and three auxiliary anodes are provided. In the form shown in Fig. 7 the tappings of the interphase transformer are connected through the windings of chokes 73, 74 which are periodically rendered ineffective by means of auxiliary windings connected between the cathode of the discharge device 10 and the auxiliary anodes 71, 72, In a further modification the chokes 73, 74 are provided with additional saturating windings connected in series in the D.C. circuit. The Specification states that grid control may be employed. Reference has been directed by the Comptroller to U.S.A. Specifications 2,082,015 and 2,085,515.