GB396954A - Improvements in and relating to the frequency transformation of three-phase current - Google Patents

Abstract

396,954. Frequency changing. AKT.- GES. BROWN, BOVERI, ET CIE, Baden, Switzerland. Sept. 26, 1932, No. 26718. Convention date, Sept. 25, 1931. [Class 38 (ii).] Means for supplying power from a polyphase network N1 to a polyphase network N2 operating at a lower frequency comprises a transformer T1 having n star-connected groups of polyphase secondary windings a, b, c (n being the number of phases of the network N2 to be fed), each group being associated with a group of anodes in a rectifier G, Fig. 1, or with the anodes of n multianode rectifiers Ga, Gb, Gc, Fig. 2 (Cancelled), and a transformer T2 the primary phases of which are connected between the cathode of the rectifier or rectifiers and the star points of the n groups of secondaries of the transformer T1. The necessary sequence of operation of the various anodes is determined by grid control effected either through a commutator switching arrangement or by A.C. potentials. The phase voltages of the secondary windings of the transformer T1 may be made of such relative magnitudes that an approximately sinusoidal voltage wave is produced in the low frequency network N2. The Specification as open to public inspection under Sect. 91 suggested that the frequency could remain invariable during transformation. Reference has been directed by the Comptroller to Specification 388,711, (as open to inspection under Sect. 91 of the Acts.)