Resistor arrangement for step switches and step switches

Abstract

Resistor arrangement (10) for a tap changer (1) for uninterrupted switching between winding taps of a transformer, the resistor arrangement (10) comprising at least one resistive element (20) which is held by at least two resistive holders (30), characterized by: - a base plate (11) with at least one opening (12) on which the at least two resistance holders (30) for receiving the resistance element (20) are arranged; - a guide (31) formed in each resistance holder (30), wherein each guide (31) positions a first end (201) or a second end (202) of the resistance element (20) with respect to a longitudinal direction (L) between the two resistance holders (30), and wherein the resistance element (20) can be inserted through the opening (12) into each of the guides (31); and - two contact points (24) of the resistance element (20) which, when a resistance element (20) is inserted into the resistance holder (30), can be electrically contacted by a respective contact (40) of the tap changer (1).

Description

[0001] The invention relates to a resistor arrangement for a tap changer and a tap changer with such a resistor arrangement.

[0002] German patent application DE 42 31 353 A1 discloses a tap changer. A current-limiting resistor is connected at one end to one of the tap selectors and at the other end to the neutral point. The resistor is fixed and immutably installed.

[0003] German utility model DE 77 07 461 U discloses a load-switching resistor. The load-switching resistor consists of round, oval, rectangular, or square resistive material with rounded edges, bent into resistance spirals and mounted in a self-supporting manner within chambers. The bent resistance spiral is mounted in a chamber formed from two insulating rods.

[0004] Other resistor arrangements of this type are known from publications US 4,935,717 and EP 0 554 914 A2.

[0005] Tap changers, especially load tap changers, are used for the uninterrupted switching between winding taps of a transformer. In known load tap changers based on the resistance-based switching principle, the circulating current flowing during the switching process, when the currently connected and the preselected new tap contact are simultaneously engaged, is limited by ohmic resistors, thus ensuring an uninterrupted change in the transformer's turns ratio. The ohmic resistance must be designed according to the specific circuit topology, the individual operating conditions, the load current, and the tap voltage—in other words, according to the specific application of the load tap changer. The tap voltage is defined as the voltage present between the currently connected and the preselected tap contact of the load tap changer.Designing the resistors is complex and impacts the entire manufacturing process, particularly the tap changer assembly. Depending on the application, a different number and size of resistors are required, potentially necessitating adjustments to the tap changer's design. This results in a large number of different tap changer variants, each tailored to its specific application. Currently, during assembly, the tap changer is fitted with the required switching resistors according to the order-specific resistance value and then fully assembled. Given the large number of variants, this approach increases the assembly effort.

[0006] The object of the invention is therefore to provide an improved concept for a resistor arrangement for a tap changer that is simple and can be quickly adapted to different applications of the tap changer while ensuring the operational reliability of the tap changer.

[0007] This problem is solved by a resistor arrangement for a tap changer comprising the features of claim 1. Further embodiments are described in the dependent claims.

[0008] The resistor arrangement according to the invention for a tap changer for uninterrupted switching between winding taps of a transformer comprises at least one resistor element held by at least two resistor holders. The resistor holders are provided on at least one base plate with at least one opening in which the at least two resistor holders are arranged to receive the resistor element. The resistor element can be inserted through the opening into the guide provided in the resistor holder. Guides are formed in each resistor holder. Each guide of the two resistor elements positions a first end or a second end of the resistor element with respect to a longitudinal direction between the two resistor holders. Furthermore, the resistor element can be inserted through the opening into one of the respective guides.Two contact points of the resistance element can be electrically contacted by a respective contact of the tap changer when the resistance element is inserted into the resistance holder.

[0009] The improved concept for the tap changer with a resistor arrangement has the advantage that it makes it possible to easily and quickly change or replace the resistors when requirements change (such as changes in the operating conditions of the tap changer) while still ensuring the operational reliability of the tap changer.

[0010] According to one possible embodiment of the resistor arrangement for a tap changer, the two contact points of the resistor element are provided in an edge region at the first end and at the second end of each resistor element.

[0011] According to one possible embodiment of the resistor arrangement for a tap changer, each resistor holder includes a guide for fixing the resistor element. Each guide can be configured as a slot with a closed end and an open end. At least partially, the slot is provided with a lateral wall that may extend partially along the slot.

[0012] The resistor element can be inserted through the open end of the slot. The resistor arrangement is designed such that, after assembly of the tap changer, the resistor element is fixed between the at least two resistor holders by means of the guide of the resistor holders.

[0013] According to a further possible embodiment, the guide can include a retaining element that can be designed as a reversibly and elastically pivotable leg with a snap hook provided at one free end. The snap hook secures the resistance element inserted into the guide and holds it in position between the two resistance holders. The elastically pivotable leg deflects when the resistance element is inserted into the guide and thereby also forms part of the guide.

[0014] According to one possible embodiment of the invention, the at least one resistance element comprises a resistance carrier and a current-limiting element.

[0015] According to one possible embodiment of the invention, the resistive element can be designed as a plate and the current-limiting element as a metallic wire wound around the plate. In another possible embodiment, the resistive element can be designed as a frame and the current-limiting element in the form of one or more metallic springs stretched within the frame.

[0016] According to one possible embodiment of the invention, each resistive element can have an edge region at both its first and second ends that is free of the current-limiting element. The closed end of the guide defines an end position for the resistive element in the resistor holder. As a result, a portion of the edge region of the resistive element essentially engages with the slot of the guide in a form-fitting manner.

[0017] Essentially, the positive-locking interaction means that the edge regions of the resistance element are at least partially surrounded by the guide on at least three sides in a positive-locking manner, i.e., with a precise fit. The open end of the guide thus forms an open side through which the resistance element can be inserted into the resistance holder. When the resistance element (at least one) is inserted into the guide, the elastically pivotable leg yields, and the resistance element (at least one) is locked in place once it reaches its end position in the guide.

[0018] According to at least one possible embodiment, the snap hook forms part of the guide for the resistor holder such that, when the resistor element reaches its end position in the guide, the snap hook at least partially surrounds it and thereby locks it in the end position. The snap hook can also be easily released from the locking position, allowing the resistor element to be removed and, for example, replaced with another one (with different specifications).

[0019] According to at least one possible embodiment, the resistor holder and the guide are formed in one piece from insulating material. According to at least one embodiment, the resistor holder, the guide, and the retaining element are formed in one piece. Preferably, the resistor holder can be manufactured from a plastic using an injection molding process.

[0020] According to at least one possible embodiment, the base plate has at least one opening in the area of ​​the at least two resistance holders, which is designed in such a way that the at least one resistance element can be fixed through the opening between the at least two resistance holders by means of the guides of the resistance holders.

[0021] This allows for the insertion of the resistance elements after assembly of the tap changer, as well as easy adaptation of the tap changer to different applications by replacing the resistance elements. This also ensures the electrical contact of the resistance elements.

[0022] According to one possible embodiment, at least one opening can be essentially rectangular.

[0023] According to one possible embodiment of the invention, the resistive element can comprise two contact points made of electrically conductive material, which are electrically connected to the current-limiting element. The contact points of the resistive element are essentially provided in a peripheral region at the first end and at the second end of each resistive element.

[0024] According to one possible embodiment, each contact point is designed as a metal plate.

[0025] According to one possible embodiment, the resistor arrangement comprises at least two contacts which can connect the resistor element to current-carrying conductors of the tap changer via at least one contact point. The contacts can be designed as spring contacts. The resistor element is preferably electrically connected to the current-carrying conductors and / or contacts and / or switches and / or other current-carrying components of the tap changer via these conductors. The contacts can, for example, be selector contacts and corresponding tap contacts via which the voltage ratio of the transformer windings is preselected or set. The switches can, for example, be designed as vacuum switching tubes and / or as other mechanical switching elements via which the load switching from the currently connected to the preselected tap contact takes place.According to at least one embodiment, the contacts are designed as spring contacts with a defined mechanical preload such that the spring contacts press against the contact points of the resistance carrier when the resistance element is positioned in the resistance holders.

[0026] According to another possible embodiment, the contacts can be integrated into the resistor holder. The contacts would, for example, also form part of the guide.

[0027] According to a possible further embodiment of the invention, the at least two resistance elements can be arranged essentially parallel to each other and / or one above the other in a vertical direction between the resistance holders.

[0028] According to one possible embodiment of the invention, the at least two resistance elements form a resistance module.

[0029] According to the improved concept, a tap switch is also specified, which includes the resistor arrangement according to the invention.

[0030] According to one possible embodiment of the invention, the tap changer comprises at least the first base plate and a second base plate, which are held in spatial relation to each other by at least two resistance holders.

[0031] According to one possible embodiment of the invention, the at least two resistance holders can be arranged perpendicular to the at least two base plates.

[0032] According to one possible embodiment of the invention, the at least two resistance holders can be arranged between the at least two base plates.

[0033] According to one possible embodiment of the invention, the two resistor holders can be arranged parallel to each other.

[0034] The invention is explained in detail below with reference to exemplary embodiments and the drawings. Components that are identical, functionally identical, or have an identical effect may be provided with identical reference numerals. Identical components or components with identical function may be explained only with respect to the figure in which they first appear. The explanation is not necessarily repeated in the subsequent figures.

[0035] They show Fig. 1 a partial view of a tap changer with the arrangement of a resistance element; Fig. 2 a perspective view of an exemplary embodiment of a resistor arrangement according to the improved concept; Fig. 3 a longitudinal section view of an exemplary embodiment of a resistor holder for a resistor arrangement according to the improved concept; Fig. 4 a detailed view of the resistor arrangement Fig. 2; Fig. 5 a perspective view of an exemplary embodiment of a resistance element according to the improved concept; Fig. 6 a perspective view of the arrangement of the resistance element made of Fig. 2 in electrical contact with the leads of the tap changer; Fig. 7 another view of the perspective representation of the arrangement of the resistance element from Fig. 6; Fig. 8 a perspective view of another exemplary embodiment of a resistor arrangement according to the improved concept; Fig. 9 a side view in longitudinal section of the resistor arrangement Fig. 8; Fig. 10 a longitudinal section view of an exemplary embodiment of several resistance elements fixed in a resistance holder according to the improved concept.

[0036] Identical reference numerals are used for identical or equivalently functioning elements of the invention. Furthermore, for the sake of clarity, only those reference numerals necessary for describing the respective figure are shown in the individual figures. Components of the tap changer that are not essential for the following description of the resistor arrangement have not been shown in these figures for the sake of clarity. The figures merely illustrate embodiments of the invention, without, however, limiting the invention to the illustrated embodiments.

[0037] Fig. Figure 1 shows a partial view of a tap changer 1. The tap changer 1 comprises at least one switching element 2, which switches from one tap (not shown) to the next tap (not shown) of a transformer winding. A resistor element 20 is associated with the switching element 2. This resistor element limits the circulating current that flows during the switching process while simultaneously connecting a currently connected and the preselected new tap contact. This ensures an uninterrupted change in the transformer's turns ratio. The resistor element 20 is held in two resistor holders 30 and thus positioned relative to the switching element 2. The resistor element 20 defines a first end 201 and a second end 202, which are used to hold it in the two resistor holders 30.An electrically conductive connection is established via electrical contacts 40 from the switching element 2 to the resistance element 20 in the area of ​​the first end 201 and the second end 202.

[0038] Fig. Figure 2 shows a perspective view of an exemplary embodiment of a resistor arrangement 10 for a tap changer 1. The resistor arrangement 10 comprises two resistor holders 30, which are arranged or mounted on a base plate 11. A resistor element 20 is held and fixed at a first end 201 and at a second end 202 by the resistor holders 30. The resistor holders 30 position the resistor element 20 in the longitudinal direction L.

[0039] Each resistor holder 30 shows, as from Fig. As can be seen in Figure 3, a guide 31 facilitates the insertion of the resistance element 20 and positions the inserted resistance element 20 in its longitudinal direction L between the two resistance holders 30. The guide 31 serves as a holder for the first end 201 and the second end 202 of the resistance element 20. According to this exemplary embodiment, the guide 31 consists of a slot 32 formed in the resistance holders 30. The slot 32 is at least partially provided with a lateral wall 33, which extends only partially along the entire length of the slot 32. The two lateral walls 33 form a lateral boundary for the resistance element 20, which facilitates the insertion of the resistance element 20 into the guide 31 of the two resistance holders 30 and prevents the resistance element 20 from being displaced in its longitudinal direction L during insertion or in the final position.The guide 31 further has a closed end 37 and an open end 36. The guide 31 is formed in the resistance element 20 such that the closed end 37 is located in the resistance holder 30 and is arranged at a distance B from the base plate 11. Furthermore, the guide 31 is inclined at an angle α to the base plate 11 when the resistance holders 30 are mounted on the base plate 11. The open end 36 of the guide 31 of the resistance holder 30, when the resistance holder 30 is mounted on the base plate 11, is positioned opposite one of the openings 12 in the base plate 11. The resistance holder 30 also includes a retaining element 34 for the resistance element 20 when the latter is inserted into the guides 31 of the resistance holders 30. The retaining element 34 is designed as a reversibly and elastically pivotable leg 38, which has a snap hook 39H at a free end 39.The pivotable leg 38 of the retaining element 34 also forms part of the guide 31. When the resistance element 20 is inserted into the resistance holder 30, the elastically designed retaining element 34 retracts, allowing the resistance element 20 to be inserted into the guide 31. One end position of the resistance element 20 in the guide 31 is reached when it comes to rest against the closed end 37 of the guide 31. Once the resistance element 20 has reached its end position in the guide 31, the pivotable leg 38 moves to its starting position and the elastic snap hook 39H at the free end 39 returns to its initial position, thus locking the resistance element 20 in the guide 31. The resistance element 20 is then essentially operatively connected to the guide 31 in the area of ​​the first end 201 and the second end 202 and the snap hooks 39H, and thus fixed in the two resistance holders 30.

[0040] Fig. Figure 4 shows a detailed view of the resistor arrangement with a resistor element 20 held by one of the resistor holders 30. As already described in the section on Fig. As mentioned in section 3, the resistance element 20 sits with its first end 201 or second end 202 in the guide 31 of the resistance holder. The elastic snap hook 39H at the free end 39 of the pivoting leg secures the resistance element 20 in the guide 31.

[0041] Fig. Figure 5 shows a perspective view of an exemplary embodiment of a resistive element 20. The resistive element 20 consists of a resistive carrier 21 and a current-limiting element 22, which, according to this exemplary embodiment, is designed as a metallic wire wound around the resistive carrier 21 and fixed at the first end 201 and the second end 202, respectively, by means of a clamp 25. Furthermore, the resistive element 20 has an edge region 23 at both the first end 201 and the second end 202, which is not in contact with the current-limiting element 22, the metallic wire. Each of the edge regions 23 of the resistive carrier 21 has a contact point 24. The contact points 24 are made of electrically conductive material and are designed, for example, as clamps or plates. Also in Fig. 5 shown and assembled in the Fig. 6 and Fig. Figure 7 shows spring contacts 40, which are connected at a first free end 42 to current-carrying lines 41 of the tap changer 1 and which are pressed at a second free end 43 against the contact points 24 of the resistance element 20 with a defined spring force.

[0042] The Fig. 6 and Fig. Figure 7 shows, from various perspective views, the contacting of the resistance element 20 with the current-carrying leads 41 of the tap changer 1. The current-carrying leads 41 of the tap changer 1 are connected to the first free end 42 of each spring contact 40. To establish electrical contact, the spring contacts 40 press against the formed contact points 24 when the resistance element 20 is inserted through the opening 12 of the base plate 11.

[0043] Fig. Figure 8 shows a perspective view of another embodiment of a resistor arrangement according to the improved concept. Fig. Figure 9 is a side view in longitudinal section of the resistor arrangement. Fig. 8. The Fig. 8 and Fig. Figure 9 shows the resistor arrangement in a three-phase tap changer 1. A base plate 11 made of insulating material has three openings 12 through which the resistor elements 20 can be inserted into the fully assembled tap changer 1. A second base plate 13 made of insulating material is arranged opposite the base plate 11. A total of six resistor holders 30 are mounted between the two base plates 11 and 13. One resistor element 20 is fixed between each pair of resistor holders 30. The two base plates 11 and 13 are connected to each other via the resistor holders 30. Preferably, the resistor holders 30 have pins 35 for this purpose, which can be inserted into corresponding holes (not shown) provided in the base plates 11 and 13 and riveted in place.

[0044] Fig.Figure 10 shows a longitudinal section of an exemplary embodiment of several resistance elements 20 fixed in a resistance holder 30 according to the improved concept. A total of three resistance elements 20 are arranged in a stacked fashion on the resistance holder 30. For this purpose, the resistance holder 30 has three guides 31 and three snap hooks 34, which are identical in design.

[0045] With a resistor arrangement 10 or a tap changer 1 according to the improved concept, it is possible to flexibly equip the tap changer 1 with the required resistor elements 20, depending on the application, with regard to their resistance value (ohmic resistance). According to the improved concept, the resistor elements 20 can also be inserted after the complete tap changer 1 has been assembled and, if necessary, for example, if the operating conditions of the tap changer 1 change, they can also be easily replaced. This allows the tap changer 1 to be manufactured independently of specific orders and kept in stock. For example, the adaptation of the tap changer 1 to the respective application could be completely outsourced from the manufacturing process, and the installation of the resistors in the tap changer could only take place on-site by the transformer manufacturer or the grid operator.

[0046] It is assumed that the present disclosure and many of its accompanying advantages are understood from the foregoing description. Furthermore, it is obvious that various modifications to the shape, construction, and arrangement of the components can be made without deviating from the disclosed subject matter or without foregoing all material advantages. The described embodiment is merely illustrative, and such modifications are included in the following claims. It is further understood that the invention is defined by the following claims. Reference symbol list 1 step switch 2 switching element 10 Resistance arrangement 11 Base plate 12 Opening 13 Base plate 20 resistance element 201 first end 202 second end 21 resistor carriers 22 current-limiting element 23 Edge area 24 contact points 25 bracket 30 resistor holders 31 Leadership 32 slots 33 side wall 34 retaining element 35 pens 36 open ending 37 closed end 38 swiveling legs 39 free ending 39H Snap hook 40 Contact 41 lines 42 first free end 43 second free end B distance L Longitudinal direction of the resistance element α angle

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