EP0014418B1 - 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

• - Die innerste Wicklungslage liegt auf der gesamten Wicklungsachsenlänge durchgehend,
• - die nach außen folgenden Wicklungslagen bestehen aus zwei im wesentlichen gleich langen, auf etwa halber Achsenlänge geteilten Abschnitten, die abwechselnd im Achsenend- bzw. Mittelbereich mit der darüber-und darunterliegenden Wicklungslage bzw. Wicklungsabschnitten elektrisch verbunden sind,
• - die Wicklungslage(n) sind von den oder der anderen konzentrisch liegenden Wicklungslage(n) durch Hohlräume, die Kühlkanäle bilden, getrennt,
• - in den Hohlräumen liegen in Achsenrichtung stabförmige Abstandselemente.

The invention relates to a winding for an air-cooled dry transformer or a choke coil with at least two winding layers and the following structure:

• - The innermost winding layer is continuous over the entire length of the winding axis,
• the winding layers following outwards consist of two sections of essentially the same length, divided on approximately half the length of the axis, which are alternately electrically connected in the axis end or middle region to the winding layer or winding sections above and below,
• the winding layer (s) are separated from the other concentrically lying winding layer (s) by cavities which form cooling channels,
• - In the cavities are rod-shaped spacer elements in the axial direction.

It is known. In the case of so-called dry transformers or similarly constructed choke coils with air cooling channels, the windings are built up to form a winding in such a way that an innermost winding layer is first laid on 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 electrical stress, a sufficient safety distance must be maintained between the windings to be insulated from one another in adjacent winding layers. 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 preferably 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 considered as an insulating material.

It is known for the type of winding mentioned at the outset (US Pat. No. 2,987,684) to lay the innermost in the winding layers continuously over the entire length of the winding axis and to lay the outermost ones in two sections of essentially the same length, divided by approximately half the length of the axis, which alternate are electrically connected in the axis end or middle region to the winding layer or winding sections lying above and below it (cf. FIG. 3 of the US patent mentioned). Since according to the task of US Pat. No. 2,987,684, only the distance between the high and low voltage windings is to be reduced as much as possible, essentially nothing is changed in the spacer elements within the high voltage windings; rather, they are arranged in the form of bars over the entire length of the winding layer.

In contrast, the present application has the task of obtaining aging-resistant insulation, especially in the area of high voltage differences, preferably within high-voltage windings. In the area of the edges of the spacer elements, dust deposits and similar sources of contamination under the influence of moisture lead to leakage current paths. In addition, the amount of material for the spacers should be kept as low as possible. It should still be possible to maintain the clear width of the cooling channels within the winding and not to complicate the construction of the coils.

This object is achieved in a winding for an air-cooled dry transformer or a choke coil of the type mentioned in that two axially successive spacing elements are arranged in the area of the electrical connections between the winding layers of the winding sections, distributed over the circumference in the cooling channels in the axial direction, the The length of the spacer elements is approximately 0.1 to 0.3, preferably somewhat longer than 0.25, the axis length, and that a peripheral air duct is embedded on the half-axis length between the winding sections.

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.

Like looking at the right side of the Fig. 1 shows, there are smaller voltage differences at the most electrically stressed points, especially 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 due to the usual consolidation of the winding layers, for. B. with cast resin, have a higher rigidity. In addition, there is advantageously a peripheral air duct which ensures reliable electrical isolation of the winding layers lying next to one another and at the same time increases the cooling capacity.

A layer winding is known from DE-AS 1242748, in which support strips are used which are shortened in relation to the layer length. However, these support strips are used in connection with windings which give channels for a forced flow in which the winding layers do not correspond to those in the configuration of the application.

Finally, it is known from DE-AS 1 039 637 to use a solid insulation that is shorter than the layer length. In the latter, known layer winding, a coolant flows around the layers. Fixed insulation is provided between the individual layers only on the side of adjacent layer ends which are not electrically connected, while on the side of adjacent layer ends which are connected to one another there are spaces between the layers through which the coolant, which also serves as insulation, can flow. This arrangement therefore serves to create flow channels. Therefore, no rod-shaped spacer elements are provided. The winding arrangement is also different from the subject of the application, to which it can therefore not be transferred.

• Fig. 1 in schematischer Gegenüberstellung Wicklungen gemäß Stand der Technik und gemäß vorliegender Erfindung mit jeweils gleicher Anzahl von Lagen,
• Fig. 2 eine Spule mit erfindungsgemäßer Wicklung im Querschnitt,
• Fig. 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

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

In the introduction to the description, the state of the art, as can be seen from the left column of FIG. 1, was already discussed. In 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. B. as is usual with an arrangement core - low voltage 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 and 15, respectively. Within the winding, the two partial windings 10 ', 11' are only electrically connected to one another via the innermost layer of turns.

Spacer elements 6, 7 are located between the individual winding layers 1, 2, 3, ..., which mechanically span cooling channels 18 between the winding layers and must also withstand the dielectric load.

If one proceeds from the schematic view and considers 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, spacer elements 6 are distributed over the circumference and a further cladding layer 25 made of impregnated, non-conductive glass fibers is applied. The spacer elements 6 are defined. A cooling channel 18 between the winding layers is also created. 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 that Axis length of the winding arrangement is. The inserted spacer elements overlap somewhat. Shorter spacer elements can also be used.

The subsequent winding layer 2 consists of two sections 10, 11 of substantially the same length, divided over half the length of the axis, which are electrically connected to one another in the axis end region with the winding layer 1 underneath via the connecting wires 12, 13. The sections 10 and 11 are then wound up to about the middle, whereby 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. The two sections belonging to the third winding layer are then wound. These end in the lower section of the winding in an external connection 14. In the upper section, a plurality of taps are provided, 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 to compensate for voltage. 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.

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 forces on the winding layers; in the range _^1/5 ... _3/5 of the length half portion.

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'.

With the present arrangement, it is possible to make do with less and lower quality insulation material, the clear width of the cooling channels can be optimally designed and thereby improve the cooling performance without having to accept significant disadvantages.

Claims (1)

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 being 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 concentrially positioned winding layer(s) by hollow spaces forming 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 fo axially aligned spacer elements (6, 7) are each positioned in the region of the electrical connections between the winding layers of said winding sections (10, 11), with the langth 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 air channel (20) is interposed between said winding sections in a position corresponding to about one-half of the axial length.

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