On-load tap changer

Abstract

The invention relates to an on-load tap changer (10) for uninterrupted switching between winding taps (N1, ..., NJ, ..., NN) of a step transformer (1), comprising: - a selector unit (30) for powerlessly pre-selecting a selected winding tap (NJ); - a load transfer switch unit (40) for the actual load switching from the previous winding tap (NJ-1) to the pre-selected winding tap (NJ); - a drive shaft (60) which is driven by a motor drive (70) and actuates the selector unit (30) and the load transfer switch unit (40); - a plate (50) on which the selector unit (30) and the load transfer switch unit (40) are located; and - a supporting structure (20) having at least one supporting rod (21); wherein - at least one guide (51) is located in an edge region (52) of the plate (50), which guide is designed to receive the supporting rod (21) such that the plate (50) can be fixed to the supporting structure (50) by means of the at least one guide (51).

Description

[0001] The invention relates to a load tap changer for uninterrupted switching between winding taps of a tap transformer.

[0002] On-load tap changers allow the transformation ratio of transformers to be changed under load and are well known in the art. They typically comprise a load changeover switch and a selector. The load changeover switch is equipped for no-load switching with switching elements, such as vacuum interrupters, and switching resistors, which are arranged in a cylindrical, oil-filled vessel. The selector is usually located below the load changeover vessel and consists of a multitude of rods arranged in a circle. Contacts are arranged on these rods at different levels, serving as connections for a control winding. Inside the selector, two selector arms are attached to a switching column. These arms make contact with the contacts on the rods. The load changeover switch and selector are connected to each other via a gearbox.The motor drive is located on the outside of the step transformer and is connected to the load tap changer via a linkage.

[0003] In another type of load tap changer, the so-called load selector, which differs structurally from the load tap changers described in the previous paragraph but is equally well-known, the functions of selecting and switching are combined in a single switch. This means that the selector and load switch are not spatially separated, but rather located in a common oil reservoir.

[0004] For both designs, the load changeover switch or load selector can be removed from the oil reservoir for necessary repairs or maintenance. This is done from above via a cover on the transformer housing. However, a disadvantage of load tap changers with a separate selector is that work on the selector is very difficult, as the selector is located below the load changeover switch insert and immersed in the transformer oil.

[0005] Furthermore, there are now novel designs of tap changers that have a fundamentally different construction without an oil reservoir and therefore require a new approach to maintenance and repair. German patent application DE102016104500 B3 discloses a load tap changer that corresponds to the preamble of claim 1.

[0006] It is therefore an object of the present invention to provide a concept for repair and maintenance work on load tap changers and / or assemblies of load tap changers without an oil reservoir, which enables a quick and easy replacement of the load tap changer and / or of service-relevant or repair-required assemblies of the load tap changer.

[0007] This problem is solved by the respective subject matter of independent claim 1. Further embodiments are the subject matter of the dependent claims.

[0008] According to the invention, a load tap changer for seamless switching between winding taps of a tap transformer is provided. The load tap changer comprises a selector unit for power-free preselection to a selected winding tap, a load switching unit for the actual load switching from the previous winding tap to the preselected winding tap, and a drive shaft driven by a motor drive that actuates the selector unit and the load switching unit. The selector unit and the load switching unit are arranged on a plate. Furthermore, the load tap changer comprises a support frame that includes at least one support rod.

[0009] At least one guide is provided in the edge area of ​​the plate, which is designed to receive the support rod in such a way that the plate can be fixed to the support frame via the at least one guide.

[0010] This allows the plate, including the selector and load tap changer unit, which typically comprises the components relevant for service and / or repair, to be quickly replaced. The support rod is released from its guide by a simple pivoting and / or linear movement of the plate, thus easily removing the plate from the support frame. The plate can be removed, for example, through an opening in a side wall of the transformer housing. Consequently, it is no longer necessary to completely remove the entire transformer housing for necessary repairs or maintenance on individual components of the load tap changer. Instead, the plates with the affected components can be removed individually from the housing.

[0011] The plate can be formed in any way, for example as a plate-shaped injection-molded part. The plate can be made of plastic, for example thermoplastic or glass-fiber reinforced plastic, or any other electrically insulating material.

[0012] The load switching unit can be configured in any way and may, for example, include mechanical and / or power electronic switching devices, one or more bridge switches, and one or more current-limiting elements. The switching devices may be, for example, vacuum interrupters and / or IGBTs and / or thyristors. The bridge switch may be actuated by a linear or rotary movement. The current-limiting elements may be resistors and / or inductors and / or varistors.

[0013] The selector unit can be configured in any way and may, for example, have one or more movable selector contacts. A movable selector contact can be configured in any way, for example, as a contact finger that moves radially. The actuation of the movable selector contacts can also be achieved in any way, for example, via a Maltese wheel or a gear. Furthermore, the selector has several fixed contacts that can be connected to the winding taps of the step-down transformer. These can be arranged on the plate in any way such that they are contactable by the movable selector contact or contacts. For example, the fixed contacts can be arranged radially on the plate.

[0014] According to a preferred embodiment, the selector unit and the load switching unit are actuated by the drive shaft via a drive unit, which is also arranged on the plate and can be connected to the drive shaft in a rotationally fixed manner.

[0015] The drive unit can be designed in any way and, for example, consist of at least one actuating element. The drive shaft and the actuating element can be designed as a single piece or in multiple parts. The actuating element can be a gear, cam profile, partially toothed gear, driver, or dual driver.

[0016] According to another embodiment, several actuating elements can be arranged on or attached to the drive shaft. These multiple actuating elements can be designed as a single piece or in multiple parts. The actuating elements can be connected to each other, for example, by gluing, screwing, or plugging them together.

[0017] According to the invention, the guide is designed as a U-shaped recess and is configured such that the at least one support rod is at least partially surrounded by the guide in a form-fitting manner.

[0018] Essentially, a form-fitting surround means that the guide surrounds the support rod on at least three sides in a form-fitting manner, i.e., with a precise fit. The support rod can be inserted into and removed from the guide via the open side.

[0019] According to one embodiment, the plate is attached to the at least one support rod in the guide area via a snap connection, for example by utilizing the deformation properties of thermoplastic materials. For example, cams, ridges, or hooks can also be provided on the support rod, which engage positively in corresponding undercuts in the guide.

[0020] According to another embodiment, the support rod can be secured in the guide by means of fixing devices, for example pins and / or screws, which extend through the at least one support rod into the plate in the area of ​​the guide.

[0021] According to another embodiment, the support structure comprises at least three further support bars and a top plate. The support bars are attached to the top plate at one end.

[0022] The end plate can be designed in any way. The plate can be made of any electrically insulating material, such as plastic, or an electrically conductive material, such as aluminum.

[0023] The support rods can also be made of plastic, for example thermoplastic or glass fiber reinforced plastic, or any other electrically insulating material.

[0024] According to another embodiment, the end plate for attaching the support rods has sleeves into which the first end of each support rod is inserted and secured by suitable means. Suitable means include, for example, bolts and / or screws and / or equivalent connecting elements. The sleeves and the plate can be made in one or more parts.

[0025] According to another embodiment, the plate has at least three further guides in the edge area, each guide being designed to receive a support rod.

[0026] According to another embodiment, a sealing flange is arranged on the end plate, by means of which the support frame can be mounted on a housing of the step-down transformer, in particular on a transformer cover.

[0027] According to another embodiment, the drive shaft extends from a first side of the plate, through the plate, to a second side of the plate. The drive shaft and the plate are arranged perpendicular to each other.

[0028] The drive shaft can be a single piece or made of multiple parts. In the case of a multi-part design, the parts can be connected to each other via couplings.

[0029] According to another embodiment, the drive shaft and the plate are detachably connected. Detachably means specifically that the drive shaft can be easily removed by pulling it out of the plate and the sealing flange, either as a whole or in parts, particularly by pulling it upwards.

[0030] According to at least one embodiment, the drive shaft can be connected to the motor drive via the sealing flange.

[0031] According to a second aspect of the improved concept, the load tap changer for the second and third phases of the tap transformer comprises a second and third selector unit, a second and third load-switching unit, a second plate on which the second selector unit and the second load-switching unit are mounted, and a third plate on which the third selector unit and the third load-switching unit are mounted. The plates are arranged longitudinally L along the drive shaft of the load tap changer and are held in position by means of the support frame.

[0032] 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 designated 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 subsequent figures. The figures merely illustrate embodiments of the invention without limiting the invention to the embodiments shown.

[0033] They show Figure 1 shows an exemplary embodiment of a load tap changer in a schematic representation; Figure 2 shows a perspective view of an exemplary embodiment of a load tap changer according to the improved concept; Figure 3 shows a detailed cross-sectional view of an exemplary embodiment of the load tap changer according to the improved concept; Figure 4 shows a perspective view of another exemplary embodiment of a load tap changer according to the improved concept.

[0034] In Figure 1Figure 1 schematically illustrates an exemplary embodiment of a load tap changer 10 for a tap-changer 1. The tap-changer 1 has a main winding 3 and a variable winding 4 with different winding taps N1, ..., NJ, ..., NN, which are switched on and off by the load tap changer 10. For this purpose, the load tap changer comprises a selector 30, which can contact the different winding taps N1, ..., NJ, ..., NN of the variable winding 4 by means of two movable selector contacts, and a load changeover switch 40, which performs the actual load switching from the currently connected to the new, preselected winding tap. In the figure shown in Figure 1, the load tap 30 is connected to the main winding 3. Figure 1 In the position of the load switch 40 shown, the load current flows from the currently connected winding tap N J+1 via the respective selector contact and the load switch 40 to a load drain 11.

[0035] Figure 2Figure 1 shows a perspective view of an exemplary embodiment of a load tap changer according to the improved concept. The load tap changer 10 has a plate 50 made of a plastic, for example, glass fiber reinforced plastic, or another electrically insulating material. The plate 50 is either milled or injection molded. A selector unit 30, a load changeover unit 40, and a current limiting element 41 are arranged on it. Fixed contacts 32 of the selector are preselected without load via the selector unit 30. These fixed contacts are electrically connected to the winding taps of the tap-changer (not shown). For this purpose, the fixed contacts 32 extend to a side wall 55 through which the selector terminals 31 of the fixed contacts 32, which are provided for connection to the winding taps (not shown), pass.

[0036] Furthermore, a drive unit 61 is arranged on the plate 50, essentially between the selector unit 30 and the load switching unit 40. The drive unit 61 is rotationally fixed to a drive shaft 60, which is designed as a hollow or solid square shaft made of plastic. The drive shaft 60 extends from a first side 53 of the plate 50 to a second side 54 of the plate 50, which is located opposite the first side 53, and is arranged perpendicular to the plate 50 and detachably connected to it. Detachable here specifically means that the drive shaft 60 can be pulled out of the plate 50. The drive shaft 60, and thus also the drive unit 61, is driven by a motor drive 70.

[0037] The load tap changer 10 further comprises a support frame 20 consisting of a total of four support bars 21 and a cover plate 23. Each support bar 21 is held in a guide 51 in the form of a U-shaped recess provided in the cover plate 50 and is positively enclosed on three sides by this guide 51. Each guide thus has one open side. The side wall 55 is therefore not continuous but formed in several parts so that the cover plate 50 can be easily removed from the support bars 21. The cover plate 50 is secured to the support frame 20 by pins (not shown) that extend through the support bars 21 into the cover plate 50 in the area of ​​the guides 51. However, it would also be conceivable to fix the support bars 21 in the guides 51 by means of a snap connection, for example by utilizing the deformation properties of thermoplastic materials.

[0038] Furthermore, each support bar 21 is attached to the end plate 23 at a first end 22. Sleeves 24 are arranged on the end plate 23 for this purpose, into which the ends 22 of the support bars 21 are inserted. The support frame 20 is mounted to a housing 2 of the step-down transformer 1 by means of a sealing flange 25, which is arranged on the end plate 23. The drive shaft 60 is connected to the motor drive 70 via the sealing flange 25. If the plate 50 is to be removed for service or repair work, the drive shaft 60 must first be pulled out of the plate 50 and through the end plate 23 and the sealing flange 25. For this, it is necessary to detach the motor drive 70 from the housing 2 of the step-down transformer 1 and then pull the drive shaft 60 out through an opening in the transformer housing 2 via the sealing flange 25.The plate 50 can then be removed from the support frame 20, as described below with reference to . Figure 3 is described.

[0039] Figure 3 Figure 1 shows a detailed cross-sectional view of an exemplary embodiment of the load tap changer according to the improved concept. Here, the first side 53 of plate 50 is shown in a top view. The essential components of the load tap changer 10 arranged on plate 50 have already been described in the section on Figure 2 explained, so this will not be discussed again.

[0040] In Figure 3It can be seen that the guides 51, or rather the U-shaped recesses, are arranged in an edge region 52 of the plate 50. Three of the U-shaped recesses are designed such that their open sides all point in the same direction, namely towards the selector terminals 31. One of the guides 51, in this case the guide located in the immediate vicinity of the current-limiting element 41, has its open side facing in the opposite direction to the other guides. In this specific embodiment, the support rod 21 located in this guide must first be removed from the support frame 20 before the plate 50 can be removed from the other three support rods 21, and thus from the support frame 20, by moving it in a transverse direction Q of the load tap changer 10. This requires that the drive shaft 60 has been removed beforehand.

[0041] The in Figure 3The embodiment shown represents only one possible variant for the design of the guides. For example, it is equally possible to design all guides with the open side pointing in the same direction.

[0042] Figure 4 Figure 1 shows a perspective view of another exemplary embodiment of a load tap changer according to the improved concept. Regarding the load tap changer 10 from Figure 4 refers to the preceding explanations regarding the Figures 2 and 3 Reference is made in an analogous manner, and only the differences are discussed below.

[0043] In Figure 4 The load tap changer 10 is designed for three phases and has a second and third plate 50, each corresponding to the one described in Figure 2 and 3The plates 50 are formed as shown in the plate. The plates 50 are arranged one above the other and spaced apart from each other in a longitudinal direction L of the load tap changer 10 along the drive shaft 60 and are held in this position by means of the support frame 20. The drive shaft 60 also extends along the longitudinal direction L of the load tap changer 10 and drives all three phases of the load tap changer 10 equally.

[0044] It is assumed that the present disclosure and many of its associated 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 embodiments are 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 MARK

[0045] 1 Step transformer 2 Housing of 1 3 Main winding 4 Control winding 10 Load tap changer 11 Load transfer 20 Support frame 21 Support rod 22 First end of 21 23 End plate 24 Sleeve 25 Sealing flange 30 Selector unit 31 Selector terminals 32 Fixed contacts of 30 40 Load tap changer unit 41 Current limiting element 50 Plate 51 Guide 52 Edge area of ​​50 53 First side of 50 54 Second side of 50 55 Side wall 60 Drive shaft 61 Drive unit 70 Motor drive N 1 , ..., NJ , ..., NN Winding taps of 4 L Longitudinal direction of the load tap changer Q Transverse direction of the load tap changer

Claims

1. On-load tap-changer (10) for uninterrupted advanced retard switch between winding taps (N1, ...NJ, ..., NN) of a tap-change transformer (1), comprising - a change-over selector unit (30) for powerless preselection to a selected winding tap (NJ); - a diverter switch unit (40) for the actual diverter switch operation from the previous winding tap (NJ-1) to the preselected winding tap (NJ); - a drive shaft (60) which is driven by a motor-drive unit (70) and actuates the selector unit (30) and the load changeover unit (40) - a supporting frame (20) with at least one supporting bar (21); characterized by - a plate (50) on which the selector unit (30) and the diverter switch unit (40) are arranged; wherein - at least one guide (51) is arranged in an edge region (52) of the plate (50), which is designed to receive the supporting bar (21) in such a way that the plate (50) can be fixed to the supporting frame (50) via the at least one guide (51); - the guide (51) is designed as a U-shaped recess and at least partially surrounds the at least one supporting bar (21) in a form-fitting manner; the plate (50) can be removed from the supporting frame (20) by a pivoting movement and / or a linear movement after the supporting bar (21) has been removed from the supporting frame (20) and from the guide (51) of the plate (50).

2. On-load tap-changer (10) according to the preceding claim, wherein - the supporting frame (20) has at least three further supporting bars (21) and an end plate (23); - the supporting bars (21) are attached with a first end (22) to the end plate (23).

3. On-load tap-changer (10) according to claim 2, wherein - the end plate (23) has sleeves (24) for fastening the supporting bars (21), into each of which sleeves the first end (22) of the supporting bars (21) is inserted and fixed.

4. On-load tap-changer (10) according to one of the preceding claims 2 or 3, wherein - the plate (50) has at least three further guides (51) in the edge region (52), each guide (51) being designed to receive a supporting bar (21) in each case.

5. On-load tap-changer (10) according to one of the preceding claims 2 to 4, wherein - a sealing flange (25) is arranged on the end plate (23), by means of which the supporting structure (20) can be mounted on a housing (2) of the tap changer transformer (1), in particular on a transformer cover.

6. On-load tap-changer (10) according to one of the preceding claims, wherein - the drive shaft (60) extends from a first side of the plate (53) through the plate (50) to a second side of the plate (54), such that the drive shaft (60) and the plate (54) are arranged perpendicular to each other.

7. On-load tap-changer (10) according to one of the preceding claims, wherein - the drive shaft (60) is formed in one or more parts.

8. On-load tap-changer (10) according to one of the preceding claims, wherein - the drive shaft (60) and the plate (50) are detachably connected to each other .

9. On-load tap-changer (10) according to one of the preceding claims 5 to 8, wherein - the drive shaft (60) is connectable to the motor-drive unit (70) via the sealing flange (25).

10. On-load tap-changer (10) according to one of the preceding claims, comprising, for a second and third phase of the step transformer (1) to be regulated - a second and third selector unit (30), - a second and third diverter switch unit (40), - a second plate (50) on which the second selector unit (30) and the second diverter switch unit (40) are arranged, - a third plate (50) on which the third selector unit (30) and the third diverter switch unit (40) are arranged, wherein - the plates (50) are arranged in a longitudinal direction L of the on-load tap-changer (10) along the drive shaft (60) and are held in position by means of the support frame (20).

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