Current rail for measuring direct and / or alternating current

Description

TECHNISCHES GEBIET DER ERFINDUNG

[0001] The application relates to a busbar for measuring the current of a direct and / or alternating current, in particular with current strengths greater than 100 amperes, a device for determining current and an electrical power transformer with a device for determining current. STAND DER TECHNIK

[0002] A busbar is a device made of electrically conductive material for conducting electrical currents between connection areas of the busbar.

[0003] For the precise measurement of electrical currents, especially high currents in the range of several hundred amperes up to several kiloamperes, low-resistance measuring resistors, so-called shunts, can be used. With shunts, measuring points are typically connected directly next to a resistive material on both sides of the connection area. The resistive material of the shunt differs from the rest of the shunt material, particularly by a (slightly) higher specific resistance and is characterized, for example, by a constant resistance value even over large temperature ranges.

[0004] For example, DE 10 2016 010 012 B4 discloses a measuring arrangement for measuring a current in which pairs of voltage taps as measuring contacts measure a voltage drop across a resistive material, wherein a measuring circuit determines a measure of the electric current flowing through the resistive material from the voltage drop and the resistance value of the resistive material based on Ohm's law.

[0005] German patent DE 10 2013 005 939 A1 describes the problem of phase errors in high-current shunts. The solution described therein for avoiding phase errors involves multiple voltage measurements at different positions on the shunt and weighted averaging using dynamic weighting factors.

[0006] In DE 10 2020 111 634 B3 a shunt with dedicated resistive material and pairs of taps is described, wherein a tap (on one side) is surrounded by a notch that prevents current flow across the notch.

[0007] From DE 2 939 594 A1 a measuring resistor is known which consists of a part made of resistance material, e.g. manganin or isotane, and has two terminals for tapping off a voltage drop over part of the resistance path of the measuring resistor, wherein the ends of the measuring resistor are flattened and widened and function as high current terminals.

[0008] In GB 2 259 783 B, a shunt is disclosed which consists of a copper alloy (manganine) and has two end regions with a larger cross-section and a central region with a smaller cross-section, wherein two measuring taps are arranged in the central region and are connected to a printed circuit board via a twisted-pair cable.

[0009] From EP 3 671 225 A1, a resistor is known which has outer terminal areas made of copper and a strip arranged centrally between them made of a material with approximately 10 times higher specific resistance, e.g. a copper-nickel-manganese alloy, wherein measuring contacts and slots are arranged on both sides of the strip in such a way that the current density at the location of the measuring contacts is reduced in order to reduce the deviation of a measuring voltage dropping across the measuring contacts at different temperatures.

[0010] A press-fit pin, pressed into a press-fit hole in the shunt, can be used as a voltage tap. Such a press-fit pin, located within a current-carrying section of the shunt, acts as a voltage divider between the different potentials on opposite sides of the press-fit hole. If, for example, the contact resistances on the opposite sides of the press-fit connection change due to mechanical stress, this results in a change in the voltage divider. This, in turn, changes the effective position of the press-fit pin and thus the effective distance between two measuring contacts, also called measuring points, across which the voltage drop is measured during shunt current measurement. A typical diameter for press-fit holes in metallic workpieces is, for example, 1 mm. With a tap length, i.e., a nominal distance between two measuring contacts of, for example,With a 20 mm effective distance between the effective positions of the voltage taps on the respective outer sides of the press-fit holes, the distance can be between 19 mm and 21 mm, i.e., different measured values ​​of up to 10% can occur under otherwise identical electrical boundary conditions.

[0011] In shunt current measurements, shunts with resistances in the microohm range are used to keep power loss within an acceptable range. To achieve such low resistances, high-conductivity resistance alloys with large cross-sections must be employed. At a nominal current in the range of several hundred amperes, this can result in measurable voltage drops in the range of a few millivolts.

[0012] In AC current measurement using large shunt resistors, significant phase errors can occur due to skin effects and induction. These phase errors are primarily caused by induced voltages within the measuring leads (depending on their routing) and by the skin effect, which, with alternating current, leads to a position-dependent phase shift in the current density within the shunt. The skin effect causes not only a frequency- and position-dependent amplitude but also a frequency- and position-dependent phase, the latter often being much more noticeable in practice. Induced voltages are generated in the measuring leads between the shunt and the evaluation unit when the measuring leads and shunt span an area penetrated by the time-varying magnetic field of the load current.This effect occurs in high-current shunts to a clearly measurable degree because, compared to typical shunt current measurements in the low ampere range, the magnetic fields increase linearly with the current, and their influence increases linearly with a decrease in the measurement voltage. The combination of these two effects means that inductive influences also have a measurable impact at low frequencies in the range of the mains frequency and its single-digit harmonics, which is primarily reflected in a frequency-dependent phase error. For example, manganin shunts with soldered-on measuring circuit boards can be used for AC current measurement at the output of an inverter bridge. These shunts exhibit a phase error of approximately 3 degrees at the mains frequency and a phase error of approximately 12 degrees in the range of an actively controlled harmonic, e.g., at 250 Hz.However, when using fast-switching power semiconductors, phase-correct measurement of the alternating currents is necessary to control harmonics at high frequencies. Furthermore, when using shunts made of resistive materials with a significant temperature coefficient of resistivity, the frequency-dependent phase error is also temperature-dependent, making digital frequency response compensation complex. AUFGABE DER ERFINDUNG

[0013] The invention is based on the objective of providing a busbar for current measurement that enables the best possible measurement with the simplest and / or most cost-effective design possible. LÖSUNG

[0014] The problem is solved by a device for current measurement with a busbar having the features of claim 1. Preferred embodiments are claimed in the dependent claims. BESCHREIBUNG

[0015] A busbar for measuring direct and / or alternating current, particularly with currents greater than one hundred amperes, has connection sections and at least one resistor section arranged between the connection sections. Two measuring contacts are arranged in the resistor section. The busbar is formed in one piece and has a geometry such that the areas of the measuring contacts are essentially currentless during operation of the busbar.

[0016] The busbar has two connection areas and a resistor area between them with a substantially flat surface. This resistor area thus provides both an electrical and a mechanical connection between the connection areas.

[0017] In such a single-piece busbar for current measurement, made of copper or aluminum, the geometry of the busbar, and in particular the geometry of the resistance zone, is selected such that the areas of the measuring contacts are currentless, while the majority of the resistance zone carries the operating current. During operation, for example in a power converter, this current can reach several hundred amperes or even several kiloamperes. This operating current flowing through the busbar can be determined by measuring the voltage or the voltage difference between the two measuring contacts using the resistance value of the resistance zone between the two measuring contacts. The largely currentless areas of the measuring contacts enable a more precise measurement, especially by making the measurement more tolerant of any displacements in the specific position of a measuring contact.Furthermore, a high homogeneity of current density can be achieved in the current-carrying area of ​​the resistance region.

[0018] The one-piece design of the busbar allows for a simpler and more cost-effective construction, simplifying, for example, the manufacturing of busbars with integrated resistor sections and current-free measuring contact areas. Furthermore, problems at the transitions between different materials could be avoided.

[0019] The busbar used for current measurement features a so-called current shadow geometry. This is based on the idea of ​​not placing the measuring points in the live area of ​​the busbar, but rather in a section of the busbar specifically designed and configured to be either not carried, or only very weakly carried, by the current being measured. Various geometries are conceivable for this purpose.

[0020] In the invention, the resistance zone is essentially formed by a reduction in cross-section compared to the cross-section of the busbar's connection areas, with the measuring contacts located within this reduction. This reduction is achieved, in particular, by decreasing the width of the resistance zone to a value between 10 and 60 percent of the width of the busbar's connection areas. This allows for a higher current density in the resistance zone than in the busbar's connection areas, which in turn results in a higher voltage drop for a given current flowing through the busbar. Any associated higher losses in the resistance zone are accepted in favor of increasing the voltage drop to a readily measurable level.

[0021] Such a locally increased current density can be accompanied by an increased temperature in the resistance range. Optionally, however, this effect can be neutralized by temperature compensation based on a temperature measurement representative of the resistance range, and overcompensated by limiting the measurement to a locally confined and well-defined range.

[0022] In a single-piece busbar for current measurement with a cross-sectional reduction as a resistance zone, the measuring contacts are located within the resistance zone. The resistance value of this zone is temperature-dependent. Therefore, a temperature sensor attached to the resistance element offers the advantage that the measured temperature can be used to determine a calibrated resistance value for the resistance zone. This value is then combined with the measured voltage drop between the measuring contacts to determine the current.

[0023] Especially when the resistive element is made of a common material with very good conductivity, such as copper, whose specific resistance is strongly temperature-dependent, it is advantageous to measure the temperature of the resistive material precisely where the relevant voltage drop occurs. This advantage is achieved by placing the temperature sensor between the measuring contacts.

[0024] In one embodiment, the busbar has a longitudinal center axis that runs lengthwise from one of the connection areas to the opposite connection area through the resistance zone, wherein the measuring contacts are arranged in the region of the longitudinal center axis and wherein the busbar is substantially symmetrical to the longitudinal center axis, at least between the respective connection areas. The busbar for current measurement thus has a current shadow geometry with measuring taps located centrally on a longitudinal center axis that lies along the direction of current flow. These taps exhibit high robustness against mechanical influences and external magnetic fields and can therefore deliver highly reproducible results.In one embodiment, the busbar is designed to be essentially symmetrical to a transverse central axis, at least between the respective connection areas, wherein the transverse central axis runs centrally between the connection areas in the transverse direction of the busbar, and wherein the measuring contacts are arranged essentially symmetrically to the transverse central axis.

[0025] In the invention, the geometry of the busbar in the resistive region has at least two recesses, which are arranged in the region of the measuring contacts and spaced longitudinally apart from the measuring contacts, with one recess being arranged in the region of each measuring contact. The recesses are arranged such that the region of the measuring contacts is largely current-free, by positioning the recesses, viewed in the direction of current flow, particularly in front of or behind the measuring contacts. The resistive region outside the areas of the measuring contacts can be referred to as the current-carrying or current-through region.

[0026] In the invention, at least one temperature sensor is arranged between the measuring contacts, particularly in the region of the longitudinal central axis and / or the transverse central axis. A single temperature sensor can preferably be arranged on both the longitudinal central axis and the transverse central axis. Alternatively, for example, two temperature sensors can be arranged on the transverse central axis and substantially symmetrically around the longitudinal central axis. The measuring contacts can be arranged substantially symmetrically with respect to the transverse central axis or around the temperature sensor(s).

[0027] In one embodiment of the busbar, at least one recess is arranged between the measuring contacts, wherein the recess is arranged between the measuring contacts and is in particular substantially symmetrical and has the longitudinal central axis and / or the transverse central axis as the axis of symmetry.

[0028] In one embodiment of the busbar, the longitudinal center axis forms an axis of symmetry for one or more recesses. Alternatively or additionally, at least two recesses can be arranged essentially symmetrically to the transverse center axis.

[0029] In one embodiment of the busbar, a recess is arranged on two sides of each measuring contact in the direction of current flow, wherein the recesses are formed substantially symmetrically to the respective measuring contact along the longitudinal central axis and / or along the transverse central axis. The recesses can, in particular, be substantially point-symmetrical to the measuring contact and / or substantially axis-symmetrical to an axis running through the measuring contact. Specifically, the recesses can be substantially axis-symmetrical to the longitudinal central axis running through the respective measuring contact.

[0030] In one embodiment of the busbar, each measuring contact area has a measuring point plateau and connecting webs, with the measuring contacts arranged on the respective measuring point plateau. The respective measuring point plateaus are connected to the current-carrying area of ​​the resistor via the connecting webs, which preferably extend transversely to the longitudinal center axis. The connecting webs are delimited, in particular, by the recesses. Via the connecting webs, the measuring point plateau is at a potential that corresponds to the potential at the interfaces of the connecting webs with the current-carrying area of ​​the resistor, so that the voltage difference between the measuring contacts essentially corresponds to the voltage difference between these interfaces.At the same time, the geometry, with its measuring point plateau and connecting bridges, is designed such that the operating current, which flows parallel to the longitudinal center axis through the current-carrying areas, does not flow via the connecting bridges and the measuring point plateau, which are oriented parallel to the transverse center axis. The measuring point plateau and the connecting bridges—and thus the area of ​​the measuring contacts—are therefore largely current-free.

[0031] In one embodiment of the busbar, the connecting webs have a width of between two and five millimeters, and the measuring point platforms have a longitudinal extent of between five and twelve millimeters. The width of the connecting webs refers to their extent perpendicular to the direction in which they connect their respective measuring point platform to the current-carrying area of ​​the resistor. Preferably, the connecting webs run parallel to the transverse central axis and, in particular, symmetrically on opposite sides of the respective measuring point platform, connecting the measuring point platform to the current-carrying area of ​​the busbar. The longitudinal extent of the measuring point platforms refers to their extent in the direction of the connecting webs and / or in a direction perpendicular to the direction of the connecting webs.In one embodiment of the busbar, recesses are arranged on both sides of the measuring point plates and the connecting webs, which are preferably cut through centrally by the longitudinal central axis and which have a width of between two and ten mm in the direction of the longitudinal central axis.

[0032] In one embodiment of the busbar, the material thickness of the resistive section and / or the connection sections is between two and six millimeters. This material thickness corresponds to the thickness of the busbar in the resistive section and in the connection sections. The cross-section of the resistive section can be considered as an area whose sides are equal to the width of the resistive section and the thickness of the busbar.

[0033] The busbar can be designed to carry currents exceeding 100 amperes, preferably exceeding 1000 amperes. The busbar is a single piece made of copper or aluminum, with the resistive section essentially formed by a reduction in cross-section compared to the cross-section of the busbar's connection sections. This avoids material transitions and reduces manufacturing and assembly costs. Significant cost savings can be achieved, particularly when using copper busbars, as shunts with a resistive section made of special resistive material, such as manganin, can be considerably more expensive. Alternatively or additionally, the recesses can be stamped. This further reduces manufacturing and assembly costs.

[0034] In one embodiment of the busbar, the measuring contacts are designed as press-fit pins, which are pressed into press-fit holes in the busbar. This minimizes measurement deviations caused by, for example, installation tolerances or aging. Furthermore, assembly can be implemented more cost-effectively. The measuring contacts can also be designed as spring contacts, soldered connections, or screw connections to the busbar. This simplifies the technical process of connecting measuring contacts to the busbar, which is designed for high currents. In particular, inaccuracies in the positioning of the measuring contacts, which can lead to measurement errors, can be avoided.

[0035] Mechanical stresses can affect the contact resistance between a press-fit pin and the busbar. It is therefore advantageous to position the press-fit contacts in a largely current-free area of ​​the busbar, minimizing the voltage drop along the press-fit pin and, in particular, along the finite width of the press-fit bore. This minimizes the potential difference or voltage drop between opposite sides of a press-fit bore in the busbar to such an extent that it becomes irrelevant for measurement purposes, regardless of whether the press-fit contact interacts with one side or the other depending on the mechanical load. This also significantly improves the long-term stability of the measurement. Measurement deviations can be minimized, even if the measuring contact shifts slightly mechanically or its electrical properties change.

[0036] The current measurement device in the invention comprises a busbar and a printed circuit board (PCB) arranged parallel to the busbar for acquiring measured values. The PCB rests parallel to the busbar. The measurement acquisition includes measuring the voltage difference between two measuring contacts of a resistance range and, optionally, measuring the temperature via the temperature sensor of the corresponding resistance range. The measuring contacts can be connected via measuring leads to a common tap point, at which, for example, a voltage sensor is arranged to measure the voltage between the endpoints of the measuring leads at the common tap point. The measuring leads can run in a plane of the PCB, which is arranged as the outermost inner layer of the PCB on the side of the PCB facing the resistance range, and / or wholly or partially in other planes.Layers of the circuit board run.

[0037] This makes it possible to position the connections between the measuring contacts and the evaluation unit very close to the resistance area, particularly to avoid conductor loops. Conductor loops can lead to significant impairments or distortions of the measurement, especially near high currents, due to electromagnetic effects, particularly if the currents contain periodic or transient components.

[0038] The circuit board can include the temperature sensor and be positioned in the resistive area on the surface of the busbar in such a way that the temperature sensor is in thermal contact with the resistive area of ​​the busbar. The measuring contacts, which electrically contact the surface of the busbar, are located, for example, on both sides of the temperature sensor and connected to the measuring leads in order to detect a voltage difference along the resistive area using a suitable voltmeter on the circuit board.

[0039] In one embodiment of the device, the circuit board lies flat on the busbar, so that the measuring contacts establish electrical contact between the surface of the busbar and the measuring leads in the circuit board via the shortest possible path, and the temperature sensor rests on the surface of the shunt. This allows for highly accurate current measurement.

[0040] In one embodiment of the device, measured values ​​are acquired via measuring leads, which are laid out as conductor tracks within the printed circuit board in such a way as to reduce frequency-dependent phase and amplitude measurement errors. The measuring leads for connecting the measuring contacts to an evaluation unit, in particular a voltmeter, can be laid out as conductor tracks within a printed circuit board along a path relative to the surface of the busbar in such a way that the phase and amplitude errors are significantly reduced compared to a conventional routing of the measuring leads, for example, compared to a direct straight connection between the measuring points and the common tap point. The routing of the measuring leads as conductor tracks can be carried out, for example, based on theoretical considerations and / or with the aid of a numerical simulation.

[0041] In one embodiment of the device, the measuring leads extend from the measuring contacts and are joined at a common tap point. For this purpose, the measuring leads, starting from at least one of the measuring contacts, which is arranged on or near the longitudinal center axis of the busbar, are routed away from the measuring contact in two directions. They first run outwards to the edge of the resistance range and then back to the other measuring contact, which is also arranged on or near the longitudinal center axis of the busbar. The measuring leads can reach their respective reversal points before the edge, reach the edge, or even extend beyond it. The path of the measuring leads towards the edge and back can be at least partially substantially symmetrical to the longitudinal center axis and / or the transverse center axis of the resistance range.

[0042] A key feature of the routing can be, for example, a path that initially runs straight across the direction of current flow along the connecting bridges into the resistance area and then diagonally to the longitudinal and transverse central axis outwards to the edge area of ​​the resistance area and diagonally back inwards to the other measuring contact, whereby this path is essentially symmetrical to the longitudinal central axis and / or to the transverse central axis.

[0043] In one embodiment of the device, the measuring leads span a substantially closed measuring lead area, which in one dimension comprises between 70 and 100 percent of the width of the resistance area and in the dimension perpendicular thereto between 70 and 100 percent of the distance between the measuring contacts, wherein the measuring leads preferably run along the connecting webs and outside of any overlap area with the recesses. The measuring leads thus preferably do not run over the recesses.

[0044] In one embodiment of the device, the measuring lines spanning the measuring line area can consist of several conductor tracks running parallel to each other, wherein the individual conductor tracks can be arranged in the same or different planes of the circuit board.

[0045] The measuring leads can, in particular, span a polygon, e.g., a hexagon, whereby the polygon may have axes of symmetry running along the transverse central axis and / or the longitudinal central axis. The width of the polygon can be approximately 70–100% of the width of the resistance area.

[0046] The special routing of the measuring leads enables a significant reduction in frequency- and temperature-dependent phase and amplitude errors in AC current measurement with busbars for current measurement in the microohm range. Furthermore, a very large measuring range between milliamperes and kiloamperes is achieved, which can exhibit a largely linear frequency response in the region of the mains frequency and beyond, in the region of the control-relevant harmonics of the mains frequency.

[0047] In conventional AC current measurement using busbars for large current measurements, significant phase errors can occur due to skin effects and induction. The phase errors that can occur during current measurement are largely avoided by the routing of the measuring leads described above. The skin effect causes not only a frequency- and position-dependent amplitude but also a frequency- and position-dependent phase, the latter of which is often much more noticeable in practice. Induced voltages are generated in the measuring leads between the busbar and the evaluation unit when the measuring leads and the busbar form an area penetrated by the time-varying magnetic field of the current being measured. The arrangement described above avoids forming such an area with the busbar.Instead, the susceptibility to interference from external alternating magnetic fields is significantly reduced, particularly because the measuring leads form a closed measuring lead section oriented parallel to the busbar. This is because voltages induced in the measuring leads cause a current flow within the practically closed measuring lead, which in turn compensates for the induced voltages through its ohmic voltage drop. Therefore, the current measuring device is well suited for use with fast-switching power semiconductors, e.g., in a power converter, where phase-correct measurement of the alternating currents is advantageous for controlling harmonics at high frequencies.

[0048] In one embodiment of the device, the circuit board includes additional conductor tracks, which are configured as a compensation structure for further compensation of the aforementioned effects and are arranged in the resistive area. The conductor tracks of the compensation structure are electrically connected in series with one of the measuring leads, thus extending the measuring lead. The compensation structure can be electrically arranged, in particular, between the measuring lead spanning the measuring lead area and the tap point, or connected at a break in a measuring lead. Due to the series connection of a measuring lead and the compensation structure, the voltages induced in the conductor tracks of the compensation structure are superimposed on the voltages induced in the measuring leads.

[0049] The compensation structure includes, in particular, compensation traces consisting of conductor tracks spanning an area oriented perpendicular to the surface of the busbar and parallel to the current flow direction. These compensation traces include, in particular, conductor tracks arranged in different planes or layers of the printed circuit board and running essentially parallel to each other, as well as vias that connect conductor tracks in different planes.

[0050] A compensation trace can consist of two compensation arms oriented in opposite directions. For example, a compensation arm can extend from a connection point and include a first trace in the first layer of the printed circuit board (PCB), a via from the first layer to the second layer, a second trace in the second layer of the PCB running parallel to the first trace back to the connection point, and another via from the second layer to the first layer of the PCB. The other compensation arm of a compensation trace can be a mirror image of the first compensation arm, i.e., extending in the opposite direction to the first compensation arm and also parallel to the longitudinal axis of the resistive area.An electrical connector, such as a wire bridge, connecting one or the other of the compensation arms to the measuring lead allows selection of which compensation arm is added to the measuring lead. The mirror-image arrangement of the compensation arms enables compensation with opposite signs. Alternatively, the entire compensation path can be bridged with a wire bridge.

[0051] In one embodiment of the device, several compensation paths can be arranged spatially parallel to each other and electrically connected in series. The compensation paths preferably have different lengths and thus cover areas of different sizes, resulting in different compensation contributions. By means of further electrical connectors, it can then be selected which compensation arms of which compensation paths are connected to the measuring line, whereby individual compensation paths can be bridged by suitable connectors and are therefore inactive.This results in various combination possibilities with different accumulated spanned areas, yielding compensation contributions from zero (no compensation arm connected) through several intermediate values ​​(one or more compensation arms connected with the same or opposite orientation) up to a maximum value (all compensation paths connected with the same orientation).

[0052] It is understood that the current measurement device comprises a busbar and a circuit board for acquiring measured values, wherein the circuit board with the features described above can be arranged on busbars that generally include a resistor section and voltage taps. In particular, the circuit board with the compensation structure is largely independent of the specific shape of the busbar or the specific design of the resistor section within the busbar.

[0053] In a power transformer with current-carrying conductors for conducting the direct and / or alternating currents processed by the power transformer, at least one of the current-carrying conductors has a current-measuring device that bridges an interruption in the at least one current-carrying conductor or is integrated into the at least one current-carrying conductor. The power transformer is configured to determine the current flowing through the current-carrying conductors during operation by means of a voltage difference detected by the measuring contacts along the resistance range of the busbar. The power transformer is designed for a rated power greater than 10 kW, preferably greater than 100 kW, and particularly preferably greater than 1000 kW.

[0054] The high measurement accuracy achievable through the registered busbar makes it possible to reduce the hardware reserves to be maintained in the power converter and / or to achieve a higher rated power with the given other hardware of the power converter.

[0055] In one embodiment, the power converter has a multi-channel current sensing device, wherein the multi-channel device includes a multi-channel busbar, the multi-channel busbar having at least two individual connection areas on a first side for connecting multiple current-carrying conductors and a common busbar as a common connection area on a second side. Each individual connection area is associated with a resistor section located between the respective individual connection area and the busbar.

[0056] The multi-channel busbar features a parallel connection of identical or differently dimensioned resistance sections, in which fundamentally different currents flow. These currents are measured via the respective voltage drop between the measuring contacts of the individual resistance sections. Each resistance section exhibits an optimized current shadow geometry as described above. The multi-channel busbar has electrically isolated first connection sections and their respective resistance sections on one side. These sections are electrically and mechanically connected on the other side of the busbar, forming a common second connection section.Such a multi-channel busbar can be used, for example, in a DC input area of ​​a central inverter of a PV system (photovoltaic system) to measure the PV input currents of several strings of photovoltaic modules individually on the one hand and to supply them as a combined total PV current to a PV busbar on the other.

[0057] Using a multi-channel busbar system allows for reduced material costs compared to multiple single-channel busbar systems. This can result in simpler manufacturing and assembly, as well as reduced logistics.

[0058] In one embodiment of the power converter, a printed circuit board for data acquisition is arranged parallel to the busbar and, in particular, rests parallel to the busbar. The printed circuit board covers several resistor sections and is connected to the measuring contacts of several resistor sections. A single printed circuit board for multi-channel busbars eliminates the need for various components, as they only require one instead of multiple units. Examples include power supplies, microprocessors, analog-to-digital converters, communication drivers, wiring, and similar components.

[0059] In one embodiment of the power converter, the circuit board includes an evaluation unit for preprocessing the measured voltages and, optionally, temperatures of the individual resistance ranges, as well as galvanic isolation. The evaluation unit is connected to a control unit of the power converter via this galvanic isolation. Using a common circuit board for the measurement electronics with galvanic isolation from a communication device or the surrounding electronics offers the advantage that the galvanic isolation only needs to be provided once for multiple measurement channels. This results in cost savings. This is particularly advantageous when galvanic isolation of the measurement electronics from the environment is necessary, for example, in the case of high DC voltages at the DC inputs of a PV inverter. Here, this isolation can be implemented only once instead of separately for each single-channel busbar.

[0060] In another embodiment, the circuit board of the multi-channel busbar has slots arranged between the resistor sections and extending parallel to the longitudinal center axis from one edge of the circuit board over at least half its length. These slots can also be arranged side by side in pairs, starting from opposite edges. They divide the circuit board into individual, mutually movable sections, each assigned to a specific resistor section. This allows the circuit board to accommodate any deformations of the individual resistor sections or connection sections of the multi-channel busbar relative to one another, thus preventing both twisting of the circuit board and partial lifting of the circuit board from the busbar surface in the event of such deformations.

[0061] A power transformer has current-carrying conductors for conducting the direct and / or alternating currents processed by the power transformer. At least one of the current-carrying conductors includes a current-measuring device as described above, wherein the device bridges a break in the current-carrying conductors or is integrated into the current-carrying conductors. The power transformer is configured to determine the current flowing through the current-carrying conductors during operation from a voltage difference detected by the measuring contacts along the resistance range and a resistance value of the resistance range. The resistance value used for the corresponding current calculation can be a function of the temperature detected by the temperature sensor.

[0062] In a preferred embodiment, the power converter is designed for a rated power output greater than 10 kW, preferably greater than 100 kW, and particularly preferably greater than 1000 kW. In these power classes, determining the direct and / or alternating currents processed by the power converter is particularly challenging due to their correspondingly high amplitudes. This determination can be carried out with particular accuracy using the described current measurement device, which can be integrated into the power converter's design with particular ease. KURZBESCHREIBUNG DER FIGUREN

[0063] The subject matter of the application will be further explained and described below with reference to exemplary embodiments shown in the figures. Figures 1a, 1b, and 1c schematically show embodiments of busbars for current measurement; Figures 2a and 2b schematically show further embodiments of busbars for current measurement; Figure 3a schematically shows a further embodiment of a busbar for current measurement; Figure 3b schematically shows an embodiment of a device for current measurement; Figure 4 schematically shows an embodiment of a multi-channel device for current measurement; and Figures 5a, 5b, and 5c schematically show an embodiment of a printed circuit board of a device for current measurement.

[0064] In the figures, identical or similar elements are designated with the same reference symbols. FIGURENBESCHREIBUNG

[0065] The Figuren 1a bis 1c schematically show busbars 11 for current measurement, as required by registration.

[0066] The in Fig. 1a The busbar 11 shown has two opposing connection sections 11a and a resistance section 11b arranged between the connection sections 11a, in which the cross-section of the busbar 11 is smaller compared to the connection sections 11a. The reduction in cross-section in the busbar 11 shown is achieved by a reduction in the width of the busbar 11 in its resistance section 11b; alternatively or additionally, the thickness of the busbar 11 in the resistance section 11b can be reduced compared to the connection sections 11a. The busbar is manufactured in one piece and is made of copper or aluminum. By connecting a current-carrying conductor (not shown) to one connection section 11a and continuing the conductor to the other connection section 11a, the busbar 11 bridges a break in the conductor.If an electric current flows through the conductor, then the busbar 11 will also be traversed by the same electric current, from one terminal area 11a via the resistance area 11b to the other terminal area 11a.

[0067] The depicted busbar 11 is essentially symmetrical about a longitudinal center axis LA and a transverse center axis QA. Two measuring contacts 12 are arranged in the region of the longitudinal center axis LA. The two measuring contacts 12 are arranged essentially symmetrically with respect to the transverse center axis QA. A voltage or potential difference between the measuring contacts 12 can be detected via the measuring contacts 12. Using the electrical resistance of the material connecting the two measuring contacts 12, the value of the current flowing through the busbar 11 can be determined from this voltage difference.

[0068] The measuring contacts 12 are preferably designed as press-fit pins, which offers advantages in manufacturing, e.g., with regard to accuracy. The above description also applies analogously to the in Fig. 1b und 1c to the illustrated busbars 11.

[0069] The in Fig. 1a The busbar 11 shown has recesses 4 adjacent to each of the measuring contacts 12, each recess being slightly spaced from the measuring contacts 12 in the direction of the longitudinal center axis LA. The recesses 4 are arranged such that they create a so-called current shadow at the measuring contacts 12; this means that the current flows essentially around the recesses 4, and the measuring contacts 12 are thus largely currentless due to their arrangement in the immediate vicinity of the recesses 4. This increases the measurement accuracy of the voltage drop between the measuring contacts 12. The recesses 4 are arranged transversely, in particular perpendicularly, to the longitudinal center axis LA. They are also arranged essentially symmetrically with respect to the longitudinal center axis LA and essentially symmetrically with respect to each other with respect to the transverse center axis QA, so that the measuring contacts 12 are located between the recesses 4.In an alternative embodiment not shown, the measuring contacts 12 can also be arranged on the opposite side of the respective recess 4, so that the recesses 4 are arranged between the measuring contacts 12.

[0070] The in Fig. 1b The illustrated busbar 11 has two recesses 4 adjacent to each of the measuring contacts 12. These recesses are arranged on opposite sides of the measuring points 12 when viewed in the direction of the longitudinal center axis LA and extend essentially transversely, in particular perpendicularly, to the longitudinal center axis LA. The recesses 4 are arranged such that they create a so-called current shadow at the measuring contacts. This means that the current flows essentially around the paired recesses 4 and does not reach the measuring contacts 12. Due to the arrangement of the recesses 4, the areas of the measuring contacts 12 are therefore largely currentless. Compared to the busbar 11 of Fig. 1a The paired arrangement of the recesses 4 per measuring contact 12 further improves this current shadow effect and allows for a further increase in measurement accuracy. The recesses 4 can be essentially symmetrical about the longitudinal center axis LA. The two recesses 4 in the area of ​​one measuring contact 12 are also essentially symmetrical, in particular essentially point-symmetrical about the measuring contact 12. At the same time, the two recesses 4 arranged in the area of ​​one measuring contact 12 can be essentially axially symmetrical to each other with respect to an axis passing through the measuring contact 12. The recesses 4 of one measuring contact 12 can also be arranged essentially symmetrically with respect to the transverse center axis QA with respect to the recesses 4 of the other measuring contact 12.

[0071] The in Fig. 1c The busbar 11 shown has a recess 4 adjacent to each of the measuring contacts 12. The recesses 4 are arranged transversely, in particular perpendicularly to the longitudinal center axis LA. They are also essentially symmetrical with respect to the longitudinal center axis LA. The two recesses 4 are also essentially symmetrical to each other with respect to the transverse center axis QA. In addition, the busbar 11 has a further recess 4a between the two measuring contacts 12. The further recess 4a is arranged in the region of the longitudinal center axis LA and / or the transverse center axis QA. The further recess 4a can, for example, be essentially symmetrical with respect to the longitudinal center axis LA and / or the transverse center axis QA and, in particular, be directly adjacent to both measuring contacts 12.

[0072] The recesses 4 and 4a are arranged to create a so-called current shadow at the measuring contacts 12; this means that the current flows essentially around the recesses 4 and 4a, which are arranged along the longitudinal central axis LA, and is guided essentially laterally to the sides of the recesses 4 and 4a in the current-carrying areas, so that the measuring contacts 12, in particular, are largely currentless due to the arrangement of the recesses 4 and 4a. The additional recess 4a results in an even lower current density in the area of ​​the measuring contacts 12 and an even more homogeneous current density in the current-carrying area of ​​the resistance section 11b. This further increases the measurement accuracy.

[0073] The Figuren 2a und 2b schematically show busbars 11 for current measurement, as required by registration.

[0074] The in Fig. 2a The illustrated busbar 11 has two opposing connection sections 11a and a resistive section 11b located between the connection sections 11a, in which the cross-section of the busbar 11 is smaller compared to the connection sections 11a. The reduction in cross-section in the illustrated busbar 11 is achieved by reducing the width of the busbar 11 in its resistive section 11b, but can also be achieved by reducing the thickness of the busbar 11 in the resistive section 11b. The busbar is made in one piece and preferably consists of a single material, e.g., copper or aluminum. When the busbar 11 bridges a break in a current-carrying conductor (not shown), an electric current flows through the busbar 11, from one connection section 11a, through the resistive section 11b, to the other connection section 11a.

[0075] The depicted busbar 11 is essentially symmetrical about a longitudinal center axis LA and a transverse center axis QA. Two measuring contacts 12 are arranged in the region of the longitudinal center axis LA. The two measuring contacts 12 are arranged essentially symmetrically with respect to the transverse center axis QA. A voltage or potential difference between the measuring contacts 12 can be detected via the measuring contacts 12. Using the electrical resistance of the material connecting the two measuring contacts 12, the resistance range 11b of this voltage difference can be used to determine the value of the current flowing through the busbar 11. The measuring contacts 12 are preferably designed as press-fit pins, which offers advantages in manufacturing, e.g., with regard to accuracy.

[0076] The connection areas 11a of the embodiments according to Fig. 2a und Fig. 2b The busbars have edge extensions towards the center, projecting into the tapered section as projections 21 or lugs. The projections 21, extending towards each other from opposite connection areas 11a, are separated from each other by a gap at the edge of the busbar 11, so that the electric current flows exclusively through the resistive section 11b. Fasteners, e.g., in the form of pins 15, preferably press-fit pins, can preferably be provided in the projections 21, allowing the busbar 11 to be attached to other components and / or, e.g., a printed circuit board 2, 20 (see Figure 1). Fign. 3b 4) to attach to the busbar 11 and, if necessary, to make electrical contacts. The pins 15 are preferably designed in the same way as the measuring contacts 12. This can further simplify manufacturing. The above description also applies analogously to the in Fig. 2b The illustrated busbar 11 is connected.

[0077] The in Fig. 2a The illustrated busbar 11 has a recess 4 around each of the two measuring contacts 12, surrounding the respective measuring contact 12 on three sides, with the "open" sides preferably facing each other. The recesses 4 are arranged such that the current flows essentially around the recesses 4 and does not reach the measuring contacts 12, so that the areas of the measuring contacts 12 are largely currentless. The recesses 4 can at least partially have a curvature of a circular segment or be composed of three or more straight segments. The two recesses 4 can preferably be arranged essentially symmetrically to each other with respect to the transverse central axis QA. Each of the recesses 4 can itself be designed essentially symmetrically with respect to the longitudinal central axis LA. The above description also applies analogously to the one in Fig. 2b The illustrated busbar 11 is connected.

[0078] The in Fig. 2b The illustrated busbar has two additional recesses 4, which are arranged in the region of the longitudinal center axis LA such that they are bisected by it in the longitudinal direction and extend from the respective measuring contact 12 to directly to the transverse center axis QA. Furthermore, the two additional recesses 4 are arranged essentially symmetrically to each other with respect to the transverse center axis QA, so that only a narrow web remains in the region of the transverse center axis QA, on which, for example, another measuring point, such as a temperature sensor, can be arranged. The current flows essentially around the recesses 4 arranged along the longitudinal center axis LA and is guided essentially laterally to the sides of the recesses 4 in the current-carrying areas.This further improves the current shadow for the measuring contacts 12 and further improves the homogeneity of the current density in the current-carrying areas of the resistance range 11b that remain laterally to the recesses 4.

[0079] Fig. 3a Figure 1 schematically shows an embodiment of a busbar 11 according to the application for current measurement. The busbar 11 has four recesses 4, each encompassing the measuring contacts 12 in a semi-circular shape. A temperature sensor 3 is arranged between the two recesses 4 that are centrally located with respect to the longitudinal center axis LA.

[0080] The busbar 11 according to Fig. 3a Analogous to the previously described busbars 11, the Fign. 1a, 1b, 1c , 2a, 2b The busbar 11 comprises two opposing terminal sections 11a and a resistance section 11b located between them, in which the cross-section of the busbar 11 is smaller compared to the terminal sections 11a. The reduction in cross-section in the illustrated busbar 11 is achieved by reducing its width in its resistance section 11b and can alternatively or additionally include a reduction in thickness. The busbar is made in one piece and preferably consists of a single material, e.g., copper or aluminum. An electric current flows through the busbar 11 when it bridges a break in a current-carrying conductor (not shown) connected to the terminal sections 11a, with the current being conducted from one terminal section 11a through the resistance section 11b to the other terminal section 11a.

[0081] The busbar 11 is essentially symmetrical about the longitudinal center axis LA, which runs longitudinally along the busbar 11 from one of the connection areas 11a to the opposite connection area 11a through the resistance area 11b. The measuring contacts 12 are preferably arranged in the region of the longitudinal center axis LA. The busbar 11 shown can also be constructed essentially symmetrically about the transverse center axis QA. The two measuring contacts 12 can be arranged essentially symmetrically about the transverse center axis QA. A voltage or potential difference between the measuring contacts 12 can be detected via the measuring contacts 12. Using the electrical resistance of the material connecting the two measuring contacts 12 in the resistance area 11b, the value of the current flowing through the busbar 11 can be determined from this voltage difference. The measuring contacts 12 are preferably designed as press-fit pins, which offers advantages in manufacturing.B. regarding accuracy.

[0082] The connection areas 11a have edge extensions towards the center of the busbar, which project into the tapered section as projections 21 or lugs. The projections 21, which extend towards each other from opposite connection areas, are separated from each other by a gap at the edge of the busbar 11, so that the electric current flows exclusively through the resistive section 11b. Fasteners, e.g., in the form of pins 15 (not shown, see figure), can preferably be provided in the projections. Fign. 2a, 2b ), preferably press-fit pins, which allow the busbar 11 to be attached to other components and / or e.g. a printed circuit board 2, 20 (cf. Fign. 3b , 4 ) to be attached to the busbar 11 and, if necessary, electrically connected. The pins 15 can be designed in the same way as the measuring contacts 12.

[0083] The in Fig. 3a The illustrated busbar 11 has a measuring point plateau 5 in the area of ​​each of the two measuring contacts 12, in which the measuring contact 12 is arranged. On two opposite sides of each measuring point plateau 5, there is a recess 4 which partially surrounds the measuring point plateau 5 in an arc. The recesses 4 can have a curvature of a circular segment, at least partially, on their side facing the respective measuring point plateau 5. The recesses 4 of one measuring contact 12 are preferably arranged substantially symmetrically with respect to the transverse central axis QA to the recesses 4 of the other measuring contact, so that the measuring point plateaus 5 are also symmetrical to each other with respect to the transverse central axis QA.

[0084] Each of the recesses 4 extends transversely, in particular perpendicularly, to the longitudinal central axis LA and can itself be substantially symmetrical with respect to the longitudinal central axis LA. The recesses 4 can each have a width of between two and ten millimeters in the direction of the longitudinal central axis. The two recesses 4, which are arranged in the area of ​​a measuring contact 12, can be substantially symmetrical with respect to the measuring contact 12, in particular substantially point-symmetrical with respect to the measuring contact 12 and / or substantially axis-symmetrical with respect to an axis passing through the measuring contact 12.

[0085] Due to the cutouts 4, the measuring point plateaus are essentially current-free, as the current flows around the cutouts 4 and does not reach the measuring point plateaus 5. The measuring point plateaus 5 are connected to the current-carrying area of ​​the resistance range 11b only via two connecting bridges 9 each. The connecting bridges 9 can run transversely, in particular perpendicularly to the longitudinal central axis LA, so that the current, which flows essentially parallel to the longitudinal central axis LA, does not penetrate the connecting bridges 5 or only very minimally. Via the connecting bridges 5, the respective measuring point plateau 5 is at a potential that corresponds to the potential at the interfaces of the connecting bridges 5 with the current-carrying area of ​​the resistance range 11b, so that the voltage difference between the measuring contacts 12 essentially corresponds to the voltage difference between these interfaces.

[0086] The connecting webs 9 can have a width, i.e., an extent in the direction of the longitudinal central axis LA, between two and five millimeters. The measuring point plateaus 5 can have a longitudinal extent, i.e., an extent in the direction of the longitudinal central axis LA and / or transverse central axis QA, between five and twelve millimeters. The in Fig. 3a The illustrated busbar 11 thus has dimensions and minimum sizes of structures (recesses 4 and remaining webs) of, for example, 3 mm, so that it can be manufactured in a cost-effective stamping process.

[0087] The temperature sensor 3 can be positioned centrally within resistance range 11b and centrally between the measuring contacts 12, so that the temperature is measured precisely in the area at the midpoint of the voltage drop between the measuring contacts 12. This allows temperature-related changes in the resistance of the busbar 11 material within resistance range 11b of the busbar 11 to be optimally compensated when determining the current flowing through the busbar 11. Both the measuring contacts 12 and the temperature sensor 3 display the mean values ​​of the corresponding voltages and temperatures from the respective adjacent, opposite current-carrying sections of the busbar 11. Therefore, an uneven current or temperature distribution in the opposite current-carrying sections of the busbar 11 does not distort the measurements.

[0088] In an embodiment not shown, two temperature sensors can be placed in the current-carrying areas of the busbar. This is particularly advantageous if the opposing recesses 4 merge into one another and form a common recess 4a, so that no material remains along the longitudinal central axis LA between the measuring point plateaus (cf. Fig. 1c Preferably, the two temperature sensors would be arranged on the transverse central axis and essentially symmetrically around the longitudinal central axis, i.e., particularly in the current-carrying areas to the sides of the recesses 4. This can improve the response behavior of the current measurement during abrupt changes in the current to be measured, because the measurement is then taken directly where the heat is generated, namely in the effectively current-carrying areas of the resistance region.

[0089] In Fig. 3b is a device for current measurement 10 with the busbar 11 of Fig. 3a and a printed circuit board 2. The printed circuit board 2 can rest on the busbar and be connected, for example, with pins 15 (see figure). Fign. 2a, 2b ) be attached to the busbar 11, in particular to the projections 21, wherein the pins 15 may be designed in the same way as the measuring contacts 12.

[0090] The circuit board 2 can lie almost flush with the surface of the resistor area 11b. Conductor traces in the circuit board 2, which connect the measuring contacts 12 as measuring leads 6a, 6b, 7a, 7b to an evaluation unit 18 (not shown) for determining the voltage drop between the measuring contacts 12, are thus also in close contact with the surface of the resistor area 11b, and conductor loops during voltage measurement are largely avoided. The geometry of the arrangement of the measuring leads 7a, 7b on the circuit board 2 can be largely independent of the busbar and current shadow geometry; however, it is advantageous if the measuring leads 7a, 7b run over the remaining material of the resistor area 11b and not over cutouts 4. A circuit board 2, as in Fig. 3b As shown, it can therefore also be used in conjunction with other busbars 11, e.g. from Fig. 1a, 1b, 1c , 2a, 2b They can be used. The arrangement of the measuring lines 7a, 7b can be adjusted accordingly.

[0091] The measuring lines 7a, 7b are laid out as conductor tracks within the circuit board 2 in such a way that frequency-dependent phase measurement errors are reduced. The measuring lines 7a, 7b for connecting the measuring contacts 12 to an evaluation unit 18 (not shown) can be laid out as conductor tracks within a circuit board 2 along a path on the surface of the busbar 11 in such a way that the phase error is significantly reduced compared to a less optimized laying of the measuring lines 7a, 7b. In the Fig. 3b In the illustrated example of device 10, the measuring leads 7a, 7b extend from the measuring contacts 12, span a measuring lead area 8 in the form of a polygon, and are joined at a common tap point 6 via measuring tap leads 6a, 6b. A suitable evaluation unit 18 (not shown) can detect the potentials of the two measuring contacts 12 at the tap point 6. The measuring leads 7a, 7b can run partially, essentially symmetrically, about the longitudinal center axis and / or the transverse center axis of the resistance area.

[0092] The measuring lead area 8 can, in particular, span a polygon, e.g., a hexagon, whereby the polygon can have axes of symmetry running along the transverse central axis and / or the longitudinal central axis. The width of the polygon can be approximately 70–100% or 70–85% of the width of the resistance area. Furthermore, the sides of the polygon can be formed by several parallel conductor tracks.

[0093] In one embodiment of the device 10, it is possible to arrange the temperature sensor 3 and the evaluation unit 18 (not shown) on the side of the circuit board 2 opposite the busbar 11.

[0094] Fig. 4 shows a multi-channel device for current measurement 13 with a multi-channel busbar 14 on which a printed circuit board 20 is arranged.

[0095] The multi-channel busbar 14 has four individual connection areas 11a with connection elements 22 for connecting multiple current-carrying conductors on one side. On a second side opposite the connection elements 22, the multi-channel busbar 14 has a common busbar 16 as a common connection area 11a for a common current-carrying conductor. Each individual connection area 11a is assigned a resistor section 11b, which is arranged between the respective individual connection area 11a and the busbar 16. The multi-channel busbar 14 thus has a parallel connection of identical or differently dimensioned resistor sections 11b, in which fundamentally different currents flow, which are measured via the respective voltage drop between the measuring contacts 12 of the respective resistor sections 11b.The resistor areas 11b have an optimized current shadow geometry as described above. The multi-channel busbar 14 has separate first connection areas 11a and respective resistor areas 11b on one side, which are electrically and mechanically connected to each other on the other side of the multi-channel busbar, so that a common second connection area in the form of a busbar 16 is formed.

[0096] The geometry of the respective resistance areas 11b corresponds in the illustrated example to the geometry of the busbar 11 from Fig. 3a The resistance area 11b has, according to the current rail 11, Fig. 3a one or more temperature sensors 3 are mounted, and the measuring contacts 12 are located according to the busbar 11 of Fig. 3a on measuring point plates 5, which are connected to current-carrying areas of the resistance range 11b by connecting bridges 9. The arrangement and shape of the recesses 4 can also be determined by Fig. 3a correspond, whereby in Fig. 4 The transverse center axis QA and the longitudinal center axes LA are shown accordingly. It is also possible to construct a multi-channel busbar from individual busbar geometries, such as those shown for busbar 11 from the Fign. 1a, 1b, 1c , 2a, 2b are equivalent to.

[0097] The circuit board 20 for data acquisition lies parallel to the busbar 14, with the circuit board 20 covering several resistor sections 11b and being connected to the measuring contacts 12 of several resistor sections 11b. Measuring leads are arranged in the circuit board 20, which are connected in an analogous manner as described above. Fig. 3a The components can be implemented as shown and, in particular, as conductor tracks in the circuit board 20. The measured values ​​are transmitted from the measuring contacts 12 to the evaluation unit 18 via the measuring leads. A common circuit board 20 for multi-channel busbars 14 eliminates the need for various components, as they only require a single component instead of multiple ones, e.g., galvanic isolation 17, power supplies, evaluation unit 18, analog-to-digital converter, communication drivers, cabling, and the like.

[0098] For the reasons already mentioned, a flush mounting of the printed circuit board 20 on the multi-channel busbar 14 is desirable. During operation of a busbar 14 in a power converter, deformations of the busbar 14, particularly of individual resistance sections 11b relative to each other, and / or of the printed circuit board 20, can occur, especially due to thermal and electromechanical effects acting on the busbar 14 at high operating currents. Such deformations can lead to at least partial lifting of the printed circuit board 20 from the busbar 14. This lifting of the printed circuit board 20 from the surface of the busbar 14 can be compensated for by slots 19 in the printed circuit board 20, which are arranged between the resistance sections 11b and extend parallel to the longitudinal center axis LA from one edge of the printed circuit board 20 over at least half the length of the printed circuit board 20.The slots 19 allow the sections of the circuit board 20 assigned to the individual resistance areas 11b to be slightly "twisted" relative to each other. This allows the circuit board 20 to follow any deformations of the individual resistance areas 11b or connection areas 11a relative to each other section by section, thus reducing mechanical stresses on the device 13.

[0099] The Figuren 5a-5c show an embodiment of a printed circuit board of a device for current measurement in different views. Fig. 5a shows a circuit board 2, which is analogous to Fig. 3b The circuit board 2 can be arranged on a busbar 11 (not shown here) and detects the voltage drop across the resistance section 11b of the busbar 11 by means of the measuring contacts 12. For this purpose, the circuit board 2 has the measuring leads 7a, 7b, which span a measuring lead section 8 and connect the measuring contacts 12 to the measuring tap leads 6a, 6b and the tap point 6. Additionally, the circuit board 2 has a compensation structure 30, which is preferably arranged in the resistance section of the busbar 11 and is electrically connected in series with the measuring lead 7b via a further measuring tap lead 6c.

[0100] A compensation structure 30 with a specific configuration is in Fig. 5b The diagram is shown enlarged. The solid lines represent conductor tracks 31 in a first layer (layer #1) of the printed circuit board 2, while the dashed lines represent conductor tracks 32 and the dotted lines represent conductor tracks 33 in a second layer (layer #2) and a third layer (layer #3), respectively, of the printed circuit board 2. Layers #1, #2, and #3 are located in different planes of the printed circuit board 2. The compensation structure 30 comprises several compensation tracks 40a, 40b, 40c, and 40d, which are arranged parallel to each other and, when the printed circuit board 2 is mounted on a busbar 11, parallel to the longitudinal axis of the busbar 11. The compensation tracks 40a, 40b, 40c, and 40d each have two oppositely oriented compensation arms, which are described further below in connection with Fig. 5c will be explained in more detail.

[0101] In the exemplary specific configuration according to Fig. 5b Only one compensation arm of the second compensation track 40b is connected to the measuring line 7b. Starting from the measuring tap line 6c, the circuit described below results as an extension of the measuring line 7b. Following the conductor track 31 in layer #1 along the horizontal central axis of the compensation structure 33, the conductor track 31 initially terminates at a solder point 34, which is assigned to the compensation track 40a. By means of an electrical connector, here exemplified by a bridge 41, this solder point 34 is connected to another solder point 34 on the central axis, so that the compensation track 40a is bridged, i.e., the compensation track 40a is unused in this example. Further along, the conductor track 31 reaches the next solder point 34, which is assigned to the compensation track 40b.A further bridge 41 connects conductor 31 to a solder point 34, which is assigned to the upper compensation arm of compensation track 40b and coincides with a via 35 between layer #1 and layer #2, so that conductor 31 is connected via bridge 41 and via 35 to conductor 32 in layer #2. At the outer endpoint of the compensation arm, conductor 32 is connected via a via 36 between layer #2 and layer #3 to conductor 33 in layer #3 of the printed circuit board 2, and conductor 33 leads back to a via 36 on the central axis of the compensation structure 30. From there, conductor 32 in layer #2, a via 35, and conductor 31 lead to a solder point 34, which is assigned to compensation track 40c. In this example, the compensation paths 40c and 40d are also not used and are bypassed by means of a bridge 41 each.Finally, a conductor track 32 leads back to the measuring tap line 6c on both sides of the central axis of the compensation structure and is joined there.

[0102] It is understood that the number of four compensation paths 40a-40d, as well as their respective lengths and sequence, are merely exemplary. Compensation structures 30 with any number of additional compensation paths are conceivable, whereby each compensation path can either be used by connecting one of the respective compensation arms to the measuring line 7b, or it can be bridged and thus remain unused.

[0103] Fig. 5c shows a detailed view of compensation path 40b from Fig. 5b The conductor track 31, which according to Fig. 5b The measuring line 6c, which is ultimately connected to the measuring line 6c, is connected via bridge 41 to a conductor 32 belonging to one of the two compensation arms of the compensation track 40b. This compensation arm is formed by the corresponding section of conductor 32 in layer #2, a via 36 between layer #2 and layer #3, a section of conductor 33 in layer #3, and another via 36, ​​so that the compensation arm forms an almost closed conductor loop that is oriented perpendicular to the surface of the printed circuit board (and thus perpendicular to the busbar 11) and parallel to the longitudinal center axis LA of the busbar. The other compensation arm of the compensation track 40b is not connected to the measuring line 7b due to the lack of a correspondingly positioned bridge and is therefore unused.

[0104] As an alternative to the upper compensation arm of compensation track 40b, the lower compensation arm of compensation track 40b can be connected to the measuring line 7b by means of a suitably positioned bridge 41, or compensation track 40b can be left unused and bridged by means of a suitably positioned bridge 41. Additionally, one or more of the compensation arms of the other compensation tracks 40a, 40c, and / or 40d can be connected to the measuring line by means of suitably positioned bridges 41. It should be noted that the oppositely oriented compensation arms of a compensation track produce a compensation effect of the same order of magnitude, but with opposite signs.

[0105] The compensation traces 40a-40d preferably span areas with different cross-sectional areas. For this purpose, both the length of the arms, i.e., the width of the respective span area, and the distance between the opposing conductor traces, i.e., the height of the span area, can be appropriately selected. Furthermore, a compensation arm can consist of several loops, thereby multiplying the span area accordingly.

[0106] In specific embodiments, the compensation arms are at least one millimeter and at most 20 millimeters long. The distance between the conductor tracks of a compensation arm in the different layers of the printed circuit board is limited by the thickness of the circuit board and the number of layers in the circuit board, and ranges from approximately 0.2 millimeters to approximately 10 mm.

[0107] The varying sizes of the spans of the compensation paths 40a-40d result in a number of possible combinations, each with different compensation effects. In the specific example according to Fig. 5b A total of 15 different combinations can be generated by using the upper compensation arms, another 15 different combinations of the lower compensation arms, and some mixed forms using lower and upper compensation arms, which exhibit different compensation effects with different amplitudes and possibly signs, especially when the spanned areas increase by powers of two.

[0108] In a specific application of the printed circuit board 2 according to Fig. 5a in a device 10, e.g. according to Fig. 3b A calibration measurement can be used to determine which effects influence the measurement result in a specific embodiment and to what extent. For example, the busbar 11 can be supplied with a defined current and the voltage signal recorded at tap point 6 evaluated while all compensation paths 40a-40b are bridged and the compensation structure is therefore inactive. Depending on the detected distortion of the measured values, which may include, for example, a non-linearity of the voltage signal relative to the current in the busbar 11, a decision is made as to whether and, if so, which compensation arms of the compensation paths 40a-40d should be connected to the measuring line 7b in order to minimize the undesirable influences of the current to be measured on the measuring lines 7a, 76 and thus on the measurement result.The result is a configuration of the compensation structure that permanently ensures optimal compensation of unwanted influences and, in particular, minimizes frequency-dependent phase and amplitude measurement errors. This configuration can be used in the case of a multi-channel busbar 14 according to... Fig. 4 individually defined for the measurements on each channel in order to optimize the measurements on each channel individually. BEZUGSZEICHENLISTE

[0109] 2 Circuit board 3 Temperature sensor 4, 4a Recess 5 Measuring point plateau 6a, 6b, 6c Measuring tap lead 7a, 7b Measuring lead 8 Measuring lead area 9 Connecting bridge 10 Current measuring device 11 Busbar 11a Connection area 11b Resistance area 12 Measuring contact 13 Multi-channel current measuring device 14 Multi-channel busbar 15 Pin 16 Busbar 17 Galvanic isolation 18 Evaluation unit 19 Slot 20 Circuit board 21 Projection 22 Connection element 30 Compensation structure 31 Trace in layer #1 32 Trace in layer #2 33 Trace in layer #3 34 Solder point 35 Via between layer #1 and layer #2 36 Via between layer #2 and layer #3 40a-d Compensation trace 41 Bridge LALlongitudinal center axis QATransverse center axis

Claims

1. Apparatus for determining current (10) with a current busbar (11, 14), wherein the current busbar (11, 14) comprises connection regions (11a) and at least one resistance region (11b) arranged between the connection regions (11a) for measuring a direct and / or alternating current, in particular with currents greater than 100 amps, wherein the resistance region (11b) is essentially formed by a taper of the cross-section relative to the cross-section of the connection regions (11a) of the busbar (11, 14), wherein two measuring contacts (12) are arranged in the resistance region (11b), wherein the busbar (11, 14) has at least two recesses (4, 4a) in the resistance region (11b), which are arranged in the region of the measuring contacts (12) and are spaced apart from the measuring contacts (12) in the longitudinal direction, so that the regions of the measuring contacts (12) are essentially currentless during operation of the busbar (11, 14), wherein the busbar (11, 14) is formed in one piece and consists of copper or aluminium, and with a printed circuit board (2, 20) arranged in a plan-parallel manner with respect to the busbar (11, 14) for measured value acquisition, wherein the measured value acquisition comprises an acquisition of a voltage difference between the two measuring contacts (12) and an acquisition of the temperature of the resistance region (11b) via at least one temperature sensor (3).

2. Apparatus according to claim 1, wherein the taper is formed in particular by a reduction in the width of the resistance region (11b) to a value between 10 and 60 percent of the width of the connection region (11a) of the busbar (11, 14).

3. Apparatus according to claim 1 or 2, wherein the measuring contacts (12) are designed as press-fit pins which are pressed into press-fit holes in the busbar (11, 14).

4. Apparatus according to one of the preceding claims, wherein the measured value acquisition takes place via measuring lines (7a, 7b), which connect the measuring contacts (12) to a common tapping point (6) and are installed as conductor paths within the printed circuit board (2, 20) in such a way that frequency-dependent phase and amplitude measurement errors are reduced.

5. Apparatus according to Claim 4, wherein the measuring lines (7a, 7b) run in a plane of the printed circuit board (2, 20) which is arranged as the outermost inner layer of the guide plate (2, 20) on the side of the printed circuit board (2, 20) facing the resistance region (11b).

6. Apparatus according to Claims 4 or 5, wherein the measuring lines (7a, 7b) originate from the measuring contacts (12) and are brought together at the common tapping point (6) in such a way that the measuring lines (7a, 7b) are routed from at least one of the measuring contacts (12) of a resistance region (11b), running in two directions away from the measuring contact (12) to the edge of the resistance region (11b), and in particular run at least in part essentially symmetrically in relation to the longitudinal center axis (LA) and / or to the transverse center axis (QA) of the resistance region (11b).

7. Apparatus according to any one of Claims 4 to 6, wherein the measuring lines (7a, 7b) span an essentially closed measurement line region (8) which comprises, in one dimension, between 70 and 100 percent of the width of the resistance region (11b), and in the dimension perpendicular thereto comprises between 70 and 100 percent of the distance between the measuring contacts (12).

8. Apparatus according to any one of Claims 4 to 7, wherein the printed circuit board (2, 20) has a compensation structure (30), wherein the compensation structure (30) comprises a plurality of compensation paths (40a, 40b, 40c, 40d) which are arranged spatially parallel to one another, and can be connected electrically in series to one of the measuring lines (7a, 7b), wherein the compensation paths (40a, 40b, 40c, 40d) consist of conductor paths (31, 32, 33) in different planes of the printed circuit board (2, 20) and in each case span a surface which is oriented perpendicular to the busbar (11, 14) and parallel to the longitudinal center axis (LA).

9. Apparatus according to Claim 8, wherein the compensation paths (40a, 40b, 40c, 40d) each have two oppositely oriented compensation arms, wherein a compensation arm can be connected to the measuring line (7a, 7b) by each compensation path (40a, 40b, 40c, 40d).

10. Apparatus according to Claims 8 or 9, wherein the compensation paths (40a, 40b, 40c, 40d) are each bridged or connected to the measuring line (7a, 7b) by a fittable electrical connector (41).

11. Power converter comprising current-carrying lines for conducting the direct and / or alternating currents processed by the power converter, wherein at least one of the current-carrying lines comprises an apparatus for determining current (10) according to any one of Claims 1 to 10, which apparatus bridges an interruption of the at least one current-carrying line or is integrated into the at least one current-carrying line, wherein the power converter is designed to determine, using a voltage difference detected by means of the measuring contacts (12) along the resistance region (11b) of the busbar (11, 14), a current flowing through the current-carrying lines during operation of the power converter, wherein the power converter is designed to have a nominal power that is greater than 10 kW, preferably greater than 100 kW, particularly preferably greater than 1000 kW.

12. Power converter according to Claim 11, comprising a multi-channel apparatus (13) for determining current, wherein the multi-channel apparatus (13) comprises a multi-channel busbar (14), wherein the multi-channel busbar (14) has, on a first side, at least two individual connection regions (11a) for connecting a plurality of current-carrying lines and on a second side comprises a common busbar (16) as a common connection region (11a), wherein a resistance region (11b) which is arranged between the respective individual connection region (11a) and the common busbar (16) is associated in each case with the individual connection regions (11a).

13. Power converter according to Claim 12, wherein a printed circuit board (20) for detecting measurement values is arranged in a plane-parallel manner with respect to the busbar (14), wherein the printed circuit board (20) covers a plurality of resistance regions (11b) and is connected to the measuring contacts (12) of a plurality of resistance regions (11b).

14. Power converter according to Claim 13, wherein the printed circuit board (20) comprises an evaluation unit (18) for preprocessing the measured voltages and the temperatures of the individual resistance regions (11b), as well as a galvanic isolation (17), wherein the evaluation unit (18) is connected to a control unit of the power converter via the galvanic isolation (17).

15. Power converter according to any one of Claims 12 to 14, wherein the printed circuit board (20) has slots (19) arranged between the resistance regions (11b) and extending parallel to the longitudinal center axis (LA) from an edge of the printed circuit board (20) over at least half of the length of the printed circuit board (20).