GB952905A - - Google Patents

Abstract

952,905. Capacitors. SIEMENS & HALSKE A.G. April 21, 1961 [April 22, 1960], No. 14534/61. Heading H1M. In a self - healing capacitor one of the metal coating electrodes is interposed between a dielectric and a healing layer and electrically connected to a second metal coating on the remote side of the healing layer. The healing layer is made of substances having an " oxidation balance " of at least 10%, e.g. paper, acetyl cellulose, ethyl cellulose, polytetrafluoroethy - lene, polyethyleneterephthalate or a mixture thereof, while the dielectric has an " oxidation balance" of less than 10% and may consist of polystyrene, polyethylene, polycarbonate, polyvinylcarbazole or a mixture thereof. The metal coatings are preferably not more than 0.1 micron thick and formed of aluminium or zinc by vapour deposition. A tape 1, Fig. 1, of healing material is metallized on both sides, the metal coatings 2, 3 being bridged at 4. Such a tape may be wound with two dielectric tapes with the second electrode therebetween to form a capacitor. Alternatively, a composite dielectric-healing tape may be made by coating a dielectric, e.g. a varnish tape 5, Fig. 2, successively with the metal layer 2, the healing layer 1 and the metal layer 3. When the dielectric 5 is formed of, e.g., stretched polystyrene, such a composite tape may be shrunk by heat treatment to increase electrical stability. Two such composite tapes may be wound in offset relationship, Fig. 7. A further dielectric varnish layer may be applied to the metal coating 3, Fig. 2, and a non-varnish dielectric layer may be used between the two composite tapes.