EP0618596A1

EP0618596A1 - Air core reactor

Info

Publication number: EP0618596A1
Application number: EP94200845A
Authority: EP
Inventors: Marinus Martinus Engelbertus Maria Jansen
Original assignee: Smit Transformatoren BV
Current assignee: Smit Transformatoren BV
Priority date: 1993-04-02
Filing date: 1994-03-29
Publication date: 1994-10-05
Also published as: NL9300590A

Abstract

The invention relates to a reactor for application in a transport or distribution network for electrical energy and comprising at least one winding arranged in a metal housing, wherein means are arranged for applying an axial pressure force to the winding, wherein the metal housing forms part of the pressure means.

This renders superfluous the use of extra constructions for applying an axial pressure force to the reactor. This avoids the problems associated with such constructions, while the possibility is likewise created of giving the reactor a smaller, lighter and less expensive form.

According to a preferred embodiment a magnetic circuit is arranged inside the housing to screen the stray field generated by the winding, wherein at least a part of the magnetic circuit functions as means for transmitting from the housing the axial pressure force to be applied to the winding.

Description

The invention relates to a reactor for application in a transport or distribution network for electrical energy and comprising at least one winding arranged in a metal housing, wherein means are arranged for applying an axial pressure force to the winding.
Such reactors are generally known.
Such reactors, also known as choke coils, serve to compensate reactive power that is generated in such a distribution network due to an excess of capacitive loads.
The windings of such reactors forming part of the prior art generate inter alia axial forces during use which press together the individual turns of the winding. In order to prevent the turns hereby being set into movement and possibly being damaged, it must be ensured at all times that the turns are situated against each other, both during operation and when inoperative. A typical method of achieving this object is to apply an axial pressure force on the winding. In the reactor constructions of the prior art constructions are arranged for this purpose in the form of tie rods and the like which are generally arranged on the outside of the winding. Such tie rods otherwise find application in transformers as well. It will be apparent that such constructions result in an increase of the cost price of such a reactor and also in an increase in the mass of such a coil. The magnetic fields generated by the winding can moreover cause eddy currents and hysteresis losses in such a construction, whereby generation of heat takes place and the coil will absorb active power, which is of course not desirable.
The object of the present invention is to provide such a reactor, wherein the above stated drawbacks are avoided.
This object is achieved in that the metal housing forms part of the pressure means.
This renders superfluous the use of extra constructions for applying an axial pressure force on the winding. This avoids the problems associated with such constructions, while the possibility is likewise created of giving the reactor a smaller, lighter and less expensive form.
According to a preferred embodiment a magnetic circuit is arranged inside the housing to shield the stray field generated by the winding, wherein at least a part of the magnetic circuit functions as means for transmitting from the housing the axial pressure force to be applied to the winding. This preferred embodiment results in an additional saving of material and weight; the relevant part of the magnetic circuit fulfills a dual function.
The present invention will be elucidated hereinafter with reference to the annexed figures, in which:

fig. 1 shows a partly broken away perspective view of a reactor according to the invention; and
fig. 2 shows a sectional view along the line II in fig. 1.

Depicted in fig. 1 is a reactor 1 according to the present invention. The reactor 1 comprises a housing 2, which housing is formed by a bottom 3, an upper wall 4, two side walls 5,6, a rear wall not shown in the drawing and a front wall 7. Front wall 7 is herein embodied for removal from the rest of the housing. The other walls are joined together by a weld construction into one housing. Side walls 5,6, bottom 3 and upper wall 4 are reinforced by means of ribs 8. A magnetic lamination 9 is arranged in the housing against bottom 3, upper wall 4 and both side walls 5,6, wherein the magnetic lamination is formed by strips of magnetic steel 10 stacked against each other.
The magnetic steel strips 10 are joined together such that each layer forms part of the magnetic circuit, wherein the strips adjoining different walls mutually engage at the corners in order to obtain an interlock. Fixed supports not shown in the drawing are arranged to secure the lamination, while the lamination is fixed in the housing by the supports 11 which are provided with set screws 12.
On the part of the lamination adjacent to the bottom 3 are arranged two beams 13 manufactured from wood or multi-ply or other insulation material. Resting in turn on beams 13 is a disc 14 which is manufactured from wood or multi-ply or other insulation material and which is provided with a shoulder 15. Placed around shoulder 15 is a hollow core 16 which is manufactured from insulating material, for instance pressed paper or plastic. The actual winding 17 wound from rectangular wire or stranded cable is arranged around the hollow core 16. Although this is not visible in the drawing, spaces are provided herein between windings mutually adjoining in a horizontal plane so that cooling channels extending in vertical direction run through the whole winding 17.
A plate 18 is arranged on the top of winding 17. This plate 18, as the disc 14, is provided with an annular shoulder 19. The shoulder 19 here also serves to center the winding 17 relative to the plate. Arranged above plate 18 is a pressure plate 20, the form and dimensions of which correspond substantially with those of plate 18. On its upper side the pressure plate rests against the underside of the upper lamination 9, while two wedge paths 21 are recessed into the pressure plate under which two pairs of wedges 22 are situated. The underside of the wedges rests on plate 18. Each pair of wedges is mutually joined by means of a threaded end 23 manufactured from insulating material and forming a tensioning device. Nuts 24 are screwed onto the ends of the threaded ends.
In order to connect the winding to the energy distribution network a high-voltage lead-through 25 is arranged, the lower end of which is connected to the middle 26 of winding 17. The middle of the winding is in any case easiest to insulate with respect to earth. Both the top and bottom end of the winding are joined to a low-voltage lead-through 27 by means of connections not shown in the drawing.
The interior of housing 1 is further filled with a suitable oil resistant to high voltage, for instance transformer oil. Use is made herein of provisions (not shown) such as a filling opening, an expansion vessel and a Buchholz protective relay.
With reference to fig. 2 it will subsequently be explained how the construction of the reactor is realized. Firstly the housing is constructed, for instance by means of welding. The front wall 7 is herein left off for the time being. The magnetic lamination 9 is then arranged in the housing. It is easy to place the housing on its rear wall during stacking of the lamination so that stacking of the lamination can take place easily. After stacking of the lamination the housing is again placed upright, the leads 25, 27 and a part of the auxiliary equipment are arranged and beams 13 are placed, whereafter the winding, already pre-wound onto the hollow core and placed on the disc 14, and already provided with the plate 18, is pushed onto the beams 13.
The combination of pressure plate, wedge paths, wedges, threaded ends, nuts forming a pressure device is subsequently arranged. It is however also possible to employ another sequence.
Once the various components have been set in place it is possible, when the wedge paths 21 are provided with a material with a low coefficient of friction such as teflon, to generate sufficient tension by means of tightening nut 23 to fixedly clamp the winding 17 such that in all conditions the windings of the coil will remain pressed against each other due to the pressure force applied from the housing, wherein only such a small deformation of the construction occurs that it is reversible.
It is also possible to bring the device to tension by means of arranging a temporary pressure element (not shown in the drawing) between the plate 18 and the pressure plate 20. For instance, use can be made herein of an inflatable pressure element, such as cushions used for instance in rescue operations. It is also possible to make use of a pressure element which can be pumped up with a liquid, for instance transformer oil. By inflating or pumping up such a cushion the tension is diverted from the wedges and the wedge paths so that these latter can be adjusted to the required tension. The temporary pressure element can then be emptied, after which it can be removed. Lastly, the front wall 7 is arranged and the housing is filled with oil.
It is possible to leave the cushion or other pressure element in place so that readjustment of the pressure, if required, can take place at any desired moment in the operational phase at the erection site of the reactor. It is optionally even possible to make the pressure cushion permanently active in generating the required pressure forces. This does of course require auxiliary equipment in the form of for instance a compressor or pump to generate the relevant force.
It should be noted here that the part of the magnetic circuit adjoining the bottom and the part of the magnetic circuit adjoining the upper wall contribute to the rigidity of the bottom respectively the upper wall, so that these wall elements can transfer the forces to be applied to the winding from the front, rear and side walls of the housing. Although the upper wall and the bottom are provided with reinforcing ribs, which of course contribute to the rigidity, the use of the relevant part of the magnetic circuit nevertheless enables considerable limitation of the dimensions of the ribs.
By dimensioning the ribs in the correct manner it is even possible to select the total rigidity of the wall, ribs and lamination such that the pressure force on the winding is optimally preserved under all conditions, also for instance under the influence of temperature differences between the winding and the side walls, whereby both said elements expand in differing degrees.
The invention is of course not limited to single-phase reactors as shown here. In similar manner a construction can be made in which several windings are accommodated in a housing, for instance two windings connected in series or in parallel, or three windings together forming a three-phase reactor. In certain conditions omission of the lamination 9 along both side walls can then be even considered, as these are no longer required as closing path for the magnetic circuit. The lamination 9 along the top and bottom wall remain present in the construction however, both to guide the magnetic field and also to reinforce the top and bottom wall.

Claims

Reactor for application in a transport or distribution network for electrical energy and comprising at least one winding arranged in a metal housing, wherein means are arranged for applying an axial pressure force to the winding, characterized in that the metal housing forms part of the pressure means.
Reactor as claimed in claim 1, wherein the winding is situated round a hollow core and a magnetic circuit is arranged inside the housing to shield the stray field generated by the winding, and the housing comprises walls extending parallel to the axis of the winding and flat walls extending perpendicularly to the axis of the winding, characterized in that at least a part of the magnetic circuit extends parallel to the walls of the housing extending perpendicularly to the axis of the winding and forms part of the pressure means.
Reactor as claimed in claim 1 or 2, characterized in that reinforcing ribs are arranged on the outside of the upper wall and the bottom.
Reactor as claimed in claim 2 or 3, characterized in that the rigidity of the upper wall, the bottom, the parts of the magnetic lamination adjacent thereto and the reinforcing ribs is chosen such that the pressure force on the winding remains within permissible limits under operating conditions.
Reactor as claimed in any of the foregoing claims, characterized in that at least one of the walls extending parallel to the axis of the winding is detachable.
Reactor as claimed in any of the foregoing claims, characterized in that a plate provided with a shoulder is present on both sides of the winding, wherein the hollow core rests all around against the shoulder and wherein between at least one of these plates and the relevant wall of the housing a pressure device is arranged for applying an axial pressure force to the winding.
Reactor as claimed in claim 6, characterized in that the pressure device is formed by a support plate resting against the relevant wall and at least a pair of wedges which are arranged between the plate and the support plate for movement toward each other and which are mutually connected by a tensioning device, wherein the support plate is provided with at least one wedge path for guiding the wedges, and wherein the incline of the wedge paths corresponds with that of the wedges.
Reactor as claimed in claim 6 or 7, characterized by a temporarily active pressure device placed between the wall and the plate.
Reactor as claimed in claim 8, characterized in that the pressure device is formed by an element which is inflatable or which can be pumped up.
Reactor as claimed in claim 9, characterized in that the element which is inflatable or which can be pumped up functions as gas bladder inside the housing filled with liquid.
Multiple reactor as claimed in any of the foregoing claims, characterized in that at least two windings are arranged inside a housing, wherein the pressure means are adapted to apply a pressure force to each of the windings.