DE102011056667A1 - Electric circuit i.e. power factor controller circuit, for use in inverter to supply electrical power from photovoltaic direct current generator into alternating current network, has storage throttle energized to produce magnetic flux - Google Patents

Abstract

The circuit has a throttling device (1) whose outer windings (8-10) are arranged on a common core (2) that comprises multiple middle and outer wound legs (3-5) running next to each other, where the legs are connected at two ends. Two storage throttles (11, 12) of a transducer are arranged with the windings on the legs. The outer windings include equal number of turns on the legs, and are connected with one another such that one of the storage throttles is energized to produce magnetic flux that is oriented relative to circumference of the core in same direction. The core is selected from EI-core, EE-core or M-core.

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to an electrical circuit having a two converter operated in time-shifted mode converter stage, wherein the two converters each comprise a storage choke to provide an inductance, wherein the two storage chokes are part of a throttle device having a plurality of windings, and to an inverter for feeding of electrical energy from a photovoltaic DC generator in an AC network with such an electrical circuit.

Under operated in time-shifted mode converters of a converter stage are those converters that are operated alternately, for example, each during a half-wave of an output alternating current or even with the frequency of a clock signal for switches of the converter alternately. Ie. the transducers are activated in rapid succession in very frequent repetition. Such transducers include u. a. so-called interleaving converter.

STATE OF THE ART

There are various electrical circuits in which two or more magnetic memories, referred to as storage chokes in this application, are provided for alternate use. These known electrical circuits include those of so-called Power Factor Controllers (PFC) for the network connection of electrical equipment and systems, those of inverters for feeding electrical energy and those of converter stages with operated in time-shifted mode converters. Each storage choke takes up a considerable amount of space and has a considerable mass. In particular, the magnetic circuit of each storage choke is always designed so that the storage of the maximum amount of energy required is possible. This sets the magnetic circuit fixed framework for the interpretation. In the conceivable use of the same magnetic circuit for two storage chokes, the problem arises that this results in a magnetic coupling which causes at least additional stress in the respective non-active circuit parts via the induction in the winding of the respective other storage choke. From the use of the same magnetic circuit for a plurality of storage chokes is therefore taken distance so far.

From the DE 100 42 283 A1 For example, a throttle device having a plurality of windings on a common core is known, wherein the core has three side by side wound legs, which are connected to each other at its two ends and wherein the two windings on the two outer legs have the same number of turns. In this case, the windings on the two outer limbs are connected to the winding on the middle limb in such a way that the windings on the outer limbs of the current fed by the energized winding on the middle limb increase magnetic flux through the core. In this case, the windings on the two outer legs opposite winding directions relative to the circumference of the core. The windings on all three legs are thus part of a single storage choke. The core of the known throttle device has two laterally without air gap juxtaposed partial cores, which in turn are each formed as a UU core, wherein the two U-elements in the two sub-cores are each opposite an air gap, the same gap width in the outer leg and the middle leg of the core.

From the US 5,600,293 A An electric circuit for a magnetic explosive device is known. This magnetic explosive device has two transformers whose windings are arranged on a common core. The core has three juxtaposed wound legs, which are interconnected at both ends. The windings of the first transformer are arranged on the middle leg, and the windings of the second transformer are respectively arranged on both outer legs, wherein both windings of the second transformer on both outer legs each have the same number of turns and are connected to one another at a Applying current generate a magnetic flux, which is oriented in the same direction relative to the circumference of the core. The primary windings of the two transformers also serve as inductors of DC / DC converters. The two transformers are never operated simultaneously. It is emphasized that an inductive interference between the two transformers is minimized by the construction of their windings. Preferably, the core of the transformer is a planar magnetic device and the windings are printed circuit traces. Alternate operation of the two transformers is in the US 5,600,293 A as well as an application of the two transformers in a different technical field than with a magnetic explosive device.

OBJECT OF THE INVENTION

The invention has for its object to provide an electrical circuit with two operated in time-shifted mode converters whose inductances are provided by a throttle device with a small space and small mass.

SOLUTION

The object of the invention is achieved by an electrical circuit with the features of independent claim 1. Preferred embodiments of the new throttle device are defined in the dependent claims 2 to 12. Dependent claim 13 is directed to an inverter for feeding electrical energy into an AC mains with the new electrical circuit.

DESCRIPTION OF THE INVENTION

In the throttle device of the electrical circuit according to the invention, a first storage choke comprises only the winding on the middle leg, while a second storage choke comprises the windings on the two outer limbs. The two windings on the two outer legs, which have the same number of turns, are connected to one another in such a way that they have the same effective winding direction around the circumference of the core, ie. h., When energizing the second storage throttle produce a magnetic flux, which is oriented in relation to the circumference of the core in the same direction.

This construction has the consequence that a current supply of the respective one of the two storage chokes does not result in the induction of voltages across the respective other storage choke. When the first storage choke is energized, the magnetic flux caused by the central leg of the core for the return flow divides on the two outer legs. Thus, in the two windings belonging to the second storage choke, although voltages are induced on the outer limbs which, because of the same number of turns of these windings, are equally large, they are opposite because of the winding direction reversed in relation to the magnetic flux from the middle leg Signs have and therefore cancel. Conversely, energization of the second storage choke causes magnetic flux to be caused either only by the circumference of the core, that is to say by the outer limbs and by the connections of the ends of the limbs, and thus no magnetic flux passes through the middle limb. the changes of which could cause stresses across the winding on that leg, or equal large opposite magnetic fluxes caused by the central leg, canceling out their effects on the winding on the middle leg. Thus, the core of the new throttle device is used by both storage chokes without inducing voltages in the other storage choke. The double use of the core saves volume and mass.

In the electrical circuit according to the invention, the two storage inductors are alternately charged with a current. That is, while one storage choke is active, the other storage choke is inactive. The common use of the same core of the throttle device leads to no problems, since it is excluded by the arrangement and design of the windings on the individual legs of the core that alternating voltages are induced by the one storage inductor in the other, inactive storage inductor. At the same time, saturation of the core is avoided since the maximum magnetization through the two storage chokes occurs at different times.

Since the two storage throttles of the throttle device are associated with two transiently operated transducers of a converter stage, the change between the energization of the respective inductors with each change between the two converters, so for example between the two half-waves of an output by the converter stage alternating current. This can be in an inverter for feeding electrical power into an AC mains z. B. be achieved in that the two storage chokes of the new electrical circuit, the inductances of two alternately operated buck converters of the inverter and are operated according to an interleaving method, that are alternately energized with the half-waves of the output AC. Each buck converter in each case forms the half-waves of a sign or a direction of current flow. In principle, in the case of the throttle device of the electrical circuit according to the invention, it is conceivable that each of the outer legs has an equally large cross-sectional area as the middle leg of the core. With regard to the saving of space and mass, however, it is preferred if the middle leg has a cross-sectional area twice as large as each of the two outer legs, or in other words, the two outer legs together have the same cross-sectional area as the middle leg.

In one embodiment of the throttle device of the electrical circuit according to the invention, which is also referred to here as variant A, the core is an EI, EE or M core; that is, it has a transverse undivided central leg.

In an embodiment of variant A, each winding on the two outer legs has half the number of turns of the winding on the middle leg, or in other words, the total number of turns of the windings on the two outer legs is the same as the number of turns of the windings on the middle leg. In this case, an equal inductance is achieved under the further condition that an air gap in the middle leg is three times as large as an air gap in the outer legs.

In another embodiment of variant A, the two outer legs have air gaps of the same width, while the middle leg has no air gap. In this embodiment, a same inductance of the two inductors results, provided that each winding on the two outer legs has the same number of turns as the winding on the middle leg. The width of the air gaps is considered to be the same here, if their dimensions at most differ so little from each other that there are no differences that are critical for the purposes of the invention. In particular, production-related tolerances of the width of the air gaps do not eliminate their equality.

Same number of turns of the windings on all three legs and a corresponding double the total winding number of the second storage throttle as the first storage throttle are also preferred in one embodiment of the new throttle device, which is also referred to as variant B. In this variant B, the core is divided between its two outer legs by a lateral air gap in two sub-cores, wherein the lateral air gap passes through the middle leg and this quasi in one to the winding on the one outer leg and another to the winding on divided into the other outer leg belonging half. Also, overall, the two partial cores of the core of the new throttle device in variant B are preferably the same. They can each be constructed as a UI or UU core.

In variant B, it is preferred if all legs of the core have the same, that is to say air gaps of the same width, in order to achieve identical inductances of the two storage chokes.

Advantageous developments of the invention will become apparent from the claims, the description and the drawings. The advantages of features and of combinations of several features mentioned in the description are merely exemplary and can take effect alternatively or cumulatively, without the advantages of embodiments according to the invention necessarily having to be achieved. Further features are the drawings - in particular the illustrated geometries and the relative dimensions of several components to each other and their relative arrangement and operative connection - refer. The combination of features of different embodiments of the invention or of features of different claims is also possible deviating from the chosen relationships of the claims and is hereby stimulated. This also applies to those features which are shown in separate drawings or are mentioned in their description. These features can also be combined with features of different claims.

BRIEF DESCRIPTION OF THE FIGURES

In the following the invention with reference to preferred embodiments with reference to the accompanying drawings is explained and described in detail.

1 shows the structure of a first embodiment of a throttle device of the electrical circuit according to the invention, which is referred to here as variant A.

2 shows a magnetic equivalent circuit diagram of the variant A of the throttle device according to 1 ,

3 shows a second embodiment of the throttle device of the electrical circuit according to the invention, which is referred to here as variant B.

4 shows a magnetic equivalent circuit diagram of the variant B of the throttle device according to 3 ,

5 shows a complete magnetic equivalent circuit diagram of the variant B of the throttle device according to 3 ,

6 shows a magnetic equivalent circuit diagram of the variant B of the throttle device according to 3 assuming a decoupling between two sub-cores of the core of this throttle device.

7 outlines the winding window of a memory choke according to the prior art with a core having two split cores, wherein the split cores are each formed of UU cores.

8th illustrates the winding window of a throttle device in variant B.

9 is a plot of the normalized copper volume versus the ratio between the width of the winding window according to FIG 8th and the width of the core of the new throttle device.

10 is a plot of the normalized core volume for different winding window heights and different core thicknesses with constant width and wrap window height of 20.

11 is a plot of the normalized core volume for different winding window heights and different core thicknesses with constant width and wrap window height of 30; and

12 FIG. 12 is a circuit diagram of one embodiment of the electrical circuit with two storage chokes according to the invention, which may be implemented by the new throttle device.

DESCRIPTION OF THE FIGURES

1 shows a throttle device 1 with a core 2 , The core 2 has a middle leg 3 and two outer thighs 4 and 5 on. The thigh 3 to 5 run parallel side by side and are at both ends by connections 6 and 7 connected with each other. The structure of the core is three times mirror-symmetrical with a first mirror symmetry plane parallel to the plane of the drawing, a second mirror symmetry plane perpendicular to the plane of the drawing, and a third mirror symmetry plane perpendicular to the plane of the drawing. The core 2 is here designed as EE core, with an air gap 42 the width δ2 between the two E elements in the region of the middle leg 3 is greater than air gaps 41 of substantially equal width δ1 between the two E-elements in the region of the outer legs 4 and 5 , On the middle thigh 3 is a winding 8th a first storage throttle 11 arranged with a number of turns N2. On the two outer thighs 4 and 5 are each windings 9 and 10 arranged with the same number of turns N1 / 2, which together to form a second storage choke 12 belong, with the windings 9 and 10 a same winding direction around a circumference of the core 2 that is, around the core 2 without the middle thigh 3 and wherein the windings 9 and 10 as a series connection along the circumference of the core 2 connected to each other. Accordingly, energization of the storage throttle calls 12 with a current I1, a magnetic flux φ1 through the circumference of the core 2 that is through the outer thighs 4 and 5 and the connections 6 and 7 , showing the middle leg 3 spares and so no influence on the storage throttle 11 takes. Conversely, an energization of the storage throttle leads 11 with a current I2 that is in the core 2 two magnetic fluxes φ21 and φ22 are created in the area of the middle leg 3 fall in the same direction, but in relation to the windings 9 and 10 the storage throttle 12 on the outer thighs 4 and 5 have different directions and so no voltage across the storage choke 12 can induce as a whole.

It is also possible the mutual induction between the storage chokes 11 and 12 thereby avoiding that the winding direction of the windings 9 and 10 Power inductor 12 on the two outer thighs 4 and 5 based on the circumference of the core 2 is chosen in opposite directions, and the windings 9 and 10 be connected together so that when energized the storage throttle 12 with a current I1 the current flow directions through the windings 9 and 10 based on the circumference of the core 2 run in opposite directions and thus the in 1 shown configuration of the magnetic flux φ1 is generated. Due to the simultaneous antisense of the winding directions and the current flow directions when energizing the windings 9 and 10 results in a same effective winding direction of the interconnected windings 9 and 10 ,

In the magnetic equivalent circuit according to 2 besides the windings, the magnetic reluctances R _m11 , R _m2 and R _m12 connected in series with _{them are} due to the air gaps 41 and 42 in the thighs 4 and 5 respectively. 3 played.

3 shows an embodiment of the throttle device 1 in which the core 2 along the plane perpendicular to the plane of the drawing and vertically extending mirror symmetry plane in two sub-nuclei 14 and 15 divided, which are each formed as UU cores. Between the two sub-nuclei 14 and 15 runs one the middle leg 3 halving lateral air gap 16 , This lateral air gap has a decoupling of the two partial cores 14 and 15 of the core 2 result. This results from the energization of the storage throttle 12 with the current I1 here two separate magnetic fluxes φ11 and φ12 with the same direction of rotation through the two partial cores 14 and 15 , Due to their identical direction of rotation, the magnetic fluxes φ11 and φ12 pass through the two halves of the middle leg 3 but in the opposite direction and compensate each other in the winding 8th the storage throttle 11 , In terms of by the energization of the storage choke 11 with the current I2 caused magnetic fluxes φ21 and φ22 corresponds to the embodiment of the throttle device 1 according to 3 according to those 1 ,

The equivalent circuit of the throttle device 1 according to 3 , this in 4 shown, takes into account the additional lateral air gap 16 only by dividing the two reluctances R _m21 and R _m22 and their series connection with the reluctances R _m11 and R _m12 .

The table at the end of the description summarizes preferred embodiments of the two variants A and B of the new throttle device, which are explained in more detail below.

option A

In variant A of the new throttle device 1 according to 1 are the two windings 9 and 10 the storage throttle 12 arranged so that the resulting magnetic flux in the middle leg 3 becomes zero. This will cause no voltage in the other storage choke 11 with the winding 8th induced. Accordingly, no energy in the air gap 42 saved. The middle leg 3 of the core 2 in this case does not contribute to energy storage at all. Therefore, for the flux density:

In this case, the current I by series connection of the two windings 9 and 10 the storage throttle 12 with the total number of turns N ₁ = 2 · N _1/2 . The two air gaps 41 add up by their series connection to an air gap of the effective width 2δ ₁ on.

If, however, the storage throttle 11 with the winding 8th is energized with the number of turns N ₂ , which is in the storage throttle 12 induced voltage to zero, since the magnetic flux in the outer legs through both windings 9 and 10 has different signs. However, the magnetic flux is nowhere zero and so energy is stored distributed to all air gaps:

If the flux densities are to be the same, one can calculate from the above equation the ratio between the air gaps and the numbers of turns to be set.

The inductance L of each storage choke can be derived directly from the equations for the flux density. In the inductance L _{1 of} the storage throttle 12 with the windings 9 and 10 It should be noted that only half of the cross-sectional area of the middle leg 3 per winding is active. In the following, let A _{Fe be} the cross-sectional area of the middle leg 3 :

The inductance L _{2 of} the storage throttle 11 with the winding 8th is:

und damitIf L ₁ = L ₂ , then (4) and (5) follow:

and thus

Under the condition of equal (maximum) flux density, it follows from (1) and (2) or from (3):

bzw. δ₁ = (δ₁ + δ₂) (10) This results from the conditions of the same inductance and the same flux density:

respectively. δ ₁ = (δ ₁ + δ ₂ ) (10)

This only applies if δ ₂ = 0.

If only the same inductance is required, it can be deduced from (7):

For the same number of turns N1 = N2 is then δ ₂ = 3δ ₁ (12)

dann führt im Fall gemäß (12) die Bestromung der Speicherdrossel 12 zur doppelten Flussdichte wie die Bestromung der Speicherdrossel 11.Now consider the ratio of the flux densities

then leads in the case according to (12), the energization of the storage throttle 12 to twice the flux density as the current supply of the storage choke 11 ,

bzw. N₁ = 2·N₂ (15) However, if one chooses δ ₂ = 0, then Eq. (11):

respectively. N ₁ = 2 · N ₂ (15)

The energy storage takes place only in the two outer air gaps 41 and the maximum flux density is the same in both cases.

By dimensioning the storage chokes 11 and 12 in a manner such that both the flux produced by the chokes and the inductance of the two storage chokes are the same, it is achieved that the storage chokes 11 and 12 behave electrically largely identically, with a common core 2 use and at the same time are decoupled from each other and do not affect each other.

Variant B

The complete equivalent circuit of variant B of the throttle device 1 according to 3 is in 5 shown. The reluctances R _m01 and R _m02 represent the lateral air gap 16 between the 4 U cores. If the distance between the sub-cores 14 and 15 of the core 2 is very small, the reluctance of this air gap 16 also small. R _m = 1 / μ · A (16)

If the lateral air gap 16 but not neglected, but assumed with a certain size, then it can be seen as a decoupling of the two built-up of each 2 U-cores sub-nuclei 14 and 15 look at. This is in 6 illustrated.

In comparison with variant A, the magnetic fluxes are through the middle leg 3 from both sub-nuclei 14 and 15 of the core 2 (assuming that only the storage choke 12 is active) separated from each other. As a result, energy can also be in the air gap 42 get saved. The flux density in each sub-core 14 and 15 of the core 2 is so:

If only the storage throttle 11 with the winding 8th is active, then the following applies to the flux density:

If the flux densities are to be equal, one can directly derive from the equations above the ratio of the widths of the air gaps 41 . 42 to calculate:

It follows:

The inductance of each winding 9 respectively. 10 the storage throttle 12 can be derived directly from the equations for the flux density. Again, for each half, only half of the cross-sectional area of the middle leg is again 3 active.

Because the two windings 9 and 10 the storage throttle 12 are connected in series, the resulting primary inductance is the sum of the values according to (21).

The inductance of the storage choke 11 with the winding 8th is:

ist. Die Induktivitäten L1 und L2 sind somit gleich. Wegen der Trennung der beiden magnetischen Kreise ist die Energiespeicherung auch in den Luftspalten 42 des mittleren Schenkels 3 möglich, wenn die Speicherdrossel 12 aktiv ist. Somit ist es auch in dieser Variante möglich, die Speicherdrosseln 11 und 12 so zu dimensionieren, dass diese einen gemeinsamen Kern 2 verwenden und gleichzeitig weitgehend identische elektrische Eigenschaften aufweisen, ohne dass eine magnetische Kopplung zwischen den Speicherdrosseln 11 und 12 auftritt.From (22) it can be concluded that

is. The inductances L1 and L2 are thus the same. Because of the separation of the two magnetic circuits, the energy storage is also in the air gaps 42 of the middle thigh 3 possible if the storage choke 12 is active. Thus, it is also possible in this variant, the storage chokes 11 and 12 to be dimensioned so that these have a common core 2 use and at the same time have largely identical electrical properties, without a magnetic coupling between the storage chokes 11 and 12 occurs.

Considerations on the volume of construction

Given a storage choke, which is to be able to store a specific energy content E at a maximum current I _max , with a saturation induction B _SAT and a predetermined iron cross section A _FE .

The necessary for storing the energy E width δ of the air gap and the product N · I _max are thus fixed.

The current I _max requires at a maximum current density J _max and a filling factor k _f a winding window of

Exemplary of a core structure according to 7 from, wherein the height of the winding window with h and the width or depth of a leg is denoted by a, the magnetization cross section A _{FE is} equal to: A _Fe = 2a ² (27)

If the winding window is optimally filled by a winding on the middle leg, then the winding volume is:

For the core receives the minimum volume:

For two individual storage chokes, this results in a winding and core volume as references to:

The gross construction volume is then:

wird daher bevorzugt eine Verdoppelung der Höhe des Wickelfensters vorgenommen, was durch den Einsatz zusätzliche I-Kerne einfach auszuführen ist. Diese in 8 illustrierte Ausführung ist im Vergleicht mit der Erhöhung der Breite des Wickelfensters bevorzugt nicht nur wegen der einfacherer Aufbau sondern auch wegen der reduzierten AC und DC Wicklungsverluste (Wicklungen mit weniger Lagen und auch weniger Leitungsgesamtlänge).At the in 8th illustrated embodiment, the situation is similar to the reference situation in 7 , However, that is too 7 Corresponding winding window is occupied almost twice, through the windings 8th and 9 respectively. 10 , Because of the relationship

is therefore preferably made a doubling of the height of the winding window, which is easy to perform by using additional I-cores. This in 8th illustrated embodiment is preferred in comparison with the increase of the width of the winding window not only because of the simpler structure but also because of the reduced AC and DC winding losses (windings with fewer layers and also less total line length).

The air gap arrangement is the same. The entire winding then has the volume:

The ratio between the two winding volumes is:

The factor A _w / h · a is a ratio between the width of the winding window and the width of the core. In the case of ferrite U cores, values of A _w / h · a are between 1.2 and more than 3.5. Above values of A _w / h · a to 5 is in 9 the copper volume normalized to the reference value is plotted. Thereafter, for higher values of A _w / h · a from 2.5, a saving of approximately 10% of copper volume is to be expected.

The core volume of variant B is equal to the reference value plus the four additional I-cores:

It follows for the ratio of the volumes:

In the 10 and 11 the ratios for A _w / h are shown graphically equal to 20 mm and 30 mm. From this it becomes clear that a possible saving in core volume decreases with the enlargement of the winding window and the reduction of the iron cross section of the core. The higher the ratio A _w / h, the higher the saving potential.

The gross construction volume of variant B is:

12 outlines an inverter 17 for feeding electrical energy from a photovoltaic DC generator 18 in an AC network 19 as an embodiment of the electrical circuit according to the invention. In this case, the inverter points 17 two half-bridges 20 and 21 on, each with a buck converter 22 respectively. 23 combined. The half bridges 20 and 21 each have switches 24 and 25 respectively. 26 and 27 on, taking the switches 25 and 27 Freewheeling diodes 28 and 29 are connected in parallel. These freewheeling diodes 28 and 29 serve as diodes of the buck converter 22 and 23 , The switches 24 and 26 are the operation of the buck converters 22 and 23 clocked switch. Next include the buck converters 22 and 23 inductors 30 and 31 , Additional switches 32 and 33 serve the current return, bypassing the other buck converter 23 respectively. 22 , The switches 25 and 27 are for a normal half-bridge operation without lowering the voltage at open switches 32 and 33 intended. In this inverter 17 are storage chokes, which are the inductors 30 and 31 provide, used alternately, that is not at the same time. In order to save space and mass in these inductors, a new throttle device with two storage chokes is used to their realization.

LIST OF REFERENCE NUMBERS

1

throttling device

2

core

3

middle thigh

4

outer thigh

5

outer thigh

6

connection

7

connection

8th

winding

9

winding

10

winding

11

Power inductor

12

Power inductor

14

part core

15

part core

16

lateral air gap

17

inverter

18

DC generator

19

AC power

20

half bridge

21

half bridge

22

Buck converter

23

Buck converter

24

switch

25

switch

26

switch

27

switch

28

diode

29

diode

30

inductance

31

inductance

32

switch

33

switch

41

air gap

42

air gap

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10042283 A1 [0004]
• US 5600293 A [0005, 0005]

Claims (13)

Electrical circuit comprising a converter stage having two transducers operated in time-shifted mode, the two transducers each having a storage throttle ( 11 . 12 ) for providing an inductance ( 30 . 31 ), the two storage chokes ( 11 . 12 ) Part of a throttle device ( 1 ) with several windings ( 8th - 10 ), characterized in that the windings of the throttle device ( 1 ) on a common core ( 2 ), the core ( 2 ) three side by side wound legs ( 3 - 5 ), which are connected to each other at its two ends, wherein the storage throttle ( 11 ) of a converter, the winding ( 8th ) on the middle leg ( 3 ), wherein the storage throttle ( 12 ) of the other converter the windings ( 9 and 10 ) on the two outer thighs ( 4 and 5 ), wherein the two windings ( 9 and 10 ) on the two outer thighs ( 4 and 5 ) have the same number of turns and are connected to one another in such a way that they are energized when the second storage choke (FIG. 12 ) generate a magnetic flux related to the circumference of the core ( 2 ) is oriented in the same direction. Electrical circuit according to claim 1, characterized in that the middle leg ( 3 ) has a cross-sectional area twice as large as each of the two outer legs (FIG. 4 and 5 ) having. Electrical circuit according to claim 1 or 2, characterized in that the core ( 2 ) is an EI, EE or M nucleus. Electrical circuit according to claim 3, characterized in that each winding ( 9 . 10 ) on the two outer thighs ( 4 and 5 ) half the number of turns of the winding ( 8th ) on the middle leg ( 3 ) having. Electrical circuit according to claim 3, characterized in that the two outer legs ( 4 and 5 ) Air gaps ( 41 ) of equal width (δ1) and the middle leg has no air gap. Electrical circuit according to one of Claims 1 to 3 and 5, characterized in that each winding ( 9 . 10 ) on the two outer thighs ( 4 and 5 ) the same number of turns as the winding ( 8th ) on the middle leg ( 3 ) having. Electrical circuit according to claim 2 or claim 6, characterized in that a lateral air gap ( 16 ) the core ( 2 ) between its outer thighs ( 4 and 5 ) into two sub-nuclei ( 14 and 15 ), whereby the lateral air gap ( 16 ) longitudinally through the middle leg ( 3 ) runs. Electrical circuit according to claim 7, characterized in that the lateral air gap ( 16 ) the core ( 2 ) into two equal sub-nuclei ( 14 and 15 ) Splits. Electrical circuit according to claim 7 or 8, characterized in that each sub-core ( 14 . 15 ) is a UI or UU core. Electrical circuit according to claim 7, 8 or 9, characterized in that all limbs ( 3 - 5 ) Air gaps ( 41 and 42 ) with the same width (δ1 and δ2). Electrical circuit according to one of the preceding claims, characterized in that the two storage chokes ( 11 and 12 ) the inductances ( 30 and 31 ) of two buck converters ( 22 and 23 ) of an inverter ( 17 ) are. which are set up for alternate operation. Electrical circuit according to claim 11, characterized in that the two buck converters ( 22 and 23 ) alternately form a half-wave of an output alternating current. Inverter ( 17 ) for the supply of electrical energy from a photovoltaic DC generator ( 18 ) into an AC network ( 19 ) with an electrical circuit according to one of the preceding claims.

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