DE102022211345A1 - Coil with coil connection between partial coils and process - Google Patents

Abstract

The invention relates to a coil (100) made of partial coils (11, 12, 13, ...), wherein the partial coils (11, 12, 13, ...) are wound from conduction strips (9) and are electrically connected to one another by an electrically conductive coil connection ('1, 1', 1'', 1'''), wherein the coil connection ('1, 1', 1'', 1''', ...) is rigid and S-shaped.

Description

The invention relates to a coil with a coil connection between partial coils and a method for producing the same.

Cast resin transformers and choke coils usually have foil windings made of aluminum or copper as conductors and plastic foil in between for insulation. In the case of coils for higher nominal voltages, several partial coils, usually 10 to 20, are arranged axially to one another to achieve the required number of turns. These must then be electrically connected to one another, i.e. connected in series. Due to the potential differences in the partial coils, this is best done by making as direct a connection as possible from the end of one partial coil to the beginning of the next partial coil.

In addition to the coil connections, the coils also have a coil start and end, as well as tap leads. These are connections from the end, start or an intermediate turn of a partial coil to a contact point on the outside of the coil.

When a partial coil has been wound, one or more strips of the conductor strip material are welded at right angles to the end. The same is done at the beginning of the next coil. For this purpose, stationary welding devices are usually provided on the winding machines. Depending on the material, the strips must not exceed a certain minimum cross-section in order to allow the strips to be bent and arranged without problems. In order to achieve the required current-carrying capacity, several strips may have to be used in parallel.

The strips face each other and, after the winding process, are cut to length, welded together and then manually bent into the desired linear connection. The connection must be led out of the channel between the coils in order to be welded there at a sufficient distance from the sensitive coil. The part with twice the thickness of the discharge strip is then bent over and represents the outermost point of the partial coil. This then determines the distance to other live parts.

The coil start, end and taps are usually made from the same flexible strips, with the difference that one end is connected to an external contact point.

With thin conductor strips made of soft material, it is also possible to fold the conductor strip directly and form the connections from it. In this case, the conductor strip is not cut off. Here, too, manual arrangement and checking of the connection is necessary afterwards. Ultimately, the connections made in this way look the same.
In both cases, the distances between the partial coils must be sufficiently large to allow manipulation in the channel between the partial coils.
The entire coil is then usually cast in an insulating molding material, usually epoxy resin, so that a cylindrical component is created. In the area of the coil connections and where the coil start, end and taps are led out, the cast coil has a thickening (sprue) in order to reliably insulate these protruding components as well.

A faulty connection with too little distance to a partial coil or another connection can lead to an electrical short circuit and thus to the destruction of the component and failure of the product during operation. Such a faulty connection can no longer be detected after encapsulation.

Due to the manual bending, the limited accessibility and the flexible nature of the connections, these can only be made with a relatively large tolerance range. The manufacturing tolerances must be taken into account by using appropriately wide channels between the partial coils.

It is therefore an object of the invention to solve the above-mentioned problem.

The object is achieved by a coil according to claim 1 and a method according to claim 6.

The subclaims list further advantageous measures which can be combined as desired to achieve further advantages.

• 1 ein Verbindungselement,
• 2, 3 einen Fertigungsschritt einer Spule,
• 4 einen Spalt und ein Verbindungselement zwischen zwei Teilspulen.

Show it

• 1 a connecting element,
• 2 , 3 a manufacturing step of a coil,
• 4 a gap and a connecting element between two partial coils.

The figures and the description represent only embodiments of the invention.

According to the invention, coil connections 1 are prefabricated. During the design phase of a coil 100, the thickness and number of layers of conductor strip 9 and insulating film are defined in advance, as is the axial distance between the partial coils 11, 12, 13, .... This makes it possible to determine the coil connection 1 geometrically precisely in the design phase.

As an alternative, flexible bands should no longer be used, but instead only a flat material should be used as a coil connection 1 with such a large cross-section and inherent rigidity that the shape once given is retained because it is rigid.
Rigid means that the coil connection 1 is many times thicker than a conductor strip 9 and does not deform itself due to gravity.

The coil connections 1; 1', 1'', 1''' then consist of a flat material which is bent at least twice, in particular only twice ( 1 ).
The connecting element 1 has at least three sections 4, 5, 6, in particular only 3 sections (apart from the curved transitions).

The first section 4 is flat, wherein the second section 5 directly adjoins the first section 4, is flat and runs at an obtuse angle a, preferably from 92° to 120°, to the first section 4.
The sections 4, 5, .. represent planes and the angle a is the angle of intersection between two planes.
The third section 6 is directly connected to the second section 5 and runs parallel to the first section 4. Thus, the connecting element 1 is S-shaped, ie resembles an S-shape.

The two mutually parallel ends 4, 6 serve to connect to the respective conductor strip 9 of two partial coils 11, 12 or 12, 13, or 13, .... The prefabricated coil connections 1', 1'', ... are welded to the partial coil end of a partial coil 11 and to the beginning of the next partial coil 12, .... during winding.

The material of the connecting element 1 comprises aluminum, aluminum alloys, copper or copper alloy.

Such coil connections 1 can be produced easily and inexpensively, particularly with a CNC bending machine, fully automatically from continuous material. According to the state of the art, the coil construction is software-supported, i.e. the geometry data can be transmitted to the bending machine via a suitable interface. This makes it possible to efficiently produce individual, non-standardized coil connections 1.

In 2 a completed first manufacturing step 100' for producing a coil 100 is shown.
A first partial coil 11 can be seen on a coil base body 30, which is completely wound, at the end of which, ie the end of the conductor strip 9, the coil connection 1 is electrically connected, in particular welded.

A welding process is carried out in particular by means of an ultrasonic welding device.

The flexible conductor band 9 of the first partial coil 11 can be arranged below or above the first section 4 of the connecting element 1.

A further partial coil 12 is then wound onto a coil base body 30 of the coil 100 to be manufactured, in addition to the first partial coil 11, wherein the beginning of the conductor strip 9 for the second partial coil 12 is or is electrically connected or welded to the third section 6 of the connecting segment 1.

The length of the 1st and 3rd sections 4, 6 of the connecting element 1 is preferably at least as long as the conduction bands of the partial coils 11, 12, 13, ... are wide.

3 shows further completed production steps for producing a coil 100'', in which 3 connecting elements 1', 1'', 1''' and 3 partial coils 11, 12, 13 have already been assembled and connected and a further conductor strip 9'''' is wound up.

4 shows a detailed section between two partial coils 11, 12.
A first partial coil 11 and the partial coil 12 arranged directly next to it can be seen, which are connected in series by the coil connection 1.
The distance between the partial coils 11, 12 gives the angled course of the 2nd section 5 of the
Connecting element 1.

The coil start, end and taps will also be implemented using the new technology.
However, it must be taken into account that these are longer, have to be bent several times and may have to be guided along the outside of the coil, which can lead to collisions during the winding process. In this case, a combination of rigid outlets in the area of the coil with a welded-on flexible outlet to the contact point is probably most advantageous.

As a rule, welding with existing welding devices is no longer possible be possible, since welding must be carried out on both sides of the connection, but the welding devices on the machines are designed to weld only the connecting strips sequentially onto the strip. A suitable device must then be used. An ultrasonic welding device is preferably used here, which allows welding points to be set quickly and flexibly in terms of space.

Such a prefabricated connection enables optimal cable routing and thus a reduction in coil spacing: The prefabricated connections can be made with tighter bending radii than those bent by hand. Furthermore, the parallel routing of the discharge strips on the outside is no longer necessary, which also saves space. The defined geometry of the connections also means that smaller safety distances are necessary. Since no further manipulation of the connections is necessary afterwards, this no longer has to be taken into account when determining the partial coil spacing.

In the new design, the electric field strength load on the insulating material (voltage divided by distance) is reduced by increasing the distance. The coil spacing can now be shortened, which results in the same field strength as in the conventional design. The reduction in the coil spacing is cumulative across the entire coil.
For example, if the coil spacing on a coil 100 with eleven sub-coils is reduced by just 4mm, the entire coil is shortened by 40mm.
This results in a saving in the insulating material that fills the coil channel (usually epoxy resin). In transformers, not only the coil is shortened, but the entire transformer including the low-voltage coil and the core legs. This allows considerable material savings, particularly in core sheet. The transformer is also more compact, which brings further advantages such as reduced no-load losses. This advantage is particularly evident in transformers with a high transformation ratio, which have a large number of turns and therefore partial coils. The same applies to low-power transformers, where the fill factor would be unfavorable due to the small conductor bandwidth in foil winding technology.
Likewise, the need for conductor material for the connection itself is minimized, as it is carried out using the shortest possible route and there is no longer any waste during production.

Another advantage is the more efficient production method of this type of connection. The prefabricated connections are welded to the end of each partial coil and the beginning of the next partial coil during winding. This completes the production process.

Subsequent cutting, welding and bending/alignment are no longer necessary. The quality risk of a connection that is incorrectly bent or subsequently bent during the process is significantly reduced.
For high currents, conventional technology requires several flexible strips, which then all have to be welded together and to the conductor strip. According to the invention, only the coil connection 1 and the conductor strip 9, i.e. two layers, have to be welded.
This also allows alternative processes to the thermal welding used previously, such as ultrasonic welding. The quality of the electrical contact connection is also correspondingly better.
In principle, the same advantages also apply to the coil start, end and taps if these are implemented using the new technology.
In the technique proposed here, the outer, bent part of the connection where the welding was carried out is omitted. This, together with the connections to the outer contact points, which also have tighter tolerances, allows the sprue to be reduced or even eliminated, which brings further material savings and process-related advantages during casting.

Claims (6)

Coil (100) made of partial coils (11, 12, 13, ...), wherein the partial coils (11, 12, 13, ...) are wound from conduction strips (9.9'''') and are electrically connected to one another by an electrically conductive coil connection ('1, 1', 1'', 1'''), wherein the coil connection ('1, 1', 1'', 1''', ...) is rigid and is S-shaped. Coil after Claim 1 , in which the coil connections (1', 1'', 1'''') comprise the same material as that of the conduction bands (9), in particular in which the coil connection (1) comprises aluminium or an aluminium alloy or copper or copper alloy. Coil after Claim 1 or 2 , in which the coil connection (1) has at least three differently aligned sections (4, 5, 6), in particular only three sections (4, 5, 6). Coil after Claim 3 , in which the first section (4) of the coil connection is flat, in which the second section (5) is directly connected to the first section (4), is flat and runs at an obtuse angle (a), in particular from 92° to 120° to the first section (4), and in which the third section (6) directly adjoins the second section (5) and runs parallel to the first section (4). Coil according to one or more of the preceding claims, in which the first section (4) and the third section (6) of the connecting element (1) are as long as the width of the conduction bands (9, 9'''') of the partial coils (11, 12, 13, ...). Method for producing a coil, in which a coil (100) is produced according to one or more of the preceding claims, wherein the connecting element (1', 1'', 1'', ..) is connected to the conduction bands (9, 9'''') of the partial coils (11, 12, 13, ...) by ultrasonic welding.

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