EP0782755B1 - Power supply conductor from the conductive foil of the foil winding of a power transformer - Google Patents

Abstract

PCT No. PCT/DE95/01230 Sec. 371 Date Mar. 20, 1997 Sec. 102(e) Date Mar. 20, 1997 PCT Filed Sep. 8, 1995 PCT Pub. No. WO96/09631 PCT Pub. Date Mar. 28, 1996The power supply conductor of a power transformer with foil winding is formed with a plurality of flag-shaped end pieces at one end due to slots running in the longitudinal direction of the foil, which flag-shaped end pieces are folded to form a stack kinked in relation to the longitudinal direction of the foil. The flag-shaped, folded end pieces of the conductor stack must be insulated at least in the area of the edge of the unslotted foil from one another, for example, using insulating foils.

Description

The invention relates to a laminated power supply conductor a power transformer with one out of one band-shaped conductor foil wound, air-cooled foil winding, whose film end due to in the longitudinal direction Foil-running slots several flag-like end pieces forms which is opposite to the film longitudinal direction folded stack of the power supply conductor folded are. Such a power supply conductor is off "Electrical Equipment", Jul./Aug. 1974, pages 60 to 62.

For high-capacity, air-cooled power transformers with so-called undervoltage windings from band-shaped Conductor foils can easily become overheated Power supply lines come with in a connection area the conductor foil of the winding are connected. With a known Embodiment of such a power transformer a line rail is provided as a power supply which is on the side the conductor foil of the undervoltage winding is welded on. This results in a current redirection in the film freely according to the induced voltages and resistance conditions a. This leads to an exponential Fall in the current in the power supply line when you are in Direction of power supply from the rail to the film, and from the first connection point (corner) of the film the rail looks to the opposite corner of the slide. As a result, very high current densities occur in the first corner of the film on that too strong local thermal loads to lead. Due to the exponential drop in electricity in the Power supply rail carries the more distant half of the Rail no longer holds useful electricity; i.e. for electricity transport it no longer makes any significant contribution in the film. Be in the more distant part of the power supply rail only induces eddy currents that generate additional losses. Particularly high eddy currents are found in the supply rails induced at the winding edges by the foil winding. Here the foil winding shows greatly increased current densities through the current displacement effect. This increased Flooding of the foil winding induces eddy currents in the Cross-sectional level of the supply rails and thus additional Losses. If the high-load transformers Sum of the losses in the area of the supply lines becomes too large, so it tries to solve this problem by changing the senior Cross section or by changes in electrical Conductivity due to the use of other material or solve by improving cooling. Even combined Measures are used for this.

From the above mentioned reference from "Electrical Equipment "is for power transformers with foil windings known that the film end in a connection area due to running in the longitudinal direction of the conductor foil Slots divided into several flag-like end pieces, which is bent or folded by a right angle be that the flag-like end pieces a stack form a laminated power supply conductor. Further concrete configurations of such a laminated power supply conductor are not entitled to the cited reference remove. It can be assumed that even in such a laminated power supply conductor considerable eddy current losses occur.

The object of the present invention is therefore the known Power supply conductor with the aforementioned Features to improve in that the eddy current losses are further diminished in its laminated stack.

This object is achieved in that the flag-like, folded end pieces of the conductor stack at least in the area of the winding edge of the unslit Foil part are mutually isolated.

With this measure, eddy currents in the Cross-sectional plane of the power supply conductor largely suppressed will. It was recognized that precisely in the Edge area of the unslit film part the risk of Eddy current formation is particularly high. The flag-like End pieces only need a few centimeters from the line the extended long side of the unslit film part to be conducted in isolation from one another; continue outside (outside the area of the film winding) one can do without isolation of the flag-like end pieces and continue this without insulation or in a massive supply rail let pass

Advantageous embodiments of the power supply conductor according to the invention emerge from the subclaims.

Figuren 1 bis 5

den sukzessiven Aufbau eines erfindungsgemäßen Stromzuführungsleiters für einen Leistungstransformator

und

Figur 6

eine weitere spezielle Ausführungsform eines solchen Stromzuführungsleiters.

Figur 7

zeigt als Diagramm den Stromabfall an einem entsprechenden Stromzuführungsleiter.

To further explain the invention, reference is made below to the drawing. Each shows schematically as supervision of them

Figures 1 to 5

the successive construction of a power supply conductor according to the invention for a power transformer

and

Figure 6

another special embodiment of such a power supply conductor.

Figure 7

shows a diagram of the current drop on a corresponding power supply conductor.

For an effective reduction in power loss in one Power supply conductor and a connection foil assigned to it the foil winding of a power transformer is one Laminating the cross section of the power supply conductor and its shortening to an electrically effective length is provided. Controlled current introduction also reduces the maximum current densities occurring in the connection foil the wrapping film; and thus the losses in the connection area the film is also reduced.

When building an appropriate power supply conductor from the "Electrical Equipment 'suggested measure assumed from the end a band-shaped conductor foil of a foil winding a number to work out of flag-like end pieces, which then by successively folding a stack of the power supply conductor with the required electrical cross-sectional area result (see Figures 1 to 5). The ones described below Steps show the construction of such a power supply conductor.

Figure 1 shows the end of a known band-shaped Conductor foil 2 with a width B. This conductor foil provides is the connection foil of a foil winding and goes into several, for example four, flag-like end pieces 3i (with i = a, b, c or d) above, which are expediently mutual are separated by narrow slits 4j. According to the accepted Embodiment have the flag-like end pieces 3i all about the same width b. If necessary, however, they can also have different widths. The width b of the End pieces 3i is preferably chosen so that the front Edge zones 2a and 2b of the connecting foil 2 remain free. In addition, the flag-like end pieces 3i can advantageously symmetrical with respect to the extended center line 5 of the connecting film 2 be arranged. The length Li of each End pieces 3i can be chosen so that after a Folding the front ends 6i of the end pieces 3i approximately a common face of a stack of the power supply conductor form.

In Figure 1, the shortest end piece 3a is the first to be folded should be seen, and that in the direction of current conduction first, the transition of current from the power supply conductor on the connection film 2 allows. According to the Representation of the figure it is to be regarded as the "top" end piece.

This uppermost end piece 3a is moved upwards according to FIG Angled by 90 ° and forming a folding area lla folded. This end piece, now designated 3a ' According to the invention on its upper flat side F, on the the next flag-like end piece (3b) will come to rest later should, at least in part, be isolated. (The folded End pieces are additionally marked with '' "below). According to FIG. 3, this flat side F can be used accordingly an insulation film 7a are covered. The insulation film can, as assumed in Figure 3, a slightly larger Width b 'as the associated flag-like end piece 3a' exhibit; the widths b 'and b of insulation film 7a and End piece 3a 'can also be the same. The insulation film 7a should at least one area 12 around the elongated lateral edge 21 of the connecting foil 2 (or by its extended cover the longitudinal edge). They are advantageous both side edges of area 12 a few centimeters from that extended edge 21 removed. It also extends advantageously the insulation film 7 up to the folding area lla of the end piece 3a (inclusive) and preferably above also covered under the folding area llb of the next end piece (3b). If necessary, the bottom of the end piece 3a 'at least in its folding area lla be provided with an insulation film.

According to FIG. 4, the second flag-like end piece 3b folded up accordingly so that the two end pieces 3a 'and 3b' together with the insulation film between them 7a, for example, overlapping one another come to lie. Then again an insulation according to the figure 3 made.

The folding of the flag-like end pieces 3i in the respective Folding area (lla to lld) and their mutual isolation continues until all end pieces are stacked together 5 one opposite the film longitudinal direction kinked stack 10 of a laminated power supply conductor 8 form. Between the individual flag-like End pieces 3i 'are located at least in the edge area 12, advantageously also down to the respective folding areas (lla to lld) each have an insulation film (7a to 7c) so that the end pieces are electrically insulated from one another are. This allows eddy currents in the cross-sectional plane of the power supply conductor 8 effectively suppress.

The flag-like end pieces 3i only need to be a few centimeters isolated outside the edge region 12 of the film winding be led from each other; after that you can go to isolation dispense between the end pieces and these without insulation continue or in a massive supply rail let pass

The distribution of the total conductor current among the individual flag-like end pieces is influenced by the different Length and thus by the electrical resistance of the respective end pieces as well as by the different axial connection positions of the end pieces on the connection film. These connection positions lay the different Flow chaining of the film over the winding height and thus the induced voltage fixed. In the axial center of the slide is the river chain higher than at the top and bottom of the Foil.

The natural uneven distribution of the total conductor current can on the individual flag-like end pieces 3i ' one advantageous in by small displacements of the end pieces Circumferential direction, i.e. in the elongated longitudinal direction of the Connection foil 2, affect each other by the induced voltage changes accordingly. In Figure 6 is one such displacement v of the flag-like end pieces 3d 'and 3c 'in a representation corresponding to FIGS. 1 to 5 illustrated. The mutual displacement of the end pieces in the longitudinal direction of the film 2 is generally in the mm range and depends on the respective winding voltage of the film transformer from. Generally the side is Displacement at most a few mm. Then it can be advantageous an equalization of the current distribution between the reach individual flag-like end pieces. Appropriate Shifts can of course also for the rest flag-like end pieces may be provided.

With a power supply line explained using the preceding figures can with a power transformer a controlled drop in power in the supply line and thus at the same time a correspondingly uniform introduction of current into a Reach the connection foil of an undervoltage winding. Figure 7 shows such a drop in current in a diagram. Are there in the ordinate direction, the current I in the current supply conductor at the end of the film and in the direction of the abscissa Length x at this end in arbitrary units applied. The respective extent a (3i ') of the individual flag-like end pieces 3i 'is by the corresponding The reference number of the respective end piece is marked the extension a (2) of the area of the connecting foil 2 Undervoltage winding entered accordingly. From the The course of the curve can be controlled, proportionately uniform current drop at the end of the power supply line detect. This increases current density increases in the connecting foil and consequently additional losses avoided.

According to the illustrated embodiments, assumed that the mutual isolation of each folded End pieces 3i 'is effected by means of insulation foils. Of course, other insulation technology are also Suitable measures. So you can e.g. the individual end pieces before or after folding them with insulating layers.

Furthermore, a symmetrical arrangement of the flag-like End pieces 3i assumed with respect to the imaginary film center line 5 (see Figure 1). However, it is also asymmetrical Arrangement possible. This leads to the advantage of shorter conductor lengths and thus smaller losses with more uneven ones Power distribution. Possible problems of a more uneven Current distribution can, however, be illustrated by that in FIG lateral displacements of the end pieces reduced will.

There are also uneven widths of the individual flag-like end pieces 3i possible in principle and can be advantageous with the lateral displacement measures mentioned can be combined. A lateral shift can, for example, by a subsequent material removal on the left and / or right-hand longitudinal edges of the end pieces.

The measures according to the invention relate essentially on the design of a power supply line of a power transformer with foil winding. Corresponding power transformers are known in principle, so that in the Drawings, the explicit representation of which has been omitted.

Claims (10)

1. A laminated power supply conductor (2) of a power transformer with an air-cooled foil winding which is wound from a strip-like conductive foil and whose foil end forms a plurality of flag-like end pieces (3a, 3b, 3c, 3d) by virtue of slots extending in the longitudinal direction of the foil, which end pieces are folded to form a stack of the power supply conductor bent at an angle relative to the longitudinal direction of the foil, characterised in that the flag-like, folded end pieces (3i') of the conductor stack (10) are insulated from one another at least in the region (12) of the edge (21) of the unslotted foil portion (2).
2. A power supply conductor according to Claim 1, characterised in that insulating foils (7) are provided for the mutual insulation of the flag-like, folded end pieces (3i').
3. A power supply conductor according to Claim 1 or 2, characterised in that prior to their folding the flag-like end pieces (3i) are arranged symmetrically in relation to a centre line (5) of the conductive foil (2).
4. A power supply conductor according to one of Claims 1 to 3, characterised in that the flag-like end pieces (3i or 3i') are equal in width (b).
5. A power supply conductor according to one of Claims 1 to 4, characterised in that prior to being folded the flag-like end pieces (3i) increase in length (Li) from end piece to end piece so that having been folded they approximately form a common front face of the power supply conductor (8).
6. A power supply conductor according to one of Claims 1 to 5, characterised in that the flag-like end pieces (3i') are folded in such manner that they are arranged in the stack (10) at least approximately in coincidence.
7. A power supply conductor according to one of Claims 1 to 5, characterised in that at least some of the flag-like end pieces (3c', 3d') are folded in such manner that they are arranged in the stack of the power supply conductor with a slight mutual lateral displacement (see Figure 6).
8. A power supply conductor according to Claim 7, characterised in that the lateral displacement (v) amounts to a maximum of a few millimetres.
9. A foil winding with a power supply conductor according to one of Claims 1 to 8.
10. A power transformer with a power supply conductor according to one of Claims 1 to 8.

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