GB396202A - A method of converting polyphase current of a given frequency into alternating current of another frequency - Google Patents

Abstract

396,202. Frequency-changing ; phasechanging. AKT.-GES. BROWN, BOVERI, ET CIE, Baden, Switzerland. June 6, 1932, No. 15916. Convention date, June 4, 1931. [Class 38 (ii).] Relates to an arrangement for interchanging power between a polyphase circuit N1 and a single phase circuit N2 of lower frequency in which the two circuits are interconnected through two sets of grid-controlled discharge paths 1 .. 6 and 1<1>.. 6<1> associated with polyphase secondary windings on a transformer T, the amplitudes of successive phases of the latter being so graded, and the grids being energized in such sequence that the single phase current is approximately sinusoidal, and consists in simultaneously energizing corresponding grids in the two sets of discharge paths in order that at all times equal and opposite voltages are present in the local circuit comprising the two discharge devices. Thus the arrangement is capable of operating with inductive loads which would otherwise cause internal short-circuit conditions to be set up, and moreover is capable of transmitting power in either direction as determined by the relative voltage conditions in the circuits N<1>, N2. The grid energization may be effected by synchronously rotating switches U1, U2 serving to connect the appropriate pairs of grids in succession to the positive pole of a battery which is so connected as to maintain the grids normally at a negative potential with respect to the cathodes K1, K2. In a modification, Fig. 2, the two sets of anodes 1 .. 6 and 1<1> .. 6<1> are located in a common discharge vessel and the two circuits through which alternate half waves of the single phase current pass each contain a primary winding P1, P2 associated with a common secondary Q connected to the single phase circuit N2. In this case, a single switch U is employed for controlling both sets of grids. In a further modification, Fig. 3 (not shown), the discharge path 1 is arranged to pass current from the associated phase winding of transformer T to form the last portion of one half wave of the low frequency current and the first portion of the succeeding half wave, the grid control switch being modified to apply positive potential to the grid of discharge path 1 for a correspondingly extended interval.