US3656077A

US3656077A - Distribution of equipotential surfaces of inductance windings comprising layers with a double series of steps

Info

Publication number: US3656077A
Application number: US70166A
Authority: US
Inventors: Georges Laser; Daniel Bornet
Original assignee: Alstom Savoisienne SA
Current assignee: Alstom Savoisienne SA
Priority date: 1969-09-08
Filing date: 1970-09-08
Publication date: 1972-04-11
Anticipated expiration: 1989-04-11
Also published as: FR2060182A7; FR2060182B3; DE2043545A1; BE755587A; NL7013107A; CA923996A

Abstract

A simply-built device for distributing the potential around a high-voltage output conductor and at the ends of the layers of windings of an inductor coil or of a transformer consisting of windings in layers arranged in a double step configuration on either side of a middle layer which is the shortest and to which is connected the high-voltage output. It consists of cages formed by conductors, each connected to an end of a winding layer by flat conductor grids placed above the layers of winding, and each connected to the end of the layer of wire.

Description

,[151 3,656,077 [451 Apr-.11, 1972 United States Patent Laser et a1. 1

3,353,129 11/1967 Leibinger.................... 3,376,531 4/1968 Fisheretal. 1,039,298 9/1912 Kurda.......... 1,942,575 1/1934 Shapiro............

[54] DISTRIBUTION OF EQUIPOTENTIAL SURFACES OF INDUCTANCE WINDINGS COMPRISING LAYERS WITH A DOUBLE SERIES OF STEPS [72] Inventors: Georges Laser, Garches; Daniel Bornet,

FOREIGN PATENTS OR APPLICATIONS Paris, both ofFrance 451,319 5/1968 Switzerland Alsthom-Savoisienne Sept. 8, 1970 Prim ary Examiner-Thomas J. Kozma [73] Assignee: [22] Filed:

AttorneySughrue, Rothwell, Mion, Zinn & Ma'cpeak ABSTRACT [21] App1.No.: 70,166

distributing the potential around a ge output conductor and at th ds of A simply-built device for [30] Foreign Application Priority'Data hi gh-yolta I e en the layers of Sept. 8, 1969 ....6930723 a ansfm'er 1 e ortest and to which U.S. i connected th hi h lt t t It i t f cages Int. Cl..........................................................I'I0lf rs each connected to an ofa [58] Field ofSw-ch .....................336/84, 69, 70; 174/35 CE tor grids placed above the layers 0fwind-' ing, and each connected to the end of the layer of wire.

7 Claims, 4 Drawing Figures [56] References Cited UNITED STATES PATENTS 3,013,102 12/1961 D011 PATENTEUAPR 11 I972 3,656,077

SHEET 3 OF 3 FIGS I kind in which the electrical field of DISTRIBUTION OF EQUIPOTENTIAL SURFACES OF INDUCTANCE WINDINGS COMPRISING LAYERS WITH A DOUBLE SERIES OF STEPS BACKGROUND OF THE INVENTION device intended to distribute correctly the equipotential electric field surfaces around a high-voltage output and at the ends of winding layers which are series-connected, two by two, and which are arranged in two sequences of steps on either side of the middle layer, the less high one, which is at the highest potential and from which defines the high-voltage output.

2. Description of the Prior Art The maximum electrical stresses are, as a matter of fact, located at the ends of the layers. Different devices have been visualized to reduce these localized stresses by distributing the potential gradient in such a way as to make the electrical field uniform. French Pat. No. 1,492,630 describes a device of this the output conductor is directed around this conductor by means of leaf-shaped screens (paper or metal conductor), arranged concentrically around this conductor, each connected electrically to one end of the winding layer and embedded in molded parts made of pressed cardboard or other insulating materials, This method is very delicate to carry out, especially as regards the metallic coating, due to the very high electrical gradients which are generated on the leaf-shaped screen section.

SUMMARY OF THE INVENTION This invention pertains to a new device intended to distribute correctly the equipotential surfaces. It does away with inconvenience and considerably facilitates production while offering excellent potential distribution. This device is for the distribution of the equipotential surfaces of the electrical field around a high-voltage output conductor and at the ends of the winding layers of an electrical induction apparatus, such as an inductance or a transformer, made up of windings consisting of layers connected in series, two by two, and distributed symmetrically and forming two sequences of steps on either side of a thin middle layer, which is the shorter one and which bears the high-voltage output. It involves screens made of conducting material installed concentrically around the output conductor and each electrically connected to a nearby end of a winding layer. It is characterized by the fact that these screens are made up of cages formed by bars made of conducting material and by the fact that other bars, made of conducting material, define flat grids. of concentric elements. Each grid is placed at the end of the assembly of two seriesconnected winding layers and are electrically connected to the neighboring end of these two winding layers. It is particularly advantageous to select bars made of conducting material having a round cross section so as to reduce the possible electrical gradients as much as possible.

These bars are preferably coated with an electrical insulation. They can, in advance, be insulated by machine as this helps avoid the coast in insulating the electrostatic screens with sheets from the prior state of the art. I

These cages are simple to make because they are first shaped flat and then bent only at the end so as to give them their final cylindrical form.

The effectiveness of the protection offered by the potential distribution device is further increased if tubes made of insulating material are inserted between the .cages.

BRIEF DESCRIPTION OF THE DRAWINGS Referring now to the attached schematic figures, we will describe examples for the implementation of the invention, given here without any restrictions.

FIG. 1 is a perspective view of a very high voltage transformer with a partial cross section showing a winding made up of layers distributed along two sequences .of steps, equipped with the potential distribution device of the present invention;

FIG. 2 is a partial cross section of this, on a larger scale, along a plane passing through the axis of the winding and through the high-voltage output conductor;

FIG. 3 is a plan view of a flat formed cage; and

FIG. 4 is'a perspective view of the cage of FIG. 3 after bending, in its final form.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to FIGS. 1 and 2, a winding made up of a middle layer 1 has on either side of, successively, pairs of layers which are symmetrical to each other, with a growing length at 2 and 3, 4 and 5. The layers of one

pair

2 and 3 or 4 and 5 are electrically connected in series, in the known manner by means (not shown). These various winding layers are formed by the spirals of a conducting material, such as 6, surrounded by an insulating coating 7. An output conductor 8 is connected to one end of the middle layer 1 which is the layer with the highest voltage.

The output conductor 8 is surrounded by two

cages

9 and 10. The first one made up of bars 11 and of short-circuit rings 12. The second one is made up of bars 13 and rings 14. These cages are made on the basis of round conductors which have previously been insulated, for example, by means of paper, which have been connected by welding, and which have been reinsulated at the places where the attachment has destroyed the insulation. The assembly is made flat and the developed cage thus obtained is bent to give it its final form.

Cage 9 is then connected to the voltage of

layers

2 and 3 by a connection 15, and cage 10 is connected to the voltage of layers 4 and 5 by a connection 16. These connections may be accomplished-by means of devices (not shown) which seriesconnect, respectively,

layers

2 and 3 and 4' and 5. The potentials of the cages thus decrease gradually in a direction away from the output conductor 8.

Between the different cages, such as 9 and 10, and between the output conductor 8 and the first cage 9, are placed insulating tubes 17 to increase the effectiveness of protection. These tubes are made of composition board, agglomerated cardboard or any other insulating substance, and are not shown in FIG. 1 so as not to overload FIG. 1. To direct the equipotential surfaces, metallic armature grids l8 and 19, visible in FIG. 1, are placed, respectively, at the ends of

layers

2 and 3, on one hand, and 4 and 5 on the other hand, in a series-connected fashion. These grids have a shape recalling the shape of resistances in electrical kitchen ranges. They are made up of a round conductor, insulated by paper or some other insulating material, and they are connected, for example, by welding, to the corresponding cages, that is grid 18 is connected to cage 9 and grid 19 is connected to cage 10. These grids are the devices that assure the series-connection of the layers. Grid 19 has spirals situated in the free space between the ends of layers 4 and 5.

In FIGS. 1 and 2, there are shown only two cages and two grids, but these can obviously be more numerous if the number of layers in the winding is greater. In FIG, I a supple mentary interior layer 20 has been shown, to which would correspond, another outside layer (not shown), series-connected with the former, and there would also be here another cage and another grid, connected to the neutral if this were to involve the last layers of the winding.

FIGS. 3 and 4 show another way of making the cages very easily. FIG. 3 shows the developed surface of such a cage in the fonn of a serpentine, made up of a conductor 21, insulated, for example, by means of paper taping. This developed surface is then bent and applied on an insulating cylinder 22,

' FIG. 4, which at the-same time plays the role of support for the conductor 21, forming the cage, and for the insulating tube 17, shown in FIG. 2.

What is claimed is:

short-circuit I windings on either side of a shorter middle winding layer bearing the high-voltage output conductor, the improvement comprising:

spaced concentric screens of conducting material surrounding the output conductor, means connecting each screen to an end of a respective winding layer, each of said screens comprising bars of conducting material, and short-circuit rings connecting said bars I concentric conductive gridsoverlying the ends of each winding layer and series-connected in the same manner as said inductance windingsand being electrically connected to corresponding ends of respective series-connected winding layers. 2. The device according to claim 1 wherein said bars of conducting material have a round cross section.

3. The device according to claim 1 wherein said bars of conducting material are coated with insulation.

4. The device according to claim 3 further comprising: insulating tubes inserted between said cages and between the output conductor and the innermost cage. 5. The device according to claim 1, where the screens are of a serpentine configuration formed from a single conducting bar, and wherein the device further includes an insulating cylinder for supporting each screen.

6. The device according to claim 1, where the spaced concentric screens further include short circuit rings connecting the bars at a distance from the ends of each winding layer.

7. The device according to claim 6 further including a conductive grid cantilevered from the outermost screen and extending without touching between the spaced ends of the innermost and outennost windings.

Claims

1. In an inductance device formed of two by two layers of series-connected and symmetrically distributed stepped windings on either side of a shorter middle winding layer bearing the high-voltage output conductor, the improvement comprising: spaced concentric screens of conducting material surrounding the output conductor, means connecting each screen to an end of a respective winding layer, each of said screens comprising bars of conducting material, and short-circuit rings connecting said bars concentric conductive grids overlying the ends of each winding layer and series-connected in the same manner as said inductance windings and being electrically connected to corresponding ends of respective series-connected winding layers.

2. The device according to claim 1 wherein said bars of conducting material have a round cross section.

4. The device according to claim 3 further comprising: insulating tubes inserted between said cages and between the output conductor and the innermost cage.

5. The device according to claim 1, where the screens are of a serpentine configuration formed from a single conducting bar, and wherein the device further includes an insulating cylinder for supporting each screen.

7. The device according to claim 6 further including a conductive grid cantilevered from the outermost screen and extending without touching between the spaced ends of the innermost and outermost windings.