EP0014418A1 - Coil for an air-cooled dry-type transformer - Google Patents

Abstract

1. A winding for an air-cooled transformer or reactor comprising at least two winding layers and having the following structure : the innermost winding layer (1) extends continuously across the full axial length of the winding ; the winding layers (2, 3 ...) joining said innermost winding layer in radial outward direction are formed of a pair of essentially equally long sections (10, 11) which are divided in a position equal to about one-half of the axial length, said section alternatingly electrically connected or coupled to the overlying and underlying winding layer or winding sections, respectively, in their axial end and central regions ; the winding layer (s) is (are) isolated from the other concentrically positioned winding layer (s) by hollow spaces froming cooling channels (18) ; bar-shaped spacers (6, 7) are disposed in said hollow spaces so as to extend in axial direction, characterized in that distributed with a spacing around the circumference in said cooling channels (18) and extending in the axial direction, a pair of axially aligned spacer element (6, 7) are each positioned in the region of the electrical connections between the winding layers of said winding sections (10, 11), with the length of each spacer element being about 0,1 to 0,3, preferably slightly more than 0,25, of the axial length ; and that a peripheral outwardly open air channel (20) is interposed between said winding sections in a position corresponding to about one-half of the axial length.

Description

The invention relates to a winding for an air-cooled dry transformer or a corresponding choke coil with at least two winding layers and cooling channels lying between the winding layers and spacing elements lying in the axial direction in the cooling channels.

It is known, in so-called dry-type transformers or similarly constructed choke coils with air cooling channels, to make the windings to form a winding in such a way that an innermost winding layer is first placed which is continuous over the entire length of the winding axis. Arrived at the axis end of the coil, after placing the spacer elements for the cooling channels, the next layer is placed in the opposite direction along the entire axis length. This process with alternating changes in direction is repeated over the number of layers present in the winding. This known method is shown schematically on the left side of FIG. 1. The winding layers denoted by the numbers 1, 2, 3, 4 are mutually connected and separated by cooling channels or spacing elements. The figure also shows that the voltage difference between the winding layers on the side facing away from the electrical connection can assume considerable values. The transformer manufacturer is aware that due to the mechanical and electrical stress, there is a sufficient safety distance between them insulating turns in adjacent turns must be observed. Furthermore, it can be observed that the originally high insulation values decrease with advancing age of the transformer, which can be caused in part by contamination, material fatigue or change or crack formation. In particular, the formation of leakage current paths can be observed.

When designing the construction, the transformer designer will keep in mind that very high-quality, high-purity insulating material that is used for the spacer elements is generally very aging-resistant. However, this material is often very expensive and is replaced by less material, which, however, has less high dielectric strength and aging resistance. On the other hand, the air that is present in the cooling channels must also be taken into account as an insulating material.

From this problem it follows that in the prior art according to the left side of FIG. 1, due to the relatively high voltage differences between winding layers lying one above the other, the insulation plays a significant role and the costs for this can make the transformer considerably more expensive.

It is therefore the task of creating a winding for an air-cooled transformer, in which the voltage differences between superimposed winding layers are generally lower in their maximum values, so that the expenditure for insulation measures is lower than for windings according to the prior art. It should still be possible to maintain the clear width of the cooling channels, not to complicate the construction of the coils.

• a) Die innerste Wicklungslage liegt auf der gesamten Wicklungsachsenlänge durchgehend;
• b) die nach außen folgenden Wicklungslagen bestehen aus zwei im wesentlichen gleich langen, auf halber Achsenlänge geteilten Abschnitten, die abwechselnd in Achsenend- bzw. Mittelbereich mit der darüber- und darunterliegenden Wicklungslagen elektrisch verbunden sind.

These tasks are solved with one winding for one air-cooled dry transformer, which has the following features:

• a) The innermost winding layer is continuous over the entire length of the winding axis;
• b) the winding layers following outwards consist of two sections of essentially the same length, divided on half the axis length, which are alternately electrically connected in the axis end or middle region to the winding layers above and below.

An upper and lower, essentially mirror-symmetrical partial winding is thus formed, each of which has an external connection; both partial windings are electrically connected to each other within the winding only via the innermost winding layer.

It should be noted that the individual current conductors preferably consist of a monofilament wire; however, it is also possible to wind several wires together at the same time if higher performance is desired.

As a view of the right-hand side of FIG. 1 shows, the use of the new winding advantageously results in smaller voltage differences at the most stressed points, in particular when layers lying one above the other are considered. These voltage differences can be adequately separated by air insulation. Spacers are then still required to determine the positions in order to increase the mechanical strength; However, these spacers do not need to be arranged over the entire length of the partial winding, since these are z. B. with cast resin have a higher rigidity.

DE-AS 1 270 167 is in cast resin cast winding for transformers known, in which each winding element consists of three concentric winding layers, in which the connections to and from the winding elements are located at the outer ends of the outer surface of the element, the winding in the outer and middle layer body each consisting of two concentric half-layers, which are connected in series with the continuous layer in the inner layer body in a meandering manner. However, the subject of the aforementioned DE-AS does not solve the task of systematically moving zones of higher voltage to air-cooled transformers where an air gap or duct prevents leakage current paths, since such a solution does not exist in a fully encapsulated transformer, even from the cited document can play a role.

• Figur 1 in schematischer Gegenüberstellung Wicklungen gemäß Stand der Technik und gemäß vorliegender Erfindung mit jeweils gleicher Anzahl von Lagern;
• Figur 2 eine Spule mit erfindungsgemäßer Wicklung im Querschnitt;
• Figur 3 den oberen Teil einer derartigen Spule im Längsschnitt.

To explain the invention, exemplary embodiments are described in detail with reference to the drawing. The figures show:

• Figure 1 in a schematic comparison of windings according to the prior art and according to the present invention, each with the same number of bearings;
• Figure 2 shows a coil with winding according to the invention in cross section;
• Figure 3 shows the upper part of such a coil in longitudinal section.

The introduction to the description had already dealt with the state of the art, as can be seen from the left column of FIG. 1. In the case of the coil arrangements according to the invention, as shown in the right column of FIG. 1, the core lies in the middle. The figures are to be seen as diagrams. It is possible that a further winding is arranged between the winding described and the core, for example as is usual with an arrangement of core - undervoltage winding - high voltage winding.

The innermost winding layer _{1, which} is closest to the core in the figure, is continuous over the entire length of the winding axis. This design is the same in all examples. The following winding layers 2, 3, ... are characterized by the fact that they consist of two sections 10, 11 of substantially the same length, divided on half the length of the axis, which alternate in the axis end or middle area with the one above and below Winding layer are electrically connected via connecting wires 12, 13. This results in an upper and a lower, essentially mirror-symmetrical partial winding (see reference numbers 10 ', 11'). Each of the partial windings has an external connection 14 or 15. Inside the winding, the two partial windings 10 ', 11' are only electrically connected to one another via the innermost winding layer.

Spacer elements 6, 7 are located between the individual winding layers, which mechanically span the cooling channels and must also withstand the dielectric load.

If one proceeds from the schematic view and looks at the specific configuration, as can be seen from FIGS. 2 and 3, the structure of the winding can be seen more clearly in the details. The winding arrangement consists of an inner jacket 21 with the first winding layer 1 lying thereon, which consists of wires lying next to one another, preferably of insulated copper or aluminum wire. A glass fiber jacket 23 is applied to the first winding layer in the wet winding process. These are glass fibers impregnated with epoxy resin, which after curing result in a mechanically very strong cylinder. After the first layer has hardened, Ab Stand elements 6 distributed over the circumference and another cladding layer 25 made of impregnated, non-conductive glass fibers applied. The spacer elements are defined. The next winding layer 27 is then wound up. This is followed by another intermediate layer made of non-conductive, hardening material. The further stratification then follows this scheme. The end forms a jacket 32 made of glass fiber reinforced plastic.

The special feature of the winding can be seen in FIG. 3. The inner layer 1 consists of wire wound close to one another, the layer extending continuously over the entire length of the axis. After the first glass fiber jacket 23 has been introduced, spacer elements 6 are introduced, the length of which is preferably somewhat more than a quarter of the axial length of the winding arrangement. The inserted spacing elements lying one above the other overlap somewhat. Shorter spacer elements can also be used. The subsequent winding layer 2 consists of two sections 10, 11 of essentially the same length, divided over half the length of the axis, which are electrically connected to one another in the axial end region with the winding layer 1 underneath via the connection 12, 13. The sections 10 and 11 are then wound up to about the middle, where they approach each other mirror-symmetrically, but leave an air gap 20 approximately in the central region of the winding layer arrangement. There they are electrically connected to the winding layer above them via the wires 29, 30. Then the two sections belonging to the third winding layer are wound. These end in a connection 14 in the lower section of the winding. A plurality of taps are provided in the upper section, so that in addition to the outermost connection 15 there are further tapping points 15 'which, as is known per se from transformer technology, enable tapping for voltage equalization. As can be seen, in the winding arrangement shown, the air gap 20 is guided to the outside; the outer jacket is therefore not closed. This arrangement further improves insulation and cooling and prevents leakage current paths.

It follows from the description that the spacing elements 6 and 7 do not occupy the entire axis length, but only about a quarter of the axis length on each side. The length of the spacer elements is determined by the mechanical layer tension; it is in the range 1/5 ... 3/5 of half the section length.

At the locations of larger voltage differences, the air gap ensures that the winding layers lying one above the other are cleanly electrically separated from one another, that is to say they have no leakage current paths. Furthermore, the air gap 20 in the middle enables the electrical isolation between the two winding sections 10 ', 11'. The present arrangement makes it possible to make do with less and lower quality insulation material, the clear width of the cooling channels being able to be designed optimally and thereby improving the cooling performance without having to accept significant disadvantages.

Claims (4)

1. winding for an air-cooled dry transformer or a choke coil with at least two winding layers and cooling channels lying between the winding layers and spacing elements lying in the axial direction in the cooling channels,
characterized by the following features: a) The innermost winding layer (1) is continuous over the entire length of the winding axis; b) the winding layers (2, 3, ...) following to the outside consist of two sections (10, 11) of essentially the same length, divided on approximately half the length of the axis, which alternate in the axis end or middle area with the one above and below Winding layer are electrically connected. 2. Winding according to claim 1, characterized by spacing elements (6, 7) lying between the winding layers (1, 2, 3, ...), which occupy only part of the height of the winding layer. 3. Winding according to claim 2, characterized by the arrangement of the spacer elements (5, 6) in the region of the electrical connections between the winding layers of the partial windings (10 ', 11'). 4. Winding according to claim 1, characterized by a circular, approximately half-axis length peripheral air duct (20) between the winding sections (10, 11).

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