EP1729310A1 - MF transformer - Google Patents

Abstract

A transformer has primary and secondary windings, and coil penetrations contained in a core. Coil penetrations of hermetically molded-in primary and secondary windings are electrically and thermally separated from each other with intermediate insulations. The cores are thermally and dielectrically insulated and are permanently fixed and held, without any gap, within the coil penetrations via ribbed-partial area/corner surfaces (28).

Description

Field of the invention

The invention relates to a transformer, in particular a medium-frequency transformer with galvanic isolation, as used for example for applications in the field of rail technology.

State of the art

Transformers are essential components in electrical engineering, in industrial plant construction, in rail vehicle construction and in many areas of technology in general (including in aircraft and satellites). However, power compression in the design of transformers and chokes has historically been improved to a limited extent.

A significant improvement in power weight and compression is the patent DE 102 03 246 B4 According to this invention, an improvement in the power density of MF transformers is achieved here with a winding.

Despite the technical advances in technical data and possible applications outlined in the abovementioned patent specification, further inventive advances toward two-arm MF transformers are possible.

For many applications, especially in the mobile sector, but also in most industrial applications, there is a need for even higher Services that can best be achieved with two-legged MF transformers.

Also, two-legged MF transformers, for industrial and rail transport, are traditionally cooled only at the windings or at gaps with air or other media. Although recent attempts to install additional cooling surfaces or indirect liquid cooling devices for the windings and the magnetic circuits bring about a certain reduction of volume and weight, but no fundamental breakthrough.

Due to the large dimensions and the relatively high specific gravity, the known MF transformers are arranged externally to the HBU or drive power converters. HBUs are mostly cooled with air of rare water. For drive converters, at least for the MF transformers, water cooling is used. As a result of the considerable heat development, recoolers are sometimes required, which require additional installation space in the underfloor area of the wagons or on the SR container.

But even the well-known, optimized air-cooled MF transformers with the lowest volume and weight are not yet suitable for noticeably increased performance and reduced overall volume.

Not only installation in close proximity to the power semiconductors requires that the primary and secondary windings be wound around the core of soft magnetic material, e.g. Ferrite can be introduced into the cooling air flow of the HBU / SR module with. This requires significantly more compact designs of transformers so that direct, low-inductance connection options to the IGBTs or other Leistungshalbeiter are possible, preferably short rail connections.

In conventional MF transformers, the windings are placed close to the grounded core for even better efficiency, wherein the windings are supported or held with holding and clamping parts. Therefore, there is a risk of partial discharges in the bearing gaps, which arise between windings, supporting parts and core.

Incidentally, it is disadvantageous that the arrangement of MF transformers outside electrical service cabinets and rooms in atmospheric air requires additional protection against contamination.

Presentation of the invention

The invention has for its object to provide a transformer, in particular a two-arm MF transformer with low volume and weight and similar design of about 40 to more than 400 KVA.

This object is achieved by a hermetically cast double-sided transformer with the features of claim 1.

Advantageous embodiments and further preferred features of the invention are set forth in the dependent claims, the contents of which are hereby incorporated by reference.

According to the invention, the coil penetrations of the hermetically encapsulated primary and secondary windings are electrically and thermally separated from each other with intermediate insulations, the cores being thermally and dielectrically insulated and durably secured and held without any gaps within the coil penetrations via fin partial surfaces or corner surfaces.

Due to the construction according to the invention a very good thermal and electrical, arc-free point isolation of the cores is given to the winding, but with the important difference to DE 102 03 24 B4 in that the attachment of the windings to the cores within the Spool breakthrough is much more stable and less vibration. Additional Gießharzangußwinkel or surfaces for indirect, self-supporting attachment of the cores in the coil breakthrough, especially when it comes to Wider (higher) windings, can not be so stable, low vibration and impact resistant.

In addition, the low heat flow at temperature differences between the windings and the cores with the on all sides free core air gap passage according to DE 102 03 246 B4 Almost comparable, but the overall concept for small, but above all high performance, is much more productive. Even large core and Jochkonfigurationen can be easily and permanently connected without any additional parts and external fasteners with the extremely stable encapsulation of the windings to "a part".

At least equally important is: The coupling inductance between primary and secondary winding reaches lows, what with the named wrapping E-core or 4 U core constructions according to patent application DE 102 03 246 B4 and similar transformers and "pot transformer" is not possible.

In contrast to fully embedded winding MF transformers, z. B. according to the patent DE 102 03 246 B4 , the natural outer and inner cooling surfaces are almost doubled with two-legged MF transformers, this two legged version incorporating further inventive components.

With the present invention shown two-arm transformer can therefore be compared to newer transformers achieved by a factor of 1.2 -1.5 times more favorable volume / power weight, the power category: 200-400 kVA so far not or only with large Expenses (water cooling, waveguides, etc.) could be built, which is important for traction, in rail transport, but also industrial applications.

The ribs or corner parts for the attachment of the cores, preferably by gluing, plane-parallel and in the direction of the cores (not the support between the encapsulation and cores) are conical. This has, among other manufacturing reasons, since in this way only once split mold inserts for the coil penetrations are needed, which can be easily expressed after the Aushärtprozess of the encapsulation.

The cores, preferably ferrite or nanocrystalline materials, are glued to the ribs and / or corner support part surfaces, wherein the cores and yokes outside and / or in the region of the glued joints to the ribs or corner contact part surfaces of the encapsulation with thin insulation material, preferably GfK , "glued". This measure is in particular because of the different thermal expansion coefficients of the materials z. As the Spulenumgußes, epoxy, and the cores, such as ferrite, required. Thus, thermal-mechanical stresses and their effects are reduced to non-hazardous levels with the thin GRP planking adhesive plates of the cores. The primary and secondary windings of the transformer are separated by intermediate insulation and the hermetic encapsulation voltage significantly oversized from each other, the cores are thermally and electrically decoupled held in corresponding Spulendurchdringungen in Spulenumguß. Thus, mechanical-metallic brackets, such as clamping profiles, fittings, etc. of conventional transformers, even MF transformers for fixing the windings and the cores completely eliminated, which makes the MF transformer compared to conventional transformers particularly quiet and vibration proof (train / aircraft applications).

In a further embodiment of the Umguß between the two windings of the two-arm transformer is separated, the separate Spulenumgüsse but via the cast-Verschaltungsräume again (4X) with each other -mechanically high strength connected to a total cast.

This "separation measure" further increases the surface of the transformers compared to the compact casting by about 25%, at the same time a further improvement, the "inner side ventilation" of the cores and yokes is achieved, which is another physical leap in quality towards optimal cooling of the cores and yokes means.

Above mentioned hermetic Spulenumgüsse realize u. a very reliable galvanic isolation between the primary and secondary windings, in all climatic conditions, including moisture / dirt. They form, with the windings, a compact block for receiving the cores, which is a problem with conventional MF transformers.

Non-hermetically encapsulated MF transformers, which are still in numerous use, often fail after 4-5 years of operation because moisture and dirt have in the meantime created creepage paths, both between grounded cores and between primary and / or secondary windings there are rollovers at the non-isolated potential arc base points. As a rule, these transformers can not be repaired.

The potting resins are preferably epoxy resins with thermally conductive fillers, preferably aluminum oxide / nitride and / or silanized quartz powder and / or other isolated metal particles composed, as far as the casting insulation properties are not affected thereby. To create a stable, thin-walled and hermetically sealed and mechanically stable Spulenumgußes the windings are preferably covered with fibers, especially glass fiber fabric.

The primary and secondary windings are preferably foil conductors, but may also be profile waveguides for direct or indirect liquid cooling. But also high frequency strands are used.

The transformer is - as already indicated - designed as a double-arm transformer, wherein a core / yoke pair is used for two windings of the transformer. The core attachment is made inside the gate, i. inside the windings.

Brief description of the drawings

Figur 1:

den Mittelfrequenztransformator in Frontansicht;

Figur 2:

den MF-Transformator in Seitenansicht;

Figur 3:

einen Querschnitt durch den MF-Transformator;

Figur 4:

eine Draufsicht auf den MF-Transformator;

Figur 5:

einen Querschnitt eines weiteren Ausführungsbeispiels des MF-Transformators;

Figur 6:

eine Draufsicht auf das weitere Ausführungsbeispiel eines MF-Transformators mit herausgenommenen Kernen;

Figur 7:

eine Darstellung des ersten Kerns des Transformators in Front-und Seitenansicht;

Figur 8:

eine Darstellung des zweiten Kerns des Transformators in Frontal- und Seitenansicht;

Figur 9:

einen Schnitt durch eine Wicklung des Transformators;

Figur 10:

eine Ansicht des Schichtaufbaus der Wicklung des Transformators

Figur 11:

eine weitere Ausführungsform eines Mittelfrequenztransformators in Frontansicht;

Figur 12:

den MF-Transformator von Fig. 11 in Seitenansicht;

Figur 13:

einen Querschnitt durch den MF-Transformator von Fig. 11;

Figur 14:

eine Draufsicht auf den MF-Transformator von Fig. 11;

Figur 15:

einen Querschnitt eines weiteren Ausführungsbeispiels des MF-Transformators;

Figur 16:

eine Draufsicht auf den MF-Transformator von Fig. 15 mit herausgenommenen Kernen;

Figur 17:

eine Darstellung des ersten Kerns des Transformators von Fig. 15 in Front- und Seitenansicht;

Figur 18:

eine Darstellung des zweiten Kerns des Transformators von Fig. 15 in Frontal- und Seitenansicht;

Show it:

FIG. 1:

the medium-frequency transformer in front view;

FIG. 2:

the MF transformer in side view;

FIG. 3:

a cross section through the MF transformer;

FIG. 4:

a plan view of the MF transformer;

FIG. 5:

a cross section of another embodiment of the MF transformer;

FIG. 6:

a plan view of the further embodiment of an MF transformer with removed cores;

FIG. 7:

a representation of the first core of the transformer in front and side view;

FIG. 8:

a representation of the second core of the transformer in front and side view;

FIG. 9:

a section through a winding of the transformer;

FIG. 10:

a view of the layer structure of the winding of transformer

FIG. 11:

a further embodiment of a medium-frequency transformer in front view;

FIG. 12:

the MF transformer of Figure 11 in side view.

FIG. 13:

a cross section through the MF transformer of Fig. 11;

FIG. 14:

a plan view of the MF transformer of Fig. 11;

FIG. 15:

a cross section of another embodiment of the MF transformer;

FIG. 16:

a plan view of the MF transformer of Figure 15 with removed cores.

FIG. 17:

a representation of the first core of the transformer of Figure 15 in front and side view.

FIG. 18:

a representation of the second core of the transformer of Figure 15 in front and side view.

Description of preferred embodiments of the invention

Figures 1 to 4 show a first embodiment of the medium-frequency transformer according to the invention in different views. The MF transformer has a Spulenumguß 1 with a substantially chamfered-rectangular cross section. In the Spulenumguß 1 a primary winding 2a and a secondary winding 2b are cast. This results in a windings 2a, 2b hermetically enclosing block. The front and the back form an end face 3, the z. B. for the Positioning of the terminals 13, 14 of the MF transformer can be used. At the lower end transformer feet 4 are preferably provided which have a sprue fitting 6 for floor or wall mounts.

In the coil encapsulation 1, for example, two three-layer windings 2a and 2b are inserted, wherein the windings are juxtaposed by a Isolierzwischenguß 19 separated from each other. Further, 1 cavities 20 can be provided on the front and back 3 of the Spulenumgußes that provide better dissipation of heat from the coils 2a, 2b to the outside in the environment. The electrical connection of the windings 2a and 2b takes place in integrated boarding rooms 11 and 12, which are also completely filled with potting compound.

According to the invention, each coil has a coil penetration 29, wherein the opposite surfaces of the coil penetration 29 are arranged plane-parallel to each other. The coil penetrations have, for example, approximately rectangular cross-sections, with chamfered parts on the narrow sides of the penetrations, wherein in each case on one longitudinal side of the coil penetration 29 mutually parallel ribs 9 or corner surfaces 28 are provided.
The ribs 9 to the surfaces of the coil penetration are arranged plane-parallel. Further, the ribs 9 and 28 are preferably conically shaped longitudinally, both laterally and in their aperture width.

The cores 21, 22 and yokes 18, as indicated in FIGS. 7 and 8, are joined into assemblies from I-cores or ribbon cores. The cores 21, 22 or yokes 18 are then externally and in the region of the adhesive joints to the ribs 9 of the Spulenumgußes 1 with a thermal insulating layer 5, preferably adhered GfK. This ensures that the cores 21, 22 can be thermally decoupled from the windings 2a, 2b. These pasted with the insulating layer 5 cores 21, 22 are now attached to one side by gluing to the ribs 9. The cores 21, 22 thus have contact only with the coil encapsulation 1 in the region of the ribs 9. Thus, according to the invention, no mechanical supporting or clamping elements are required for the cores 21, 22 and yokes 18, since the cores lie directly on the ribs 9 within the coil penetrations 29 are applied.
As already mentioned, the primary and secondary connections 13, 14 are arranged in the region of the bridge connections or boarding spaces 11, 12 and are contained directly in the casting-over concept. Further connection techniques are used which, with the appropriate SR design, make electrical creepage paths or strike distances obsolete. On both sides of the cores 21, 22 a space for the yokes 18 and the cooling air inlet and outlet is provided. Finally, an insulation plate 17 can be applied to the yokes 18.

In addition to the ferrite cores and yokes, soft magnetic materials can also be used as magnetic components. This has the advantage that at low frequencies e.g. ≤4000 Hz almost the full rated power of higher frequencies 7,500 - 15,000 Hz (with ferrite) can be maintained. Another big advantage is that with just a few coil cross sections at variable widths or heights, the entire power range of current and future SR transformers can be realized.

The primary and secondary terminals 13, 14 are preferably circularly insulated and arranged at 180 ° or laterally offset above and below. Depending on the installation position of the transformer, vertical or horizontal chimneys or forced air ducts, which are actively or passively flowed through by cooling air, remain through the remaining gaps 10 between the core and the coil encapsulation.

As stated, with the proposed two- or multi-leg design is by varying the height and / or width and adaptation to different core cross-sections and distances a wide variation of Transmission power possible. The cores 21, 22 are freely suspended in the windings on all sides and attached to the ribs 9 and / or in the corners 28 only on one side. As a result, the cores 21, 22 due to the adhesion "elastic-solid", noise-damping held in the Spulenumguß 1. All parts for fixing the cores 21, 22 are made of non-conductive materials, so that the cores can float freely in terms of potential. The cores are not grounded in contrast to conventional transformers. Preference is given to using ferrite cores or nanocrystalline or amorphous cores.

The transformer according to the invention opens with its small volume, size and low weight, for example, to be arranged directly in cooler currents different power converter or modules. Due to its hermetic construction, it also requires no further measures for mechanical or sealing protection against environmental influences.

Figures 5 and 6 show a slightly modified embodiment of an MF transformer according to the invention, in which case somewhat narrower ribs 9 are used for fastening the cores 21, 22. Depending on the design of the coil openings and the ribs, the transformer can be optimized either with respect to its leakage inductance or its noise emission.

FIGS. 9 and 10 show, by way of example, a cross section and a plan view, respectively, of one of the two windings 2a and 2b. The conductors are inter alia copper foil conductors 23, which are wound with the interposition of an intermediate insulation 24 substantially square or rectangular. The Cu conductors 23 are externally connected in the terminals 13, 14 of the Spulenumgußes 1. All windings are firmly and hermetically sealed with a potting compound of a resin, preferably epoxy resin, with thermally conductive fillers. The windings are further wrapped with a coarse mesh glass silk tape to allow the winding encapsulation highly stable, heat and cold shock resistant. The conventional mica insulation is replaced according to the invention by thermal bridges 25 and casting resin cast intermediate insulations. The magnetic cores are provided with thin GfK plates for stress compensation and as adhesion promoter. Furthermore, side recesses 16 remain for the air bubble rise to the middle or outside for the process improvement during the casting process of the windings.

FIGS. 11 to 14 show a transformer similar to that of FIGS. 1 to 4, identical components being provided with the same reference numerals. In contrast to FIGS. 1 to 4, two three-layer windings 2 a and 2 b are inserted here in the coil encapsulation 1, wherein the windings are electrically and thermally separated from one another next to each other by a central gap channel 27.

FIGS. 15 to 18 show a transformer similar to FIGS. 5 to 8, wherein identical components are provided with the same reference numerals. In contrast to FIGS. 5 to 8, the windings are hereby also electrically and thermally separated from one another by a center gap channel 27.

LIST OF REFERENCE NUMBERS

1

Coil encapsulation (transformer)

2a

Molded winding

2 B

Molded winding

3

Face (for connections)

4

Trafofuß

5

Insulation plate (on core)

6th

Pouring fitting (transformer foot)

7

Intermediate insulation (coils)

8th.

I-cores parallel bonding

9th

ribs

10

Gap (chimney ventilation)

11

Boarding space (primary winding)

12

Boarding room (secondary winding)

13

Connection (secondary)

14

Connection (primary)

15

Cast connection (coils)

16

Side recess (cores)

17

Insulation plate (yoke)

18

yoke

19

Coil insulation

20

erosion

21

core

22

core

23

Cu winding

24

Intermediate insulation (coils)

25

potting compound

26

soft magnetic u. a nanocrystalline nuclei

27

Intermediate slit channel

28

corner surfaces

29

Spulendurchdringung

Claims (20)

Transformer, in particular two-arm medium-frequency transformer, having at least one primary and secondary winding (2a, 2b) whose windings are directly, also indirectly, interleaved and magnetically coupled and cores receiving coil penetrations (29), characterized in that the coil penetrations (29 ) of the hermetically encapsulated primary and secondary windings with intermediate insulation, electrically and thermally separated from each other, wherein the cores (21, 22) thermally and dielectrically isolated and permanently secured gap-free within the coil penetrations over fin partial surfaces (9) or corner surfaces (28) being held. Transformer according to Claim 1, characterized in that the coil penetration has on at least one of its inner surfaces a plurality of integrally formed ribs (9) and / or corner surfaces (28) and / or support points to which the respective core (21, 22, 28) is fastened. Transformer according to claim 1 or 2, characterized in that the upper sides of the ribs (9) are formed plane-parallel to the opposite and bottom surface of the Spulendurchdringung and laterally in the core direction (21, 22) are tapered. Transformer according to one of the preceding claims, characterized in that the cores (21, 22) are glued to the tops of the ribs (9) or the corner supports (28). Transformer according to one of the preceding claims, characterized in that the cores (21; 22) are glued together by yokes (18) applied on both sides on both free sides. Transformer according to one of the preceding claims, characterized in that the cores (21; 22) and yokes (18) on the outside and / or in the region of the adhesive beading to the Spulenumguß (1) with a thin insulating material (5; 17) with compensating thermal expansion coefficient and high Strength, preferably GfK, are glued. Transformer according to one of the preceding claims, characterized in that it has long or magnetically highly loaded cores (21, 22) for the purpose of better heat dissipation, which are partially or completely filled with AL, Cu or thermally conductive plastic plates (eg graphite as filler). are covered. Transformer according to one of the preceding claims, characterized in that the cores (21; 22) and yokes (18) are medium to high voltage insulated from the cast-in windings, irrespective of the required earth insulation (voltage). Transformer according to one of the preceding claims, characterized in that between the cores (21; 22) and the surfaces of the coil penetrations on all sides chimney air gaps or for forced cooling air flows leading channels (8, 27) are provided. Transformer according to one of the preceding claims, characterized in that the two- or Mehrfach-Spulenumguß (1) to the windings (2a, 2b) is integrally formed and one of the primary and secondary windings separating from each other Intermediate casting (15), the mold is preferably executed rectangular with bevelled corners. Transformer according to one of the preceding claims, characterized in that on the surface of the Spulenumgusses (1) in the region of the intermediate casting (15) recesses (20) are provided. Transformer according to one of the preceding claims, characterized in that in the area above and below the windings (2a, 2b) hermetically insulated interconnection and bridge connections (15) for the supply and discharge of the electrical connections (13, 14) are present, which in essentially merge the enclosures of the partial windings by casting technology and mechanically. Transformer according to one of the preceding claims, characterized in that electrical end connections (13, 14) are formed in isolation with high creepage current-resistant primary / secondary connections. Transformer according to one of the preceding claims, characterized in that on the Spulenumguß (1) insulating feet (4) are cast with integrated and mechanically high-strength screw-in fittings (6) for all types and types of suspension (layers). Transformer according to one of the preceding claims, characterized in that the Spulenumguß (1) is a primary and secondary winding with interconnections (2a, 2b) hermetically sealed potting compound. Transformer according to one of the preceding claims, characterized in that the potting compound of a resin, preferably epoxy resin with thermally conductive fillers, preferably Aluminum oxide / nitride and / or silanized quartz powder, is composed. Transformer according to one of the preceding claims, characterized in that the primary and secondary windings (2a, 2b) are covered with fibers, preferably glass fibers, as internal reinforcement. Transformer according to one of the preceding claims, characterized in that the primary and secondary windings (2a, 2b) are foil conductors (23), preferably copper foils, but can also be high-frequency strands between which insulating intermediate layers (24) with and without voltage cut-offs are arranged , Transformer according to one of the preceding claims, characterized in that primary and / or secondary winding (2a; 2b) profile waveguide made of CU or AL or brass are also provided for primary and secondary windings for liquid cooling. Transformer according to one of the preceding claims, characterized in that the connections for the liquid-cooled profile waveguide are housed in the Umguß Verschaltungsblöcken.

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