Load tap changer

Abstract

Load tap changer (1) for uninterrupted load switching, comprising: - a first module (20) with a first module wave (22); - a second module (40) with a second module wave (42); wherein: - each module (20, 40) is assigned to a phase of a step-down transformer, - each module (20, 40, 60) has a load switch (30, 50, 70) and a selector (35, 55, 75), - the first module wave (22) actuates the first module (20); - the second module shaft (42) actuates the second module (40); - the first and second module shafts (22, 42) are mechanically coupled to each other in such a way that the first module shaft (22) drives the second module shaft (42) and the second module (40) is actuated at a time offset from the first module (20).

Description

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

[0002] Load tap changers are known from the prior art and usually consist of a load changer and a selector. The load changer, with its vacuum switching tubes and switching resistors, is housed in a container. The selector is constructed from a multitude of rods arranged in a circle. Contacts are arranged on these rods at different levels, serving as connections for the individual stages of the control windings. Inside the selector, two selector arms are attached to a switching column. These arms make contact with the contacts on the rods. The load changer and selector are connected to each other via a gearbox.

[0003] DE 724 502 A discloses a load-operated tap changer arrangement for multiphase tap changers. According to the invention, a spring coupling is provided between the common shaft and the actual drive shaft, allowing an angle of rotation between the two shafts. This is intended to ensure that the spring coupling is pre-tensioned and that sufficient energy can be released abruptly to actuate all three individual tap changers. This spring coupling thus connects the shaft that actuates the individual tap changers with the transmission shaft that is actuated by the switching motor. Therefore, the shaft is assigned to all individual tap changers and thus to all phases of a tap changer, whereas the transmission shaft is not assigned to any phase of a tap changer.

[0004] DE 298 14 184 U1 discloses a wave joint for the mechanical connection of a drive with a tap changer to be operated by it.

[0005] AT 224 219 B discloses a power storage device for converting a reciprocating continuous drive motion into a sudden rotary motion.

[0006] DE 10 2011 013 749 A1 discloses a load tap changer with a drive shaft that can be operated in any direction of rotation.

[0007] The load tap changer is actuated by a drive that, on the one hand, winds a spring energy storage device to actuate the load changer, and on the other hand, moves the selector arms to preselect the contacts to be switched. In both the load changer and the selector, the contacts and switching elements of all three phases are always actuated simultaneously. This inevitably leads to torque peaks, as the same contacts of each phase must be actuated at the same time. The drive, spring storage device, and gearbox must be designed to handle these torque peaks.

[0008] The object of the invention is to create a load tap changer that generates significantly smaller torque peaks during operation, is simple and compact in design, and ensures safe operation.

[0009] This problem is solved by a load tap changer according to claim 1. The features of the dependent claims constitute advantageous further developments of the invention.

[0010] According to a first aspect, the invention proposes a load tap changer for uninterrupted load switching between different winding taps of a tap transformer, comprising: - a first module with a first module wave; - a second module with a second module wave, wherein: - the first module wave activates the first module; - the second module wave actuates the second module; - the first and second module shafts are mechanically coupled in such a way that the first module shaft drives the second module shaft and the second module is actuated at a time offset from the first module.

[0011] By dividing the load tap changer into individual modules and coupling them mechanically in a staggered manner, torque peaks are significantly reduced. This is achieved by driving the actuated elements of the modules simultaneously, but sequentially with a slight offset. The offset is precisely such that no negative electrical interactions occur between the individual phases of a tap changer, while ensuring that the resulting torque increases are slightly staggered. This allows for the use of a significantly simpler and therefore less expensive motor. Furthermore, the individual components of the drive shaft can be made smaller, as they have to withstand lower torque loads. This also has a positive effect on the overall price of the tap changer. Without mechanically staggered coupling, the same elements in each module would be moved simultaneously.It would need to be operated. The required force would add up, which would necessitate a drive with corresponding power.

[0012] Each module can be configured in any way required and comprises a module shaft. The first module shaft of the first module is mechanically coupled to the second module shaft of the second module. The module shafts are mechanically connected in a way that offsets them from each other, such that the actuation of the individual modules occurs sequentially. In other words, although the two module shafts begin to rotate simultaneously, their effect (opening and closing vacuum switching tubes) on the elements within the modules occurs with a time delay.

[0013] The module shafts can be interconnected in any way required, for example via insulating rods, insulating shafts or chains.

[0014] The offset between the modules, and especially the module shafts, can be designed in any way required, for example, as offset connecting pins on the module shafts and identically designed insulating shafts, or insulating shafts with offset mounts and identical module shafts. How the offset between the module shafts is ultimately implemented is irrelevant.

[0015] The load switch can be configured in any way required and may, for example, comprise at least two or more modules. Each module is assigned to a phase of a step-down transformer.

[0016] Each module comprises at least one load switch and one selector. The load switch may include at least one switching element and one current-limiting element. The at least one switching element may be designed as a vacuum switching tube or a simple mechanical switch. The current-limiting element is preferably a resistor, an inductor, or a current-dependent resistor. The selector has at least one selector arm, preferably two selector arms as fine selectors and / or a preselector arm as a preselector.

[0017] Each module shaft can be configured in any way required, for example, by having a connecting pin, bolt, keyway, or any other connecting element at each end. The connecting pins are not axially parallel and are preferably offset from each other by a maximum of 15 degrees. The connecting pins, bolts, or keys can be inserted on only one side or extend through the entire module shaft.

[0018] Each module shaft can be configured in any desired way, for example, by having a first connecting pin at one end and a second connecting pin at the other. The first connecting pin can extend along a first axis A, and the second connecting pin can extend along a second axis B, wherein axes A and B are not parallel and are preferably offset by an angle of no more than 15 degrees.

[0019] The drive system can be configured in any way required and may, for example, include at least one motor and / or a gearbox. The motor can be a synchronous motor with a multi-turn absolute encoder or a DC motor with microswitches.

[0020] It may be provided that the module shafts and the insulating shafts are connected via couplings and / or couplings with multiple coupling shells.

[0021] It may be provided that a motor is connected directly to the drive shaft or indirectly, via a gearbox, bevel gear or linkage, to the insulating shaft or the first module shaft of the load tap changer.

[0022] The invention and its advantages are described in more detail below with reference to the accompanying drawings. These show: Fig. 1 a first embodiment of a load tap changer; Fig. 2a a detailed view of a module wave; Fig. 2b a front view of a module shaft; Fig. 3 several module shafts of a load tap changer according to the invention; Fig. 4 another detailed view of a module wave.

[0023] 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. The illustrated embodiments merely represent examples of how the load tap changer according to the invention can be configured and thus do not constitute an exhaustive limitation of the invention.

[0024] Fig. Figure 1 shows a schematic diagram of a load tap changer 1 according to the invention. This module comprises a first module 20, a second module 40, and a third module 60. Each of the modules 20, 40, 60 is assigned to a phase of a tap-changer. The first module 20 has a first module shaft 22. The first module shaft 22 is connected or coupled at its first end 23 to a drive 2. The drive 2 is designed as a motor drive with or without a gearbox and is preferably mechanically connected to the first end 23 of the first module shaft 22 via a first insulating shaft 21. The first module 20 comprises a load changeover switch 30 and a selector 35. The load changeover switch 30, and in particular its vacuum switching tubes, are actuated directly via the first module shaft 22. Two cam disks 32 are mounted on the first module shaft 22, which open and close the vacuum switching tubes as they rotate.Furthermore, a first bevel gear 36 is arranged on the first module shaft 22, which drives a second bevel gear 37, which in turn actuates the individual selector arms of the selector 35. When the first module shaft 22 is driven, the load switch 30 and the selector 35 are thus actuated in a specific sequence; the first module 20 of the load tap changer 1 is actuated.

[0025] Furthermore, the load tap changer 1 has a second module 40 and a third module 60. The three modules 20, 40, 60 are identical in construction. The three modules are mechanically coupled to each other via a second and a third insulating shaft 41, 61. The drive 2 drives the first module 20 via the first insulating shaft 21, the first module 20 drives the second module 40 via the second insulating shaft 41, and the second module 40 drives the third module 60 via the third insulating shaft 61. The second and third modules 40, 60 each also have a load changeover switch 50, 70, a selector 55, 75, and module shafts 42, 62. The respective selectors 55, 75 are driven via bevel gears 56, 57, 76, 77.

[0026] Fig. Figure 2a shows a detailed view of the first module shaft 22, which has a first connecting pin 24 at its first end 23. The first module shaft 22 is connected to the drive 2, for example via a first insulating shaft 21, via this first connecting pin 24. Furthermore, the first module shaft 22 has a second connecting pin 26 at its second end 25. The second connecting pin 26 is not arranged axially parallel to the first connecting pin 24 on the module shaft 22. In other words, the second connecting pin 26 is offset by a few degrees from the first connecting pin 24. As an alternative to the connecting pins, bolts, keys, or any other connecting elements can be used. The connecting pin can protrude only on one side or extend from one side to the other, opposite side.

[0027] Fig. Figure 2b shows a front view of the module shaft 22. Axis A indicates the orientation of the first connecting pin 24. Axis B indicates the orientation of the second connecting pin 26. Axes A and B are offset from each other at an angle W1 of preferably a maximum of 15 degrees. If a second module shaft 42 were placed behind the first module shaft 22 and connected to it, the first connecting pin 44 of the second module shaft 42 would be parallel to axis B of the second connecting pin 26 of the first module shaft 22. Each module shaft 22, 42, 62 is configured identically, i.e., the second connecting pin 26, 46, 66 is offset from the respective first connecting pin 24, 44, 64. Axis C shows the orientation of the second connecting pin 46 of the second module shaft 42, which is not shown here. The angle W2 between axes B and C is identical to the angle W1 between axes A and B.

[0028] Fig. Figure 3 shows a detailed view of two interconnected module shafts, in particular the first module shaft 22 and the second module shaft 42. The first connecting pin 24 at the first end 23 of the first module shaft 22 is offset from the second connecting pin 26 at the second end 25. The first end 23 of the first module shaft 22 is connected to a drive 2 via a first insulating shaft 21. The connection between the first insulating shaft 21 and the first module shaft 22 is realized by means of a coupling 19, which preferably has two coupling shells. However, any type of coupling can be used. The second end 25 of the first module shaft 22 is connected to the first end 43 of the second module shaft 42 via a second insulating shaft 41. As can now be clearly seen, the first connecting pins 24, 44 of the respective module shafts 22, 43 are connected to each other offset from one another. As soon as the drive 2 begins to rotate the first insulating shaft 21, the first connecting pin 24 of the second module shaft 42 is connected to the first module shaft 45.When the other shafts are driven, they also rotate. However, the actuation of modules 20, 40, and 60 is offset, since the cam discs and the first bevel gear of the second module 40 and third module 60 are arranged offset from the cam discs and the first bevel gear of the first module 20.

[0029] The insulating shafts 41 and 61 are identical in design, meaning the couplings 19 at their respective ends are the same. As an alternative to the module shafts with offset connecting pins, the insulating shafts can also have offset couplings at their respective ends. This also achieves an offset mechanical coupling of the modules. The modules are driven simultaneously and together, but with a time delay.

[0030] Fig.Figure 4 shows a detailed view of one of the module shafts 20, 40, 60, in particular the first module shaft 20, with the second and third module shafts 40, 60 being identical in construction. Two cam disks 32 for actuating the vacuum switching tubes and a first bevel gear 36 for actuating the selector 35 are arranged on the module shaft 20. Within a 360-degree rotation of the module shaft 20, the load switch 30 and the selector 35 are actuated. Depending on the position of the module shaft 20, individual actions in the load tap changer, such as opening or closing the vacuum switching tubes of a switching sequence, are carried out at a specific time. As soon as at least two module shafts 40, 60 are coupled offset from each other, the actions in the second module 40 take place slightly offset from the first module 20; ultimately, the modules 20, 40, 60 are identical in construction.The second module 40 is driven simultaneously with the first module 20, but the actual actuation of the second module 40 (opening or closing the vacuum switching tubes) takes place at different times.

[0031] As an alternative to the module shafts 20, 40, 60 with offset connecting pins, the insulating shafts could also have offset receptacles at both ends. This also results in the module shafts being mechanically connected with an offset relative to each other. Reference symbol list 1 load step switch 2 Drive 19 Clutch 20 first module 21 first insulating wave 22 first module wave 23 first end of 22 24 first connecting pin of 22 25 second end of 22 26 second connecting pin of 22 30 load switches 32 cam discs 35 voters 36 first bevel gear 37 second bevel gear 40 second module 41 second insulating wave 42 second module wave 43 first end of 42 44 first connecting pin of 42 45 second end of 42 46 second connecting pin of 42 50 load switches 55 voters 60 third module 61 third insulating wave 62 third module wave 63 first end of 62 64 first connecting pin of 62 65 second end of 62 66 second connecting pin of 62 70 load switches 75 voters

Claims

[1] Load tap changer (1) for uninterrupted load switching, comprising: - a first module (20) with a first module wave (22); - a second module (40) with a second module wave (42); wherein: - each module (20, 40) is assigned to a phase of a step-down transformer, - each module (20, 40, 60) has a load switch (30, 50, 70) and a selector (35, 55, 75), - the first module wave (22) actuates the first module (20); - the second module shaft (42) actuates the second module (40); - the first and second module shafts (22, 42) are mechanically coupled to each other in such a way that the first module shaft (22) drives the second module shaft (42) and the second module (40) is actuated at a time offset from the first module (20). [2] Load tap changer (1) according to claim 1, wherein - a drive (2) drives the first module shaft (22). [3] Load tap changer (1) according to one of claims 1 to 2, wherein - the load tap changer (1) comprises a third module (60) with a third module shaft (60); - the third module (60) is assigned to a phase of the step-down transformer, - the third module shaft (62) actuates the third module (60) and the second and third module shafts (42, 62) are mechanically coupled to each other in such a way that the second module shaft (42) drives the third module shaft (62) and the third module (60) is actuated at a time offset from the second module (40). [4] Load tap changer (1) according to any one of claims 1 to 3, wherein - the modules (20, 40, 60) are connected to each other via insulating waves (21, 41, 61). [5] Load tap changer (1) according to any one of claims 1 to 4, wherein - each module shaft (22, 42, 62) has a first connecting pin (24, 44, 64) and a second connecting pin (26, 46, 66) and - the first connecting pin (24, 44, 64) is arranged offset from the second connecting pin (26, 46, 66). [6] Load tap changer (1) according to any one of claims 1 to 5, wherein - the first module wave (22) is connected to the second module wave (42) via a second insulating wave (42) and the second module wave (42) is connected to the third module wave (62) via a third insulating wave (61).

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