EP2735005B1 - Press frame structure for a transformer - Google Patents

Description

The invention relates to a press frame structure for a transformer, in particular for a power transformer.

Electromagnetic alternating fields induce eddy currents in press frames and tension plates or tie rods of (power) transformers. This leads to a significant increase in additional losses and possibly thermal problems.

It is known to magnetically shield the press frame with a core sheet. It is also known to use press frames made of non-magnetic steel.

Out DE 23 39 972 is a support and pressing device for magnetic cores and windings of transformers and inductors known. Out JP 61099314 A a stationary induction apparatus is known.

The object of the invention is to reduce the unwanted eddy currents in a transformer and at the same time to provide new possibilities for the construction of power transformers, in particular press frame structures for power transformers.

This object is achieved according to the features of the independent claims. Preferred embodiments are in particular the dependent claims.

To achieve the object, a press frame structure for a transformer according to the features of claim 1 is given.

This press frame structure provides additional degrees of freedom in the design of the transformer and allows a redistribution of forces from the edge of the core in an area outside the Windings. As a result, the magnetically active portion of the required Zugpressplatten can be reduced at or near the core, which significantly reduces the resulting eddy currents losses and torque on the Zugpressplatten.

A press frame structure is proposed, e.g. not over the entire length of a transformer core rests. The press frame structure nevertheless serves for the horizontal support of the transformer core, which is e.g. is constructed of core lamination packages. In this case, it is advantageous that axial winding forces between the upper and lower pressing frames can also be transmitted in spaces between windings on adjacent legs. As such, the space around the transformer can be used, e.g. using struts to allow the cohesion required by the press frame structure.

For example, the press frame structure comprises braces, so that the press frame structure (in particular the struts) magnetic field lines as small as possible cross-sectional areas in which eddy currents could be induced. With the help of numerical magnetic field calculations, the shape of the press frame structure can be optimized so that a reduction of the additional losses is achieved.

At the same time, starting points for an axial force transmission can be determined according to a mechanically favorable distribution, which results in that the torques on the press frame structure are reduced. Optionally, the height of the press frame structure can thus be reduced compared to the height of a known press frame, which has a favorable effect on the space required for the transformer.

A further development is that the struts are designed obliquely so that the magnetic flux is reduced by the strut, in particular minimal.

Thus, the geometry of the press frame structure can be optimized based on the respective dimensions of the individual scenario so that the eddy current losses are minimized or at least significantly reduced.

Another development is that the struts are made of sheet metal. Alternatively, the struts can also be made of plastic or carbon. Combinations of different materials are possible.

In particular, it is a development that the Zugpressplatten connect an upper press frame of the transformer with a lower pressing frame of the transformer.

This (shortest) connection between the upper and the lower pressing frame also characterizes the axial direction described here.

It is also a development that the tension elements connect the upper press frame of the transformer with the lower press frame of the transformer.

Furthermore, it is a development that the tension elements are at least partially made of an electrically insulating material.

As part of an additional development, the Zugpressplatten are at least partially made of an electrically insulating material.

This has the advantage that the tension elements and / or the Zugpressplatten can be placed arbitrarily, because the magnetic flux is not significantly affected by the electrically insulating material.

A next development is that the Zugpressplatten are at least partially incorporated in windings of the transformer.

One embodiment is that the Zugpressplatten are at least partially disposed in a stray channel of the transformer.

An alternative embodiment is that the Zugpressplatten are at least partially disposed in a space between windings of adjacent legs and in an area between the legs and a boiler wall of the transformer.

A next embodiment is that the Zugpressplatten are at least partially disposed in the core of the transformer.

The above-described characteristics, features, and advantages of this invention, as well as the manner in which they will be achieved, will become clearer and more clearly understood in connection with the following schematic description of exemplary embodiments which will be described in detail in conjunction with the drawings. In this case, the same or equivalent elements may be provided with the same reference numerals for clarity.

Fig. 1

schematisch einen Kern eines Transformators mit einem oberen und einem unteren Pressrahmen und mehreren Zugpressplatten, die den oberen und den unteren Pressrahmen verbinden;

Fig. 2

schematisch eine Sicht auf den einen Transformator von oben, wobei der Transformator den Kern, den Pressrahmen und die Zugpressplatten gemäß Fig.1 aufweist;

Fig. 3

eine von Fig.1 und Fig.2 unterschiedliche Pressrahmenstruktur mit einer Vielzahl von Zugelementen und Verstrebungen, die außerhalb der Wicklungen des Transformators angeordnet sind.

Show it:

Fig. 1

schematically a core of a transformer having an upper and a lower pressing frame and a plurality of Zugpressplatten connecting the upper and the lower pressing frame;

Fig. 2

schematically a view of the one transformer from above, wherein the transformer according to the core, the pressing frame and the Zugpressplatten Fig.1 having;

Fig. 3

one of Fig.1 and Fig.2 different press frame structure with a plurality of tension elements and Struts, which are arranged outside the windings of the transformer.

Fig.1 schematically shows a core 101 of a known transformer with a plurality of legs and a lower yoke in a mounting state (without already attached upper yoke). The legs are provided with a bandage, the windings are not present in this state of assembly. The transformer has upper and lower press frames 102 and a plurality of tensile press plates 103 connecting the upper and lower press frames 102. The core 101 is preferably constructed of several layers of core sheet. By the pressing frame 102 and the Zugpressplatten 103, a mechanical stability of the core 101 is ensured. The Zugpressplatten 103 with the press frame 102 ensure that the transformer is held together in the assembled state along the legs (axially).

Fig.2 schematically shows a view of a known transformer from above, wherein the transformer, the core 101, the pressing frame 102 and the Zugruckplatten 103 similar Fig.1 having. Furthermore, in Fig.2 symbolically shown windings 201 of the transformer. The in Fig.2 illustrated transformer comprises in contrast to the in Fig.1 shown transformer three legs and in the representation of Fig.2 are already schematically applied windings on the legs.

The in Fig.2 shown press frame 102 may be performed substantially continuously in the upper and lower regions of the transformer (see. Fig.1 ); Fig.2 here selects a symbolic cross-sectional representation to illustrate that in addition to the pressing frame 102 at certain intervals and approximately in each center of the winding 201 is a respective Zugressplatte 103 is arranged, which connects the pressing frame 102 at the upper and lower end of the transformer.

The press frame 102 provides the magnetic flux with a high cross-section, resulting in high losses.

Figure 3 shows one of Fig.1 and Fig.2 different, inventive press frame structure in a plan view with a plurality of tension members 302 and struts 301, which are arranged outside of, in particular next to or laterally offset to windings 201. Further shows Figure 3 a plurality of draft plates 304. The tension members 302 and the draft plates 304 are respectively fixed in the upper portion of the transformer and in the lower portion of the transformer, so that the core is effectively axially fixed and the core sheets are held together. Based on the struts 301, the tension members 302 are at least partially connected to the Zugpressplatten 304.

The press frame structure provides the magnetic flux according to the embodiment according to Fig.2 significantly reduced cross-section, which causes a reduction in the losses due to eddy currents.

The press frame structure permits a redistribution of the axial forces from the edge of the core into an area outside the windings 201. The tension elements 302 are also preferably connected to the upper and the lower press frame (not in FIG Figure 3 shown) fixed. Thus, the tension members 302 as well as the Zugpressplatten 304 extend axially along the transformer and in particular at the top and bottom of the transformer (eg on the press frame) fixed. For example, the tension members 302 may be suspended below and bolted to the top of the transformer.

The required axial force holding the windings 201 of the transformer together is determined according to FIG Figure 3 on the Zugpressplatten 304, the tension members 302 and the struts 301 distributed. Preferably, such a construction is dimensioned such that the core and the windings 201 (at least) held together with the same forces as in a conventional press frame structure.

Thus, the proposed approach on the one hand ensures the required mechanical stability and on the other hand reduces the proportion of Zugpressplatten 304 in the core cross-section. This results in less losses in the Zugpressplatten 304. Furthermore, the volume of the core can be reduced, which has a beneficial effect on the cost of the transformer. Also, thus the torque is reduced to the Zugpressplatten 304.

One option is that the axial force transmission between upper and lower pressing frame (not in Figure 3 shown) via the tension elements 302 and / or the Zugpressplatten 304, which are for example at least partially made of an electrically insulating material.

It is advantageous that these Zugpressplatten 304 may have a lower mechanical strength, since they can also be used in places of the transformer, which are unfavorable for electrically conductive Zugpressplatten 304 and thus more space for Zugpressplatten 304 is available. In particular, the axial forces (pre-pressing force, short-circuit forces) are absorbed by the tension elements 302.

For example, the tension members 302, e.g. in the form of Zugpressplatten, are made of electrically insulating material axially in the windings or wrapped, located in a stray channel and / or located in a space between windings of adjacent legs and in an area between the legs and a boiler wall of the transformer.

It should be noted that the transformer is located inside a boiler, which is filled eg with a liquid.

1. (1) Eine zwischen zwei Wicklungen übertragene Leistung wird im Magnetfeld im Streukanal transportiert.
2. (2) Die Geometrie des Streukanals ist für die Kurzschlussimpedanz des Transformators maßgeblich. Diese Kurzschlussimpedanz begrenzt den Strom in einem Fehlerfall (d.h. bei einem Kurzschluss). Die Kurzschlussimpedanz kann z.B. im Rahmen eines Designs des Transformators vorgegeben sein, z.B. basierend auf einer Netzplanung.

The stray channel has in particular the following two functions:

1. (1) A power transmitted between two windings is transported in the magnetic field in the scattering channel.
2. (2) The geometry of the stray channel is decisive for the short-circuit impedance of the transformer. This short-circuit impedance limits the current in the event of a fault (ie in the event of a short circuit). The short-circuit impedance can be predetermined, for example, within the scope of a design of the transformer, eg based on a network planning.

The (main) leakage channel corresponds to a gap between two windings, e.g. a primary and a secondary winding or an upper and an undervoltage.

If a transformer has more than two windings, there can be multiple stray channels. In multi-concentric design, there may be more than one stray channel between two (split) windings, e.g. from inside to outside: undervoltage, high voltage, undervoltage (in series with an internal undervoltage).

For example, modified strips in layer windings, stray channel, winding gaps can be designed as insulating tension elements. Also, such tension elements may be arranged in the core volume of the transformer core itself.

The upper and lower press frames can each be made largely conventionally. However, the losses in the pressing frame can be almost completely avoided: The favorable distribution of the axial pressure over a plurality of insulating tension elements can be achieved at the same time a volume optimization of the upper and lower pressing frame.

The option of tension elements made of electrically insulating material thus enables a reduction of the power loss in the press frame and allows to maintain the mechanical stability of the press frame at the same time.

Accordingly, the tension elements of electrically insulating material in the example of Fig.2 be arranged or incorporated almost anywhere in an area 401. The use of the insulating material for the tension elements results in additional degrees of freedom in the design of the transformer; In particular, the Zugpressplatten 103 can be completely replaced by Zugpressplatten of electrically insulating material.

While the invention has been further illustrated and described in detail by the at least one embodiment shown, the invention is not so limited and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

Claims (12)

1. Press frame structure for a transformer

   - having a plurality of tensioning elements (302),

   - having a lower press frame and an upper press frame and also a plurality of tensioning press plates (304) which connect the upper press frame and the lower press frame,

   - wherein the tensioning elements (302) and the tensioning press plates (304) can be fixed to the transformer at the top and bottom,

   - having a plurality of struts (301) which can be formed to project at least partially obliquely from a core of the transformer,

   - wherein the plurality of tensioning press plates (304) can be arranged on or in the vicinity of the core of the transformer,

   - wherein the tensioning elements (302) can be arranged laterally outside windings (201) of the transformer,

   - wherein the tensioning elements (302) are connected at least partially to the tensioning press plates (304) using the struts (301),

   - wherein the tensioning elements (302) and the tensioning press plates (304) can be arranged axially along the transformer and can be fixed to the said transformer.
2. Press frame structure according to Claim 1, in which the struts (301) are formed obliquely in such a way that the magnetic flux of a transformer through the strut (301) is reduced.
3. Press frame structure according to either of the preceding claims, in which the struts (301) are formed from sheet metal.
4. Press frame structure according to one of the preceding claims, in which the tensioning press plates (304) connect the upper press frame to the lower press frame.
5. Press frame structure according to Claim 4, in which the tensioning elements (302) connect the upper press frame to the lower press frame.
6. Press frame structure according to one of the preceding claims, in which the tensioning elements (302) are formed at least partially from an electrically insulating material.
7. Press frame structure according to one of the preceding claims, in which the tensioning elements (302) and the tensioning press plates (304) can each be fixed in the upper region and in the lower region of the transformer, in particular to the press frame structure.
8. Press frame structure according to one of the preceding claims, in which the tensioning press plates (304) are formed at least partially from an electrically insulating material.
9. Press frame structure according to Claim 8, in which the tensioning press plates (304) can be inserted at least partially into windings.
10. Press frame structure according to either of Claims 8 and 9, in which the tensioning press plates (304) can be arranged at least partially in a leakage flux channel of the transformer.
11. Press frame structure according to one of Claims 8 to 10, in which the tensioning press plates (304) can be arranged at least partially in a space between windings (201) of adjacent limbs and in a region between the limbs and a tank wall of the transformer.
12. Press frame structure according to one of Claims 8 to 11, in which the tensioning press plates (304) can be arranged at least partially in the core of the transformer.

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