GB1173249A - Electrical Transformer - Google Patents

Abstract

1,173,249. Transformers. WESTINGHOUSE ELECTRIC CORP. 29 March, 1968 [April 14, 1967], No. 15121/68. Heading H1T. A transformer, suitable for electrically driven vehicles, comprises a laminated core, as 82 (Fig. 4), windings 80 on at least one of the legs of the core and a casing 12, the walls of which are disposed against the outer edge surfaces of the core and the outer layer of turns of the windings so as to form four chambers 160, 162, 164, 166 for the fluid dielectric. Solid insulation, as 150, of wood, pressboard or cast resin is disposed between the casing and the adjacent parts of the core and windings. The windings preferably have a generally rectangular crosssection (Fig. 5). Insulating baffles 172 are provided at the corners of the winding to separate chambers 160 and 162 and chambers 164 and 166. Fluid flow between these pairs of chambers is thus confined to cooling ducts 110 inserted between layers of the windings. A duet 170 interconnects chambers 162, 166 and circulation of the dielectric in the loop shown by the arrows is maintained by a motor-driven pump connected in series with a heat exchanger between the inlet and outlet ducts in chambers 160, 164. Core structure.-The core structure is disposed horizontally and, for a single phase transformer, may comprise two core-type cores 84, 86 (Fig. 5) disposed adjacent one another to form overall a shell-type structure. Alternatively, a single core-type structure, with windings on both legs, may be used (Fig. 9, not shown), in which case insulating baffles (232, 234) are needed to separate the upper fluid chambers from the lower ones. For a three-phase transformer a shell-type core with windings on all three legs is used, the arrangement otherwise being similar to that of Fig. 9. The casing may be constructed in two halves which, when welded together, clamp the laminations of two core legs between the two halves of the casing. Inwardly extending projections (as 258, 268, Fig. 10, not shown) may be provided so that the yoke laminations are also clamped by the casing. The laminations may be silicon steel. Windings.-The windings may be wound from a flat copper or aluminium strip 180 (Fig. 6) which is either coated with an insulating enamel, e.g. epoxy, or interleaved with an insulating strip. The cooling ducts are formed by inserting a sheet of corrugated insulating material 190 of, for example, pressboard, between adjacent winding layers. The corrugations preferably run at 45 degrees to the axis of the coil and shallow saw cuts are made across the corrugations to provide a tortuous path for the cooling fluid. High voltage bushing assemblies, as 26, are provided at one end of the casing, communicating directly with fluid chamber 162. A number of low voltage bushings, as 30, are provided at the other end of the casing. The mechanism for a tap-changer may be provided in a housng (54, Fig. 1, not shown) disposed on one end of the casing. An expansion tank 50 is provided for the dielectric fluid which may be oil or a synthetic insulating fluid.