EP3021332A1 - Inductivity and method for producing same - Google Patents

Abstract

In order to improve the function of an electrical inductance, the parts of the iron core (24) are held only positively in the coil unit (31) by appropriate construction of the inductance.

Description

I. Field of application

The invention relates to a method for producing "inductors with iron core", including generally electrical transformers, electric reactors, electrical filters, electromagnets, etc., hereinafter referred to as "inductance", as well as an inductance produced by this method.

The present application focuses on inductors for use as electrical reactors (line and commutating reactors, filter reactors, motor reactors, etc.) and electrical filters for use with frequency converters (sine-wave filters and du / dt filters, etc.).

II. Technical background

Electrical inductances are contained in a great many electrical and electronic devices, and their main purpose is to convert or separate one or more, in particular different, voltage potentials, in current limitation, the reduction of voltage rising edges, the compensation of harmonic components or in the formation of a magnetic field.

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

Their windings can be wound on a bobbin, which is usually made of an electrically non-conductive material, usually plastic be present or as so-called air coils, which have no bobbin as a winding core.

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

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

In order to avoid eddy currents, this is usually made of a stack of superimposed individual, rolled sheets, so-called dynamo sheets or transformer sheets, wherein the individual sheets must be electrically isolated from each other. For this purpose, the individual sheets are coated on the rolled surfaces usually with an electrically insulating insulating or possess here an electrically insulating oxidation layer.

To hold the sheets permanently as an iron core (hereinafter also referred to as a laminated core), these are often isolated with each other through through holes in the sheets screwed with screws, clamped by means of pressure pieces or welded at the edge.

In this case, the usually required mounting bracket or other attachments to the inductor, with the laminated core, screwed, welded or braced.
The laminated core can enclose the coil partially or fully encircling, wherein the sheets of different formats and sizes joined together form the iron core of the inductor. Thus, among other standardized sheets so-called E, UI or M blanks can be merged into a laminated core.

In order to get to the required thickness of the laminated core, two or more sheets per layer and in particular from layer to layer are rotated by 180 ° usually piled up, which is a very high and usually only manually manageable workload.

In this case, yes, the visible in the plan view of the sheet metal contour of each layer in a circumferentially closed iron core is not a single sheet, but this is composed because of the mountability of at least two sheets.

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

• 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 same structure of transformers on the one hand and chokes or filters on the other hand, they should have different properties in operation, which in detail also requires different structural details, if one wants to optimize the desired function in each case in the foreground:

• For example, in the case of transformers, the focus is on efficiency, ie the reduction of power loss:
  • For this purpose, an attempt is made to minimize the magnetic resistance of the iron core as possible. In the case of the mostly circumferentially closed iron cores, which for assembly reasons can not be composed of individual, annularly closed metal sheets, this means that the occurring at the contact point between adjacent plates of the laminated core magnetic resistance should be kept as low as possible, which is attempted by measures such as minimizing the air gap between them or even stuffing with magnetic material in the joint.

On the other hand, with chokes and filters, which are a passive attenuator, for example, for filtering out the harmonic harmonics, a defined air gap is needed just because it just causes the desired damping. The desired damping behavior in each case is determined by the size and arrangement of the air gaps in the iron core, ie in or between the laminated cores.

Another issue that is most prevalent with chokes and filters is often the reduction in noise emission on frequency controlled motors and protection of the motor insulation by reducing the voltage ramp edges (e.g., by long motor supply lines).

III. Presentation of the invention a) Technical task

It is therefore the object of the invention to provide an inductance, in particular for use as a choke or filter, as well as a method for its production, so that the production cost is reduced and the function of the inductance is improved, in particular as a choke and filter.

b) Solution of the task

This object is solved by the features of claims 1, 10 and 13 . Advantageous embodiments will be apparent from the dependent claims.

• 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.

The specific design of the inductance according to claim 1 results in a number of advantages:

• By the two projections at the ends of each yoke, which protrude into the inner space of each a coil, the assembly is facilitated 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 protrusion in the middle, so that the middle longitudinal leg is just as long or longer than the coil that is arranged around it. In order not to be able to displace the middle coil together with the central longitudinal leg out of the plane of the iron core, securing strips (made of electrically insulating material) are inserted on both sides of the longitudinal limb, which are longer than the central longitudinal limb and extend into the region of the yokes extend into it and thereby form a positive locking against lateral withdrawal of the central coil and the central longitudinal leg.

Functional advantages, namely a good electrical damping by means of this inductance, is achieved by first of all the air gaps can be dimensioned as needed by 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 longitudinal legs do not have to be each one piece, but in their direction of extension may consist of several sections.

In the case of the outer longitudinal limbs, the coil preferably extends over the air gaps between the outer longitudinal limb and the extension of the yoke, so that there - even if additional air gaps are provided - all the air gaps are within the length of the coil, which is very advantageous for the function as throttle or filter (minimization of stray fields).

• 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.

The fact that the yokes are free from breakdowns and that the entire iron core - except for the two large interiors between the longitudinal limbs - is free of breakdowns, since, for example, no through holes through the plates are required for cross-threaded connections, makes the magnetic field much more homogeneous , as in the presence of 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 the ends, and not in the middle area:

• By means of the corresponding C-shaped sheets yokes can be produced without internal openings in this way, in which the sheet plane of the individual sheets runs transversely to the main plane of the finished iron core.

The iron core is held together by a tensioning device acting only from the outside, which does not penetrate the iron core, and which is additionally variable in the spacing of its clamping plates, that is, when e.g. different thickness spacers are used in the air gaps.

Preferably, the longitudinal legs should have the same cross-section as the extensions of the yoke, and in particular the sheet planes in the longitudinal limbs run in alignment with those in the extensions in order to achieve a homogenization of the magnetic field forming.

Preferably, the central longitudinal leg thus ends in front of the inner surfaces of the C-shaped yoke in its central region, usually with an air gap to the yoke. The thus not existing positive securing the middle longitudinal leg is achieved by the additional, already mentioned securing strips.

The air gaps are usually effected by inserted spacers made of electrically insulating material, which is a very easy way to produce air gaps defined width.

The longitudinal legs are generally cuboid and then consist of stacked rectangular plates. The coils around the individual longitudinal limbs have an axial length, that extends in the longitudinal direction of the longitudinal leg, which fills the distance between the two yokes as completely as possible in order to effect a positive securing of the longitudinal position of the coils within the iron core alone.

The yokes are not bent at the transition from their main part in the extension just 90 °, but cranked twice by 45 ° and thus have at their ends a slope, both in its outer contour and in its inner contour, and all the 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 inductance, the individual longitudinal limbs may be formed in several parts in their course, with free choice between the length of these items as well as the width of the air gaps therebetween. 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 dielectricity in the interior of the air gap.

The cross-sectional area of the longitudinal legs and the extensions of the yokes is dimensioned so that they fill together with the inserted on both sides of the fuse strip exactly the inner space of each coil and Thereby, a precisely fitting positive locking between the coil on the one hand and iron core on the other hand is given.

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

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

The tensioning device is preferably made of two clamping plates which are placed on the outer sides of the yokes and have a projection either in the main plane of the iron core or transversely thereto or both. At their supernatant, the two clamping plates are clamped by means of clamping screws in the longitudinal direction against each other, and thus press the yokes against each other, so that a pressure on the spacers, which define the air gaps, constructed and maintained.

This pressure on the spacers causes the noise emissions of the inductor to be much lower during operation than with little or no bias against the spacers.

In order to ensure a positive securing of the clamping plates with respect to the iron core transversely to the main plane, the clamping plates are preferably formed as hat profiles.

Preferably, the clamping plates also have further passage openings in addition to the holes for the clamping screws that penetrate them. in order to drain the casting agent in the subsequent wetting or potting the entire assembled inductance.

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

Preferably, the clamping plates are wider than the iron core measured transversely to its main plane and also wider than the coils in this direction, firstly to be able to attach clamping screws in the projection, but also to provide a protective projection 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.

Because of this constructive construction of the inductance, a modular system can be created, so that a very wide range of differently designed inductances can be produced by means of a relatively small number of different components:

• Of course, the kit must always contain at least one sort of the compelling components, ie coil, yoke, tensioning device, middle and outer longitudinal leg and securing strips.

If only several types of spacers of different thickness are already part of the kit, inductances with different damping behavior can be produced depending on the chosen spacer.

Of course, the variation width is even greater, although the modular system contains several varieties, for example several partial longitudinal limbs, in order to be able to assemble middle and outer longitudinal limbs from these partial longitudinal limbs. The resulting changing dimensions of the iron core in the longitudinal direction of the longitudinal struts can without problems by correspondingly long external thread on the Clamping screws of the clamping device can be compensated or for large differences in length by differently long clamping screws within the kit.

Preferably, the kit can also include several varieties of different lengths coils and fuse 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 inductance according to claim 1 by the method steps of claim 21 :

• To build up the inductance, however, a very simple device is used, theoretically, the assembly could also be done purely manually: After assembling the yokes of individual sheets, a coil is attached to the extensions of the first yoke, or - if the three coils before unit - the entire coil unit.

Subsequently, after inserting the spacers into the inner free spaces of the coils, the outer longitudinal limbs are inserted into the outer coils, and the middle longitudinal limb is inserted into the middle coil.

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

Now, the second yoke can be inserted with its extensions in the outer coils - again with the interposition of a spacer - and the clamping device are mounted, which presses in this position, the two yokes against each other. 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 screwed the clamping screws.

c) embodiments

Fig. 1:

die Induktivität in Explosionsdarstellung,

Fig. 2a-c:

verschiedene Varianten des Eisenkerns,

Fig. 3a-c:

die Induktivität im zusammengebauten Zustand.

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

Fig. 1:

the inductance in exploded view,

Fig. 2 a-c:

different variants of the iron core,

Fig. 3a-c :

the inductance in the assembled state.

The iron core 24 off FIG. 1 is in FIG. 2a shown in the plan on its main plane 16 , and in FIG. 2b in the side view, ie in the direction of view of this main plane 16th

As in FIG. 2a to recognize the iron core 26 in the plan view of its main plane 16 of an annular encircling laminated core with approximately square shape and bevelled corners, consisting of an upper and a lower, C-shaped yoke 2. Each of the yokes 2 has at its ends in right angle to the direction of extension of the yoke 2 in the same direction projecting extensions 7 a, b.

The extensions 7 a, b of the lower yoke 2 are directed upward, the extensions 7 a, b of the upper yoke 2 are directed downward, and are aligned with the projections 7 a, b of the lower yoke . 2

The transition of the main part of the yoke 2 to the extensions 7 a, b has in each case a slope 14 , so two bends by 45 °.

The yokes 2 are composed of individual, in this form C-shaped, sheets 4 a, b, which are placed inside each other and fit into each other, built.

Between the mutually aligned extensions 7 a on the one hand and 7 b on the other hand is in each case an outer longitudinal leg 1 a, also consists of individual, in this case rectangular, parallel to each other laid sheets.

In addition, located in the inner space 5 of this annular rotating laminated core 24, a middle longitudinal leg 1 b, which extends substantially from the inner sides of a yoke 2 in its central region to the inside of the other yoke 2 and also from parallel to each other, not at all interconnected, rectangular sheets 4 x, y and runs parallel to the outer longitudinal limbs 1 a.

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

The cross-sectional area of the outer longitudinal limbs 1 a, b is the same and preferably coincides with the cross-sectional area of the central longitudinal limb 1 b, so that the same spacers 15 can be used for all longitudinal limbs, if the thickness of the air gap 13 should also be the same.

Both the central longitudinal limb 1 b and the outer longitudinal limb 1 a can also each consist in their extension direction of several partial longitudinal limbs 1 b 1 , 1 b 2 , as in an alternative embodiment in Figure 2c shown.

Both the structure of the longitudinal limbs of one or more partial longitudinal limbs and the thickness of the spacers 15 depends on the respective intended use of the inductance. In simple terms, the purpose of the invention is to have as many possible variations as possible the structure and the details of the iron core to have despite an easy to implement construction of the inductance.

• Zunächst muss - siehe linke Bildhälfte der Figur 1 - der Eisenkern 24 mit der Spuleneinheit 31 zusammengebaut werden, von der in Figur 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 19a, b aufgebracht sind unter Verwendung des Spulenkörpers 3 als Wickelkern 20, wie in Figur 3a - c zu sehen.

The procedure for the construction of the inductance can best be seen from the exploded view of the FIG. 1 be explained:

• First of all - see the left half of the picture FIG. 1 - The iron core 24 are assembled with the coil unit 31 , from the in FIG. 1 only the usually made of plastic, sleeve-shaped bobbin 3 are shown, around their outer surfaces around but before assembly, the electric coil 3 with its windings 19 a, b are applied using the bobbin 3 as a hub 20, as in FIG. 3a - to see c .

• 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 is as follows:

• After the lower yoke 2 is composed of sheets 4 a, b, the two outer bobbin 3 are attached to the upwardly projecting extensions 7 a, b of this lower yoke 2 , and also set the middle bobbin 3 between the two outer bobbin 3 , the then seated on the top of the yoke 2 in its central region.

Subsequently, one of the plate-shaped spacers 15 are inserted from above into the coil interiors 29 of the bobbin 3 , so that they rest with their main surface on the end face of one of the extensions 7 a, b and thus lie transversely in the coil interior 29 , the Cross sections of the extensions 7 a, b also substantially fill.

However, the iron core 24 has a measured transversely to its main plane 16 depth which is less than the corresponding extension of the cross section of the coil interior space 29, namely lower by so much that both sides of the iron core 24 are each just a securing strip 12 along each of the longitudinal limb 1 a, b can be interposed, what is now performed as the next step by inserting from above into the coil interior 29th

The securing strips 12 are longer than the central longitudinal leg 1 b, and are pushed in the central bobbin 3 so far down that its lower end extends into the region of the lower yoke 2 .

On the other hand, this represents the form-fitting securing so that, in the assembled state, the middle bobbin 3 can not be pulled out of it transversely to the main plane 16 of the laminated core 24 .

Now, the longitudinal legs 1 a, b are inserted from above into the individual bobbin 3 between the respective two securing strips 12. If one of the longitudinal legs 1 a, b consists of several partial longitudinal limbs 1 b 1 , 1 b 2 , these are used successively , each with the interposition of a spacer 15th

On the upper ends of the inserted longitudinal legs 1 a, b spacers 15 are also placed and then the previously composed of sheets upper yoke 2 with its extensions 7 a, b pointing down into the coil interiors 29 of the two outer bobbin 3 inserted between the there backup strip 12th

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

The transversely projecting rear and forward projections 23 a, b of the hat profile have mutually aligned holes 26 through which the two clamping plates 17 can be braced against each other by means of clamping screws 25 , and thereby hold the iron core 24 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 this from the clamping plates 17 and the clamping screws 25 existing clamping device 6 on the iron core 24 6 other components can be attached to the jig:

• Thus, on the upper clamping plate 17, a so-called. NS rail 27 can be screwed, which serves for the positive fastening of transformers 28 , which are required for some applications of this inductance.

Likewise, at the bottom of the lower clamping plate 17, a further clamping plate 17 are fixed so that the hat-shaped bulges are directed against each other. This lowermost clamping plate 17 can serve, for example, the screwing against the ground or another machine part.

Likewise, either at the lower clamping plate 17 or an additional lowermost clamping plate 17, a support plate may be attached, which protrudes from the cross section of the hat profile of the clamping plate 17 to the side and the fastening of capacitors 30 , which are also required for certain applications of the inductance.

The FIGS. 3a c show the assembled state in various views of the inductance according to FIG. 1 ,

LIST OF REFERENCE NUMBERS

1a, b

longitudinal leg

1a1, 1a2

Partial longitudinal legs

2

yoke

3

bobbins

3 '

Kitchen sink

4 a, b, x,

y sheet metal

5

inner space

6

jig

7 a, b

extension

8th

Glue

9 a, b

face

10

longitudinal direction

11

Transverse direction, direction yoke

12

Security strips

13

air gap

14

slope

15

spacer

16

main level

17

chipboard

18

thickness

19 a, b

winding

20

winding core

21

faceplate

22

Through opening

23a, b

Got over

24

magnetic flux guide, iron core

25

clamping screw

26

drilling

27

NS rail

28

transformer

29

Coil interior

30

capacitors

31

coil unit

Claims (15)

Electrical inductance, in particular electrical passive attenuator, with - One of mutually insulated sheets ( 4 a, b) to form a laminated core iron core (24) as a magnetic flux guide ( 24 ) - Three parallel spaced apart, in the longitudinal direction (10) extending longitudinal limbs ( 1 a, 1 b, 1 a), - two yokes (2), each yoke (2) connecting the ends pointing to the same side of the longitudinal limbs ( 1 a, b) to form an air gap, - The yokes (2) made of C-shaped, accurately nested sheets ( 4 a, b) exist, - Three annularly closed circumferential coils (3), each of which fits around one of the longitudinal legs ( 1 a, b) passes around characterized in that - each yoke (2) at both ends of the course (11) of the yoke (2) in the longitudinal direction (10) abstrebende extensions ( 7 a, b), - Between each two oppositely directed projections ( 7 a, b) of the two yokes (2) each have an outer longitudinal leg ( 1 a) is arranged to form an air gap (13) , - The yokes (2) by means of a clamping device (6) whose parts ( 6 a, b) are arranged outside the laminated core, are braced against each other, - The finished iron core (24) except the two interiors between the longitudinal legs ( 1 a, b) is free from breakthrough, - Between the middle longitudinal leg ( 1 b) and the inner wall of the coil (3 ') or the bobbin (3) a securing strip (12) of electrically insulating material is arranged, which is longer than the length of the central longitudinal limb ( 1 b) and on both sides to the area of the yokes (2) ranges. Inductance according to claim 1,
characterized in that
the outer longitudinal limbs ( 1 a) have the same cross-section as the extensions ( 7 a, b), and / or
the central longitudinal limb ( 1 b) ends at an interval around 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
in the air gaps (13) spacers (15) are arranged made of insulating electrical insulating material, and / or
the longitudinal limbs ( 1 a, b) consist of stacked rectangular sheets (4 x, y) whose sheet planes are aligned with the sheet planes of the sheets ( 4 a, b) in the extensions ( 7 a, b). 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) , and / or
the coils (3) have a bobbin (3 ') made of plastic, on which the winding ( 19 a, b) is applied. Inductance according to one of the preceding claims,
characterized in that
the sheets ( 4 a, b) of the yokes (2) at the transition from the main part of the yoke (2) in the extension a slope (14), in particular by cranking at 45 °, have, and / or
the coils (3 ') on the outer longitudinal limbs ( 1 a) are so long that they cover the air gaps (13) between the outer longitudinal limbs ( 1 a) and the extensions ( 7 a, b) of the yokes (2) . Inductance according to one of the preceding claims,
characterized in that
the longitudinal legs ( 1 a, b) can be designed in several parts by being interrupted in their extension in the longitudinal direction (10) by air gaps (13) in which spacers (15) are located, and / or the particular plate-shaped spacers (15) have the same area as the cross section of the longitudinal limbs ( 1 a, b), in whose air gaps (13) they are located. Inductance according to one of the preceding claims,
characterized in that
the tensioning device (6) consists of two clamping plates (17) which lie on the outer sides of the yokes (2) and are braced against each other on their projections ( 23 a, b) by clamping screws (25) in the longitudinal direction (10) , and in particular the Clamping plates (25) consist of a hat profile. Inductance according to one of the preceding claims,
characterized in that
the inductance of a curing plastic wetted, in particular in this shed is, and / or
the clamping plates (17) except the holes (26) for the clamping screws (25) through openings (22) for the drainage of the casting agent. Inductance according to one of the preceding claims,
characterized in that
on the clamping plate (17), and in particular between the clamping plate (17) and yoke (2), a rail, in particular an NS rail (27) for fixing transformers (28) is arranged, and / or
the clamping plate (17) viewed in the plan view is at least as wide as the coils (3 '). Building block for producing an inductance, with at least one sort of coils (3 '), - at least one variety of yokes (2), - at least one kind of tensioning device (6), - at least one kind of medium longitudinal limb ( 1 b), - at least one sort of outer longitudinal limb ( 1 a), - at least one sort of securing strip (12),
characterized in that
the kit comprises several types of spacers (15) of different thicknesses. Building kit according to claim 10,
characterized in that
the modular system comprises a plurality of partial longitudinal limbs (1 a 1, 1 a 2 ) for creating middle ( 1 b) and outer ( 1 a) longitudinal limbs. Building kit according to one of the preceding claims,
characterized in that
the modular system comprises a plurality of different lengths of coils (3 ') and / or fuse strips (12) of different lengths and / or clamping devices (6) of different lengths, in particular with different clamping screws (25) . Method for producing an inductance, the - An iron core (24) with three spaced longitudinal limbs ( 1 a, 1 b, 1 a) and two C-shaped yokes (2) with end extensions (7 a, b) and - Three coils (3 ') and a tensioning device (6)
comprising the following steps: a) assembling a first yoke (2) from sheets ( 4 a, b) and arranging the yoke (2) with upwardly pointing projections ( 7 a, b), b) placing the two outer coils (3 ') on the extensions ( 7 a, b) and inserting the middle coil (3') between the two outer coils (3 ') thus positioned , c) insertion of two securing strips (12) 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) insertion of the outer and the central longitudinal limb ( 1 a, b) into the interiors (29) of each of the three coils (3 ') or the plurality of partial longitudinal limbs ( 1 b 1 , 1 b 2 ) successively in each inner space (29 ) with interposition of a spacer (15), f) placing spacers (15) on the upper end faces of the three longitudinal limbs ( 1 a, b), g) assembling a second yoke (2) of C-shaped cranked sheets ( 4 a, b), h) inserting the second yoke (2) with the projections (7a, b) down into the coil inner spaces (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. Method according to claim 13,
characterized in that
before attaching the three coils (3 '), the three coils (3') are mechanically connected to a coil unit, and / or the inductance on the outside electrically insulating coated, in particular electrically insulating shed, is. Method according to one of the preceding method claims,
characterized in that
the attachment of the clamping device (6) is carried out by - applying a clamping plate (17) above and below the iron core (24) on the outer sides of the yokes (2), - Arranging and clamping of clamping screws (25) between the two clamping plates (17) laterally adjacent to the iron core (24) and the coils (3 ').

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