EP4308941A1

EP4308941A1 - Measuring device for a current converter

Info

Publication number: EP4308941A1
Application number: EP22717559.3A
Authority: EP
Inventors: Erik Winkelmann; Iaroslav SHEVCHENKO
Original assignee: Maschinenfabrik Reinhausen GmbH; Maschinenfabrik Reinhausen Gebrueder Scheubeck GmbH and Co KG
Current assignee: Maschinenfabrik Reinhausen GmbH; Scheubeck GmbH and Co
Priority date: 2021-04-09
Filing date: 2022-03-22
Publication date: 2024-01-24
Also published as: WO2022214307A1; CN117136311A; JP2024513471A

Abstract

The invention relates to a measuring device (2) for a current converter (4). The measuring device (2) comprises a peripherally extending core (6), a measuring coil (8) and a reference terminal (10). The measuring coil (8) is formed by a current conductor (12) which is wound around the core (6) and which extends from a first conductor end (14) to a second conductor end (16). The reference terminal (10) is electrically connected to the current conductor (12) centrally between the first conductor end (14) and the second conductor end (16). The invention also relates to a current converter (4), comprising a measuring device (2) and a differential amplifier (36).

Description

Measuring device for a current transformer

The invention relates to a measuring device for a current transformer.

Current transformers are basically known from the prior art. A current transformer has a measuring device. A primary current through an electrical, primary power line can be detected contactlessly by means of the measuring device. The primary power line can be formed, for example, by a cable, in particular a copper cable, through which the primary current flows. In order to record the primary current using the measuring device of the current transformer, the primary current line is passed through the measuring device. In a known embodiment, the measuring device has a circumferential, ring-shaped core, with a measuring coil of the measuring device being formed by a current conductor wound around the core. This current conductor can also be referred to as a secondary current line of the measuring device. In the example mentioned, the primary current line can be passed through the inner space formed by the core. The primary current flowing through the primary power line causes a secondary current in the secondary power line of the measuring device by electromagnetic induction. The secondary current is less than the primary current, preferably inversely proportional to the ratio of the turns of the primary power line to the turns of the secondary power line.

When using a current transformer in practice, it was found that electromagnetic interference fields can affect the secondary current. In other words, the secondary current may have a component caused by noise. This component can also be referred to as the spurious component of the secondary current. The spurious component reduces the measurement accuracy with which the primary current can be detected by the current transformer.

The object of the invention is to provide a measuring device for a current transformer that allows a current to be detected as robustly as possible with respect to disturbance variables.

According to a first aspect of the invention, the object is achieved by a measuring device having the features of claim 1 Measuring device for a current transformer, the measuring device having a rotating core, a measuring coil and a reference connection. The measuring coil is formed by a current conductor which is wound around the core and extends from a first conductor end to a second conductor end. The reference connection is electrically conductively connected to the current conductor centrally between the first conductor end and the second conductor end. The measuring coil is preferably electrically insulated from the core. For example, the current conductor can be electrically insulated from the core.

The measuring device is preferably designed to form part of a current transformer. The measuring device can thus be electrically connected to other parts of the current transformer by means of the associated conductor ends (first and second conductor end).

The current conductor of the measuring device wound around the core can be designated and/or configured as the secondary current line. A current flowing through the current conductor wound around the core may be referred to as secondary current or secondary current. When a primary current conductor is passed through the inner space formed by the core and a primary current flows through the primary current conductor, this primary current causes the secondary current in the current conductor of the measuring device by electromagnetic induction. The induction preferably takes place over the entire length of the current conductor of the measuring device. The reference terminal, which is electrically connected to the current conductor of the measuring device centrally between the first conductor end and the second conductor end, preferably serves to generate a differential signal at the two conductor ends when the aforementioned electromagnetic induction leads to a secondary current in the current conductor of the measuring device. The reference connection can be coupled to a predetermined electrical voltage potential, which is also referred to as a reference voltage potential. The voltage signal generated at the two conductor ends then relates to the reference voltage signal predetermined by the reference connection. If the reference voltage connection is connected to ground potential, for example, a positive current is caused by electromagnetic induction at the first conductor end, whereas a negative current is caused by electromagnetic induction at the second conductor end, or vice versa. The voltage potential at the two conductor ends is also different. If the reference voltage potential is assumed to be the ground potential again, the voltage potential at the first conductor end can have an opposite sign to the voltage potential at the second conductor end. Basically that is Reference voltage potential not necessarily the ground potential. Rather, any desired voltage potential can be applied to the reference connection.

Electromagnetic interference that affects the measuring device from outside, and in particular the measuring coil, can cause a common-mode interference current in the measuring coil. The central arrangement of the reference connection causes the interference current to be impressed evenly on the two partial lengths of the current conductor wound around the core. The partial lengths mean the first partial length of the current conductor, which extends from the reference connection to the first conductor end, and the second partial length of the current conductor, which extends from the reference connection to the second conductor end. If the measuring device is coupled to a differential amplifier of the current transformer in order to measure the secondary current of the current conductor of the measuring device, the common-mode interference current causes no or only a small interference component at the output of the differential amplifier. The output signal of the differential amplifier is therefore not or only slightly influenced by the electromagnetic interference acting on the measuring device due to the centrally arranged reference connection. The measuring device thus contributes to the fact that the primary current of a primary power line can be detected by means of a current transformer, which includes the measuring device, in a robust manner in relation to electromagnetic interference acting on the measuring device from the outside.

In an advantageous embodiment, the central arrangement of the reference connection between the first conductor end and the second conductor end can mean that the first partial length of the current conductor, which extends from the reference connection to the first conductor end, and the second partial length of the current conductor, which extends from the reference connection extends to the second conductor end, are the same or have a deviation of maximum 5% or maximum 10%. For example, the first partial length may be a maximum of 5% or a maximum of 10% longer than the second partial length, or vice versa.

The current conductor of the measuring device is preferably formed by an electrically conductive wire. The wire can be formed as a copper wire, for example.

The core of the measuring device is preferably designed as a core that is circular in its external cross section or as a core that is rectangular in its external cross section. The core of the measuring device can also be designed and/or designated as a toroidal core. The core of the measuring device preferably forms a ring running around the core in the circumferential direction, in particular in the manner of a toroid. The ring can also be designed as a rectangular ring.

The current conductor can be wound around the core in such a way that several winding sections are formed, which are connected in series by means of the current conductor and thereby together form the measuring coil. The measuring coil can also be referred to as a measuring winding and/or can be designed as such. Each winding section preferably comprises a plurality of turns of the current conductor. The measuring coil is preferably formed exclusively by the uninterrupted current conductor wound around the core.

The measuring coil of the measuring device is preferably formed by at least two symmetrically arranged winding sections. In principle, further winding sections can also be provided. The winding sections are preferably distributed in the circumferential direction of the core in such a way that the current conductor is wound around the core in a uniformly distributed manner in the circumferential direction of the core. It has proven to be advantageous if the measuring coil is formed by four winding sections, for example. The winding sections are connected in series and thus form the measuring coil. The current conductor extends from winding section to winding section. The reference terminal can be connected to the current conductor between two of the multiple winding sections of the measuring coil. This facilitates a particularly precise central arrangement of the reference connection between the first conductor end and the second conductor end of the current conductor.

An advantageous embodiment of the measuring device is characterized in that the reference connection is electrically connected to the current conductor in such a way that a first impedance of the current conductor between the reference connection and the first conductor end and a second impedance of the current conductor between the reference connection and the second conductor end are the same or have a maximum deviation of 5% or 1%. According to this embodiment, it is preferably provided that the maximum deviation of the impedances of the first and second partial lengths of the current conductor is a maximum of 5%. The current conductor preferably has an at least essentially constant diameter. The above-mentioned restriction with regard to the deviation of the impedances can thus be particularly advantageously ensured that an electromagnetic interference signal acting on the measuring device from the outside is distributed equally over the two partial lengths of the current conductor, so that the same interference component is impressed in each of the two current conductors becomes. These spurious components cause a common-mode noise current that is applied to a differential amplifier as a a common-mode signal is not amplified or at most leads to minor interference at the output of the differential amplifier.

A further advantageous embodiment of the measuring device is characterized in that the reference connection is connected to a predetermined electrical reference potential. The reference potential can, for example, be a predetermined electrical voltage or be formed by the ground potential.

A further advantageous embodiment of the measuring device is characterized in that the measuring coil is distributed symmetrically to a radial plane of the core. A central opening is preferably defined by the rotating core. A longitudinal axis of the core can run in a passage direction through this central opening of the core. The passage direction is therefore also referred to as the axial direction of the core. A radial direction of the core is perpendicular to the axial direction of the core. This preferably also applies when the core is not designed as a circular core, but when the core is, for example, rectangular in cross section. The radial plane of the core is preferably spanned by the axial direction of the core and the radial direction of the core. The symmetrical distribution of the measuring coil to the radial plane of the core offers the advantage that the electrical properties of the first partial length of the current conductor and the electrical properties of the second partial length of the current conductor are at least essentially the same or at most have a maximum deviation of 5%. For example, it is possible that the symmetrical distribution contributes to the first and second impedance being equal or having a maximum deviation of 5%. The same can apply to the lengths, electrical resistances and/or the number of turns of the first and second partial lengths of the current conductor.

A further advantageous embodiment of the measuring device is characterized in that the core has or is formed from magnetic, in particular ferromagnetic, and/or amorphous material. The core preferably consists of at least 80%, 90% or 95% magnetic, in particular ferromagnetic, material. The remainder of the core may be formed from a non-ferromagnetic material or substance. Iron, cobalt and nickel are ferromagnetic. They therefore form exemplary magnetic or ferromagnetic metals. The magnetic material of the core may be one or more magnetic metals. Particularly preferably, at least 80%, 90% or 95% of the magnetic material of the core is formed by MgZn ferrite. The material of the core can also be in the form of an amorphous material. As special it has turned out to be advantageous if the material of the core, in which a magnetic circuit is formed, is made of ferromagnetic and/or amorphous material. Magnetic material is preferably understood to mean magnetizable material. This material need not be designed to cause a magnetic field. A further advantageous embodiment of the measuring device is characterized in that the core is designed in several parts. For example, the core can be formed from several parts. A first part of the core can be formed, for example, as a part with a C-shaped cross section. A second part of the core can be formed, for example, as a cross-section I-shaped part. The I-shaped part can be arranged on the C-shaped part in such a way that the two parts of the core form a peripheral core that has a rectangular cross section and encloses a laterally open inner space. The parts of the core can be placed in direct contact with each other.

A further advantageous embodiment of the measuring device is characterized in that the measuring coil is designed in several parts. The measuring coil is basically formed by the current conductor wound around the core. The current conductor extends uninterruptedly from the first conductor end to the second conductor end. However, the current conductor can comprise at least one detachable connection point. The current conductor preferably comprises a number of detachable connection points. At each connection point, the continuous connection of the current conductor can be interrupted and restored, for example to mount the measuring device. The current conductor can be wound around the core in such a way that several winding sections are formed, which are connected in series by means of the current conductor and thereby together form the measuring coil. The measuring coil can have three winding sections, for example. The first winding section of the measuring coil can be formed by the current conductor, for example, in such a way that the current conductor in the first winding section extends from the first conductor end to a first connection end. The second winding section of the measuring coil can, for example, be formed by the current conductor in such a way that the current conductor in the second winding section extends from a second connection end to a third connection end. The third winding section of the measuring coil can be formed by the current conductor, for example, in such a way that the current conductor in the third winding section extends from a fourth connection end to the second conductor end. A first, detachable connection point of the current conductor can be formed, for example, by the first and second connection ends, which are detachably connected to one another. A second, detachable connection point of the current conductor can be formed, for example, by the third and fourth connection end, which can be detachable are connected to each other. The two connection points ensure that the current conductor extends continuously and/or uninterruptedly from the first end of the conductor to the second end of the conductor. The current conductor can be interrupted at the connection points, in particular for assembly or for production purposes. For example, it has proven to be advantageous if the first and third winding sections of the current conductor are arranged on the C-shaped part of the core. Thus, the part of the current conductor forming the first winding section can be wound around a first leg of the C-shaped part of the core. A part of the current conductor forming the third winding section may be wound around a second leg of the C-shaped part of the core. A part of the current conductor forming the second winding section may be wound around the I-shaped part of the core. If the C-shaped part and the I-shaped part of the core are arranged relative to each other in such a way that the rotating core is formed, it can also be provided that the first and second connection ends are/are connected in order to form the first, detachable connection point of the to form a conductor. In addition, the third and fourth connection ends can be connected to one another to form the second, releasable connection point of the current conductor. Once the two connection points have been established, the current conductor wound around the peripheral core extends from the first conductor end to the second conductor end.

The measuring coil can also be referred to as a measuring winding and/or can be designed as such. Each winding section preferably comprises a plurality of turns of the current conductor. The measuring coil is preferably formed exclusively by the uninterrupted current conductor wound around the core.

A further advantageous embodiment of the measuring device is characterized in that the core has at least one section with a plurality of magnetic plates which are arranged opposite one another, in particular parallel, and spaced from plate to plate by a gap. The magnetic plates are preferably designed as ferromagnetic plates. It has been found advantageous that when the magnetic permeability of the core is small, the possible problem of core saturation can be prevented with a primary current through the primary power line having a frequency equal to or higher than the operating frequency. For example, the operating frequency is less than 100 Hz. In order to achieve a reduction in the magnetic permeability of the core, the multiple gaps between the plates are therefore provided. The multiple gaps cause the lowering of the magnetic permeability of the core, which can prevent the problem of core saturation. It should be taken into account that the core in this embodiment is formed by the plurality of magnetic, in particular ferromagnetic, plates and the gaps. Each gap between two oppositely arranged plates is preferably designed such that the plates are arranged without contact with one another and/or the maximum distance between the plates is less than 1 mm, less than 0.5 mm, or less than 0.1 mm. The distance between the plates arranged without contact with one another is preferably between 0.02 mm and 0.08 mm, preferably between 0.05 mm and 0.06 mm. Each gap may be referred to and/or configured as a non-magnetic or non-ferromagnetic gap. The gaps are preferably distributed symmetrically to the radial plane of the core. In addition, it is preferably provided that the plates of the core are distributed symmetrically to the radial plane of the core.

A further advantageous embodiment of the measuring device is characterized in that the core has a plurality of sections, each with a plurality of magnetic, in particular ferromagnetic plates, the plates of the respective section being arranged opposite one another, in particular parallel, and in direct contact from plate to plate , and wherein the sections of the core are arranged in tandem and spaced from section to section by a gap. A core that is rectangular in cross-section may have four edges (eg, two parallel horizontal edges and two parallel vertical edges). At least one of the edges can be divided into at least two parts. Thus, the core, which is rectangular in cross-section, can have, for example, five sections, each with a plurality of plates. However, it is also possible for the core to have a smaller or larger number of sections. Thus, each edge of the core can in turn be divided into a large number of sections. It is preferably provided that the plates of a respective section are in direct contact from plate to plate and are therefore arranged one behind the other. A plurality of sections, each having a plurality of magnetic, in particular ferromagnetic plates, can be arranged one behind the other in one edge, with the sections being spaced from section to section by a respective gap. Each gap separates the panel located at an adjacent end of one section from an opposing panel of the subsequent section. Within each section, it is preferably provided that the plates are arranged one behind the other without any gaps. Each section can comprise, for example, between two tiles and 50 tiles, in particular between five tiles and 30 tiles, preferably between five tiles and 15 tiles. It should be noted that the core can have a large number of sections, with the aforementioned characteristics of the sections in particular, relates only to a subset of this larger number of sections. However, it is also possible for the aforementioned features to relate to each section of the core. For the section-to-section gap, reference is made to the advantageous explanations, preferred features, effects and advantages in a manner analogous to that previously explained for the plate-to-plate gap.

A further advantageous embodiment of the measuring device is characterized in that each gap is designed as an air gap or a spacer is placed in each gap. If a spacer is introduced into a gap, the respective gap can be formed entirely by the spacer. Each spacer can be made of paper, in particular laminated paper, or plastic, in particular glass fiber plastic.

A further advantageous embodiment of the measuring device is characterized in that each spacer is formed from a non-ferromagnetic material. This can reduce or even prevent the possible problem of core saturation.

A further advantageous embodiment of the measuring device is characterized in that the plates of each pair of plates spaced apart from a gap are arranged in a contact-free manner spaced apart from one another with a plate spacing of between at least 0.001 mm and a maximum of 0.7 mm. As a result, a magnetic flux that occurs when current flows through the primary power line is bundled and guided with little loss.

A further advantageous embodiment of the measuring device is characterized in that the measuring device has a first shielding, which has a first protective element and preferably a second protective element. The first shielding can also be referred to as a first shielding device and/or be designed as such. The first shield forms part of the measuring device. The first shield can be formed exclusively by the first protective element. However, it is also possible for the first shielding to include further parts, in particular the second protective element, in addition to the first protective element. The first shielding can serve and/or be designed to prevent and/or dampen electromagnetic interference that affects the measuring device from the outside. Provision can also be made for the first shielding to be designed in order to prevent electromagnetic fields from penetrating the first shielding and emitting them into the environment as electromagnetic interference. The first protective element is preferably designed as a shielding plate or as a shielding grid. The first shield can include the first protection element and have the second protective element and/or be completely formed by these protective elements. However, it is also possible for the first shielding to be formed solely by the second protective element. The second protective element is preferably designed as a shielding plate or as a shielding grid.

A further advantageous embodiment of the measuring device is characterized in that the first protective element is designed as an electrically conductive protective element which is arranged on the outside of the core and the measuring coil and runs at least essentially completely around the core in the circumferential direction. The first protective element is preferably arranged on the outside of the core and/or the measuring coil in the radial direction. The first protective element preferably has no direct contact with the measuring coil and/or the core. Rather, it is preferably provided that the first protective element is at a distance from the measuring coil and/or the core. In addition, it is preferably provided that the first protective element is electrically conductive. The first protective element can thus form at least part of a cage, in particular a Faraday cage, which is arranged on the outside of the core and at least essentially completely surrounds the core in the circumferential direction. The first protective element provides protection against electromagnetic interference for the measuring coil and/or the core. The first protective element is preferably interrupted at one point in the circumferential direction. Alternatively, however, it is also possible for the first protective element to be designed to run completely and/or uninterruptedly in the circumferential direction of the core.

A further advantageous embodiment of the measuring device is characterized in that the second protective element is designed as an electrically conductive protective element arranged on the inside of the core and the measuring coil and running at least substantially completely around the core in the circumferential direction. The second protective element is preferably arranged on the inside of the core and/or the measuring coil in the radial direction. The second protective element can thus be arranged at least partially or completely in the interior space which is enclosed by the core of the measuring device. The second protective element preferably has no direct contact with the measuring coil and/or the core. Rather, it is preferably provided that the second protective element is at a distance from the first measuring coil and/or the core. In addition, it is preferably provided that the second protective element is electrically conductive. The second protective element can thus form at least part of a cage, in particular a Faraday cage, which is arranged in the interior of the core and/or is designed to run at least essentially completely around the core in the circumferential direction. The first element of protection provides for the Measuring coil and / or the core protection against electromagnetic interference. The second protective element is preferably interrupted at one point in the circumferential direction. Alternatively, however, it is also possible for the second protective element to be designed to run completely and/or uninterruptedly in the circumferential direction of the core.

A further advantageous embodiment of the measuring device is characterized in that the first shielding is designed as a ring-shaped shield running in the circumferential direction of the core, which encloses the core and the measuring coil at least essentially in the form of a tube, with the ring-shaped shield being formed of two in the circumferential direction of the Core circumferential, shell-shaped protective elements is formed, which form the first and second protective element. The cross-sectional area of the ring-shaped shield, which is aligned perpendicularly to the circumferential direction, is preferably rectangular, in particular square. Particularly effective shielding against electromagnetic interference can be achieved by the core and the measuring coil being enclosed at least essentially in the form of a tube by the ring-shaped shield. In addition, it has proven to be advantageous if the ring-shaped shielding is designed to run around in a rectangular shape. This applies in particular when the core is designed as a rectangular peripheral core. The ring-shaped shield is preferably divided in a dividing plane in which the circumferential direction of the core runs. Due to the division of the ring-shaped shield in the plane of separation, the ring-shaped shield forms the first and second shell-shaped protective elements, each running around in the circumferential direction. In the separation plane, the first and second protective elements are preferably detachably connected to one another. However, it is also possible for the first and second protective element to be permanently connected to one another in the parting plane, for example welded to one another. The ring-shaped shielding with the two cup-shaped protective elements offers the advantage that each of the two cup-shaped protective elements can be pushed over the core and the measuring coil from opposite sides, so that the two cup-shaped protective elements touch in the parting plane to create an electrical and/or mechanical to be able to make contact.

A further advantageous embodiment of the measuring device is characterized in that an outer contour of the ring-shaped shield and/or each shell-shaped protective element is rectangular, and/or an inner contour formed by the ring-shaped shield and/or by each shell-shaped protective element is rectangular. As stated above, it is preferably provided that the annular shield Core and the measuring coil encloses tubular. In practice, it has turned out to be advantageous if the core is designed to run around in a rectangular shape. In order to follow this rectangular circumferential contour, it has proven to be advantageous if the outer contour of the ring-shaped shield, and thus preferably also the outer contour of each of the two shell-shaped protective elements, is rectangular. An interior space that is open on opposite sides is formed by the core of the measuring device running around in a rectangular shape. The two shell-shaped protective elements, which also run around in the circumferential direction, can engage in this interior space. It has therefore turned out to be advantageous if the inner contour of the ring-shaped shield and/or the inner contour of each of the two shell-shaped protective elements is rectangular. Because in this case, the passage area of the interior that is still open between the two opposite sides is particularly large.

A further advantageous embodiment of the measuring device is characterized in that the first protective element and the second protective element are electrically connected to one another or are formed integrally as a common protective element. If the first and second protective elements are electrically connected to one another, the first and second protective elements can form a Faraday cage, which protects the core and the measuring coil from electromagnetic interference. If the first and second protective element are formed integrally or are detachably connected to one another in such a way that they are in electrical contact with one another, it is possible for the first and second protective element to form a common protective element. The common protective element can run in the circumferential direction of the core in the manner of a torus, so that the core and the measuring coil are arranged within an interior space formed by the protective element. The interior formed by the common protective element does not necessarily have to be closed. For example, it is possible that the first protective element and the second protective element are each formed by a grid, so that the common protective element is also formed by a common grid or by two grids.

A further advantageous embodiment of the measuring device is characterized in that the first shielding is electrically connected to the reference connection. The reference connection can thus be electrically connected to the first protective element and/or the second protective element. This refinement is particularly advantageous when the reference connection is coupled to ground potential. A further advantageous embodiment of the measuring device is characterized in that a protective distance between the core and/or the measuring coil on the one hand and the at least one protective element of the first shield on the other hand is predetermined in such a way that a predetermined electrical capacitance between the core and/or the Measuring coil and on the other hand the first shield is formed. The electrical capacity affects the transfer function between the measuring device and a differential amplifier of the current transformer. For example, the electrical capacitance can determine a limit frequency of a low-pass characteristic of the transfer function or at least have an influence on it. The electrical capacitance can be set and/or predetermined by the predetermined selection of the protective distance. This also allows the cut-off frequency for the transfer function to be determined. With a suitable choice of the limit frequency, it is therefore possible to dampen high-frequency noise or high-frequency interference signals, whereas low-frequency useful signals are transmitted from the measuring device to the differential amplifier. It is therefore possible by means of the measuring device to detect the primary current in a primary current conductor in a manner that is robust in relation to high-frequency interference signals by means of the current transformer.

A further advantageous embodiment of the measuring device is characterized in that the measuring device can also be actuated as a feed device, such that a current is fed into a primary current conductor that is routed through the interior space formed by the core.

In order to feed the current into the primary current conductor by means of the current transformer's measuring device, which in this case acts as a feed device, the primary current line is guided through the measuring device and a current is coupled into the current conductor wound around the core. The current flowing through the current conductor causes a current in the primary current conductor, which is passed through the measuring device, by electromagnetic induction. It is thus possible, using one and the same measuring device, both to measure a current flowing through the primary current conductor and to feed a current into the primary current conductor.

According to a second aspect of the invention, the object mentioned at the outset is achieved by a current converter having the features of claim 20. A current converter is therefore provided which has a measuring device and a differential amplifier. The measuring device is designed according to the first aspect of the invention and/or one of the associated advantageous configurations. The current transformer stands out characterized in that a first input connection of the differential amplifier is electrically connected to the first conductor end of the current conductor of the measuring device by means of a shielded, first connecting line. In addition, a second input connection of the differential amplifier is electrically connected to the second conductor end of the current conductor of the measuring device by means of a shielded, second connecting line. The reference connection is preferably coupled to or can be coupled to a predetermined electrical reference potential.

For the measuring device of the current converter, reference is made to the advantageous configurations, preferred features, effects and/or advantages as have already been explained above for the measuring device according to the first aspect of the invention and/or one of the associated advantageous configurations.

The differential amplifier is preferably designed to generate a measurement signal at the output of the differential amplifier as a function of the signals at the input terminals of the differential amplifier. The differential amplifier preferably generates the measurement signal in such a way that the measurement signal represents a primary current which flows through a primary current conductor which runs through an interior space formed by the core of the measuring device. The measurement signal from the differential amplifier can thus form an output signal from the current converter. The current converter can have an output connection which is electrically connected to the output of the differential amplifier, so that the measurement signal can be made available at the output connection.

The first and second connection lines are each shielded. This can effectively prevent electromagnetic interference signals acting on the connecting lines from the outside leading to noise in the measurement signal.

Coupling the reference connection to a predetermined electrical reference potential offers the advantage that the measuring device generates differential signals at the first and second input connection. These can be used particularly advantageously by the differential amplifier in order to generate the measurement signal at the output of the differential amplifier.

An advantageous embodiment of the current transformer is characterized in that the reference connection is coupled to ground potential. In principle, however, it is also possible for the reference connection to be coupled to a different, predetermined electrical potential than the ground potential. A further advantageous embodiment of the current transformer is characterized in that each of the two connecting lines has an associated line shielding, each of which is coupled to ground potential, with the reference connection being separated from the line shielding in such a way that no direct electrical connection is made that is not via ground potential runs, is formed from the reference potential to at least one of the line shields. Each of the two line connections can be formed by a coaxial cable with a shield on the jacket side, which forms the respective line shield.

A further advantageous embodiment of the current transformer is characterized in that the differential amplifier has a second shielding which is coupled to ground potential, the second shielding being separated from the line shielding in such a way that no direct electrical connection which does not run via ground potential from the second shield to at least one of the line shields.

Further features, advantages and possible applications of the present invention result from the following description of the exemplary embodiments and the figures.

All features described and/or illustrated form the subject matter of the invention on their own and in any combination, also independently of their composition in the individual claims or their back-references. In the figures, the same reference symbols continue to stand for the same or similar objects. Fig. L shows an advantageous embodiment of the measuring device in a schematic sectional view.

2 shows the advantageous embodiment of the measuring device in a schematic block diagram representation.

3 shows an advantageous embodiment of the core of the measuring device in a schematic sectional view.

FIG. 4 shows a first advantageous embodiment of a section of the core in a schematic representation. FIG. 5 shows a second advantageous embodiment of a section of the core in a schematic representation. 6 shows a second advantageous embodiment of the measuring device in a schematic sectional view.

7 to 9 each show an advantageous embodiment of the current transformer in a schematic representation. 10 shows a third advantageous embodiment of the measuring device in a schematic sectional view.

11 shows a fourth advantageous embodiment of the measuring device in a schematic sectional view.

12 shows a fifth advantageous embodiment of the measuring device in a schematic sectional view.

13 to 14 show an advantageous embodiment of the first shielding of the measuring device.

A first, advantageous embodiment of a measuring device 2 is shown schematically in FIG. The measuring device 2 serves as a measuring device 2 for a current transformer 4, which is shown in an advantageous embodiment, for example, in FIG.

The measuring device 2 has a revolving core 6 , a measuring coil 8 and a reference connection 10 . The measuring coil 8 is formed by a current conductor 12 wound around the core 6 . The current conductor 12 extends uninterruptedly from a first conductor end 14 to a second conductor end 16. The reference connection 10 is electrically conductively connected to the current conductor 12 in the middle between the first conductor end 14 and the second conductor end 16.

The core 6 is preferably made up of at least 80%, at least 90%, or at least 95% of a magnetic, in particular ferromagnetic, material such as, for example, an MgZn ferrite. As can be seen from FIG. 1, it is also preferred for the core 6 to be in the form of a peripheral, rectangular core 6 . The core 6 thus has an interior space 54 on the inside. The interior space 54 is designed to be open on opposite sides in the axial direction, which is perpendicular to the plane of the drawing. The radial direction R of the core 6 is perpendicular to the axial direction. A radial plane of the core 6 is defined by the axial direction and the radial direction R. Reference is made to this radial plane where appropriate.

The current conductor 12 is wound around the core 6 and extends from the first conductor end 14 to the second conductor end 16. The winding of the current conductor 12 around the core 6 results in a large number of turns. The current conductor 12 therefore forms a measuring coil 8 of the measuring device 2. Preferably, the plurality of windings of the measuring coil 8 is distributed in the circumferential direction U of the core 6, in particular distributed in such a way that so that the same number of turns of the measuring coil 8 are arranged on both sides of the radial plane. The large number of windings of the measuring coil 8 is particularly preferably arranged in a uniformly distributed manner in the circumferential direction U of the core 6 . In addition, it is preferably provided that the measuring coil 8 is arranged symmetrically to the radial plane of the core 6 . A part of the measuring coil 8 can be arranged on one side of the radial plane and the other part of the measuring coil 8 can be arranged on the other side of the radial plane such that the measuring coil 8 is distributed symmetrically to the radial plane of the core 6 .

As can be seen schematically in FIG. 1, the measuring coil 8 can be formed by a plurality of winding sections 62 which are electrically connected in series by the current conductor 12 . Each of the winding sections 62 has a multiplicity of windings which are formed by the current conductor 12 . The current conductor 12 thus extends, for example, from the first conductor end 14 to a first winding section 64, in which the current conductor 12 is wound around the core 6 in a large number of turns. The current conductor 12 extends from the first winding section 64 to a second winding section 66 in which the current conductor 12 is wound around the core 6 in a large number of turns. In this way, a plurality of winding sections 62 can be distributed in the circumferential direction U of the core 6 . The winding sections 62 can be distributed in such a way that the measuring coil 8 is distributed symmetrically to the radial plane of the core 6 .

The reference connection 10 is electrically connected to the current conductor 12 in the middle between the first conductor end 14 and the second conductor end 16 . The reference connection 10 can thus be arranged directly on the current conductor 12 . However, it is also possible for the reference connection 10 to be arranged a maximum of 10 cm, a maximum of 20 cm, a maximum of 30 cm or a maximum of 40 cm from the center between the first conductor end 14 and the second conductor end 16 . Nevertheless, it is understood that the reference connection 10 is electrically connected to the current conductor 12 in the middle between the first conductor end 14 and the second conductor end 16 . Centered between the two conductor ends 14, 16 can mean that a first partial length 56 of the current conductor 12 from the reference connection 10 to the first conductor end 14 and a second partial length 58 of the current conductor 12 from the reference connection 10 to the second conductor end 16 are of the same length or one have a deviation in length of no more than 10% or no more than 5%.

The current conductor 12 wound around the core 6 can also be referred to as a secondary current conductor 12 . In an example, if a further, primary current conductor (not shown) guided in the axial direction through the inner space 54, and a primary current flows through the primary current conductor, the primary current causes a current in the secondary current conductor 12 by electromagnetic induction, this current also being referred to as the secondary current. The reference connection 10 which is electrically connected to the current conductor 12 centrally between the two conductor ends 14 , 16 offers the advantage that a predetermined electrical potential can be caused at the connection point between the reference connection 10 and the electric current conductor 12 . For example, the reference connection 10 can be connected and/or coupled to ground potential 46 so that the point on the current conductor 12 that is connected to the reference connection 10 must have the predetermined potential, here the ground potential 46 . The current induced in the current conductor 12 therefore causes what is known as a differential current signal at the conductor ends 14, 16. The differential current signal is also referred to as a symmetrical current signal or as a push-pull current signal. The differential current signal serves as a useful signal for the current transformer 4. Electromagnetic interference acting on the measuring device 2 from the outside can, however, only cause common-mode interference signals at the conductor ends 14, 16 due to the reference connection 10, which is preferably coupled to a predetermined electrical potential .

If the measuring device 2 is used for a current transformer 4, as is shown, for example, and schematically in FIG. 42 of the differential amplifier 36 generates an output signal at the output terminal 60 of the differential amplifier 36 . The common-mode interference signal has little or no influence on the output signal. The output signal is therefore at least essentially influenced by the useful signal. The useful signal depends on the primary current through the primary current conductor 12 . The measuring device 2 thus offers the advantage that the measuring device 2 contributes to being able to detect the primary current as robustly as possible with respect to external electromagnetic interference. It has been found to be advantageous if the reference connection 10, which is electrically connected centrally to the current conductor 12, is electrically connected to the current conductor in such a way that a first impedance of the current conductor 12 between the reference connection 10 and the first conductor end 14 and a second impedance of the current conductor 12 between the reference connection 10 and the second conductor end 16 are the same or have a maximum deviation of 5% or 10%. The deviation is particularly preferably not more than 5%. Furthermore, it can be advantageous if the deviation is a maximum of 2%. The smaller the deviation between the first and second impedance, the more precisely the differential useful signal is generated at the conductor ends 14, 16.

FIG. 2 shows a schematic block diagram of the first advantageous embodiment of the measuring device 2. As can be seen from the block diagram, the measuring coil 8 is symbolized by two parts, one part being arranged in each partial length between the reference connection 10 and the two conductor ends 14,16.

In order to protect the measuring device 2 even better against electromagnetic interference acting from outside, it is preferably provided that the measuring device 2 has a first shielding 30 . The first shielding 30 can also be referred to as a first shielding device 30 and/or can be designed as such. The first shield 30 preferably includes a first protective element 32 . The first protective element 32 can be designed as a first protective plate 32 or as a first protective grid 32 . The first protective element 32 is formed from an electrically conductive material. In addition, provision is preferably made for the first protective element 32 to be arranged on the outside of the core 6 and the measuring coil 8 . For example, the first protective element 32 can be arranged completely surrounding the core 6 in the circumferential direction U and on the outside of the core 6 and the measuring coil 8 . The first protective element 32 has no immediate and direct contact with the core 6 and/or the measuring coil 8 . Rather, it is preferably provided that there is at least a first minimum distance M between the inside of the first protective element 32 and the point on the measuring coil 8 and/or the core 6 that is the least far away. The first minimum distance M can be at least 2 mm, at least 5 mm or at least 10 mm, for example. The first protective element 32 can form at least part of a Faraday cage for protection against external electromagnetic interference.

The first shield 30 can alternatively or additionally have a second protective element 34 . The second protective element 34 can be designed as a second protective plate 34 or as a second protective grid 34 . The second protective element 34 is formed from an electrically conductive material. In addition, provision is preferably made for the second protective element 34 to be arranged in the interior space 54 . The second protective element 34 can Circumferential direction U of the core 6 be formed completely circumferentially. The second protective element 34 has no immediate and direct contact with the core 6 and/or the measuring coil 8 . Rather, it is preferably provided that there is at least a second minimum distance K between the outside of the second protective element 34 and the point on the measuring coil 8 and/or the core 6 that is the least far away. The second minimum distance K can be at least 2 mm, at least 5 mm or at least 10 mm, for example. The second protective element 34 can form at least part of one or the aforementioned Faraday cage for protection against electromagnetic interference acting from the outside. Preferably, the first protection element 32 and the second protection element 34 are electrically connected to one another. The two protective elements 32, 34 can have direct contact with one another. However, it is also possible for the first protective element 32 and the second protective element 34 to be designed as a common and/or integral protective element. This protective element can thus form both protective elements 32, 34. A second advantageous embodiment of the measuring device 2 is shown schematically in FIG. This configuration of the measuring device 2 differs from the previously explained measuring device 2 only in the configuration of the shielding 30. With regard to all other advantageous properties, features, advantages and/or effects, reference is made to the previous explanations. The advantageous embodiment of the shielding 30 shown in FIG. 6 is formed by a common protective element, with this common protective element forming the first protective element 32 and the second protective element 34 . The common protective element can be designed in one piece. In addition, it is preferably provided that the first protective element 32 does not run all the way around in the circumferential direction U of the core 6 , but has a first recess 70 extending in the circumferential direction U. The second protective element 34 is also not designed to be completely circumferential in the circumferential direction U of the core 6 , but has a second recess 72 extending in the circumferential direction U. In the area of the first and second recess 70, 72, the first and second protective element 32, 34 are electrically and/or mechanically connected to one another. In order to influence the transmission behavior of the useful signal from the measuring device 2 to the differential amplifier 36 positively, in particular such that only the frequency spectrum of the useful signal, but not the frequency spectrum of the interference signal from of the measuring device 2 is transmitted to the differential amplifier 36, it is preferably provided that an electrical capacitance between the core 6 and/or the measuring coil 8 on the one hand and the first shielding 30 on the other hand has a predetermined value. The electrical capacity is therefore preferably predetermined. In order to achieve this, an average protective distance B between the core 6 and/or the measuring coil 8 on the one hand and the at least one protective element 32, 34 of the shielding 30 on the other hand is designed in such a way that the predetermined electrical capacitance is achieved. The electrical capacitance is selected by designing the average protective distance B in such a way that the useful signal is transmitted from the measuring device 2 to the differential amplifier 36, but an interference signal that acts on the measuring device 2 from the outside is preferably strongly damped and thus at most with a reaches the differential amplifier 36 with a very small signal level.

An advantageous embodiment of the core 6 of the measuring device 2 is shown schematically in FIG. It can be seen from FIG. 3 that the core 6 can be formed by four edges 74, specifically two edges 74 running in the horizontal direction and two edges 74 running in the vertical direction. Each edge 74 can also be used as an edge element 74 of the core 6 designated and/or designed. The edges 74 of the core 6 may be in contact with each other such that the core 6 is circumferentially continuous and formed entirely by the edges 74 .

It has also proven to be advantageous if the core 6 has at least one section 18 with a plurality of magnetic, in particular ferromagnetic plates 20 which are arranged opposite one another, in particular parallel, and spaced from plate 20 to plate 20 by a gap 22 . This advantageous configuration of a section of the core is shown schematically in FIG. Preferably, the panels 20 of section 18 are not in intimate and direct contact with each other. Each pair of opposed plates (plate pair) of section 18 is separated by a gap 22 associated therewith. The plates 20 of each plate pair of section 18 spaced apart by a gap 22 are thus non-contact with a plate spacing D of between at least 0.001 mm and a maximum of 2.5 mm, preferably between 0.005 mm and 1 mm. spaced apart from each other. Plate spacing D is preferably the minimum distance between plates 20 of the plate pair. In the case of the plurality of magnetic, in particular ferromagnetic plates 20 of a section 18, a plurality of gaps 22 consequently also arise in section 18. The plurality of plates 20 and the plurality of gaps 22 can effectively saturate the core 6 be prevented. Each section 18 includes at least 5 panels, at least 10 panels, or at least 20 panels. It is preferably provided that each section 18 has at most 500, at most 200 or at most 100 plates.

In an advantageous embodiment, it can be provided that each edge 74 has at least one section 18 with the plurality of magnetic, in particular ferromagnetic, plates 20 . However, it is also possible for a single section 18 to extend over the entire length of the respective edge 74 . In this case, provision can be made for the core 6 to be formed by four such sections 18 which each have a plurality of magnetic, in particular ferromagnetic, plates 20 .

At least part of a further advantageous embodiment of the core 4 is shown schematically in FIG. According to this configuration, the core 4 has a plurality of sections 24 . Each section 24 in turn has a plurality of magnetic, in particular ferromagnetic plates 26, the plates 26 of the respective section 24 being arranged opposite one another, in particular parallel, and in direct contact from plate 26 to plate 26. The plurality of sections 24 of the core 4 are arranged one behind the other and spaced apart from one another by a gap 28 from section 24 to section 24 . Each gap 28 thus separates the panel 26 located at one end of one section 24 from an opposite panel 26 of the subsequent section 24. Within each section 24 there is no gap between the panels 26. Rather, the plates 26 are arranged one behind the other within the respective section 24 without a gap and in immediate and direct contact. Each section 24 can, for example, comprise between 2 and 50 plates, in particular between 5 and 30 plates, preferably between 5 and 15 plates. Saturation of the core 6 can be effectively prevented by the plurality of sections 24 and the corresponding plurality of gaps 22 .

In the last-mentioned configuration, it is possible for each of the edges 74 shown in FIG. 3 to be formed by a plurality of sections 24. These sections 24 are each separated from section 24 to section 24 by a gap 28 .

In the figure 7, the first advantageous embodiment of the current converter 4 is shown schematically. The current converter 4 has the measuring device 2 and the differential amplifier 36 . A first input connection 38 of the differential amplifier 36 is connected to the first conductor end 14 of the current conductor by means of a shielded, first connecting line 40 12 of the measuring device 2 is electrically connected. A second input connection 42 of the differential amplifier 36 is electrically connected to the second conductor end 16 of the current conductor 12 of the measuring device 2 by means of a shielded, second connecting line 44 . The reference connection 10 of the measuring device 2 is coupled to a predetermined electrical reference potential. The reference potential is preferably the ground potential 46.

A differential useful signal generated by the measuring device 2 at the conductor ends 14 , 16 is generated by a primary current of a primary current conductor (not shown), which is routed through the interior 54 of the measuring device 2 . The differential useful signal is transmitted to the two input terminals 38, 42 of the differential amplifier 36 by means of the two connecting lines 40, 44. The differential amplifier 36 is designed to generate an output signal at the output terminal 60 of the differential amplifier 36 based on a voltage difference at the two input terminals 38, 42. The output signal is thus dependent on the primary current via the useful signal. Preferably, the output signal represents the primary current.

In order to prevent the influence of external, electromagnetic interference signals on the measuring device 2, a number of measures have already been explained above. These apply in an analogous manner to the measuring device 2 of the current transformer 4. It should also be mentioned that the two connecting lines 40, 44 are shielded in order to be protected from external, electromagnetic interference signals. As shown purely by way of example in FIG. 7, the connecting lines 40, 44 can be shielded by a common line shield 76. The common line shielding 76 is arranged at a distance from the two connecting lines 40, 44 in an electrically insulated manner. The common line shield 76 may be formed from a coiled and/or braided metal tape.

In addition, it is preferably provided that the differential amplifier 36 has an associated shielding 52 . This tuning 52 is referred to as the second shield 52 . The second shield 52 can be formed by a grid housing, for example. The second shielding 52 is preferably arranged and/or designed in such a way as to protect the differential amplifier 36 from external, electromagnetic interference signals.

As is shown purely by way of example in FIG. 7, provision can be made for the second shielding 52 and the common line shielding 76 to be electrically connected to one another are connected. Provision can also be made for a further electrical connection to be routed from ground potential 46 to second shielding 52 and/or common line shielding 76 , so that second shielding 52 and/or common line shielding 76 is or is coupled to ground potential 46 .

A further advantageous embodiment of the current converter 4 is shown schematically in FIG. The current converter 4 essentially corresponds to the current converter 4 explained above. Reference is therefore made to the corresponding explanations in an analogous manner. However, the current transformer 4 shown in FIG. 8 differs in that the common line shielding 76 is also electrically connected to the first shielding 30 of the measuring device 2 . In particular, it is provided that there is an electrical connection between the common line shielding 76 and the first protective element 32 of the first shielding 32 .

A further advantageous embodiment of the current converter 4 is shown in FIG. The current converter 4 essentially corresponds to the current converter 4 explained above. Reference is therefore made to the corresponding previous explanations for this current converter 4 in an analogous manner. However, the current transformer 4 shown in FIG. 9 differs in that the current transformer 4 has the measuring device 2 shown in FIG. 6 and not the measuring device 2 from FIG. In addition, the current transformer 4 shown in FIG. 9 differs in that each of the two connecting lines 40, 44 has a separate, associated line shield 48, 50. The two line shields 48, 50 are preferably separately coupled to ground potential 46, as shown in FIG. In addition, it is preferably provided that the reference connection 10 is separated from the line shields 48, 50 in such a way that no direct electrical connection that does not run via the ground potential 46 is formed from the reference connection 10 to at least one of the line shields 48, 50. Each of the two line connections 40, 44 can be designed in the manner of a coaxial cable with the associated shielding 48, 50 on the jacket side, which forms the respective line shielding 48, 50. Each of the two shields 48, 50 can be formed by a wound and/or braided metal band.

Furthermore, it is preferably provided that the second shielding 52 of the differential amplifier 36 is coupled separately to ground potential 46, the second shielding 52 being separated from the two line shields 48, 50 in such a way that no direct electrical connection other than ground potential 46 is formed from the second shield 52 to at least one of the line shields in 48,50.

A third advantageous embodiment of the measuring device 2 is shown schematically in FIG. This configuration of the measuring device 2 differs from the first, advantageous configuration (Fig. 1) of the measuring device 2 in the multi-part configuration of the core 6, the multi-part configuration of the measuring coil 8 and the multi-part configuration of the first shield 30. With regard to all other advantageous ones Properties, features, advantages and/or effects are referred to the explanations for the first advantageous embodiment of the measuring device 2 .

As can be seen from FIG. 10, the core 6 is formed from two parts. The first part 78 of the core 6 is preferably designed as a part 78 of the core 6 which is C-shaped in cross section. The second part 80 of the core 6 is preferably designed as a part 80 of the core 6 with an I-shaped cross section. The I-shaped part 80 of the core 6 can be placed on the leg-shaped ends of the C-shaped part 78 of the core so that the respective leg ends of the C-shaped part 78 of the core 6 are connected by the I-shaped part 80 of the core 6 . A direct, mechanical and/or electrical contact can thereby occur between the I-shaped part 80 and the C-shaped part 78 of the core 6 . In addition, the I-shaped part 80 can be arranged relative to the C-shaped part 78 in such a way that the core 6 has a rectangular cross-section that runs all the way around.

The multi-part, in particular two-part design of the core 6 offers the advantage that the core 6 can be arranged particularly easily around a primary power line, so that the core 6 surrounds the primary power line in the form of a ring. In other words, in this case the primary current line will pass through the interior space 54 formed by the core 6 .

FIG. 10 also shows the advantageous embodiment of the measuring coil 8 as a multi-part measuring coil 8 . The measuring coil 8 is basically formed by the current conductor 12 wound around the core. The current conductor 12 extends from the first conductor end 14 to the second conductor end 16. In the embodiment shown in FIG. The interruptions to the two However, connection points 82, 84 are only selected for better representation in FIG. 10 and/or can be used for assembly.

In practical use of the measuring device 2, the current conductor 12 extends uninterruptedly from the first conductor end 14 to the second conductor end 16. With a first winding section 86 of the measuring coil 8, the current conductor 12 extends from the first conductor end 14 to a first connection end 92. With a second Winding section 88 of the measuring coil 8, the current conductor 12 extends from a second connection end 94 to a third connection end 96. With a third winding section 90 of the measuring coil 8, the current conductor 12 extends from a fourth connection end 98 to the second conductor end 16.

At the first connection point 82 , the continuous connection of the electrical conductor 12 can be achieved by connecting the first connection end 92 to the second connection end 94 . This can be an integral connection or a detachable connection. The same applies to the second connection point 84. The uninterrupted connection of the current conductor 12 can be achieved at the second connection point 84 by the third connection end 96 being connected to the fourth connection end 98. This can be an integral connection or a detachable connection.

It can also be seen from FIG. 10 that the first shield 30 is designed as a multi-part shield. The shield 30 may include and/or be formed from a first protective element 32 and a second protective element 34 . The first protective element 32 can enclose the C-shaped part 78 of the core 6 and the first and second winding section 86, 88 of the measuring coil 8 in the form of a hose. The result of this is that the first protective element 32 can also be designed with a C-shaped cross section. The second protective element 34 can completely surround the I-shaped part 80 of the core 6 . Thus, the second protective element 34 can also have an I-shaped cross section.

The reference connection 10 is preferably electrically conductively connected to the current conductor 12 in the middle between the second connection end 94 and the third connection end 96 . If the I-shaped part 80 of the core 6 is placed on the C-shaped part 78 of the core 6 and the aforementioned pairs of connection ends 92, 94 or 96, 98 are also connected to one another, the result is that the reference connection 10 is centered between the first Conductor end 14 and the second conductor end 16 is electrically conductively connected to the current conductor 12 .

A fourth advantageous embodiment of the measuring device 2 is shown schematically in FIG. This fourth embodiment of the measuring device 2 differs from the third advantageous embodiment of the measuring device 2, as shown in Figure 10, in that the I-shaped part 80 of the core 6 has no winding section, in particular not the second winding section 88. With regard to all other advantageous properties, features, advantages and/or effects, reference is made to the explanations relating to the first and third advantageous embodiment of the measuring device 2 . As can be seen from FIG. 11, the first connection end 92 in the third advantageous embodiment of the measuring device 2 is not used for the detachable connection to a further connection end, but rather the first connection end 92 is electrically conductively connected to the first protective element 32 . The same applies to the fourth connection end 98, which is also electrically conductively connected to the first protective element 32. The first protective element 32 is designed to be electrically conductive. An electrically conductive connection between the first connection end 92 and the fourth connection end 98 is therefore produced by the first protective element 32 . This connection formed by the first protective element 32 between the two connection ends 92, 98 thus simultaneously forms part of the current conductor 12, which extends from the first conductor end 14 to the second conductor end 16. It has therefore turned out to be advantageous if the reference connection 10 is electrically conductively connected to the first protective element 32 in the middle between the first connection end 92 and the fourth connection end 98 . This ensures that the reference connection 10 is electrically conductively connected centrally between the first conductor end 14 and the second conductor end 16 to the current conductor 12 , in particular formed here in sections by the dual function of the first protective element 32 .

A fifth advantageous embodiment of the measuring device 2 is shown schematically in FIG. This fifth embodiment of the measuring device 2 differs from the third and fourth advantageous embodiment of the measuring device 2, as shown in FIGS /or Effects, reference is made to the explanations relating to the first, third and fourth advantageous embodiment of the measuring device 2 . In the fifth advantageous embodiment of the measuring device 2 , the measuring coil 8 is formed by the uninterrupted current conductor 12 wound around the core 6 and extending uninterruptedly from the first conductor end 14 to the second conductor end 16 . No detachable connection points are provided in the current conductor 12 . As a result, the production of the measuring coil 8 is particularly simple and at the same time imprecise. The measuring coil 8 is arranged exclusively on the C-shaped part 78 of the core 6 . The reference connection 10 is electrically conductively connected to the current conductor 12 in the center between the first conductor end 14 and the second conductor end 16 . The reference termination 10 is preferably also electrically connected to the first protection element 32 . In addition, it has proven to be advantageous if the first reference connection 10 is coupled to the ground potential 46 .

A further advantageous embodiment of the first shielding 30 for the measuring device 2 is shown schematically in FIG. The first shielding 30 is designed as an annular shielding 30 running around in the circumferential direction U of the core 6 and enclosing the core 6 and the measuring coil 8 at least essentially in the form of a tube. This configuration of the first shield 30 is also referred to as an annular shield 30 . The ring-shaped shield 30 is formed by two shell-shaped protective elements 32, 34, each running around in the circumferential direction U of the core. These two shell-shaped protective elements 32, 34 form the first and second protective elements 32, 34 of the first shield 30.

The first shield 30 from FIG. 13 is shown in a sectional illustration in FIG. As can be seen from the synopsis of FIGS. 13, 14, the first protective element 32 and the second protective element 34 are mirror-symmetrical and/or shell-shaped, in particular annular shell-shaped. Each of the two protective elements 32, 34 runs in the circumferential direction U of the core 6 in a rectangular shape. The outer contour 100 of the annular shield 30 and the outer contour 100 of each of the two shell-shaped protective elements 32, 34 are each rectangular, at least in cross section. The inner contour 102 formed by the ring-shaped shield 30 is also rectangular, at least in cross section. Each of the two shell-shaped protective elements 32, 34 forms part of the inner contour 102, so that the inner contour formed by each of the two protective elements 32, 34 is also rectangular, at least in cross section. The embodiment of the first shielding 30 shown in FIGS. 13 and 14 offers the advantage that the two shell-shaped protective elements 32, 34 can be pushed over the core 6 and the measuring coil 8 from the front or rear. so that a closed protective space 104 is formed by the first shielding 30, in which both the core 6 and the measuring coil 8 are arranged (not shown). This ensures effective protection against electromagnetic interference.

Additionally, it should be noted that "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. Furthermore, it should be pointed out that features that have been described with reference to one of the above exemplary embodiments can also be used in combination with other features of other exemplary embodiments described above. Any reference signs in the claims should not be construed as limiting.

REFERENCE LIST

B Safety distance

D plate spacing

K second minimum distance

M minimum distance

R radial direction

U circumferential direction

2 measuring device

4 current transformers

6 core

8 measuring coil

10 reference port

12 conductors

14 first conductor end i6 second conductor end i8 section

20 plate

22 column

24 section

26 plate

28 column

30 first shield

32 first protection element

34 second protection element

36 differential amplifiers

38 first input port

40 first connection line

42 second input port

44 second connection line

46 ground potential

48 first line shield

50 second line shield

52 second shield 54 interior space 56 first partial length 58 second partial length 60 output connection 62 winding section

64 first winding section 66 second winding section 68 common protective element 70 first recess 72 second recess

74 edge

76 common line shield

78 first part of the nucleus

80 second part of core 82 first joint

84 second connection point 86 first winding section 88 second winding section 90 third winding section 92 first connection end

94 second connection end 96 third connection end 98 fourth connection end 100 outer contour 102 inner contour

104 shelter

Claims

PATENT CLAIMS

1. Measuring device (2) for a current transformer (4), comprising: a rotating core (6), a measuring coil (8), and a reference connection (10), the measuring coil (8) being wound by a coil around the core (6). Current conductor (12) is formed, which extends from a first conductor end (14) to a second conductor end (16), and wherein the reference connection (10) is electrically conductive centrally between the first conductor end (14) and the second conductor end (16). is connected to the conductor (12).

2. Measuring device (2) according to the preceding claim, characterized in that the reference connection (10) is electrically connected to the current conductor (12) such that a first impedance of the current conductor (12) between the reference connection (10) and the first Conductor end (14) and a second impedance of the current conductor (12) between the reference connection (10) and the second conductor end (16) are the same or have a maximum deviation of 5%.

3. Measuring device (2) according to one of the preceding claims, characterized in that the reference connection (10) is connected to a predetermined electrical reference potential.

4. Measuring device (2) according to one of the preceding claims, characterized in that the measuring coil (8) is arranged distributed symmetrically to a radial plane of the core (6).

5. Measuring device (2) according to any one of the preceding claims, characterized in that the core (6) is magnetic, in particular ferromagnetic

Material has or is formed from.

6. Measuring device (2) according to one of the preceding claims, characterized in that the core (6) is designed in several parts.

7. Measuring device (2) according to one of the preceding claims, characterized in that the measuring coil (8) is designed in several parts.

8. Measuring device (2) according to one of the preceding claims 1 to 6, characterized in that the core (6) has at least one section (18) with a plurality of magnetic, in particular ferromagnetic plates (20) which are opposite, in particular parallel, are arranged relative to one another and spaced apart from plate (20) to plate (20) by a gap (22).

9. Measuring device (2) according to any one of the preceding claims 1 to 6, characterized in that the core (6) has a plurality of sections (24) each having a plurality of magnetic, in particular ferromagnetic plates (26), wherein the

Plates (26) of the respective section (24) are arranged opposite, in particular parallel, to each other and in direct contact from plate (26) to plate (26), and wherein the sections (24) of the core (6) are arranged one behind the other and from section (24) are spaced from section (24) by a gap (28).

10. Measuring device (2) according to one of the preceding claims 8 to 9, characterized in that each gap (22, 28) is designed as an air gap or in each gap (22, 28) a spacer is introduced.

11. Measuring device (2) according to the preceding claim, characterized in that each spacer is formed of a non-magnetic material.

12. Measuring device (2) according to one of the preceding claims 8 to 11, characterized in that the plates (20, 26) of each of a gap (22, 28) spaced plate pair contact-free with a plate distance D between at least 0.001 mm and a maximum of 2, 5 mm are arranged spaced apart.

13. Measuring device (2) according to one of the preceding claims, characterized in that the measuring device (2) has a first shield (30) having a first protective element (32) and preferably a second protective element (34).

14. Measuring device (2) according to the preceding claim, characterized in that the first protective element (32) as an electrically conductive, outside to the Core (6) and the measuring coil (8) arranged and in the circumferential direction U of the core (6) at least substantially completely circumferential protective element (32) is formed.

15. Measuring device (2) according to the preceding claim, characterized in that the second protective element (34) is an electrically conductive element arranged on the inside of the core (6) and the measuring coil (8) and in the circumferential direction U of the core (6) at least substantially completely circumferential protective element (34) is formed.

16. Measuring device (2) according to the preceding claim, characterized in that the first shielding (30) is designed as an annular shielding that runs around in the circumferential direction U of the core (6) and surrounds the core (6) and the measuring coil (8). at least essentially tubular, with the ring-shaped shield (30) being formed by two shell-shaped protective elements which each run around in the circumferential direction U of the core (6) and form the first and second protective element (32, 34).

17. Measuring device according to the preceding claim, characterized in that an outer contour (100) of the annular shield (30) and/or each cup-shaped protective element is rectangular, and/or wherein a through the annular shield (30) and/or each cup-shaped Protective element formed inner contour (102) is rectangular.

18. Measuring device (2) according to one of the preceding claims 13 to 17, characterized in that the first protective element (32) and the second protective element (34) are electrically connected to one another or are integrally formed as a common protective element.

19. Measuring device (2) according to one of the preceding claims 13 to 18, characterized in that a protective distance B between the core (6) and/or the measuring coil (8) on the one hand and the at least one protective element (32, 34) of the first Shielding (30) is predetermined in such a way that a predetermined electrical capacitance is formed between, on the one hand, the core (6) and/or the measuring coil (8) and, on the other hand, the first shielding (30).

20. Measuring device (2) according to one of the preceding claims 1 to 19, characterized in that the measuring device (2) can also be actuated as a feed device, such that a current is guided into an interior space (54) formed by the core (6). primary conductor is fed.

21. Current transformer (4), comprising: a measuring device (2) according to one of the preceding claims, and a differential amplifier (36), wherein a first input connection (38) of the differential amplifier (36) is connected to the first conductor end (14) of the current conductor (12) of the measuring device (2), a second input connection (42) of the differential amplifier (36) being connected to the second conductor end (16) of the current conductor ( 12) is electrically connected to the measuring device (2), and wherein the reference connection (10) is coupled to a predetermined electrical reference potential.

22. Current transformer (4) according to the preceding claim, characterized in that the reference connection (10) is coupled to ground potential (46).

23. Current transformer (4) according to one of the preceding claims 21 to 22, characterized in that each of the two connecting lines (40, 44) has an associated line shield (48, 50), which are each coupled to ground potential (46), the Reference connection (10) is separated from the line shields (48, 50) in such a way that no direct electrical connection that does not run via the ground potential (46) is formed from the reference connection (10) to at least one of the line shields (48, 50). is.

24. Current converter (4) according to any one of the preceding claims 21 to 23, characterized in that the differential amplifier (36) has a second shield (52) which is coupled to ground potential (46), the second shield (52) being such from the line shields (48, 50) is separated, so that no direct electrical connection that does not run over the ground potential (46), from the second Shield (52) to at least one of the line shields (48, 50) is formed.