EP1797573B1 - Toroidal core transformer - Google Patents

Description

The invention relates to a toroidal transformer, in particular a multiphase transformer having a plurality of axially adjacent arranged cores, each adjacent ring cores carry phase windings of different phases.

Such toroidal transformers are known from EP 0 557 549 A1 known.

Other transformers with stacked ring cores are from the US Pat. No. 2,832,012 , of the EP 0 510 252 A and the WO 95/11514 A known, wherein in these transformers, the different phase nuclei are not assigned to different phases.

In multi-phase transformers with adjacently arranged toroidal windings, there is the problem that exist between the individual phase windings high voltage potential differences and accordingly complex isolation measures are required, for example, to avoid flashovers in dripping, condensation or ice formation and to ensure the reliability of the polyphase transformer. Optionally, it may even be necessary to provide a heater to the polyphase transformer to avoid, for example, flashovers between the individual phase windings due to ice formation.

The insulation measures are very expensive. In addition, the isolation measures require a certain size of the multiphase transformer, whereby its space requirement is increased.

From the European patent EP 0 510 252 is known a three-phase toroidal transformer, the toroidal cores are arranged adjacent to each other in the axial direction and each carry different phases.

This toroidal transformer is designed for operation at low voltage. When used in the medium-voltage range, there would be high potential differences and thus arcing both in the area of the terminals and the windings themselves.

In contrast, the object is to provide a toroidal transformer of the type mentioned, for the only reduced isolation measures are required and the size is reduced. In addition, a high power density should be possible with a small size.

The achievement of this object is that the connection points of the phase windings of two adjacent ring cores are arranged offset from one another in the circumferential direction. The electrical phase shift between the individual phase windings of the polyphase transformer is practically canceled or reduced by a mechanical offset of the phase windings. As a result, the potential difference between adjacent winding sections of different phases is reduced, so that correspondingly less costly insulation measures for insulating adjacent phase windings against each other are required and thus the cost of the insulation measures are also reduced. Due to the lower potential differences between the phase windings of adjacent ring cores, these can also be arranged at a smaller distance from each other, whereby the size of the multiphase transformer is reduced.

A particularly favorable embodiment provides that the offset or the geometric angle between the connection points of the phase windings of two adjacent ring cores corresponds to the phase shift or the electrical phase angle between the voltage signals of these toroidal cores. Between directly adjacent winding sections of two ring cores, there is virtually no potential difference. In a three-phase system, the connection points of the three phase windings are each offset by 120 ° relative to one another in order to mechanically compensate for the phase angle between the individual phases.

Since a spacer is usually provided between the individual toroidal cores for mechanical stabilization and mounting, it is possible to allow small potential differences between two adjacent phase windings, so that a mechanical rotation of the toroidal cores which is reduced in relation to the electrical phase shift is sufficient to cause voltage flashovers between the phase windings to avoid with reduced or completely omitted isolation measures. The requirements for precision in the production of the multiphase transformer are thereby reduced and the production is simplified.

An embodiment of the toroidal transformer according to the invention of independent significance provides that one of the design of toroidal transformers adapted, preferably substantially cylindrical housing is provided for the ring cores with phase windings, and that preferably at one axial end of the housing, a fan or the like fan is provided. The ring cores with the phase windings are arranged protected in the housing from dirt and damage. With the fan, the arrangement is cooled to a thermal To avoid overloading the polyphase transformer.

The housing with the planned cooling measures favors a compact design of the transformer with high power density. In particular, in a polyphase transformer according to claim 1 or claim 2, this has an advantageous effect, because even these measures lead to a compact design that makes appropriate cooling measures required.

For cooling the polyphase transformer, it is also possible that in the region of the ring cores hollow lines are arranged for a coolant and that preferably the housing of the transformer is designed as a heat exchanger and connected to the hollow conduits. The housing can be double-walled, in order to dissipate the heat particularly well to the outside. The coolant can be pumped through the waveguides and housing with a pump.

A particularly advantageous embodiment provides that on the outside of the housing heat sink or the like protruding elements are provided to increase the housing surface, or that the housing has a profiled surface. Due to the enlarged surface, the heat is better dissipated and thermal overloads can be avoided.

It is also possible to cast the transformer coils individually with casting resin, wherein a housing for the respective coil is formed by the casting resin. In this case, a complementary shape to the desired heat sinks or cooling fins molded mold may be provided so as to obtain the desired outer contour with protruding elements for surface enlargement directly when casting the coils. By casting the coils on the one hand a achieved mechanical stabilization of the phase winding as well as a direct thermal coupling between the winding and the housing formed by the casting resin. Furthermore, a high dielectric strength is achieved with the casting.

An initially smooth housing surface can also be increased by the surface roughened by a suitable method, such as etching or sandblasting, structured or profiled.

Preferably, the surface has a structure with which the heat can be better dissipated. It should be mentioned that the spacer and insulation elements can be poured simultaneously with the casting of the transformer coils.

Another way to cool the toroidal transformer is that a receptacle is provided with a cooling medium for partially or completely inserting the transformer.

A particularly advantageous embodiment provides that the toroidal cores of the multiphase transformer are formed in a modular manner with their respective phase windings and that a holding device is provided for holding and for fixing the module-like toroidal cores to each other. Several modules can be interconnected in such a way that the power of the transformer can be increased. As a result, transformers with outputs over 100MVA can be realized. Furthermore, it is possible by the modular structure to continue to operate the transformer in case of failure of one of the modules by a spare module is optionally connected provisionally and thus the entire transformer remains operational. It is therefore not necessary to have a whole reserve transformer available can be switched to the case of a defect. As a result, costs are saved and the space required for a spare module is small compared to the space requirement of a whole reserve transformer.

The individual modules are held with a holding device and fixed in position relative to each other. On the holding device and insulation elements for insulating the phase windings, in particular to the outside, can be provided. In the axial direction need only be provided as supports for the toroidal cores between adjacent toroidal cores or their phase windings only to support the toroidal cores in their position and to prevent slippage of the toroidal cores. Special isolation measures are not necessary because of the mechanical rotation of the connection points of the phase windings according to the electrical phase position in the respective phase windings and the advantages thus achieved.

The invention is explained in more detail with reference to a figure.

Fig. 1 shows a schematic representation of a lateral section through a multi-phase transformer according to the invention with three axially adjacent arranged ring cores.

In FIG. 1 is a generally designated with 101 polyphase transformer having three stacked axially in the axial direction of ring cores 102. In each case adjacent ring cores 102 carry phase windings of different phases, wherein the phase windings are respectively applied to the ring cores 102 annularly enclosing coil bobbins 103. there can alternately bobbin 103 are each arranged with primary and secondary windings next to each other or one above the other. It is also possible for primary and secondary windings to be applied together to a bobbin 103.

The ring cores 102 are arranged in a holding device 104 which has outer and inner guide rails 105a, 105b for forming a receiving region for the toroidal cores 102. The guide rails 105a, 105b are each made of insulating material, so that the ring cores 102 and the phase windings on the bobbin 103 of the ring cores 102 are laterally outwardly insulated.

The holding device 104 has on its underside a bottom part 107, which likewise consists of insulating material. On the bottom part 107 insulating support elements 108 are provided for the lower ring core 102. In this case, a plurality of spaced bearing elements 108 may be provided, or it is a continuous ring as a support element 108 is provided. Spacers 109 are respectively provided between the individual ring cores 102 with which the ring cores 102 or the coil cores 103 respectively assigned to the toroidal cores 102 are fixed relative to one another in their position. Insulating support elements 108 are again provided above the upper ring core 102, on which a cover part 110 rests and the toroidal cores 102 are also insulated on the upper side towards the outside.

The Indian FIG. 1 shown polyphase transformer 101 is formed as a three-phase transformer. The connection points of the individual phase windings of the toroidal cores 102 or of the spool bodies 103, which are not illustrated in more detail, are each offset by 120 ° relative to one another. The phase windings are thereby mechanically um an angle offset from one another, which corresponds to the electrical phase shift or the electrical phase angle between the voltage signals of these phase windings.

In particular, in the region of the spacers 109, that is, where adjacent ring cores have the smallest distance from each other, there is practically no potential difference at two opposite regions of two ring cores 102 or bobbin 103. Voltage flashovers between adjacent toroidal cores 102 are thus not possible even if the toroidal cores 102 are arranged close together. The multi-phase transformer 101 can thereby be constructed compact and with reduced space requirements. In addition, between the individual ring cores 102, in the region of the spacers 109, no or only little insulation measures are required, whereby costs are saved and the construction is simplified.

The ring cores 102 are formed with their respective bobbins 103 like a module. In the event of a defect in one of these modules, the affected toroidal core can be exchanged for a replacement module or the defective module is electrically disconnected and a replacement module is provisionally connected to the polyphase transformer 101. Thus, it is not necessary to keep ready a complete transformer as a backup device, but it is sufficient to keep ready a ring core with the coil windings supporting the phase windings as a reserve module. As a result, costs are saved and the space required for a reserve device is reduced.

Claims (8)

1. Toroidal core Transformer, particularly a polyphase transformer (101) having a plurality of toroidal cores (102) arranged adjacent to one another in the axial direction, adjacent toroidal cores (102) having phase windings of different phases, characterised in that the connection points of the phase windings of two adjacent toroidal cores (102) are arranged offset from one another in the circumferential direction.
2. Transformer according to claim 1, characterised in that the offset or the geometric angle between the connection points of the phase windings of two adjacent toroidal cores (102) corresponds to the phase shift or electrical phase angle between the voltage signals of these toroidal cores (102).
3. Transformer according to one of claims 1 or 2, characterised in that a preferably substantially cylindrical housing adapted to the design of toroidal core transformers is provided for the toroidal cores (102) with phase windings, and in that preferably a ventilator or fan is provided at an axial end of the housing.
4. Transformer according to one of claims 1 to 3, characterised in that hollow lines for a coolant are arranged in the region of the toroidal cores (102), and preferably the housing of the transformer (101) is embodied as a heat exchanger and connected to the hollow lines.
5. Transformer according to one of claims 3 or 4, characterised in that cooling members or similar projecting elements for enlarging the surface area of the housing are provided on the exterior of the housing, and in particular the housing has a profiled surface.
6. Transformer according to one of claims 1 to 5, characterised in that a receptacle containing a cooling medium is provided into which the transformer (101) is inserted partly or totally.
7. Transformer according to one of claims 1 to 6, characterised in that the toroidal cores (102) of the polyphase transformer (101) with their respective phase windings are of modular construction and in that a holding device (104) is provided for holding the modular toroidal cores (102) and securing them against one another.
8. Transformer according to one of claims 1 to 7, characterised in that the transformer coils are individually encapsulated in casting resin and preferably have an exterior profiling to enlarge their surface area.

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