GB613045A - Improvements in or relating to transformers - Google Patents

Abstract

613,045. Transformers. AKT.-GES. BROWN, BOVERI, & CIE. Nov. 15, 1945, No. 30586. Convention date, Dec. 15, 1944. [Class 38 (ii)] A single-phase auto-transformer provided with a tertiary winding and adapted for use in the coupling of three-phase, high-tension, longdistance networks, is characterised in that windings arranged on a cylindrical core with laminations arranged radially or in the form of an involute curve receive a reactance voltage of the order of magnitude usual with transformers of separate windings by so dimensioning the width of the auto-connected winding- radially in cylindrical windings and axially in sandwich windings-that they generate a corresponding leakage flux, the whole winding body being cage-wise surrounded by return path packets of laminations arranged all round the core in such manner that the leakage flux produced is practically absorbed by the edges of the laminations of the magnet frame. The tertiary windings are connected in delta across the three phases. Fig. 1 shows the cylindrical core a with U-shaped return laminations rranged radially in packets b which have collector laminations g secured laterally on the intermediate limbs to ensure that the leakage flux is substantially absorbed by the edges of the laminations; the leakage flux distribution is shown in Fig. 1a. The auto-transformer windings, in disc or sandwich form, comprise the high voltage winding c with input lead U<SP>1</SP>, and the lower voltage winding divided into two portions d<SP>1</SP>, d<SP>2</SP> with a common lead u, the latter portions having their outer ends connected to the earthed star-point o. The tertiary winding is divided into two parts e<SP>1</SP>, e<SP>2</SP> with leads x<SP>1</SP>, x<SP>2</SP>. A concentric or cylindrical form of winding may be employed, particularly when the tertiary winding is connected to a synchronous motor for power factor improvement. In this case, the tertiary winding is in two cylindrical parts on the inside and outside respectively of the other cylindrical windings and thus has a double flux field linkage with the auto-connected windings. The collector laminations for the linkage flux are secured on each side of the shorter limbs of the U-shaped laminations.