DE202014105157U1 - Inductive component with improved cooling - Google Patents

Abstract

Transformer core (10), comprising: - a ferromagnetic base body (5) with a plurality of sections (11, 12, 13), - a plurality of heat dissipation layers (1, 2, 3) of a highly thermally conductive, electrically insulating material, between each two adjacent sections (11, 12, 13) of the base body (5) a heat dissipation layer (1, 2, 3) is arranged.

Description

The present disclosure relates to a device for removing heat from inductive components, in particular from transformers, more specifically for the cooling of medium frequency transformer cores. Furthermore, it relates to corresponding transformer cores and transformers.

The increase in the power density of an inductive component such as a transformer or a choke coil is limited mainly by the maximum permissible operating temperature. The operating temperature results inter alia from the ambient temperature, the losses occurring in the ferromagnetic core and the windings, the thermal resistance between the main regions of origin of heat loss and the surface of the component, as well as the thermal resistance between the component surface and the environment, the before everything is determined by convection.

A reduction of the thermal resistances thus leads to a possible higher power density, since the same maximum permissible operating temperature then occurs only at higher power or higher current.

With the same component rated power or rated current, the possible higher power density thus also leads to a reduction of volume, weight and thus costs of the component. These efforts are opposed by the fact that the necessary in particular for medium and high voltage components electrical insulation is a limiting factor for the reduction of thermal resistance, since measures for insulation usually reflected in an increase in the effective total thermal resistance.

Methods are known in the art for improving heat dissipation from transformer cores.

So is out of the US 2,990,524 a device for removing heat from cores made of ferromagnetic material for inductive components known. This comprises a plurality of layers of electrically and thermally conductive material which adjoin the cores and via which the cores can be thermally coupled to a heat sink.

From the DE 19637211 there is known a device for removing heat from ferrite cores, in which an electrically and thermally conductive metal layer is mounted on the ferrite core, wherein the metal layer is thermally coupled to an external heat sink. The metal layer is provided with interruptions to avoid inducing loss-promoting eddy currents in the metal layer.

The known solutions leave room for improvement. An object of the invention is therefore to provide a transformer core or a transformer with improved heat dissipation or cooling.

Brief summary of the invention

According to a first aspect of the invention, a transformer core is provided. The transformer core comprises a ferromagnetic base body with a plurality of sections and a plurality of heat dissipation layers of a highly thermally conductive, electrically insulating material, a heat dissipation layer being arranged between each two adjacent sections of the base body. In another aspect, a transformer is provided with such a transformer core.

Advantages of embodiments are a significant weight reduction and / or a decrease in external dimensions, depending on which conventional technology is compared. In addition, there is a homogeneous temperature distribution over the magnetic core, accompanied by a reduction of local hot spots. The direct dissipation of heat to the surface very simple and inexpensive cooling concepts can be used, there is an improved direct cooling of the magnetic core. Despite improved cooling, it is possible to dispense with complex cooling structures, such as pipes and channels for guiding cooling liquids, which conventionally extend within the structures and insulation spaces within the inductive component.

Other features, advantages, and objects will become apparent from the following detailed description of the invention.

Description of the figures

The present description will now be described by way of example only with reference to the accompanying drawings which illustrate embodiments of the invention. Show it:

1 shows a perspective view of a transformer core according to an embodiment of the invention;

2 shows a perspective view of another transformer core according to an embodiment of the invention;

3 a perspective view of a transformer according to an embodiment of the invention.

Detailed description of the figures

In general, in embodiments, the maximum power density of an inductive component is increased, while at the same time a very simple external cooling system can be used.

A design is proposed for a liquid or solid based electrical insulation transformer, such as silicone gel, oil or epoxy potting compound, in which highly thermally conductive layers or plates are used as additional heat sink layers in the transformer core. For this purpose, these heat-dissipating layers are embedded in the main body of the transformer core or designed as intermediate layers in the ferromagnetic base material. It does not matter which basic material consists of the core. Possible are e.g. conventional transformer plate, ferrite, or nanocrystalline cores.

The heat sink layers divide the core into multiple sections, each serving as a heat sink and drain path for the heat loss produced in the core sections. Overall, thus the average thermal conductivity of the transformer core is increased.

1 shows a transformer core 10 according to embodiments. The transformer core 10 comprises a ferromagnetic body 5 in several sections 11 . 12 . 13 is divided. Between the sections 11 . 12 . 13 is each a heat dissipation layer 1 . 2 . 3 a highly thermally conductive, electrically insulating material attached. The heat dissipation layers 1 . 2 . 3 are made of a material having a thermal conductivity of more than 50 W / Km in at least one material direction, preferably more than 200 W / Km, more preferably more than 400 W / Km. In this case, the heat-dissipating layers are typically each designed as flat thin plates having a cross-sectional area corresponding to that of the adjacent portions of the core. The thickness of the heat-dissipating layers 1 . 2 . 3 is typically between 1 mm and 30 mm, more typically between 2 mm and 8 mm.

2 schematically shows another transformer core 10 according to embodiments. The heat-dissipating layers protrude 1 . 2 . 3 on at least one side of the body 5 out of this, in the non-limiting example of 2 up. The over the main body 5 of the transformer core 10 protruding parts of the heat sinks 1 . 2 . 3 can act as a surface for a cooling fluid 16 are used, typically for air, another gas, or a cooling liquid. This can be moved by natural convection or by forced ventilation, for example with a fan (not shown).

3 shows a transformer 30 with a transformer core 10 as in 1 shown. In the example shown, (as a non-limiting example) is on the top and bottom of the transformer core 10 each a heat sink in the form of a heat sink 15 appropriate. The heat sinks 15 are thermally conductive with the Wärmeableitschichten 1 . 2 . 3 connected, for example by means of thermal paste. The heat sink may, for example, also be a heat pipe or a cold plate (not shown).

Generally, the heat dissipation layers 1 . 2 . 3 typically mounted parallel to each other. Preferably, they are substantially equidistant from each other. The heat sink layers typically occupy between about 2% and about 10% of the total volume of the transformer core 10 one. The main body 5 can be made of ferrite, transformer sheet, or nanocrystalline material. The heat dissipation layers 1 . 2 . 3 are typically made of electrically non-conductive material to prevent the formation of eddy currents.

One possible material for the heat dissipation layers is highly oriented pyrolytic graphite (HOPG). This has a heat conductivity of 600 W / Km or higher in one material direction. The orientation of the HOPG material with respect to the heat sink layer in embodiments is conveniently determined to be in the direction of heat flow to the edge of the heat sink layer 1 . 2 . 3 directed. At this edge, the heat dissipation layers are or are connected to a heat sink. HOPG also offers the advantage of relatively low costs. As an alternative to HOPG, it is also possible to use other highly thermally conductive materials which are electrically insulating.

The insulation is used in embodiments, in particular when using silicone gel or oil, as a thermal interface between the Wärmeableitschichten and the surface of the adjacent core layers or sections 11 . 12 . 13 of the ferromagnetic body 5 of the transformer core 10 , Schematically is in 3 a primary winding 50 , a secondary winding 60 and a potting compound or a potting body 100 shown, the latter is shown transparently for purposes of illustration.

In other embodiments, the concept described with respect to a transformer core is used in other inductive components, such as inductors. In addition, the concept can be implemented in three-phase transformers. Due in part to the higher hysteresis losses in the transformer core in the case of medium-frequency transformers-in comparison to mains transformers-the advantages of the described concept are particularly evident in the case of medium-frequency transformers according to exemplary embodiments.

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

• US 2990524 [0006]
• DE 19637211 [0007]

Claims (13)

Transformer core ( 10 ), comprising: - a ferromagnetic base body ( 5 ) with several sections ( 11 . 12 . 13 ), - several heat-dissipating layers ( 1 . 2 . 3 ) of a highly thermally conductive, electrically insulating material, wherein between each two adjacent sections ( 11 . 12 . 13 ) of the basic body ( 5 ) a heat-dissipating layer ( 1 . 2 . 3 ) is arranged. The transformer core of claim 1, wherein the heat dissipation layers ( 1 . 2 . 3 ) are each a plane thin plate, and the heat dissipation layers ( 1 . 2 . 3 ) have a thermal conductivity of more than 50 W / Km in at least one material direction. A transformer core according to claim 1 or 2, wherein the heat dissipation layers ( 1 . 2 . 3 ) highly oriented pyrolytic graphite (HOPG). Transformer core according to one of the preceding claims, wherein the heat-dissipating layers ( 1 . 2 . 3 ) each have a thickness between 1 mm and 30 mm. A transformer core according to any one of the preceding claims, wherein at least one of the heat sink layers ( 1 . 2 . 3 ) on at least one side of the basic body ( 5 protrudes out of this, so that it offers a surface for a cooling fluid. A transformer core according to any one of the preceding claims, wherein at least one of the heat sink layers ( 1 . 2 . 3 ) is connected on one side with a heat sink, preferably with a heat sink ( 15 ) or a heat pipe. Transformer core according to one of the preceding claims, wherein the heat-dissipating layers ( 1 . 2 . 3 ) parallel to each other in the main body ( 5 ) are provided, preferably substantially equidistantly from each other. The transformer core of claim 7, wherein the heat sink layers between about 2% and about 10% of the total volume of the transformer core ( 10 ). Transformer core according to one of the preceding claims, wherein the base body ( 5 ) comprises at least one of ferrite, transformer sheet, and a nanocrystalline material. A transformer with a transformer core according to one of claims 1 to 9. Transformer according to claim 10, comprising a liquid as insulating means, which preferably also in intermediate spaces between at least one heat-dissipating layer ( 1 . 2 . 3 ) and the basic body ( 5 ) is present and thereby improves the heat conduction. A transformer according to claim 10 or 11, wherein the liquid comprises at least one of silicone gel, biologically derived oil and mineral oil. Transformer according to one of claims 10 to 12, which is designed for medium frequency.

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