EP0058232B1 - Pancake coil winding with interleaved turn single or double coils - Google Patents

Abstract

Disk coil winding formed of interwound single or double coils wherein insulation of outer turns opposite inner and outer generated surfaces, respectively, of the winding is reinforced in comparison with normal insulation of conductors of the winding including auxiliary insulations angularly surrounding at least one edge of at least two turns, respectively, in at least the coils disposed at an input of the winding, starting from the inner and the outer generated surface, turn capacitance between turns free of auxiliary insulation being increased with respect to turn capacitance at turns provided with the auxiliary insulations.

Description

The invention relates to disc coil windings made of single or double coils, in which the insulation of the outer turns against the inner or outer surface of the winding is reinforced compared to the normal insulation of the winding conductor.

Simple disk coil windings have a non-linear surge voltage distribution in the axial direction along the individual coils, so that breakdowns can occur between two adjacent coils when subjected to voltage surges.

From DE-C-975 856 it is known that a much more uniform impulse voltage distribution is forced by winding the coils into one another, which largely prevents breakdowns.

1 and FIG. 2 show cross sections of exemplary embodiments of interwoven disc coils.

1 is an example of two inter-wound single coils and FIG. 2 is an example of a pair of inter-wound double coils. The windings of these disc coils are traversed by the load current in the order of the digits entered in them.

The disc coils are wound from two winding conductors fed simultaneously and spatially parallel to each other during the winding process. Subsequently, the wedge conductor sections lying within the individual disk coils are electrically connected in series by soldering together in such a way that the windings are removed from the high-voltage connection and thus also from the point of introduction of the impulse voltage pulses in accordance with the order of their digits. Correspondingly, the voltage against earth potential decreases with an increasing number of turns. The winding indices can therefore also be viewed as a multiple of the winding voltage compared to the winding input. The voltage drop in a single pass through a disc coil is called the branch voltage that occurs along the conductor. Accordingly, the single branch voltage is present in the case of a single coil winding between adjacent turns and twice the branch voltage in the case of a double coil winding between the turns. The single-coil circuit is therefore preferred for higher surge voltage stresses.

Unfortunately, however, the known interwoven disc coil windings also have their disadvantages. These are due to the increased winding stress, since instead of the single winding voltage which occurs in double coils which are not wound into one another, the single or multiple branch voltage occurs between adjacent turns, which is a multiple of the linearly calculated value during collision processes. As a result, pre-discharges in or between the disc coils are not excluded. The winding insulation is therefore reinforced in interwoven coils compared to simple coils so that no winding breakdown occurs, but pre-discharges at the winding edges are accepted. As a result, part of the longitudinal capacity gained by wrapping one another is lost again.

Analogous to the input turns of the arrangement according to DE-C-2 246 398, which relates to a layer winding, disc coil windings which have been carried out to date to protect against the preliminary discharges due to the occurrence of the edge fields are those on the inner and / or the outer lateral surface of the winding lying turns have been increasingly insulated. A disadvantage of the design of the reinforced insulation from this point of view, however, is that either the longitudinal capacitance is again reduced or that a weak point in the insulation compared with the branch voltage due to a cumulative effect of the branch voltage between the two windings adjacent to the inside or outside in a disk coil other disc coils. So pre-discharges at the coil edge are avoided, but not between the turns.

This arises from the problem of the longitudinal strength of inter-wound coil windings. By winding one another, the surge voltage difference between two neighboring coils is reduced to such an extent that no breakdown takes place between them, in the case of conductor insulations which are reinforced compared to coils which are not wound into one another. However, if the voltage is increased further, there is a longitudinal rollover across several coils before the breakdown between two adjacent turns or coils.

The cause of such rollovers has been controversial to date. According to a prevailing opinion, the oil field strength on the outer edges of the two peripheral windings of a disk coil compared to other coils is assumed to be the cause of such discharges. For this reason, these windings were insulated in a manner analogous to the arrangement according to DE-C-2 246 398, or the winding conductor insulation was reinforced by edge protection angles. Despite these measures, however, when the test voltage rises above the nominal voltage, longitudinal arcing initially took place along the outer lateral surface to a coil further away from the input. This is not prevented by the edge protection bracket.

The invention is based on the object of selecting the reinforcement of the conductor insulation while taking into account the economic viability and while maintaining the high longitudinal capacitance achieved by the interweaving so that pre-discharges are adjacent to one another ten turns as well as between different disc coils with the intended test voltage are excluded.

The solution to this problem according to the invention is based on the assumption that the high field strength between adjacent windings contributes to the cause of the longitudinal rollover if the voltage between the two radially most inner or outer windings of a disk coil is rectified with the axially extending voltage along several disk coils overlaid. This is particularly the case at the edge areas on the inside and outside of the disc coils. In contrast, in the radially central area of the individual disk coils, the tension does not increase monotonically from turn to turn, but alternately increases and decreases, so that there are no crossovers. It is therefore possible to make the conductor insulation weaker in this area.

The above object is therefore achieved according to the invention in that at least in the coils located at the winding input, starting from the inner and the outer jacket surface, at least two turns each are equipped with additional insulation, which comprise at least one highly stressed edge of these turns, and that the winding capacity between additional insulation free turns compared to the turn capacity of turns equipped with additional insulation is increased.

For reasons of simple production, more than two, in particular all, windings of the coils located at the winding input can be made with additional insulation, the thickness of which decreases to zero at the coils that are further away from the input.

According to expedient developments of the invention, in addition to the additional insulation, an axial cooling channel is arranged in each case between the winding lying on the inner or outer jacket surface and the respective neighboring winding. The additional insulation can consist of a paper casing surrounding the windings on all sides, U-shaped or angled pressboard covers.

According to advantageous refinements of the invention, in the case of windings lying on the inner lateral surface of the winding, the additional insulation decreases one after the other at the locations outside, bottom inside and top inside, and in the case of the neighboring turn, the bottom inside and top inside decreases. Here means below towards earth potential and above towards the high voltage input. Correspondingly, in the case of windings lying on the outer circumferential surface of the winding, the insulation reinforcement decreases in order at the locations inside, top outside, bottom inside, and in the neighboring turn in turn upwards outside and bottom outside, again in the downward direction Earth potential and above means towards the high voltage input.

According to further design features of the invention, the windings lying on the inner surface of the winding on the lower outer edge and their respective neighboring winding on the lower inner edge are covered with an additional insulation angle and, accordingly, the windings lying on the outer surface of the winding on the upper inner edge and their each adjacent turn on the upper outer edge is covered with an additional insulation angle and the turns are otherwise insulated like the turns in the middle part of the disc coils. The middle turns in the individual disc coils advantageously have a common paper wrap. This paper wrapping avoids pre-discharges in the oil channel between two coils if pre-discharges in the edge conductor gussets are avoided.

According to another development of the invention, the additional insulation and / or additional axial cooling channels are provided at least in the disk coils located near the high-voltage input of the winding and the thickness of the additional insulation is reduced with increasing distance from the high-voltage input of the winding.

The disc coil arrangement according to the invention can be used very advantageously in interwoven disc coils because it significantly improves their dielectric strength in the winding assembly without significantly reducing the high longitudinal capacitance obtained by the interweaving. Despite the better fill factor, the impulse voltage of the coil winding is increased by increasing its longitudinal strength due to the winding design according to the invention. This enables the construction of a more cost-effective winding for higher voltages compared to the conventional design. The arrangement of additional axial cooling channels also partially compensates for the higher temperature rise in the more insulated edge turns. A complete compensation of the higher heating in the edge turns of the arrangement according to the invention is, if necessary, possible by a slight reinforcement of their cross sections, the 1 ² R losses then decreasing with R more than the eddy current losses increase.

Embodiments of the invention are explained in more detail with reference to a drawing.

• Fig. 1 durch zwei Einzelspulen,
• Fig. 2 durch ein Doppelspulenpaar,
• Fig.3 durch zwei Einzelspulen gemäß Fig. 1 mit bekannter Isolierung durch Winkelringe,
• Fig. 4 bis 12 durch jeweils eine Einzelspule mit Variationen von erfindungsgemäßen Zusatzisolierungen, wobei in Fig. angedeutet ist, daß nicht nur die mindest erforderlichen je zwei Randwindungen, sondern alle Windungen der Eingangsspulen eine Zusatzisolierung 32 erhalten, und nur die vom Eingang entfernten Normalspulen ohne Zusatzisolierung 32 ausgeführt sind. Die Zusatzisolierungen 32 können dabei bei den Eingangsspulen in Richtung abnehmender Spannung bis Null, bei den Normalspulen abnehmen, was eine wirtschaftliche Auslegung ermöglicht.
• Fig. 13 bis 17 stellt jeweils eine Einzelspule mit erfindungsgemäßer Zusatzisolierung und zusätzlichen axialen Kühlkanälen dar.

In the drawing, cross sections of interwoven coils are shown in principle, namely in

• 1 by two individual coils,
• 2 by a pair of double coils,
• 3 by two individual coils according to FIG. 1 with known insulation by angle rings,
• Fig. 4 to 12 each with a single coil with variations of additional insulation according to the invention, which is indicated in Fig. That not only the minimum required two edge turns each, but all turns of the input coils receive additional insulation 32, and only the normal coils removed from the input are designed without additional insulation 32. The additional insulations 32 can decrease in the direction of decreasing voltage in the direction of the input coils, in the case of the normal coils, which enables an economical design.
• 13 to 17 each represent a single coil with additional insulation according to the invention and additional axial cooling channels.

Corresponding parts are provided with the same reference symbols in all figures.

Usual, so-called interwoven disc coils are wound from two simultaneously and spatially parallel winding conductors, the windings 1 through n of which the load current flows through in the order of the digits entered. There is a multiple of the winding voltage between adjacent turns. To determine this voltage, the difference between the numbers in the windings under consideration must be multiplied by the simple winding voltage, from which the voltage difference between neighboring conductors, which occurs in the case of linear distribution, for example with alternating voltage, is obtained, which is increased by a multiple of the linear component in the case of surge voltage. The continuous insulation of the winding conductors is designed for this voltage difference.

To improve the dielectric strength and to simultaneously protect the winding mechanically, as shown in FIG. 3, angle rings 30 have so far been provided on the innermost and outermost turns of each individual disk coil. In this arrangement, too, arcing is often observed with increasing voltage along the lines 31 indicated by dashed lines (see FIGS. 1 to 3). In this case, the inner lines 31 often run from the uppermost input coil drawn to the innermost adjacent conductor gap (gusset) of a coil four or more coils away. However, the outer lines 31 extend from the outer winding (not shown) of the uppermost input coil to the outermost adjacent conductor gap (gusset) of the lower coil drawn in, which is four or more coils away from the input coil.

The high field strength at the point of separation between the two adjacent edge conductors of the input coils is considered to be the cause of the first preliminary discharges.

The invention is based on the idea that these pre-discharges from these "critical oil gussets", which arise at the edge of the neighboring conductor gap, only along the line 31, i. H. run in the radial direction to the coil surface and then in the axial direction along this surface or vice versa, because only starting from these critical gussets in both directions the voltage applied to 31 increases or decreases monotonously and there are always lengths of 31 at which the permissible Slip resistance is exceeded, so that there is a longitudinal rollover along 31.

However, the lengths and tensions can be changed less effectively and thus less increase their assigned sliding resistance than eliminating the pre-discharges in the critical gussets as the cause of the sliding by reducing the oil field strengths there. The latter happens through the measures according to the invention.

The permissible slip resistance of 31 is to be understood as the experimentally determined surge voltage applied to a length 31, which just does not yet lead to a breakdown along 31 if pre-discharges occur at one end of 31 due to high oil field strengths.

To strengthen the disk coil arrangement, an additional insulation 32 is provided according to the invention at least on the two innermost and outermost windings in each disk coil lying close to the input, the thickness of the additional insulation 32 decreasing to zero for all turns of these input coils with decreasing voltage to earth Normal coils. This additional insulation 32 is supported in its effect in the exemplary embodiments according to FIGS. 13 to 17 by an axial cooling channel 33 at the above-mentioned separation points, as a result of which the critical conductor gussets are avoided entirely.

With regard to the voltage load that actually occurs, it is sufficient in itself for all input coils to insulate the two outermost or innermost turns of each disk coil only on the outside top and inside below. 14, 16 and 17. In contrast to this, in the embodiment according to FIG. 15, these windings are insulated to the same extent on all sides. However, these solutions are relatively complex and confusing, but make optimal use of the available changing space.

6, 16 and 17, the additional insulation 32 is shown by simple edge angles and in the embodiment according to FIG. 14, the innermost and outermost turns of the disc coil are surrounded by a plurality of edge protection angles which are staggered in accordance with the decreasing field strength.

To avoid narrowing of the radial cooling channels, in the exemplary embodiments according to FIGS. 4, 5, 7, 9, 10, 11, 12 and 17, isolating agent parts protruding in the axial direction from the disc coils are dispensed with, for example by B. the edge turns receive a modified turn cross-section that the axial height including the additional insulation 32 is equal to the normal height of a normal turn. In the exemplary embodiments according to FIGS. 4 and 5, this is represented by a joint turn of the middle windings of the disk coil.

The inventive examples of FIGS. 4 to 17 are drawn for the example of interwoven single coils according to FIG. 1, but also apply according to the invention for interwoven double coils according to FIG. 2. In FIGS. 4 to 17 with the exception of FIG. 9, only the two inner and outer edge turns additional insulation 32, of course, embodiments according to the invention are also conceivable if all turns of the coils located at the winding input are provided with this additional insulation, so that they look when using insulated turn insulation 32 as shown in FIGS. 1, and 9, and that only the coils further away from the input are designed with turns without additional insulation.

Claims (9)

1. A pancake coil winding with interleaved turn single or double coils, in which the insulation of the outer turns in relation to the inner and outer surfaces of the winding is strengthened in comparison to the normal insulation of the winding conductor, characterised in that:

- at least in the coils located at the inlet of the winding, commencing from the inner and outer surfaces, in each case at least two turns are equipped with additional insulation (32) embracing at least one edge of the turns in angular fashion and

- that the turn capacity between turns which are free of additional insulation is increased in comparison to the turn capacity of the turns which are equipped with additional insulation.

2. A pancake coil winding as claimed in claim 1, characterised in that between the turn located on the inner or outer surface, as the case may be, and the particular adjacent turn, an axial cooling channel (33) is in each case provided in addition to the additional insulation (32) (Fig. 13 to 17).

3. A pancake coil winding as claimed in claim 1, characterised in that the additional insulation (32) consists of a paper wrapping composed if U-shaped or angular pressboard coverings which surrounds the turns on all sides.

4. A pancake coil winding as claimed in one of claims 1 to 3, characterised in that in the case of turns located on the inner surface of the winding, the additional insulation (32) is decreased in turn at the lower outside, lower inside and upper inside locations and in the case of the adjacent turn, decreases consecutively at the lower inside and upper inside locations, where »lower« is to be understood as the direction towards earth potential whereas »upper« is to be understood as the direction towards the high voltage input.

5. A pancake coil winding as claimed in one of claims 1 to 4, characterised in that in the case of turns at the outer surface of the winding the additional insulation (32) reduces consecutively at the upper inside, upper outside and lower inside locations, and in the case of the adjacent turn it decreases consecutively in the upper outside and lower outside locations, where again »lower« is to be understood as the direction towards earth potential and »upper« is to be understood as the direction towards the high voltage input.

6. A pancake coil winding as claimed in one of claims 1 to 3, characterised in that the turns at the inner surface of the winding are clad at the lower outer edge with an additional insulating angle, whereas the adjacent turn is clad at the lower inner edge with an additional insulating angle, but are otherwise insulated in an identical manner to the turns in the central part of the pancake coils.

7. A pancake coil winding as claimed in one of claims 1 to 3, characterised in that the turns at the outer surface of the winding are clad at their upper inner edge with an additional insulating angle and the adjacent turn is in each case clad at the upper outer edge with an additional insulating angle, but are otherwise insulated in identical fashion to the turns in the central part of the pancake coils.

8. A pancake coil winding as claimed in one of claims 1 to 7, characterised in that the additional insulation (32) and/or additional axial cooling channels (33) are provided at least in the pancake coils located close to the high voltage input of the windings, and that the thickness of the additional insulation reduces with increasing distance from the high voltage input of the winding.

9. A pancake coil winding as claimed in one of claims 1 to 3, characterised in that the central turns on the indicidual pancake coils are provided with a common paper covering.

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