Current transformer with integrated short-circuit bridge

Abstract

The invention relates to a current transformer with a primary circuit coupling and a secondary circuit, as well as with an integrated short-circuit bridge, wherein the short-circuit bridge is adjustable between a short-circuited position and an open position, such that the secondary terminals of the secondary circuit are conductively connected to one another via the short-circuit bridge in the short-circuited position, wherein the short-circuit bridge is a spring that is relaxed in the open position and tensioned in the short-circuited position, or which is tensioned in the open position and relaxed in the short-circuited position. The invention also relates to a generic current transformer that has a cover which covers the secondary terminals in the operating state and which is displaceable, in particular rotatable, so that the secondary terminals are exposed in an open position.

Description

[0001] The invention relates to a current transformer with an integrated short-circuit bridge according to claim 1.

[0002] Current transformers are transformers that convert or transform a current into a processable, especially measurable, current. Typically, high currents and often high voltages are converted into smaller, e.g., measurable values. In other words, a primary current is converted into a smaller, more useful secondary current, i.e., stepped down or up.

[0003] Current transformers have a primary circuit and a secondary circuit. The primary circuit carries the current to be measured, and the secondary circuit provides the transformed current. Often, the primary side is simply represented by the conductor through which the current to be measured flows. The primary side is therefore only coupled to the current transformer or its secondary circuit.

[0004] The secondary circuit must not be open when current is applied to the primary circuit, as otherwise high voltage spikes may occur. These can be damaging to the current transformer and dangerous to personnel.

[0005] Therefore, it is imperative to short-circuit the secondary side or circuit when working on the current transformer. This is often done using short-circuit jumpers that connect the secondary terminals.

[0006] From US 3,208,021 B, for example, a short-circuit mechanism for an approximately square current transformer is known. In this case, a short-circuit bridge is brought into a conductive position between the secondary terminals by rotating it into a short-circuit position. For this purpose, a housing cover for the entire upper side, including the secondary terminals, engages with a central extension in a form-fitting manner in a central coupling, which in turn is form-fittingly connected to the plate-shaped short-circuit bridge, so that when the housing cover is rotated, the extension and thus the coupling as well as the short-circuit bridge rotate centrally in a circular manner in order to conductively connect the secondary terminals by bringing them into contact with the plate ends, whereby the housing cover covers the entire upper side, including the secondary terminals. To rotate or remove the housing cover, a screw lock must first be loosened.

[0007] This structure is complex and rotation can be difficult if the corresponding screw or its fastening nut is tightened too much or if contaminants (e.g. dust) create resistance.

[0008] In contrast, the object of the present invention is to provide a simplified short-circuit mechanism of a current transformer.

[0009] This object is achieved by the current transformer recited in claim 1. Advantageous embodiments emerge from the subclaims and the description.

[0010] According to the invention, it has been recognized that if the short-circuiting bridge is a spring which is relaxed in the open position and tensioned in the short-circuiting position, or vice versa, i.e. alternatively tensioned in the open position and relaxed in the short-circuiting position, it is possible to simplify the short-circuiting or opening mechanism, since it allows a displacement between the two positions and thus a short-circuiting of the secondary terminals to be effected by the spring itself.

[0011] In other words, the relative movement of the spring ensures that the short-circuit or open position is assumed as desired when it relaxes. Preferably, the tensioned position is the short-circuit position, and the relaxed position is the open position. This also helps prevent stiffness.

[0012] The short-circuit bridge is therefore arranged and dimensioned between the secondary terminals of the secondary circuit in such a way that it conductively connects the secondary terminals in the short-circuit position.

[0013] In a preferred embodiment, the short-circuit bridge and the cover are designed such that when the cover is moved to its open position, the short-circuit bridge is moved to the short-circuit position. This forced coupling of the movements ensures a high level of safety.

[0014] If the short-circuit bridge is designed and arranged to be tensioned, in particular spread or squeezed, by the cover displacement to assume the short-circuit position, the above-mentioned reset can be easily achieved.

[0015] In particular, the cover displacement can cause the rotation of a rotary cam, which, through displacement or rotation, causes the short-circuit bridge to assume the short-circuit position. The rotation of the rotary cam can be centric or eccentric. The rotary cam can be designed to act on the short-circuit bridge from one side or both sides.

[0016] For example, an eccentric, single-acting rotary cam could press the shorting bridge against one of the two secondary terminals through rotation, while the other secondary terminal remains permanently connected. The cam's axis of rotation could be aligned with the cover's axis of rotation.

[0017] In particular, the cover can have a centric or eccentric rotary cam, in particular an elliptical projection, and the short-circuit bridge can be designed to be movable by the movement of the rotary cam from the open position to the short-circuit position.

[0018] For example, the cover may have an elliptical projection as a double-acting rotary cam, and the short-circuit bridge may be designed to be movable by the elliptical projection as the cover is shifted from the open position to the short-circuit position. The elliptical projection may be directed inward and preferably positioned centrally.

[0019] It is conceivable that the short-circuit bridge has a U- or V-shape in cross-section.

[0020] In a preferred variant, the cover and the short-circuit bridge are arranged in such a way that the elliptical projection dips centrally into the U- or V-shape and contacts the legs of the short-circuit bridge in the open position of the cover in order to short-circuit the secondary terminals in the end position.

[0021] For example, the cover can be rotated toward the opening, which in turn causes the ellipse to rotate and thus causes the main apex areas of the ellipse to contact the legs of the shorting bridge. This naturally causes the legs to spread, so that they—as mentioned—touch the secondary terminals and thus form a conductive connection. The axis of rotation of the ellipse preferably lies on the axis of rotation of the cover.

[0022] Another independently inventive embodiment comprises a cover for releasing the secondary connections in the open position.

[0023] The current transformer therefore has a cover that covers the secondary terminals when in use and is designed to be movable, particularly rotatable, so that the secondary terminals are exposed in an open position. This prevents accidental contact.

[0024] If the current transformer housing or the arrangement of the secondary terminals is approximately rectangular in cross-section (or in a top view of the secondary terminals), a 90-degree rotation of the then elongated cover may be sufficient to vary between the open and closed operating positions. For this purpose, the pivot point of the cover is preferably positioned centrally between the externally arranged secondary terminals.

[0025] The cover may have a locking element with which it can be rotatably locked onto a mating element for releasable attachment to the housing. Preferably, the locking element and the mating element are arranged concentrically around the elliptical projection.

[0026] The cover can also have a preferred rotation direction, e.g., counterclockwise. Additionally, the underside of the cover can have a guide that only allows this rotation.

[0027] Primary circuit coupling means that the current transformer has a coupling for connection to an internal or external primary circuit.

[0028] Another independently inventive design includes coupling points for coupling to other components. These coupling points can, for example, enable the snap-in or form-fitting reception of additional components or current transformers.

[0029] If the current transformer has a rectangular housing in cross-section, coupling points can be provided at all outer corners. The coupling points are preferably located in the corner areas of the flat front and rear sides.

[0030] This also makes it possible to couple several current transformers according to the invention together, for example to provide a three-phase current transformer set.

[0031] Other components that can be considered include mounting adapters, such as plug-in feet, for mounting on sheet metal or DIN rails.

[0032] The coupling points can be designed as V- or L-shaped openings connecting the flat front and back sides of the housing, with the legs of the V or L running at an angle.

[0033] The special design of the "outside corners" allows for maximum flexibility when mounting the current transformer on a busbar, on mounting plates, and on DIN rails. Cable ties can also be threaded through them for all types of fastening.

[0034] A further independently inventive embodiment comprises the central through-opening, if present, which is designed symmetrically, preferably C4-rotationally symmetrically in section.

[0035] The through-hole is preferably designed in a stepped manner in the quadrants of the frame in order to accommodate conductors of different dimensions.

[0036] In one embodiment, the central through-hole can have dovetail-like recesses at the 12 o'clock, 3 o'clock, 6 o'clock, and 9 o'clock positions, allowing for clamping. For example, a primary rail clamp can be inserted there, allowing a primary conductor inserted into the central through-hole to be secured using screws, threaded rods, etc.

[0037] The current transformers according to the invention are preferably plug-on / winding current transformers, cable split-core current transformers, rail split-core current transformers, protective current transformers, summation current transformers, differential current transformers or current transformers with measuring transducers.

[0038] The current transformers according to the invention are particularly suitable for primary rated currents up to 6000 A.

[0039] Further details of the invention emerge from the following description of embodiments with reference to the drawing, in which Fig. 1 shows a schematic perspective view of a plug-in current transformer according to the invention in the closed and open position of the cover as well as in the front view; Fig. 2 shows a partially sectioned front view of a plug-in current transformer according to the invention in the fully open, half-open and closed position of the cover from Figure 1 ; Fig. 3 various perspective, side and front views as well as a longitudinal section of the cover from Figure 1 ; Fig. 4 various perspective, side and front views as well as partial sections of the housing from Figure 1 ; Fig. 5 various perspective, side and front views as well as partial sections of the housing with cover made of Figure 1 ; Fig. 6 - 8 each show a partially sectioned front view and a top view of the current transformer from Figure 1in the closed, half-open and fully open position of the cover; Fig. 9 a schematic perspective view of a fastening of the current transformer from Figure 1 to a busbar; Fig. 10 a schematic perspective view of an alternative fastening of the current transformer from Figure 1 to a busbar; Fig. 11 a schematic perspective view of a fastening of the current transformer from Figure 1 to a top hat rail; Fig. 12 a schematic perspective view of a mounting of the current transformer from Figure 1 on a sheet show.

[0040] In the Figures 1 to 8 the structure of a current transformer according to the invention, designated as a whole with 1 and designed as a plug-on transformer, is shown in different views.

[0041] The current transformer 1 comprises a housing 2, which is approximately square in front view and rectangular in plan view and has a protruding smaller connection area 4 for the secondary connections 5 on the head area 3, which can be covered by a rotatable cover 6 (see Figure 1A or Figure 2C ) or releasable (see Figure 1B or Figure 2A ) is.

[0042] Approximately centrally in the housing 2 in the front view or front side, a central through-opening 7 is arranged, which is designed with C4 rotational symmetry in section and has dovetail-like recesses 8 in the 12 o'clock, 3 o'clock, 6 o'clock and 9 o'clock positions, wherein the side walls 9 of the central through-opening 7 are stepped.

[0043] At the outer corners 10 of the front and rear sides 11, 12, coupling points 13 are formed as L-shaped openings connecting the flat front and rear sides of the housing 2, wherein the legs 13A, B of the L run around the corner.

[0044] As in the Figures 2 , 4 and 5 As can be clearly seen, an approximately circular installation space 14 surrounds the central through-opening 7 in the interior of the housing 2, for example for accommodating secondary circuit windings or coils (not shown).

[0045] These can be connected to terminal plates 15 of the secondary connections 5.

[0046] Since the housing 2 of the current transformer 1 and the arrangement of the secondary terminals 5 are approximately rectangular in cross-section (or in a top view of the secondary terminals), a 90-degree rotation of the then elongated cover 6 is sufficient to vary between the open and closed operating positions. The pivot point of the cover 6 is positioned centrally between the externally arranged secondary terminals 5.

[0047] The cover 6 has a locking element 16 with which it can be rotatably locked onto a counter element 17 for releasable attachment to the housing 2. The locking element 16 and the counter element 17 are arranged concentrically around the elliptical projection and form the central pivot point.

[0048] The cover 6 also has a preferred anti-clockwise rotation direction, which is achieved by means of a link 18 on the underside of the cover 6, which, in cooperation with the walls of the smaller connection area 4 for the secondary connections 5, only allows this rotation.

[0049] A short-circuit bridge 19 made of conductive spring material has a U-shape in cross-section and is arranged around the pivot point in order to be spread by the cover displacement (rotation around the pivot point) to assume the short-circuit position.

[0050] For this purpose, the cover 6 has an elliptical projection 20 as a rotary cam and the short-circuit bridge 19 is spread by the cover displacement from the open position to the short-circuit position by the elliptical projection, for which purpose the elliptical projection 20 is directed inwards on the underside of the cover and is preferably arranged centrally within the latching element 16, i.e. at the pivot point.

[0051] The cover 6 and the short-circuit bridge 19 are thus arranged in such a way that the elliptical projection 20 dips centrally into the U-shape of the short-circuit bridge 19 and spreads its legs 19A, B in the open position of the cover 6 (cf. Figure 8 dashed legs 19A, B) and thus presses against the secondary terminals 5 arranged laterally thereto, thus short-circuiting them.

[0052] Thus, the cover 6 can be rotated counterclockwise around the pivot point to open it, which in turn causes the elliptical projection 20 to rotate around the pivot point and thus causes the main apex regions 20A, B of the ellipse to contact the legs 19A, B of the short-circuit bridge 19. This leads to the legs 19A, B spreading against the spring force, so that they - as mentioned - touch the secondary terminals 5 arranged laterally thereto and thus form a conductive connection. This is clearly visible in the Figures 6 to 8 .

[0053] The cover 6 has oval locking projections 21 on the underside, which, in the closed position of the cover, correspond to the recessed connection points 22 of the secondary connections 5, so that the cover 6, in the closed position, on the one hand additionally locks into place there and, on the other hand, the secondary connections 5 are covered in a dust-tight manner.

[0054] In accordance with the preferred anti-clockwise rotation direction of the cover 6, the walls 23 of the smaller connection area 4 for the secondary connections 5 have bevelled or rounded wall areas 23A analogous to the course of the guides 18.

[0055] The cover 6 has a side wall 6A, B on each end face, followed by a stub longitudinal side wall 6C, D, each of which abuts the corresponding wall 23 when the cover 6 is closed. Since the remaining area of ​​the longitudinal sides is free, rotation is not impaired. A sealing hole 24 can also be provided in the side walls 6A, B, C, D, which has a corresponding hole 25 in the connection area 4.

[0056] A circular opening 26 (cf. Figure 4) in the connection area 4, which has two opposite extensions 26A so that the elliptical projection 20 can be inserted through and then rotated about its shaft 20C with a reduced diameter.

[0057] If the cover 6 is now pushed in further, the locking element 16 snaps into the circular opening 26 with its projections and engages behind it in a form-fitting manner (cf. Figures 5c and 5D ). The circular opening 26 thus forms the counter element 17.

[0058] The locking element 16 and the counter element 17, or the circular opening 26, are arranged concentrically around the elliptical projection 20 and form the central pivot point. At the same time, a guide for the rotational movement is thus formed.

[0059] In the Figures 9 - 12 Examples of mounting options are shown.

[0060] In Figure 9a busbar 27 is passed through the central through-opening 7 of the current transformer 1 and fixed by means of a securing element 28 on both sides of the circular opening 7.

[0061] For this purpose, the securing element 28 is inserted into the corresponding dovetail-like recesses 8 and fixes the busbar 27 by means of a screw 29 received in a threaded hole.

[0062] The busbar 27 itself is inserted laterally into opposite dovetail-like recesses 8 and thus held in a clamping manner.

[0063] The cover 6 is shown rotated 90 degrees in the open position.

[0064] Compared to the connection area 4 or the cover 6, the current transformer 1 is virtually on its side.

[0065] In Figure 10In contrast, a vertical attachment to the busbar 27 is shown. The viability of the mounting options can be seen.

[0066] In Figure 11 the current transformer 1, on the other hand, is clamped to a top hat rail 30 in a lateral arrangement.

[0067] For this purpose, clamping parts 31 are provided which, on the one hand, engage in the respective coupling points 13 with locking elements 32 and, on the other hand, clamp around the top-hat rail 30 with locking elements 33.

[0068] The cover 6 is shown in the closed position.

[0069] It is evident that the alignment of the current transformer 1 to the top-hat rail 30 depends solely on the use of the respective coupling points 13.

[0070] In Figure 12 The current transformer 1 is screwed vertically to a plate 34.

[0071] For this purpose, screw parts 35 are provided which, on the one hand, are clamped into the respective coupling points 13 and, on the other hand, are designed with holes for screws 38.

[0072] The cover 6 is shown rotated 90 degrees in the open position. List of reference symbols

[0073] 1Current transformer 2Housing 3Head area 4Connection area 5Secondary connection 6Cover 6A, BSide wall 6C, DStub longitudinal side wall 7Through opening 8Recess 9Side wall 10Outer corner 11Front 12Rear 13Coupling point 13A, BLeg 14Installation space 15Connection terminal plate 16Snap-in element 17Counter element 18Link 19Short-circuit bridge 19A, BLeg 20Elliptical projection 20A, BEllipse main apex area 20CShaft 21Snap-in projection 22Connection point 23Wall 23AWall area 24Seal hole 25Equivalent 26Circular opening 26AExtension 27Busbar 28Securing element 29Screw 30DIN rail 31Clamping part 32Locking element 33Locking element 34Sheet 35Screw part 38Screw

Claims

1. Current transformer with a primary circuit coupling and a secondary circuit and with an integrated short-circuit bridge, wherein the short-circuit bridge is adjustable between a short-circuit position and an open position, so that secondary terminals of the secondary circuit are conductively connected to one another via the short-circuit bridge in the short-circuit position of the short-circuit bridge, characterized in that the short-circuit bridge is a spring which is relaxed in the open position and tensioned in the short-circuit position or which is tensioned in the open position and relaxed in the short-circuit position.

2. Current transformers with a primary circuit coupling and a secondary circuit and with an integrated short-circuit bridge, wherein the short-circuit bridge is adjustable between a short-circuit position and an open position, so that secondary terminals of the secondary circuit are conductively connected to one another via the short-circuit bridge in the short-circuit position of the short-circuit bridge, characterized in thatthe current transformer has a cover which covers the secondary terminals in the use state and which is designed to be rotatable into an open position in which the secondary terminals are free.

3. Current transformer according to claim 1 and 2, characterized in that the short-circuit bridge and the cover are designed in such a way that when the cover is moved to the open position, the short-circuit bridge is moved to the short-circuit position.

4. Current transformer according to claim 3, characterized in that the short-circuit bridge is designed and arranged to be relaxed or tensioned, in particular spread, by the cover displacement to assume the short-circuit position.

5. Current transformer according to claim 3 or 4, characterized in thatthe cover has a centric or eccentric rotary cam, in particular an elliptical projection, and the short-circuit bridge is designed to be movable from the open position into the short-circuit position by the movement of the rotary cam.

6. Current transformer according to claim 5, characterized in that the short-circuit bridge has a U- or V-shape in cross-section.

7. Current transformer according to claim 6, characterized in that the cover and the short-circuit bridge are arranged in such a way that the rotary cam, in particular the elliptical projection, dips centrally into the U- or V-shape and contacts the legs in a spreading manner in the open position of the cover.

8. Current transformer according to one of the preceding claims, characterized in that the current transformer has a housing which is square in cross-section and which has coupling points, preferably at all outer corners.

9. Current transformer according to claim 8, characterized in thatthe coupling points are designed as V- or L-shaped openings connecting the flat front and rear sides of the housing, with the legs of the V or L running at an angle.

10. Current transformer according to one of the preceding claims, characterized in that the current transformer has a central through-opening which is designed symmetrically, preferably C4-rotationally symmetrically in section.

11. Current transformer according to claim 10, characterized in that the central through-hole has dovetail recesses at the 12 o'clock, 3 o'clock, 6 o'clock and 9 o'clock positions.

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