GB442280A - Improvements in and relating to electric current converting arrangements, particularly for high voltage rectification - Google Patents

Abstract

442,280. Converting. BRITISH THOMSON - HOUSTON CO., Ltd., Crown House, Aldwych, London. May 28, 1934, No. 15884. Convention date, May 27, 1933. [Class 38 (ii)] In a polyphase converter comprising electric discharge devices A, B in association with a synchronously operated switch S arranged to relieve the discharge paths of reverse voltage during their nonconducting periods, means are provided to advance the moment at which commutation is completed in order to reduce the amount of reverse voltage present at the discharge path from which current is being transferred prior to opening of the switch contacts associated with that discharge path. In one arrangement, a condenser 4 is inductively coupled through a winding 20 with windings 11 ... 16 in series with the discharge paths in order to expedite commutation by neutralizing the leakage reactance of the main transformer 3. Alternatively, condensers may be connected directly in series with the discharge paths. In another arrangement, Fig. 2 (not shown), commutating voltages are introduced through a transformer connected between the neutrals of the two groups of main transformer windings, these voltages causing the voltage on the discharge path from which current is being transferred to fall more steeply, or the voltage on the discharge path to which current is being transferred to rise more steeply. The discharge devices may have a mercury vapour or other gaseous filling or they may be air spark gaps. The Specification as open to inspection under Sect. 91 comprises also arrangements in which discharge devices having suppressor grids are employed, and arrangements in which a number of discharge devices are connected in parallel to shorten the commutation period for a given load current. This subject-matter does not appear in the Specification as accepted.