GB728319A - Improvements in or relating to electrical apparatus and the method of cooling same - Google Patents

Abstract

728,319. Cooling transformers and dynamoelectric machines. METAL CARBIDES CORPORATION. Jan. 28, 1953, No: 2428/53. Classes 35 and 38 (2). [Also in Group XIII] The cooling of electrical apparatus such as a transformer generator, motor, rectifier or condenser immersed in a liquid such as oil, includes subjecting part of the fluid to a high unidirectional potential, whereby the electrostatic field produced therein produces relatively rapid currents in the liquid. Thus, if high potential is applied from sources 3 between the earthed casing 6 of transformer 5, and the high voltage windings 2, oil currents pass from this winding to the casing and back again, thus transferring the heat more rapidly than the normal thermal convection currents. In modifications, the voltage may be applied between an electrode immersed in the oil, and the casing and/or high voltage winding, Figs. 2, 3 (not shown), or between a cooling coil 10 in the oil, and the high voltage winding 2, Fig. 4, and, if desired, an electrode, Fig. 5 (not shown). Where, as shown in Fig. 7, the oil is circulated by pump 16 through an external heat exchanger, the potential may be applied not only in the transformer, e.g. between casing 6 and electrode 8, but also in the heat exchanger between an electrode 20 and the walls 14, 17 which contain respectively the oil and the cooling fluid such as water. Connection of the potential between the casing and high voltage winding of one transformer may be effective in all transformers connected to the system, Fig. 8 (not shown). Fig. 9 shows a shell type transformer with a high voltage winding composed of two layers of bare flat strip 22 wound with insulation 23 between the turns, and a low tension winding of tubing 4 through which cooling fluid is passed. The potential is set up between the winding 4 and casing 6 and the winding 22, the bare edges of which enhance the cooling. Electrodes may be placed in various parts of the transformer, including in the oil ducts, and any part of the transformer which acts as electrode, which may include the core, may bear points or sharp edges. The spacing between the electrodes should be small, compatible with insulation needs.