EP2847770A1

EP2847770A1 - Three-phase choke

Info

Publication number: EP2847770A1
Application number: EP13717964.4A
Authority: EP
Inventors: Wojciech GIENGIEL
Original assignee: Wobben Properties GmbH
Current assignee: Wobben Properties GmbH
Priority date: 2012-05-07
Filing date: 2013-04-24
Publication date: 2015-03-18
Also published as: WO2013167382A1; MX2014012102A; RU2014149233A; AU2013258290A1; KR20150002731A; TW201405596A; JP2015520948A; ZA201407046B; AR090946A1; CN104285263A; DE102012207557A1; CL2014003006A1; CA2868697A1; BR112014027162A2; US20150102881A1

Abstract

The invention relates to a magnetic core (20) of a three-phase choke (10) comprising a first, second and third magnetic leg (1, 2, 3) for receiving a respective first, second and third electrical winding (L₁, L2, L3) of a respective first, second and third electrical phase, wherein the first, second and third legs (1, 2, 3) are arranged in a star-shape or a triangular shape.

Description

Three-phase choke

The present invention relates to a three-phase reactor and a magnetic core for such a reactor.

Chokes, in the electrical engineering sense, are well known. Depending on the application, they have a filtering effect. In particular at the output of an inverter, they serve to ensure that a pulse-width-modulated current runs as sinusoidally as possible, before it is fed into an electrical supply network. Accordingly, the respective throttle between the inverter and the electrical supply network is arranged here, is to be fed into the.

In the case of a three-phase system, one reactor is required for each phase. Frequently, such chokes of a three-phase system are combined into a three-phase choke. For this purpose, a composed of stacked sheets magnetic core is provided, which has approximately the appearance of a digital display 8. Thus, three magnetically interconnected legs are present, each receiving a winding of a phase. A magnetic field, which results from a current of a winding in the magnetic leg of this winding, runs in part through the other two magnetic legs of the other two windings. In this way, the magnetic fields of all three windings and thus all three phases overlap.

This approximately achtförmige magnetic core has a very high magnetic permeability, so that determine the electrical properties of the throttle substantially through the windings.

Such a magnetic core is relatively easy to produce by the layering of stamped sheets. The disadvantage, however, is that such a three-phase choke is not completely symmetrical, because two coils are arranged on each of an outer magnetic leg, whereas one of the coils is disposed on a magnetic leg between the two outer legs. As a result, the magnetic fields of the windings, namely in particular between the two outer windings on the one hand and the winding arranged centrally in between, on the other hand, can differ. There may be any stray fields and that for the middle Winding effective magnetic resistance may be slightly less than the effective each for the two outer windings magnetic resistance.

Moreover, such a three-phase reactor requires a three-phase system in which the sum of the currents is zero. In other words, it assumes a system or is used in a system that does not use or need a neutral.

From US Pat. No. 6,452,819 an inverter with an output choke with four legs is known in which the fourth leg transmits unbalanced magnetic fluxes from unbalanced harmonics. However, this does not solve the problem of asymmetries within the first three legs. The German Patent and Trademark Office has in the priority application the following state of the art research: DE 10 2008 031 296 A1, DE 10 74 146 A, DE 750 987 A, DE 412 872 A, US 2 359 173 A, DE 20 2010 008 961 U1, US Pat. No. 2,617,090 A, US Pat. No. 4,099,066 A, US Pat. No. 1,157,730 A, EP 0 602 926 A1.

The present invention is therefore based on the object to address at least one of the above problems. In particular, an improved three-phase choke is to be created, which can also take into account an asymmetrical portion of a three-phase system. At least an alternative solution should be found.

According to the invention, a magnetic core for a three-phase choke is thus proposed according to claim 1. Such a magnetic core has a first, second and third magnetic leg for receiving a first, second or third electrical winding of a first, second and third electrical phase, wherein the first, second and third legs are arranged in a star shape or a triangular shape.

There are thus three in particular the same magnetic legs present, which are arranged star-shaped relative to a common center. In particular, these three legs are aligned parallel to one another and parallel to a common longitudinal direction or longitudinal axis and each have connecting legs which meet at a common center. They are arranged in a star shape with respect to this center. These connecting legs are arranged in a plan view, namely in a view along the longitudinal axis, approximately Y-shaped. Preferably, these three connecting legs in plan view at an equal angle, namely in each case of 120 °, to each other. In principle, however, too be provided different angles. Correspondingly, the three magnetic legs, namely the first, second and third magnetic legs, which can also be referred to as the main leg, are distributed uniformly around the common center, namely offset relative to this center by 120 ° to each other. Based on the mentioned center, the three main legs are arranged in a star shape. If you connect them directly through three imaginary lines, a triangle is created and, to that extent, the three main legs are arranged in triangular form. The three main legs are not arranged in a straight line to each other. Preferably, the three main legs are arranged so that they form the vertices of an imaginary, equilateral triangle.

By virtue of this star-shaped or triangular arrangement, a magnetic connection of the same type and size between the three main legs can be achieved. None of the three main legs occupies a special position, as was the case with the middle leg according to the prior art. The proposed construction now allows a magnetically symmetrical design of the throttle.

Preferably, a fourth magnetic leg is provided and the first, second and third legs are arranged in a star shape with respect to this fourth magnetic leg. The fourth magnetic leg may be prepared to receive a fourth winding. The fourth magnetic leg is preferably made smaller than the first, second and third leg, that is smaller than the main leg. The fourth leg can carry a magnetic field, which can be due to asymmetries of the three-phase system. These include in particular unbalanced harmonics. Accordingly, can be expected in the fourth leg with magnetic alternating fields of high frequency, compared to the frequency of the fundamental phase of the current of the three-phase system.

In particular, therefore, it may be provided to carry out the fourth leg as a ferrite core or as a ferrite rod. Such a ferrite rod is particularly suitable for driving high-frequency magnetic alternating fields. For deriving or processing such an asymmetrical component, a winding may be provided on the fourth leg. Preferably, the first, second and third legs and possibly the fourth leg are arranged parallel to each other. They can be connected to the magnetic core of the three-phase choke on two sides by means of three connection legs connected to one another in approximately Y-shaped fashion. The fourth limb is provided here as a central limb, if present, and forms both a magnetically center, and in mechanical terms for the stable connection of these two Y-shaped sets of connecting limbs.

It is advantageous if the first, second and third legs are arranged at a same, first distance from one another and / or are arranged at the same distance to the fourth leg, thereby mechanically and magnetically forming a symmetry.

Preferably, therefore, the first, second and third legs are each connected via at least one magnetic connecting leg, in particular in each case via two magnetic connecting legs with the fourth magnetic leg. Preferably, the three main legs and the fourth leg parallel to each other and the connecting legs transversely, in particular at right angles thereto.

According to one embodiment, it is also proposed that the first, second and third legs are magnetically connected in parallel with each other. Preferably, they are also connected in parallel to the fourth leg. Ideally, the three magnetic fields of the three main legs in the fourth leg are superimposed by this parallel connection to zero. Or arise in the fourth leg in this superposition, only the unbalanced shares, which can be detected in a possible fourth winding of the fourth leg as a corresponding current and can be removed or connected via a corresponding interconnection with a neutral or otherwise.

According to one embodiment, it is proposed that the first and second legs form part of a first magnetic circuit, that the second and third legs form part of a second magnetic circuit, and that the third and first legs form part of a third magnetic circuit. In each of these three magnetic circuits, a magnetic field with a mean path length can be correspondingly guided, wherein the first, second and third magnetic circuits have an equal length, in particular equal average path lengths of one respective leading length. have the magnetic field. In addition or alternatively, they have the same magnetic resistance, in particular without providing an air gap for this purpose.

The same magnetic resistance for each of these magnetic circuits results in particular from the fact that all these three magnetic circuits have the same mechanical construction when using the same materials. Accordingly, due to such an identical construction with identical materials, it is also possible to prove the feature that the magnetic circuits have the same magnetic resistance.

According to the invention, a three-phase choke is also proposed, which is provided with a magnetic core of a three-phase choke according to at least one of the embodiments described. Such a three-phase choke thus has a first, second and third magnetic leg, which carries a first, second or third winding of a first, second and third electrical phase. Such a three-phase choke can thus realize the advantages and options afforded by the underlying magnetic core.

Preferably, the fourth magnetic leg carries a fourth winding and is prepared for guiding an unbalanced magnetic component of a three-phase system. Additionally or alternatively, the fourth winding is prepared for guiding an asymmetrical electrical component of a three-phase system. In particular, the proposed solution provides a symmetrical three-phase choke in which any imbalance components that appear in the fourth leg and / or that occur in the fourth winding are not due to any imbalances of the three-phase choke, but actual asymmetries of the three-phase system reflect. An insert can find such a three-phase choke, in particular at the output of a frequency inverter. In particular, when it is intended to be fed with such into a three-phase electrical supply system. Due to the function of such an inverter, in particular by the IGBTs used there, an unbalanced load which can be considered by the three-phase choke together with the proposed fourth leg arises. In particular, in the interconnection with inverters or converters that generate zero currents, ie currents in a neutral, so one to the three-phase conductors additional conductor, such a three-phase reactor can be used. In such an application, by controlling the valves of a frequency inverter, so the semiconductor switch, such as the IGBTs a small zero current finally generated in the fourth leg or in the winding of the fourth leg of a correspondingly interconnected three-phase reactor. Previously, three-phase chokes themselves were also responsible for unbalanced components. A symmetrical, in particular as proposed star-shaped three-phase choke thus leads to the fact that only those asymmetrical currents occur, which are actually generated by the inverter, in particular the control of the valves or semiconductor switches. Overall, the asymmetry, namely the unbalanced components, smaller and accordingly also a load of the semiconductor switches, ie the IGBTs is uniform and in the result smaller.

Not optimal, at least not uniform inductance distribution on individual phases of previous chokes are avoided.

In addition to the achievable uniform loading of the IGBTs, it is also possible to increase a cooling surface of the copper of the windings. In particular, cooling of the winding is uniform with uniform distribution of the main leg. In a throttle according to the prior art, in which three legs are arranged in a row, can be assumed in the middle leg and thus the winding of the middle leg of a poorer cooling ability. Preferably, the legs of the throttle are each mechanically offset by 120 °. The magnetic distances are preferably the same from limb to limb, namely from main limb to main limb. The fourth leg can consist of a ferrite core or a ferrite rod, in order to take into account high-frequency alternating currents with a small amplitude. At least one of the embodiments shown thus provides symmetry, equal inductance values and better air cooling through larger free copper surfaces.

The use of different air gaps in known chokes, thereby achieving a homogenization of at least the magnetic resistance of individual magnetic circuits, can be avoided. The invention will be explained in more detail by means of embodiments with reference to the accompanying figures. Fig. 1 shows a three-phase throttle in a perspective principle view.

Fig. 2 shows a three-phase throttle as a schematic representation in a plan view.

Fig. 3 shows a three-phase throttle schematically in a perspective view with indicated windings. Hereinafter, identical reference numerals may designate similar but possibly non-identical elements to better clarify existing relationships. In particular, FIGS. 1 and 2 are schematic diagrams that may therefore differ in detail from concrete values such as concrete dimensions of an underlying subject matter and thus also among themselves, without this having any significance for the described subject matter.

1 shows a three-phase choke 10 with a magnetic core 20. The magnetic core 20 has a first magnetic leg 1, a second magnetic leg 2 and a third magnetic leg 3, which may also be referred to as main legs 1, 2 and 3. In addition, the magnetic core 20 has a fourth magnetic leg 4 seen.

The three skin limbs 1, 2 and 3 are each connected via an upper connecting leg 6 and a lower connecting leg 8 with the fourth leg 4. Thus, each of the three main legs 1, 2 and 3 is connected to each of the two remaining main legs 2, 3 or 3, 1 and 1, 2 via two upper connecting legs 6 and two lower connecting legs 8. In any case, with symmetrical mechanical design and use of the same material, the connection of the three main legs 1, 2 and 3 with each other and the connection of the three main legs 1, 2 and 3 to the fourth leg 4 is the same. All legs of FIG. 1, namely the three main legs 1, 2 and 3, the fourth leg and the two connecting legs 6 and 8 are shown only schematically as a line. In fact, the three main legs 1, 2 and 3 are the same thickness and the connecting legs 6 and 8 are also the same thickness per se. In any case, the fourth leg 4 is significantly thinner than the main legs 1, 2 and 3.

In addition, the first, second and third legs carry a first, second or third winding Li, l_2 or I_3, which may also be referred to as the main winding, and the fourth leg carries a fourth winding L ₄ . The three main windings L- ₁ , L ₂ and L ₃ are the same large dimensions and the fourth winding L ₄ can be substantially smaller dimensions than the three main windings L-ι, L ₂ and L ₃ .. In particular, the fourth winding L ₄ in terms of number of turns and / or in terms of line cross section of each turn designed considerably smaller be. Preferably, the three main windings L- ₁ , L ₂ and L _{3 are} each connected to one phase of a three-phase system. The fourth winding L ₄ may be connected to a neutral conductor. The three upper connecting legs 6 are each arranged at an angle of 120 ° to each other. The same applies to the three lower legs 8. At the same time, the lengths of the three upper connecting legs 6 and the three lower connecting legs 8 are of equal length and the three main legs 1, 2 and 3 are correspondingly symmetrical to each other and in particular arranged in a star shape around the fourth leg 4 ,

2 shows schematically a top view of the three-phase throttle 10 of FIG. 1. Here, too, it is particularly clear that the three upper connecting legs 6 are arranged at an equal angle to one another, namely 120 ° to each other. Accordingly, there is a symmetrical arrangement of the three main windings L- ₁ , L ₂ and L ₃ to each other. The three main windings L- ₁ , L ₂ and L _{3 are} mechanically arranged uniformly around the fourth winding L ₄ . Fig. 2 illustrates in particular the star shape of the arrangement of the three main legs 1, 2 and 3, which occur here only as a point at the end of the respective upper connecting leg 6 in appearance.

3 illustrates a perspective view of a possible specific embodiment of the three-phase choke 310, in particular of the magnetic core 320. The magnetic core 320 has a first, second and third magnetic leg 301, 302 and 303. Each of these three main legs 301, 302 and 303 has a winding L- ₁ , L ₂ and L ₃ , which, however, are shown only schematically so far to the required winding space or even the required space for these windings Li, L ₂ and L. ₃ to clarify. Accordingly, it can be seen that each of the windings Li, L ₂ and L _{3 have} much and the same place for radiating heat. For this purpose, in particular on the winding L-ι a large radiating surface 31 can be seen, which is present in the same size and type in the two windings L ₂ and L ₃ , in the Fig. 3 but hardly recognizable and therefore not with a Reference number has been provided.

In addition, a fourth leg 304 is present. The fourth magnetic leg 304 is connected to a connecting middle part 46. The main legs 301, 302 and 303 are each connected to an upper connecting leg 306 with the central connecting means 46 and thus with the fourth leg 304. A corresponding construction also results on the underside of the throttle 310, which can be seen only very vaguely in FIG. The throttle 10, in particular the individual legs 301-304, are thereby assembled and also the respective magnetic circuit is closed by using stacked sheets of different lengths. By mutual overlaps of the sheets creates a correspondingly durable connection and the desired magnetic circuit can be closed.

Thus, a symmetrical three-phase choke 10 or 310 has been proposed, which has a compact structure with symmetrical arrangement and thus symmetrical properties with respect to a three-phase system. Also with regard to the mechanical and thus thermally relevant structure, each phase of such a three-phase system is considered equal. Any unbalanced portions are thus not generated by this three-phase choke 10 or 310, but can be taken into account in the fourth magnetic leg 4 and 304 and it may possibly be provided a derivative to a neutral.

Claims

claims

1. magnetic core (20) of a three-phase choke (10), with

a first, second and third magnetic leg (1, 2, 3) for receiving a first, second and third electrical winding (L-ι, L ₂ , L ₃ ), a first, second and third electrical phase, wherein

the first, second and third legs (1, 2, 3) are arranged in a star-shaped or triangular shape.

Second magnetic core (20) according to claim 1, characterized in that a fourth magnetic leg (4), in particular for receiving a fourth winding (L ₄ ), is provided and the first, second and third legs (1, 2, 3) are arranged in a star shape with respect to the fourth magnetic leg (4).

3. Magnet core (20) according to claim 1 or 2, characterized in that the first, second and third legs (1, 2, 3) and possibly the fourth leg (4) are arranged parallel to each other and / or the fourth or a fourth leg (4) is designed as a ferrite core or ferrite rod.

4. Magnet core (20) according to one of the preceding claims, characterized in that the first, second and third legs (1, 2, 3) are arranged to each other in a same, first distance and / or to the fourth leg (4) in a same, second distance are arranged.

5. magnetic core (20) according to any one of the preceding claims, characterized in that the first, second and third legs (1, 2, 3) in each case via at least one magnetic connecting leg (6, 8), in particular in each case via two magnetic connecting legs (6 , 8) are connected to the fourth magnetic leg (4).

6. magnetic core (20) according to any one of the preceding claims, characterized in that the first, second and third legs (1, 2, 3) are connected in parallel to each other magnetically.

7. Magnetic core (20) according to one of the preceding claims, characterized marked, that

the first and second legs (1, 2) form part of a first magnetic circuit, the second and third legs (2, 3) form part of a second magnetic circuit,

the third and first legs (3, 1) form part of a third magnetic circuit and

the first, second and third magnetic circuits have the same length, in particular the same average path length of a respective magnetic field to be conducted and / or

have the same magnetic resistance.

8. Three-phase choke (10) with a magnetic core (20) according to any one of the preceding claims, characterized in that the first, second and third magnetic legs (1, 2, 3) a first, second and third winding (L-ι , L ₂ , L ₃ ) carries a first, second and third electrical phase.

9. Three-phase choke (10) according to claim 8, characterized in that the or a fourth magnetic leg ( ₄ ) carries a fourth winding (L ₄ ) and the fourth magnetic leg (4) for guiding a single-ended magnetic component of a three-phase system is prepared and / or the fourth winding (L ₄ ) is prepared for guiding an asymmetrical electrical component of a three-phase system.

10. Three-phase choke according to claim 7 or 8, characterized in that

- The choke is connected to the output of an inverter and that

- The 4th winding is connected to a neutral.

1 1. Three-phase choke according to one of claims 7 to 9, characterized in that

the fourth leg is designed as a ferrite rod.

12. Three-phase choke according to one of claims 7 to 10, characterized in that

the fourth magnetic leg is made smaller than the main leg.

13. Arrangement, suitable for feeding electrical current into an electrical supply network, comprising

- an inverter and - A arranged between the inverter and the electrical supply network three-phase choke, wherein

- The three-phase choke (10) is designed according to one of claims 7 to 1 1 and the fourth magnetic leg (4) and the fourth winding (L ₄ ) are prepared for guiding a single-ended electrical component of a three-phase system.

14. Arrangement according to claim 12, characterized in that the fourth winding is connected to a neutral conductor.