DE102014107829B4 - Inductance and manufacturing processes therefor and modular system - Google Patents

Abstract

Electrical inductance, as an electrical passive attenuator, with an iron core (24) assembled from mutually insulated metal sheets (4a, b) to form a laminated core as a magnetic flux guide body (24) with three parallel longitudinally spaced legs (1a , 1b, 1a), with one end on each side, - two yokes (2), of which each yoke (2) connects the ends of the longitudinal legs (1a, b) pointing to the same side to form at least one air gap, - the Yokes (2) consist of sheets (4a, b) that are bent into a C-shape and fit one inside the other, - three coils (3) that are closed in a ring, each of which fits around one of the longitudinal legs (1a, b), with each yoke ( 2) at both ends of the yoke (2) in the direction of extension of the longitudinal legs (1a, 1b, 1a) struts extensions (7a, b), - between two mutually directed extensions (7a, b) of the two yokes (2) each uh the outer longitudinal leg (1a) is arranged to form an air gap (13), - the yokes (2) are braced against each other by means of a tensioning device (6), the parts (6a, b) of which are arranged outside the laminated core, - the finished iron core ( 24) apart from the two interior spaces between the longitudinal legs (1a, b), there is no breakthrough, - a securing strip (12) made of electrically insulating material is arranged between the middle longitudinal leg (1b) and the inner wall of the coil (3 ') or the coil former (3) is longer than the length of the central longitudinal leg (1b) and extends into the area of the yokes (2).

Description

field of use

The invention relates to a method for producing “inductors with an iron core”, which generally include electrical transformers, electrical chokes, electrical filters, electromagnets, hereinafter referred to as “inductor”, and an inductor produced by this method, and a kit for the production.

In the context of the present application, the focus is on inductors for use as electrical reactors (line and commutation reactors, filter circuit reactors, motor reactors, etc.) and electrical filters for use on frequency converters (sine filters and du / dt filters, etc.).

Technical background

Electrical inductors are contained in a large number of electrical and electronic devices, and their main purpose is to convert or separate one or more, in particular different, voltage potentials, to limit the current, to reduce voltage rising edges, to compensate harmonic components or to form a magnetic field.

For this purpose, electrical inductors contain one or more electrical coils.

Their windings can be wound on a coil former, which generally consists of an electrically non-conductive material, usually plastic, or can be present as so-called air coils, which have no coil former as the winding core.

In order to make the principle of inductance with an iron core function as a unit, the at least one coil is structurally connected to the iron core. In this case, the at least one coil is placed over the iron core in such a way that a magnetic flux is generated in the iron core due to the applied coil voltage and the induction that occurs.

In transformers and also in chokes and filters, the two coils in the form of the windings are often penetrated by a common, closed, rotating iron core, which improves the operating behavior and the efficiency of the inductance.

In order to avoid eddy currents, this is generally produced from a stack of individual, rolled sheets, so-called dynamo sheets or transformer sheets, one on top of the other, the individual sheets having to be electrically insulated from one another. For this purpose, the individual sheets on the rolled surfaces are usually coated with an electrically insulating insulating varnish or have an electrically insulating oxidation layer.

In order to keep the sheets together permanently as an iron core (hereinafter also referred to as a laminated core), these have so far often been screwed together with screws, isolated by means of thrust pieces or welded together at the edge through through holes in the sheets.

The mounting brackets or other add-on parts usually required on the inductance, with the laminated core, are also screwed, welded or clamped.

The laminated core can partially or completely enclose the coil, the laminations of different formats and sizes joined together forming the iron core of the inductor. Among other things, standardized sheets, so-called E, UI or M cuts, can be combined to form a sheet package.

In order to achieve the required thickness of the laminated core, two or more laminations per layer and in particular rotated by 180 ° from layer to layer are generally piled up, which represents a very high and usually only manually manageable amount of work.

The contour of each layer that is visible from the top of the sheet metal plane does not consist of a single sheet metal in the case of an all-round closed iron core, but because of the fact that it can be assembled, it is composed of at least two sheets.

With the welding method, the laminated core is joined on one side (without changing the sheet metal direction) to form a block and then welded together as a block on the outside of the abutting edges of the sheets. The resulting magnetic short circuit at the edge of the magnetic field is accepted for economic reasons.

Are from the prior art with the patents US 2014/0 002 229 A1 , DE 92 13 190 U1 , US 3,686,561 A , US 7 242 275 B2 , DE 31 11 391 A1 and DE 101 57 009 A1 Inductors with coils and iron cores known.

• So steht bei Transformatoren beispielsweise die Effizienz, also die Verringerung der Verlustleistung, im Vordergrund:
  • Zu diesem Zweck wird versucht, den magnetischen Widerstand des Eisenkerns möglichst zu minimieren. Bei den meist umlaufend geschlossenen Eisenkernen, die aus Montagegründen nicht aus einzelnen, ringförmig geschlossenen Blechen zusammengesetzt werden können, bedeutet dies, dass die an der Kontaktstelle zwischen aneinander grenzenden Blechen des Blechpaketes auftretende magnetische Widerstand möglichst gering gehalten werden soll, was durch Maßnahmen wie Minimierung des Luftspaltes dazwischen oder gar Anfüllen mit magnetischem Material in der Fuge versucht wird.

Despite the fundamentally identical construction of transformers on the one hand and chokes or filters on the other hand, they should have different properties during operation, which in detail also requires different design details if one wants to optimize the desired function in the foreground:

• In the case of transformers, for example, the focus is on efficiency, i.e. reducing the power loss:
  • For this purpose, attempts are made to minimize the magnetic resistance of the iron core as much as possible. With the mostly all-round closed iron cores, which for assembly reasons cannot be assembled from individual, annularly closed sheets, this means that the magnetic resistance occurring at the contact point between adjacent sheets of the sheet stack should be kept as low as possible, which is achieved by measures such as minimizing the Air gap in between or even filling with magnetic material in the joint is tried.

In the case of chokes and filters, on the other hand, which represent a passive attenuator, for example, for filtering out the harmonic harmonics, a defined air gap is just required, since this just causes the desired damping. The damping behavior desired in the individual case is determined by the size and arrangement of the air gaps in the iron core, that is to say in or between the laminated cores.

Another point that is in the foreground with chokes and filters is often the reduction of noise emissions from frequency-controlled motors and protection of the motor insulation by reducing the voltage rising edges (e.g. through long motor leads).

Presentation of the invention

Technical task

It is therefore the object of the invention to provide an inductor, in particular for use as a choke or filter, as well as a method for its manufacture and a modular system, so that the manufacturing outlay is reduced and the function of the inductor, in particular as a choke and filter, is improved .

Solution of the task

This object is solved by the features of claims 1, 18 and 21. Advantageous embodiments result from the subclaims.

• Durch die beiden Fortsätze an den Enden jedes Joches, die in den inneren Freiraum je einer Spule hineinragen, wird die Montage erleichtert, denn die äußeren Spulen erstrecken sich über die Fortsätze der Joche und halten damit die Joche und die äußeren Längsschenkel zusammen.

Due to the specific design of the inductor according to claim 1, there are a number of advantages:

• The assembly is made easier by the two extensions at the ends of each yoke, which protrude into the inner free space of each coil, because the outer coils extend over the extensions of the yokes and thus hold the yokes and the outer longitudinal legs together.

There is no extension in the middle, so that the middle longitudinal leg is as long or even longer than the coil that is arranged around it. So that you can not move the middle coil together with the middle longitudinal leg out of the plane of the iron core, security strips (made of electrically insulating material) are inserted on both sides of the longitudinal leg, which are longer than the middle longitudinal leg and each in the area of the yokes extend into and thereby form a positive locking against lateral pulling out of the middle coil and the middle longitudinal leg.

Functional advantages, namely good electrical damping by means of this inductance, are achieved in that the air gaps can first be dimensioned as required, in that the spacers inserted for this can have different thicknesses.

In addition, the positions of the air gaps and their number can be selected by the fact that the longitudinal legs do not have to be in one piece, but can consist of several sections in their direction of extension.

In the case of the outer longitudinal legs, the coil preferably extends over the air gaps between the outer longitudinal leg and the extension of the yoke, so that there - even if additional air gaps are provided - all air gaps are within the length of the coil, which means that they function as a choke or filter is very advantageous (minimizing stray fields).

• - außer den beiden großen Innenräumen zwischen den Längsschenkeln - durchbruchsfrei ist, da beispielsweise keine Durchgangsbohrungen durch die Bleche für Querverschraubungen benötigt werden, führt dazu, dass sich das magnetische Feld sehr viel homogener ausbilden kann, als bei Vorhandensein weiterer Durchbrüche. Vor allem wird ein Durchbruch in der Mitte des Joches vermieden durch die Bauform des Joches mit nur je einem Fortsatz an den Enden, und nicht im mittleren Bereich:
  • Mittels der entsprechend C-förmig gebogenen Bleche können auf diese Art und Weise Joche ohne innere Durchbrüche hergestellt werden, bei denen die Blechebene der einzelnen Bleche quer zur Hauptebene des fertig gestellten Eisenkerns verläuft.

That the yokes are breakthrough-free in themselves and also the entire iron core

• - Except for the two large interiors between the longitudinal legs - there is no breakthrough, since, for example, no through holes through the sheets are required for transverse screw connections, this means that the magnetic field can be formed much more homogeneously than if there are further breakthroughs. Above all, a breakthrough in the middle of the yoke is avoided by the design of the yoke with only one extension at each end, and not in the middle area:
  • In this way, by means of the correspondingly C-shaped sheets, yokes can be produced without internal openings, in which the sheet level of the individual sheets runs transversely to the main plane of the finished iron core.

The iron core is held together by a clamping device that only acts from the outside, which does not penetrate the iron core, and which is additionally variable with regard to the spacing of its clamping plates, i.e. if e.g. spacers of different thickness can be inserted into the air gaps.

The longitudinal legs should preferably have the same cross-section as the extensions of the yoke, and in particular the sheet metal planes in the longitudinal legs should also be flush with those in the extensions in order to achieve a homogenization of the magnetic field which is formed.

The central longitudinal leg thus preferably ends in front of the inner surfaces of the C-shaped yoke in its central region, normally with an air gap to the yoke. The form-fitting securing of the middle longitudinal leg, which is not present as a result, is achieved by the additional securing strips already mentioned.

The air gaps are usually caused by inserted spacers made of electrically insulating material, which is a very simple way of creating air gaps of a defined width.

The longitudinal legs are generally cuboid and then consist of rectangular sheets placed one on top of the other. The coils around the individual longitudinal legs have an axial length, that is to say in the longitudinal direction of the longitudinal legs, which fills the distance between the two yokes as completely as possible, in order to thereby ensure positive locking of the longitudinal position of the coils within the iron core.

At the transition from their main part to the extension, the yokes are not simply cranked by 90 °, but cranked twice by 45 ° each and therefore have a bevel at their ends, both in their outer contour and in their inner contour, and also all sheets from which the yoke is formed have this slope.

This prevents the formation of so-called hot spots, at least on the inner corners of the iron core, and thus achieves a more homogeneous magnetic field.

Depending on the design of the inductor, the individual longitudinal legs can be made in several parts, with free choice between the length of these individual parts and the width of the air gaps between them. The spacers should preferably have the same area as the cross section of the longitudinal leg in which they are located, in order not to cause a different dielectric in the interior of the air gap.

The cross-sectional area of the longitudinal legs and also the extensions of the yokes is dimensioned such that, together with the securing strips inserted on both sides, they exactly fill the inner free space of the respective coil, thereby providing a form-fitting, secure locking between the coil on the one hand and the iron core on the other.

The securing strips are also used for the outer legs, although they would not be needed there for the positive locking, since the extensions of the yokes protrude into the inside of the coil in the outer coils.

The security strips are therefore also arranged on the outer longitudinal legs so that the iron core can be made from sheet metal strips of constant thickness, because otherwise the width of the sheet metal strips used for the yoke would have to change from the central region to the extensions, which is disadvantageous for the function and is complex for the production of these sheets.

The tensioning device preferably consists of two tensioning plates which are placed on the outer sides of the yokes and have a protrusion either in the main plane of the iron core or transversely thereto or both. At their overhang, the two clamping plates are clamped against one another in the longitudinal direction by means of clamping screws, and thus press the yokes against one another, so that pressure is built up and maintained on the spacers that define the air gaps.

This pressure on the spacers has the effect that the noise emissions of the inductance during operation are much lower than with no or only a slight preload against the spacers.

In order to ensure a form-fitting securing of the tensioning plates with respect to the iron core transversely to its main plane, the tensioning plates are preferably designed as hat profiles.

In addition to the bores for the clamping screws penetrating them, the clamping plates preferably also have further through openings in order to allow the potting compound to run off during the subsequent wetting or casting of the entire assembled inductor.

On the clamping plate, a conventional LV rail for fastening transformers can also be arranged - if necessary between the yoke and the clamping plate - which are required for operation as a choke or filter.

The clamping plates are preferably wider than the iron core measured transversely to its main plane and also wider than the coils in this direction, on the one hand in order to be able to attach tensioning screws in the overhang, but on the other hand to provide a protective overhang over the coil and the iron core .

• Der Baukasten muss natürlich jeweils mindestens wenigstens eine Sorte der zwingend vorhandenen Bauteile, also Spule, Joch, Spannvorrichtung, mittlerer und äußerer Längsschenkel und Sicherungstreifen enthalten.

Due to this structural design of the inductor, a modular system can be created so that a very wide range of differently designed inductors can be produced using a relatively small number of different components:

• The kit must of course contain at least one type of the mandatory components, i.e. coil, yoke, tensioning device, middle and outer longitudinal leg and securing strip.

If several types of spacers of different thicknesses are already part of the modular system, inductors with different damping behavior can be produced depending on the spacer selected.

Of course, the range of variation is even greater, even if the construction kit contains several types of the other components, for example several partial longitudinal legs, in order to be able to put together middle and outer longitudinal legs from these partial longitudinal legs. The resulting changing dimensions of the iron core in the longitudinal direction of the longitudinal struts can be compensated without problems by correspondingly long external threads on the tensioning screws of the tensioning device or, in the case of large differences in length, by tensioning screws of different lengths within the modular system.

The modular system can preferably also comprise several types of coils of different lengths and security strips of different lengths.

• Zum Aufbau der Induktivität wird bevorzugt eine allerdings sehr einfach aufgebaute Vorrichtung benutzt, theoretisch könnte der Zusammenbau auch rein manuell erfolgen: Nach Zusammensetzen der Joche aus einzelnen Blechen wird auf die Fortsätze des ersten Joches jeweils eine Spule aufgesteckt, oder - falls die drei Spulen vorher zu einer Einheit verbunden wurden - die gesamte Spuleneinheit.

With regard to the method, the object is achieved in a generic inductor according to claim 1 by the method steps of claim 21:

• To build the inductance, a very simple device is preferably used, theoretically, the assembly could also be done purely manually: after assembling the yokes from individual sheets, a coil is attached to the extensions of the first yoke, or - if the three coils previously were connected to one unit - the entire coil unit.

Then - after inserting the spacers into the inner free spaces of the coils - the outer longitudinal legs are inserted into the outer coils, and the middle longitudinal leg is inserted into the middle coil.

At the latest, possibly before, the two security strips are inserted into the interior of each coil.

Now the second yoke with its extensions can be inserted into the outer coils - again with a spacer in each case - and the tensioning device can be attached, which presses the two yokes against each other in this position. If the clamping device consists of the two clamping plates and connecting clamping screws, the - preferably hat-shaped - clamping plates are placed on the outside of the yokes and the clamping screws are screwed.

Figure list

• 1: die Induktivität in Explosionsdarstellung,
• 2a-c: verschiedene Varianten des Eisenkerns,
• 3a-c: die Induktivität im zusammengebauten Zustand.

Embodiments according to the invention are described in more detail below by way of example. Show it:

• 1 : the inductance in exploded view,
• 2a-c : different variants of the iron core,
• 3a-c : the inductance when assembled.

The iron core 24th out 1 is in 2a in supervision of its main level 16 shown, and in 2 B in the side view, i.e. in the direction of view of this main level 16 .

As in 2a to recognize, there is the iron core 24th in supervision of its main level 16 from a circular sheet metal package with an approximately square shape and bevelled corners, consisting of an upper and a lower, C-shaped yoke 2nd . Each of the yokes 2nd has at its ends at right angles to the direction of extension of the yoke 2nd extensions protruding in the same direction 7a , b .

The extensions 7a , b of the lower yoke 2nd are directed upwards, the extensions 7a , b of the upper yoke 2nd are directed downwards and are aligned with the extensions 7a , b of the lower yoke 2nd .

The transition of the main part of the yoke 2nd to the extensions 7a , b each has a slope 14 on, i.e. two bends of 45 ° each.

The yokes 2nd are made of individual sheets bent in this shape in a C-shape 4a , b that are nested and fit exactly into each other.

Between the aligned processes 7a on the one hand and 7b on the other hand there is an outer longitudinal leg 1a , which also consists of individual, in this case rectangular, parallel sheet metal.

In addition, there is internal space 5 this ring-shaped sheet metal package 24th a middle longitudinal leg 1b which is essentially from the inside of one yoke 2nd in the middle area to the inside of the other yoke 2nd extends and also from parallel, mutually connected, not interconnected, rectangular sheets 4x , y exists and parallel to the outer longitudinal legs 1a runs.

At the front ends of the longitudinal legs 1a , b and the yokes 2nd there is an air gap in each case 13 which is in the assembled state of the iron core 24th is obtained in that in particular plate-shaped spacers 15 whose area is the cross-sectional area of the longitudinal leg 1a , b corresponds, are inserted.

The cross-sectional area of the outer longitudinal legs 1a is the same and preferably agrees with the cross-sectional area of the central longitudinal leg 1b match, so that the same spacers for all longitudinal legs 15 can be used if the thickness of the air gap 13 should also be the same in each case.

Both the middle longitudinal leg 1b as well as the outer longitudinal legs 1a can also consist of several partial longitudinal legs in their direction of extension, as in an alternative embodiment in 2c shown.

Both the structure of the longitudinal legs from one or more partial longitudinal legs and the thickness of the spacers 15 depends on the particular application of the inductor. To put it simply, the purpose of the invention is to have as many possible variations, particularly with regard to the structure and details of the iron core, in spite of a simple construction of the inductance.

• Zunächst muss - siehe linke Bildhälfte der 1 - der Eisenkern 24 mit der Spuleneinheit 31 zusammengebaut werden, von der in 1 lediglich die in der Regel aus Kunststoff bestehenden, hülsenförmigen Spulenkörper 3 dargestellt sind, um deren Außenflächen herum jedoch vor dem Zusammenbau die elektrischen Spulen 3 mit ihren Wicklungen 19 aufgebracht sind unter Verwendung des Spulenkörpers 3 als Wickelkern 20, wie in 3a - c zu sehen.

The best way to build up the inductance is to use the exploded view of the 1 are explained:

• First of all - see left half of the picture 1 - the iron core 24th with the coil unit 31 be assembled by the in 1 only the sleeve-shaped bobbins, which are usually made of plastic 3rd are shown, but around the outer surfaces of the electrical coils before assembly 3rd with their windings 19th are applied using the bobbin 3rd as a winding core 20 , as in 3a - c to see.

• Nachdem das untere Joch 2 aus Blechen 4a, b zusammengesetzt ist, werden die beiden äußeren Spulenkörper 3 auf die nach oben ragenden Fortsätze 7a, b dieses unteren Joches 2 aufgesteckt, und auch der mittlere Spulenkörper 3 zwischen die beiden äußeren Spulenkörper 3 gesetzt, der dann auf der Oberseite des Joches 2 in dessen mittleren Bereich aufsitzt.

This assembly works as follows:

• After the lower yoke 2nd from sheet metal 4a , b is composed, the two outer bobbins 3rd on the protruding projections 7a , b this lower yoke 2nd attached, and also the middle bobbin 3rd between the two outer bobbins 3rd then put on top of the yoke 2nd sits in the middle area.

Then, from above, into the coil interior 29 the bobbin 3rd one of the plate-shaped spacers 15 inserted so that their main surface on the end face of one of the extensions 7a , b rest and thus across the coil interior 29 lie the cross sections of the extensions 7a , b also fill in essentially.

However, the iron core has 24th one across its main level 16 measured depth, which is less than the corresponding extent of the cross section of the coil interior 29 , and so much less that on both sides of the iron core 24th one security strip at a time 12th along each of the longitudinal legs 1a , b can be pushed in between, which is now carried out as the next step by pushing from above into the coil interior 29 .

The security strips 12th are longer than the middle longitudinal leg 1b , and are in the middle bobbin 3rd pushed down so far that its lower end extends into the area of the lower yoke 2nd enough.

On the other hand, this is the form-fitting securing, so that in the assembled state the middle coil body 3rd not across the main level 16 of the laminated core 24th can be pulled out of this.

Now the longitudinal legs 1a , b from above into the individual bobbins 3rd inserted between the two security strips 12th . If one of the longitudinal legs 1a , b from several partial longitudinal legs 1b exists, these are used one after the other, each with the interposition of a spacer 15 .

On the upper ends of the longitudinal legs used 1a , b also become spacers 15 and then the upper yoke previously made of sheet metal 2nd with its extensions 7a , b facing downwards into the coil interior 29 of the two outer bobbins 3rd inserted between the security strips there 12th .

So that this unit can no longer be dismantled undesirably, only the two yokes 2nd against each other. This is achieved in the next step by using one clamping plate each 17th in the form of a hat-shaped rail that is dimensioned so that it is transverse to the main level 16 measured depth of the iron core 24th the top of the upper yoke fits exactly into the recess of the cross-section of the hat profile 2nd and from below against the lower yoke 2nd is placed.

The protrusions protruding backwards and forwards 23a , b the hat profile have mutually aligned holes 26 through which the two clamping plates 17th using clamping screws 25th can be braced against each other, and thereby the iron core 24th stick together.

• So kann auf der oberen Spannplatte 17 eine sog. NS-Schiene 27 verschraubt werden, die dem formschlüssigen Befestigen von Trafos 28 dient, die für manche Anwendungen dieser Induktivität benötigt werden.

Before or after attaching them from the clamping plates 17th and the clamping screws 25th existing jig 6 on the iron core 24th can on the jig 6 other components are attached:

• So on the top clamping plate 17th a so-called NS rail 27 be screwed, the form-fitting fastening of transformers 28 serves that are required for some applications of this inductance.

Likewise, on the underside of the lower clamping plate 17th another clamping plate 17th are attached so that the hat-shaped bulges face each other. This bottom clamping plate 17th can serve, for example, the screw connection to the ground or another machine part.

Likewise, either on the lower clamping plate 17th or an additional bottom clamping plate 17th a support plate be attached by the cross section of the hat profile of the clamping plate 17th protrudes to the side and attaching capacitors 30th serves, which are also required for certain applications of inductance.

The 3a-c show the assembled state in different views of the inductance according 1 .

Reference list

1a, b

Longitudinal leg

2nd

yoke

3rd

Bobbin

3 '

Kitchen sink

4a, b, x, y

sheet

5

inner space

6

Jig

7a, b

Process

8th

Glue

9a, b

Face

10th

Longitudinal direction

11

Transverse direction, direction of yoke

12th

Security strip

13

Air gap

14

Weird

15

Spacers

16

Main level

17th

Clamping plate

18th

thickness

19a, b

Winding

20

Winding core

21

Faceplate

22

Through opening

23a, b

Got over

24th

magnetic flux guide, iron core

25th

Clamping screw

26

drilling

27

NS rail

28

transformer

29

Coil interior

30th

Capacitors

31

Coil unit

Claims (24)

Electrical inductance, as an electrical passive attenuator, with - an iron core (24) assembled from mutually insulated sheets (4a, b) to form a sheet stack as a magnetic flux guide body (24) with - three spaced parallel longitudinal legs (1a, 1b, 1a), with one end on each side, - two yokes (2), each yoke (2), the ends of the longitudinal legs pointing to the same side (1a, b) connects with the formation of at least one air gap, - the yokes (2) consist of C-shaped bent sheets (4a, b) that fit precisely into one another, - three coils (3) that are closed in a ring shape, each of which fits around one of the longitudinal legs (1a, b) runs around - each yoke (2) at both ends of the yoke (2) in the direction of extension of the longitudinal legs (1a, 1b, 1a) has struts (7a, b), - between two against each other directed projections (7a, b) of the two yokes (2) each have an outer longitudinal leg (1a) to form an air gap (13), - the yokes (2) by means of a clamping device (6), the parts (6a, b) of which are arranged outside the laminated core, chipping each other nt, - the finished iron core (24), apart from the two interior spaces between the longitudinal legs (1a, b), has no breakthrough, - between the middle longitudinal leg (1b) and the inner wall of the coil (3 ') or the coil body (3) a security strip (12) is arranged from electrically insulating material which is longer than the length of the central longitudinal leg (1b) and extends into the area of the yokes (2). Inductance after Claim 1 , characterized in that the outer longitudinal legs (1a) have the same cross section as the extensions (7a, b). Inductance according to one of the preceding claims, characterized in that the central longitudinal leg (1b) ends spaced apart by an air gap (13) in front of the inner surfaces of the C-shaped yokes (2). Inductance according to one of the preceding claims, characterized in that spacers (15) made of electrically insulating insulating material are arranged in the air gaps (13). Inductance according to one of the preceding claims, characterized in that the longitudinal legs (1a, b) consist of rectangular sheets (4 x, y) placed one on top of the other, the sheet levels of which match the sheet levels of the sheets (4a, b) in the extensions (7a, b ) align. Inductance according to one of the preceding claims, characterized in that the coils (3) in the longitudinal direction (10) fill the distance between the two yokes (2). Inductance according to one of the preceding claims, characterized in that the coils (3) have a coil body (3 ') made of plastic, on which the winding (19a, b) is applied. Inductance according to one of the preceding claims, characterized in that the sheets (4a, b) of the yokes (2) at the transition from the main part of the yoke (2) into the extension have a slope (14) of 45 ° each. Inductance according to one of the preceding claims, characterized in that the coils (3 ') on the outer longitudinal legs (1a) are so long that they have the air gaps (13) between the outer longitudinal legs (1a) and the extensions (7a, b) cover the yokes (2). Inductance according to one of the preceding claims, characterized in that the longitudinal legs (1a, b) can be constructed in several parts by being interrupted in their extension in the longitudinal direction (10) by air gaps (13) in which there are spacers (15). Inductance after Claim 10 , characterized in that the in particular plate-shaped spacers (15) have the same area as the cross section of the longitudinal legs (1a, b), in whose air gaps (13) they are located. Inductance according to one of the preceding claims, characterized in that the clamping device (6) consists of two clamping plates (17) which lie on the outer sides of the yokes (2) and on their projection (23a, b) by means of clamping screws (25) in the longitudinal direction (10) are braced against each other. Inductance after Claim 12 , characterized in that the clamping plates (25) consist of a hat profile. Inductance according to one of the Claims 12 or 13 , characterized in that the inductance is wetted by a hardening plastic. Inductance according to one of Claims 12 to 14, characterized in that the clamping plates (17), in addition to the bores (26) for the clamping screws (25), have through-openings (22) for the potting compound to run off. Inductance according to one of the Claims 12 to 15 , characterized in that on the clamping plate (17), a rail, in particular an NS Rail (27) for attaching transformers (28) is arranged. Inductance according to one of the Claims 12 to 16 , characterized in that the clamping plate (17) viewed in the top view is at least as wide as the coils (3 '). Modules for producing an inductance according to at least one of the Claims 1 to 17th , with - at least one type of bobbins (3 '), - at least one type of yokes (2), - at least one type of tensioning device (6), - at least one type of middle longitudinal leg (1b), - at least one type of outer longitudinal leg (1a), - At least one type of security strip (12), characterized in that the kit comprises several types of spacers (15) with different thicknesses. Construction kit after Claim 18 , characterized in that the kit comprises several partial longitudinal legs (1a1, 1a2) for creating middle (1b) and outer (1a) longitudinal legs. Construction kit according to one of the Claims 18 or 19th , characterized in that the kit comprises several types of coils (3 ') of different lengths and / or securing strips (12) of different lengths and / or tensioning devices (6) of different lengths with tensioning screws (25) of different lengths in particular. Process for producing an inductor, the - An iron core (24) with three spaced-apart longitudinal legs (1a, 1b, 1a) and two C-shaped yokes (2) with end extensions (7a, b) and - three coils (3 ') and - Has a tensioning device (6), with the following method steps: a) assembling a first yoke (2) from sheets (4a, b) and arranging the yoke (2) with projections (7a, b) pointing upwards, b) plugging the two outer coils (3 ') onto the extensions (7a, b) and inserting the middle coil (3') between the two outer coils (3 ') thus positioned, c) inserting two security strips (12) made of electrically insulating material into each coil interior (29) along the outer surfaces of the yoke (2), d) inserting a plate-shaped spacer (15) into each coil interior (29) of the three coils (3 '), e) inserting the outer and middle longitudinal legs (1a, b) into the interiors (29) of each of the three coils (3 ') or the several partial longitudinal legs (1b1, 1b2) one after the other in each interior (29) with one in between Spacers (15), f) placing spacers (15) on the upper end faces of the three longitudinal legs (1a, b), g) assembling a second yoke (2) from C-shaped bent sheets (4a, b), h) inserting the second yoke (2) with the extensions (7a, b) downward into the coil interior (29) of the two outer coils (3 ') between the securing strips (12), i) Applying the tensioning device (6) to the iron core (24) and bracing the two yokes against each other. Procedure according to Claim 21 , characterized in that before the three coils (3 ') are plugged in, the three coils (3') are mechanically connected to one another to form a coil unit. Method according to one of the preceding method claims, characterized in that the clamping device (6) is attached by - placing a clamping plate (17) above and below the iron core (24) on the outer sides of the yokes (2), - arranging and tightening clamping screws (25) between the two clamping plates (17) laterally next to the iron core (24) and the coils (3 '). Method according to one of the preceding method claims, characterized in that the inductor is coated on the outside in an electrically insulating manner.

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