US2153090A - Electric transformer for high tension - Google Patents

Description

April 4, 1939.- A. LIBBE 2,153,090

ELECTRIC TRANSFORMER FOR HIGH TENSION Filed Jan. 20, 1958 Patented Apr. 4, 1939 ELECTRIC TRANSFGRMER FOR HIGH TENSION Alfred Libbe, Gentilly, France, assignor to Socit Anonyme Transformateurs de Mesure E. Walter, Gentilly, France, a corporation of France Application January 20, 1938, Serial No. 185,956 In Germany January 14, 1937 4 Claims. (01. 175356) The present invention relates to transformers and particularly pertains to the insulation of transformers having open magnetic circuits.

In Patent No. 2,107,9'7 3 issued February 8, 1 938 to Adolphe Bajon, there is disclosed an electric transformer for high tension, having high and low voltage windings which are mounted on an open iron core. In order to compensate for the wattless currents which are particularly unfavorable when the transformer is used for measurements, there are inserted, at different points on the high-tension winding, suitable capacities whose dielectric consists of insulating sleeves with conducting sheets located between the insulating sleeves affording a regular distribution of the drop of potential in the insulation. On the other hand, the windings can be so varranged as to greatly reduce the magnetic leakage, thus obviating the drawbacks attending the use of an open magnetic circuit for measuring transformers.

In the construction above mentioned, the insulation is open on the high-tension end, and in order to obtain a sufficient path to prevent fiashovers, the part of the insulating elements which projects from the end of the iron core must be transportation and the assembling. This result can be obtained by an arrangement accordin to the present invention in which the insulation is closed on the high tension end so that it surrounds the free end of the core. When the insulation consists of paper bands wound according to a cylinder and having conducting sheets between them, the layers of paper can be bent over, at the free ends, towards the interior, and the insulating elements can be closed on the upper side by insulating discs. It is preferable to mount conducting sheets between the discs, and such sheets should be electrically connected to the cyq lindrical conducting sheets.

The accompanying drawing shows by way of example a constructional form of a transformer according to the invention. The figure is a view in which the right-hand half represents, in elevation; the outer parts of the transformer, and the left-hand half is a vertical section showing the insulating elements and the windings. The magnetic iron core 2 is secured to an iron base I which serves to reduce the reluctance of the magnetic circuit. The base I is attached to the core by means of a spindle passing through the core, and by a. disc 3 which is urged against the upper end of the core 2 by means of a nut 4. The core 2 carries a low-tension winding 5 which is cylindrical and surrounds the core. The winding 5 rests upon an insulating disc 6, and the insulating covering 1 consisting of layers of paper 5 9 surrounding the insulating tube 8, also rests upon the disc 6.

These layers 9 are obtained by winding single bands of paper, with the interposition of metal sheets, as shown in the figure by the dotted lines. 10 The thickness of the insulating sheath increases from the bottom to the topand this increase corresponds to an increasing number of layers of paper, so that the surface portion provided with the high-tension winding ID, has a tapered form, which spreads out at the top. At their upper ends, the layers of paper are folded, one by one, towards the interior, and the edge of the first layer 9 which follows the insulating tube 8 is applied against the cover ll of this tube. A disc of paper I2 rests upon the folded end of the first layer 9 and this disc comprises a sheet metal piece which is shown in dotted lines electrically connected to the sheet metal piece which surrounds the layer of paper 9. The sheet metal is also connected with the end of the first fraction (counting from the bottom) of the high-tension winding Ill. The beginning of this fraction of the winding I0 is electrically connected to the core which is grounded and to the metallic layer with which the insulating cylinder 8 is covered.

Upon the first paper piece I2 is applied the edge of the next cylindrical layer 9, upon which is placed another paper piece i2 and the metallic sheets form, in all cases, closed conducting coverings, as shown in the drawing.

When the transformer is used in connection with relatively high voltages it is preferable to place the whole apparatus in an oil tank. Holes can then be formed in the discs l2 and I2 for the oil circulation. These holes preferably have a staggered arrangement, and may thus be loextending above the windings at the high tension end consisting of layers oi paper, metallic sheets between said layers for forming condenser coatings, said layers being bent towards the interior at the upper part of the insulating assembly, and insulating discs inserted between said bent parts for holding'them.

2. An electric transformer for high tension as claimed in claim 1, the insulating discs of which are provided with metallic sheets connected to the metallic sheets of the insulating covering.

3. An electric transformer for high tension as claimed in claim 1, the insulating discs 01' which ing of a plurality of cylindrical sleeves'formed of paper and metal sheets, and said assembly extending beyond the high tension end of the windings and formed in such a manner as to cover the end of the magnetic core.

ALFRED LIBBE.

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