EP4189712A1

EP4189712A1 - Magnetic component with controlled leakage flux

Info

Publication number: EP4189712A1
Application number: EP21734842.4A
Authority: EP
Inventors: Boris Bouchez; Stéphane FONTAINE
Original assignee: Valeo eAutomotive France SAS
Current assignee: Valeo eAutomotive France SAS
Priority date: 2020-07-29
Filing date: 2021-06-23
Publication date: 2023-06-07
Also published as: JP2023535968A; FR3113178B1; FR3113178A1; CN116034441A; WO2022022896A1; US20230274869A1

Abstract

The present invention relates to a magnetic component comprising two ferromagnetic half-cores stacked and superimposed to form a ferromagnetic core comprising three legs (11, 12, 13) including two first legs (11, 13) and a second leg (12), each leg (11, 12, 13) being formed by two half-legs facing each other and separated by a gap, each leg (11, 12, 13) comprising a primary winding (111, 121, 131) and a secondary winding (112, 122, 132) having a winding direction on each of the half-legs thereof, respectively, the magnetic component being characterised in that, on the second leg (12), the primary winding (121) and the secondary winding (122), as well as their winding direction, are inverted with respect to those (111, 112, 131, 132) of the first legs (11, 13).

Description

MAGNETIC COMPONENT WITH LEAKAGE FLUX CONTROL

TECHNICAL AREA

The present invention relates to the field of magnetic components, in particular electrical transformers.

The present invention relates more particularly to the field of electrical transformers, for example integrated with resonant voltage converters or any other type of power converters, or with electrical chargers. In particular, the present invention relates to a magnetic component such as a three-phase electrical transformer.

STATE OF THE ART

An electrical transformer allows the transfer of electrical energy from a primary circuit to a secondary circuit.

As is known, in an electric transformer, a magnetic core and windings are used in which an electric current circulates which generates a magnetic field allowing the transfer of electric energy from the primary circuit to the secondary circuit. More specifically, in an electric transformer, in particular in a magnetizing inductance power converter or in a resonant power converter, there is a primary winding and a secondary winding, formed by windings around a magnetic core, between which is transferred electrical energy.

In a three-phase electrical transformer, more particularly there are three primary windings and three secondary windings wound on different portions of a ferromagnetic core of suitable shape. E-shaped ferromagnetic cores are known in particular, as represented in FIG. 1, or triangle-shaped, as represented in FIG. 2.

Any electrical transformer has a leakage inductance, which results in a loss of efficiency because part of the magnetic flux created in the primary circuit is not picked up by the windings of the secondary circuit. Additional losses may also appear on the primary and secondary windings. In the case of non-resonant voltage converters, overvoltages may also occur. The geometry of the windings of an electrical transformer, as well as the choice of the magnetic materials used for the magnetic core, or even the geometry of said magnetic core, in particular, are configured to comply with electrical and magnetic criteria. One objective of the dimensioning of an electric transformer resides in particular in the control of the value of the leakage inductance of the electric transformer. [0007] Two main methods of manufacturing such electrical transformers, in particular three-phase, are known. In the example of Figure 1, the windings are flat and the primary winding 310 and the secondary winding 320 form two superposed layers on each leg 31, 32, 33 of the ferromagnetic core 30. Such a known electric transformer 3, assembled through a flat winding technique, exhibits low leakage inductance. In addition, the parasitic capacitance is in this case very high at the level of the primary circuit as at the level of the secondary circuit. Furthermore, the cooling of the winding arranged below, in other words of the “buried” winding, is very difficult.

On the same type of ferromagnetic core in E, it is also possible to produce stacked windings. An advantage of this known architecture lies in the fact that it is easy to integrate and to cool. However, such an architecture has a high leakage inductance.

Another known solution for making a three-phase electrical transformer 4 consists of arranging the windings on a ferromagnetic core in an equilateral triangle, and thus having legs at 60° to each other, as shown in Figure 2.

[0010] Such a triangular structure is however difficult to integrate mechanically.

[0011] In this context, it is known, on the basis of an architecture based on windings stacked on a ferromagnetic core in E, to use the leakage inductance to act as a resonance inductance and therefore to promote the transfer of energy from the primary windings to the secondary windings. Thus, the leakage inductance, a priori detrimental, is valued.

This known principle is illustrated in Figure 4. As can be seen in Figure 4, there are primary windings on the upper E-shaped ferromagnetic half-core and secondary windings on the upper E-shaped ferromagnetic half-core. low.

[0013] The technical problem linked to the implementation of this technology resides in the fact that the leakage magnetic flux does not loop. In fact, it is concentrated in the legs and “jumps” from the side legs 21, 23 towards the central leg 22, as illustrated in FIG. 4. The flow lines are thus parallel to the air gaps.

[0014] There is therefore a need for a three-phase electrical transformer that is easy to integrate and cool and whose leakage inductance is controlled.

PRESENTATION OF THE INVENTION [0015] To this end, the subject of the invention is a magnetic component comprising two ferromagnetic half-cores stacked and superimposed to form a ferromagnetic core comprising three legs including two first legs and a second leg, each leg being formed of two half- legs facing each other and separated by an air gap, each leg comprising a primary winding and a secondary winding having a direction of winding, respectively on each of the half-legs which constitute it, the magnetic component being characterized in that, on the second leg, the primary winding and the secondary winding as well as their direction of winding are reversed with respect to those of the first legs.

[0016] In particular, the first legs can be side legs and the second leg a central leg.

[0017]According to one embodiment, the two ferromagnetic half-cores have a so-called "triangle" arrangement according to which, on each ferromagnetic half-core, the three branches respectively forming each half-leg are at 60° to one of the other. In particular, the three branches respectively forming each half-leg are located on the vertices of an equilateral triangle.

Advantageously, the two ferromagnetic half-cores have an E shape.

The invention also relates to an electrical transformer comprising a magnetic component as briefly described above.

The invention also relates to electrical equipment comprising an electrical transformer as briefly described above.

Advantageously, said electrical equipment comprises a cooling module comprising a cavity forming a cooling basin housing said electrical transformer.

According to one embodiment, said electrical equipment forms an electrical charger.

According to another embodiment, said electrical equipment forms a power converter.

PRESENTATION OF FIGURES The invention will be better understood on reading the following description, given solely by way of example, and referring to the accompanying drawings given by way of non-limiting examples, in which identical references are given to similar objects and on which:

Figure 1 is a schematic representation of a first known electrical transformer, with primary and secondary windings arranged in superimposed layers;

Figure 2 is a schematic representation of a first known electrical transformer, with primary and secondary windings arranged on a ferromagnetic core triangle;

[0027] Figure 3 is an electrical diagram of an electrical transformer;

[0028] Figure 4 is a schematic representation of an electrical transformer in E, having the known drawbacks;

[0029] Figure 5 is a schematic representation of an example of an electrical transformer according to the invention, assembled on a ferromagnetic core in E.

It should be noted that the figures expose the invention in detail to allow the invention to be implemented, said figures can of course be used to better define the invention if necessary.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to a magnetic component, in particular a three-phase transformer.

FIG. 3 represents an equivalent electric diagram of a resonant voltage converter circuit, comprising an electric transformer, for converting an input voltage VIN into an output voltage V ₀ . The electrical transformer includes primary and secondary windings. The magnetic flux created by the circulation of an electric current in the primary winding allows the transfer of energy to the secondary circuit. In the primary circuit, there is a resonant LLC circuit consisting of a resonance capacitance Cr, a resonance inductance Lr and a magnetizing inductance Lm which can be integrated into the electrical transformer. The electrical transformer is controlled by a half-bridge of switches Q1, Q2 connected to the primary winding. The diodes D1, D2 connected to the secondary circuit make it possible to avoid current returns. [0033] Figures 4 and 5 represent respectively schematic representations of an electrical transformer 20 according to the state of the art and of an example of an electrical transformer 10 according to the invention, both based on a ferromagnetic core in E Said ferromagnetic core is formed of two half-cores having the shape of an E, stacked head to tail.

The ferromagnetic core has three legs 11, 12, 13, 21, 22, 23, namely two side legs 11, 13, 21, 23 and a central leg 12, 22. Each leg 11, 12, 13, 21 , 22, 23 is formed of two half-legs facing each other separated by an air gap. Each leg 11, 12, 13, 21, 22, 23 corresponds to a phase of the three-phase electrical transformer 20, respectively 10. In an electrical transformer based on an E-core, each branch of the E, in other words each leg 11, 12, 13, 21, 22, 23 of said ferromagnetic core, corresponds to a phase of the electrical transformer. Similarly, in a triangle transformer, each leg corresponding to a vertex of the triangle is linked to a phase of the electrical transformer.

In Figure 4, the windings 211, 212, 221, 222, 231, 232 are made in the same direction for all of the primary windings, which are all on the upper half-legs, and, respectively, for the secondary windings, which are all on the lower half-legs.

The drawback of this architecture, which represents the state of the art shown schematically in FIG. 4, lies in the fact that part of the magnetic leakage fluxes are in opposite directions. These leakage magnetic fluxes do not loop through the leg corresponding to their phase but jump from one leg to the other. In particular, magnetic fluxes are created parallel to the air gaps and jump from each lateral leg 21, 23 towards the central leg 22. In other words, a coupling appears between each lateral leg 21, 23 and the central leg 22.

This leads to increased losses and a risk of overheating in the center of the electrical transformer 20, at the level of the central leg 22.

[0038] A solution to avoid this coupling would be to move the side legs 21, 23 away from the central leg 22, to prevent these magnetic flux jumps from the side legs 21, 23 towards the central leg 22, thereby increasing the size of the ferromagnetic core. However, this would obviously lead to an increase in the size of the electrical transformer, which would be detrimental.

Figure 5 shows the solution proposed by the present invention, according to one embodiment. At the central leg 12, the primary winding 121 and the secondary winding 122 are inverted and the winding direction of these primary 121 and secondary 122 windings is reversed. The primary winding 121 of the central leg 12 is located thus on the same side of the ferromagnetic core as the secondary windings 112, 132 of the legs sides 11, 13. Conversely, the secondary winding 122 of the central leg 12 is thus on the same side of the ferromagnetic core as the primary windings 111, 131 of the side legs 11, 13. In addition, the winding direction of the windings primary and secondary 121, 122 of the central leg 12 is reversed with respect to that of the windings 111, 112, 131, 132 of the side legs 11, 13.

Thanks to the architecture according to the invention, inter-leg magnetic flux jumps are avoided. As shown in Figure 5, in fact, instead of concentrating on the central leg 12 as in Figure 4, the magnetic fluxes created on the different legs 11, 12, 13 repel each other in pairs. Therefore, the magnetic fluxes created on the side legs 11, 13 do not jump onto the central leg 12.

[0041] Thus, the magnetic flux on the central leg 12 does not increase and the risk of overheating is therefore reduced.

An advantage related to the implementation of the invention according to the embodiment of Figure 5 lies in the use of a standard E-core because it is easy to integrate mechanically and easy to cool via standard cooling technologies, in particular via a cooling basin, as is known, making it possible to obtain adequate cooling of the windings and of the core.

It should also be noted that a three-phase electrical transformer with a linear E-shaped core is not symmetrical, in the sense that the phases formed on the side legs 11, 13 are further apart from one another. other than the central leg 12. Conversely, in an electric transformer in the shape of a triangle, in particular equilateral, the phases are equidistant because the legs are. In the case of an E-shaped electrical transformer, the present invention is all the more indicated to prevent the leakage magnetic flux from taking the same magnetic path as the controlled magnetic flux. Thanks to the invention, the leakage magnetic flux does not interfere with the controlled magnetic flux. In other words, the leakage magnetic flux does not oppose the controlled magnetic flux and does not create additional losses.

In the case of a triangle transformer, in particular an equilateral triangle, thanks to the invention, there is no need for an external inductive component. Also, in this case, all the legs are equidistant.

Such an electrical transformer according to the invention, as said above, can advantageously be integrated into electrical equipment, in particular for automobiles, in particular an electrical charger or a power converter. In addition, in the case of an E-shaped electrical transformer, such an electrical transformer according to the invention can easily be integrated into an electrical equipment chassis comprising a cooling module with a cavity forming a cooling basin housing said electrical transformer.

Claims

1. Magnetic component comprising two stacked and superposed ferromagnetic half-cores to form a ferromagnetic core comprising three legs (11, 12, 13) including two first legs (11, 13) and a second leg (12), each leg (11, 12, 13) being formed of two half-legs facing each other and separated by an air gap, each leg (11, 12,

13) comprising a primary winding (111, 121, 131) and a secondary winding (112, 122, 132) having a direction of winding, respectively on each of the half-legs which constitute it, the magnetic component being characterized in that , on the second leg (12), the primary winding (121) and the secondary winding (122) as well as their direction of winding are reversed with respect to those (111, 112, 131, 132) of the first legs ( 11, 13).

2. Magnetic component according to claim 1, in which the two ferromagnetic half-cores have a so-called “triangle” arrangement according to which, on each ferromagnetic half-core, the three branches respectively forming each half-leg are at 60° one from the other.

3. Magnetic component according to claim 1, in which the two ferromagnetic half-cores have an E shape.

4. Electrical transformer (10) comprising a magnetic component according to one of the preceding claims.

5. Electrical equipment comprising an electrical transformer (10) according to the preceding claim.

6. Electrical equipment according to the preceding claim, comprising a cooling module comprising a cavity forming a cooling basin housing said electrical transformer (10).

7. Electrical equipment according to claim 5 or 6, forming an electric charger.

8. Electrical equipment according to any one of claims 5 to 7, forming a power converter.