Busbars for measuring direct and / or alternating current

Abstract

A busbar (11, 14) for measuring direct and / or alternating currents, in particular with a current strength of more than 100 Amperes, has connection areas (11a) and at least one resistive area (11b) arranged between the connection areas (11a) and with two measurement contacts (12) arranged in the resistive area (11b), the busbar (11, 14) having a shape such that essentially no current flows in the area of ​​the measurement contacts (12) during operation of the busbar (11, 14) and the busbar (11, 14) is integrally formed with it. A device (10) for determining a current with such a busbar (11, 14) and a power converter with such a device are also disclosed.

Description

[Technical field]

[0001] The present application relates to a busbar for measuring direct and / or alternating currents, in particular of current strengths above 100 Amperes, a current determining device and a power converter having a current determining device. [Background technology]

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

[0003] To accurately determine electric currents, especially large currents in the range from several hundred amperes to several kiloamperes, low-resistance measuring resistors, so-called shunts, can be used. In a shunt, the measuring taps are usually contacted at the connection areas on both sides immediately adjacent to the resistive material. The resistive material of the shunt differs from the rest of the shunt material in particular by a (slightly) increased resistivity and is characterized, for example, by a constant resistance value of the electrical resistor even over a wide temperature range.

[0004] For example, a measuring device for measuring current is known from DE 102016010012 B4, in which a pair of voltage taps as measuring contacts measure the voltage drop across a resistive material, and from the voltage drop and the resistance of the resistive material a measuring circuit determines, using Ohm's law, a measured value of the current flowing through the resistive material.

[0005] DE102013005939A1 describes the problem of phase errors in shunts in the high current range. The solution described there to avoid phase errors involves multiple voltage measurements at different positions on the shunt and weighted averaging with dynamic weighting factors.

[0006] DE102020111634B3 describes a shunt comprising a dedicated resistive material and a pair of taps, one tap (on one side) being surrounded by a notch which prevents current flow across the notch.

[0007] A press-in pin that is pressed into a press-in hole of a shunt can be used as a voltage tap. Such a press-in pin in a press-in hole in the area of ​​the shunt through which the current flows acts as a voltage divider between the different potentials at both ends of the press-in hole. A change in the voltage divider occurs if the transition resistance at the different ends of the press-in connection changes, for example due to mechanical effects. This changes the effective position of the press-in pin and thus the effective distance between the two measurement contacts (also called measuring points) at which the voltage drop is measured during the shunt current measurement. A typical diameter of the press-in hole is, for example, 1 mm for a metal workpiece. If the tapping length, i.e. the nominal distance between the two measuring contacts, is, for example, 20 mm, the effective distance between the effective positions of the voltage taps at the respective outer ends of the press-in hole can be 19 mm to 21 mm, i.e. the measured values ​​can differ by up to 10% at otherwise identical electrical boundary conditions.

[0008] For shunt current measurements, shunts in the range of a few microohms are used to keep the power losses within acceptable limits. To achieve such a low measurement resistance, it is necessary to use resistor alloys with high conductivity and large cross-sectional area. With nominal currents in the range of several hundred amperes, the voltage drop measured from them can be in the range of a few millivolts.

[0009] In AC current measurements with shunt resistors of large dimensions, significant phase errors can additionally occur due to the skin effect and induction. Phase errors that can occur during shunt current measurements are essentially caused by induced voltages in the measuring lines (depending on the wiring of the measuring lines) and by the skin effect, which in the case of alternating currents results in a phase position that is dependent on the position of the current density in the shunt. The skin effect not only causes a frequency- and position-dependent amplitude but also a frequency- and position-dependent phase, the latter often being much more important in applications. Induced voltages are induced in the measuring leads between the shunt and the evaluation unit when the measuring leads spread in the shunt over a surface through which the time-varying magnetic field of the load current passes. In high-current shunts, this effect occurs of a clearly measurable order of magnitude, since the magnetic field increases linearly with the current and its influence increases linearly with the reduction of the measuring voltage, in comparison with normal shunt current measurements in the low ampere region. The combination of these two effects means that the inductive effects have a measurable effect even at low frequencies in the range of the mains frequency and its single-digit harmonics, which is mainly reflected in a frequency-dependent phase error. For example, for AC current measurements at the output of an inverter bridge, manganin shunts can be used with a soldered measurement circuit board that have a phase error of about 3 degrees at the mains frequency and about 12 degrees in the range of actively controlled harmonics (e.g. 250 Hz). However, when using fast-switching power semiconductors, the phase of the AC current needs to be measured precisely to control high-frequency harmonics. Furthermore, if shunts made of resistive materials with a large temperature coefficient of resistivity are used, the frequency-dependent phase error also depends on temperature, so digital frequency response compensation is costly. Summary of the Invention

[0010] The invention is based on the object of providing a busbar for current measurement which allows the best possible measurements with the simplest and / or most cost-effective design possible.

[0011] This object is achieved by a busbar having the features of claim 1. Preferred embodiments are set out in the dependent claims.

[0012] The busbar for measuring direct and / or alternating currents, in particular with a current strength of more than 100 Amperes, has connection areas and at least one resistive area arranged between the connection areas. Two measurement contacts are arranged in the resistive area. The busbar is integrally formed and has a shape such that essentially no current flows in the area of ​​the measurement contacts during operation of the busbar.

[0013] The busbar preferably has two connection regions and further a resistive region, the resistive region being located between the connection regions and having an essentially flat surface, thus establishing an electrical and mechanical connection between the connection regions.

[0014] In monolithic busbars for current measurements, preferably made of a single material such as copper or aluminum, the shape of the busbar, and in particular the shape of the resistive area, is selected in such a way that no current flows in the area of ​​the measuring contacts, but the main part of the resistive area carries an operating current, which during operation, for example in a power converter, can flow hundreds of amperes or even kiloamperes. This operating current through the busbar can be determined by measuring the voltage or voltage difference between the two measuring contacts using the resistance value of the resistive area between the two measuring contacts. The largely current-free area of ​​the measuring contacts here allows a more accurate measurement, in particular since the measurement is more tolerant to shifts in the specific position of the measuring contacts. Also, a high uniformity of the current density within the current-carrying area of ​​the resistive area can be achieved.

[0015] The one-piece design of the busbar allows for a simpler and more cost-effective construction and simplifies the manufacture of busbars with, for example, integrated resistive and current-free measuring contact areas. It also avoids problems when transitioning between different materials.

[0016] Busbars for measuring currents can in particular have a so-called current shadow geometry. This is based on the idea of ​​arranging the measuring taps not in the current-carrying area of ​​the busbar, but in a part of the busbar specially made for this purpose, designed in such a way that no or only very weakly the current to be finally measured flows through it. For this purpose, various geometries are conceivable.

[0017] In one embodiment of the busbar, the resistive area is essentially formed by a taper of the cross section relative to the cross section of the connection area of ​​the busbar, and the measurement contacts are arranged within the cross section taper. The taper here is formed in particular by reducing the width of the resistive area to a value between 10 and 60 percent of the width of the connection area of ​​the busbar. This allows a higher current density to be achieved in the resistive area than in the connection area of ​​the busbar, which results in a higher voltage drop for a given current flowing through the busbar. Here, the associated higher losses within the resistive range are tolerated with the aid of bringing the voltage drop up to a range where it can be easily measured.

[0018] Such a localized increase in current density may be accompanied by a temperature rise within the resistive region, however, this effect may optionally be countered by temperature compensation based on a temperature measurement representative of the resistive region, and overcompensated by restriction to a locally limited and well-defined measurement range.

[0019] In an integral busbar for measuring current with a cross-sectional taper as resistive area, the measurement contacts are arranged at the resistive area in the cross-sectional taper, where the resistance value of the resistive area is temperature dependent. A temperature sensor arranged on the resistive element therefore has the advantage that the measured temperature can be used to determine a calibrated resistance value of the resistive area, which is then offset against the measured voltage drop across the measurement contacts to determine the current.

[0020] In particular, when the resistive element is made of a common material, such as copper, which has very good electrical conductivity, but whose resistivity is significantly temperature dependent, it is advantageous to measure the temperature of the resistive material precisely at the location where the associated voltage drop occurs. Placing a temperature sensor between the measurement junctions provides this advantage.

[0021] In one embodiment, the busbar has a central longitudinal axis running through the resistive regions in the longitudinal direction of the busbar from one of the connection regions to the opposite connection region, the measurement contacts being arranged in the region of the central longitudinal axis, and the busbar being essentially symmetrical with respect to the central longitudinal axis at least between the respective connection regions. Thus, busbars for measuring current have a current shadow shape with a measurement tap located centrally on the central longitudinal axis along the current flow direction. They have good robustness against mechanical influences and external magnetic fields and therefore can provide highly reproducible results.

[0022] In one embodiment, the busbar is designed to be essentially symmetrical about a lateral central axis between at least the respective connection areas, the lateral central axis running centrally between the connection areas in the lateral direction of the busbar, and the measurement contacts being arranged essentially symmetrical about the lateral central axis.

[0023] In one embodiment, the shape of the busbar has at least two recesses in the resistance area, which are arranged in the area of ​​the measurement contacts and are longitudinally spaced from the measurement contacts, in particular in the area of ​​each measurement contact. The recesses are arranged in such a way that the majority of the area of ​​the measurement contacts is current-free, in that the recesses are arranged in particular in front of or behind the measurement contacts when viewed in the direction of current flow. The area of ​​the resistance area outside the area of ​​the measurement contacts can be referred to here as the current-carrying area or current-passing area.

[0024] In one embodiment of the busbar, at least one temperature sensor is arranged between the measurement contacts, in particular in the region of the central longitudinal axis and / or the central lateral axis. Separate temperature sensors can preferably be arranged on the central longitudinal axis and on the central lateral axis. Alternatively, for example, two temperature sensors can also be arranged on the central lateral axis and essentially symmetrically with respect to the central longitudinal axis. The measurement contacts can be arranged essentially symmetrically with respect to the central lateral axis or around the temperature sensor(s).

[0025] In one embodiment of the busbar, at least one recess is arranged between the measurement contacts, the recess being arranged between the measurement contacts and is in particular designed to be essentially symmetrical and having the longitudinal and / or lateral central axes as axes of symmetry.

[0026] In one embodiment of the busbar, the central longitudinal axis forms an axis of symmetry of the one or more recesses. Alternatively or additionally, at least two recesses may be arranged essentially symmetrically with respect to the central lateral axis.

[0027] In one embodiment of the busbar, a respective recess is arranged on either side of each measurement contact in the direction of current flow, the recesses being formed essentially symmetrically with respect to the respective measurement contact along the central longitudinal axis and / or along the central lateral axis. The recesses may in particular be essentially point-symmetric with respect to the measurement contacts and / or essentially axis-symmetric with respect to an axis passing through the measurement contacts. In particular, the recesses may be essentially axis-symmetric with respect to the central longitudinal axis passing through the respective measurement contacts.

[0028] In one embodiment of the busbar, the respective areas of the measuring contacts each have a measuring point flat and a respective connecting crosspiece, the measuring contacts being arranged on the respective measuring point flat. The respective measuring point flat is connected to the current-carrying area of ​​the resistor area via a respective connecting crosspiece, the connecting crosspiece preferably extending transversely to the longitudinal central axis. The connecting crosspiece is delimited, in particular, by a recess. Via the connecting crosspiece, the measuring point flat is at a potential corresponding to the potential of the interface between the connecting crosspiece and the current-carrying area of ​​the resistor area, such that the voltage difference between the measuring contacts essentially corresponds to the voltage difference between these interfaces. At the same time, the shape with the measuring point flat and the connecting crosspiece is designed in such a way that the operating current flowing parallel to the longitudinal central axis through the current-carrying area does not flow through the connecting crosspiece oriented parallel to the transverse central axis and the measuring point flat. This ensures that no current flows through the measuring point flat and the connecting crosspiece, and thus through the majority of the area of ​​the measuring contacts.

[0029] In one embodiment of the busbar, the connecting crosspiece has a width of 2 to 5 millimeters and the longitudinal extent of the measuring point flat is 5 to 12 millimeters. The width of the connecting crosspiece here refers to the extent perpendicular to the direction in which the connecting crosspiece connects the respective measuring point flat to the current-carrying area of ​​the resistance area. The connecting crosspieces preferably run parallel to the transverse central axis, in particular symmetrically on both sides of the respective measuring point flat, and connect the measuring point flat to the current-carrying area of ​​the busbar. The longitudinal extent of the measuring point flat refers to the extent of the measuring point flat in the direction of the connecting crosspiece and / or perpendicular to the direction of the connecting crosspiece.

[0030] In one embodiment of the busbar, recesses are arranged on both sides of the measuring point flat and the connecting crosspiece, which recesses are preferably intersected in the middle by the longitudinal central axis and in each case have a width of 2 to 10 mm in the direction of the longitudinal central axis.

[0031] In one embodiment of the busbar, the material thickness of the resistive and / or connecting regions is between 2 and 6 millimeters, where the material thickness corresponds to the thickness of the busbar in the resistive and connecting regions, where the cross section of the resistive region can be considered as a surface with side lengths equal to the width of the resistive region and the thickness of the busbar.

[0032] The busbars can be designed to carry currents with a current strength of more than 100 Amperes, preferably more than 1000 Amperes. Here, the busbars are preferably integrally formed from a material such as copper or aluminum, and the resistance area is essentially formed by a taper of the cross section relative to the cross section of the connection area of ​​the busbar. This avoids material transitions and reduces manufacturing and assembly expenditures. Since shunts with resistance areas made of special resistive materials such as manganin can be rather expensive, significant cost savings can be achieved, especially when using copper busbars. Alternatively or additionally, recesses can also be punched out. This allows further reduction in manufacturing and assembly expenses.

[0033] In one embodiment of the busbar, the measurement contacts are designed as press-in pins, which are pressed into press-in holes in the busbar. In this way, measurement variations due to installation tolerances or ageing, for example, can be minimized. Also, assembly can be realized more cost-effectively. The measurement contacts can optionally also be designed as spring contacts, soldered connections or screw connections to the busbar. In this way, the contacting of the measurement contacts on busbars designed for high currents can be technically simplified. In particular, inaccuracies in the positioning of the measurement contacts, which can cause measurement errors, can be avoided.

[0034] The transition resistance between the press-in pin and the busbar can be influenced by mechanical influences. It is therefore advantageous to arrange the press-in contacts in an almost current-free area of ​​the busbar so that the voltage drop along the press-in pin, and in particular along the finite width of the press-in hole, is minimized. As a result, the potential difference or voltage drop across the press-in hole of the busbar can be minimized to such an extent that it is not a problem for the measurement technology whether the press-in contact touches one end of the press-in hole and the other from time to time, depending on the mechanical load. This also significantly increases the long-term stability of the measurement. In this way, the measurement variations can be minimized even if the measuring contacts are slightly mechanically displaced or their electrical properties change.

[0035] The current determination device has a busbar and a printed circuit board arranged plane-parallel to the busbar for measurement acquisition. The printed circuit board is preferably arranged plane-parallel on the busbar. The measurement acquisition can include acquisition of a voltage difference between two measurement contacts of a resistive area and, optionally, temperature detection via a temperature sensor of the associated resistive area. Here, the measurement contacts can be connected via a measurement line to a common tapping point, for example, where a voltage sensor is arranged which detects the voltage between the end points of the measurement line at the common tapping point. Here, the measurement line can extend in the plane of the printed circuit board, which is arranged as the outermost inner layer of the printed circuit board on the side facing the resistive area of ​​the printed circuit board, and / or can extend completely or partially in other planes or layers of the printed circuit board.

[0036] This makes it possible to arrange the connections between the measuring contacts and the evaluation unit very close to the resistive area in order to prevent conductor loops, which can cause serious disturbances or distortions in the measurement due to electromagnetic effects, especially in the vicinity of large currents and especially if the currents contain periodic or transient components.

[0037] The circuit board may comprise a temperature sensor and may be arranged on the resistive area on the surface of the busbar such that the temperature sensor is arranged in thermal connection with the resistive area of ​​the busbar, where measurement contacts in electrical contact with the surface of the busbar are arranged, for example, on either side of the temperature sensor and connected to the measurement lines for detecting a voltage difference along the resistive area by using a suitable voltmeter on the printed circuit board.

[0038] In one embodiment of the device, the printed circuit board is placed flat on the busbar, the measurement contacts establish electrical contact between the surface of the busbar and the measurement traces of the printed circuit board over the shortest path, and the temperature sensor is placed on the surface of the shunt. In this way, highly accurate current measurements can be achieved.

[0039] In one embodiment of the device, the measurement acquisition takes place via measurement lines, which are installed as conductor paths in a printed circuit board in such a way that frequency-dependent phase and amplitude measurement errors are reduced. Measurement lines for connecting the measurement contacts to an evaluation unit, in particular a voltmeter, can be installed as conductor paths in the printed circuit board along paths relative to the surface of the busbar in such a way that the measurement errors are significantly reduced compared to a conventional installation of measurement lines, e.g. compared to a direct connection of the measurement points and the common tapping point with a straight line. The installation of the measurement lines as conductor paths can be performed, for example, on the basis of theoretical preliminary studies and / or with the aid of numerical simulations.

[0040] In one embodiment of the device, the measurement lines start from the measurement contacts and are collected at a common tapping point. For this purpose, starting from at least one of the measurement contacts arranged on or near the longitudinal central axis of the busbar, the measurement lines are routed away from the measurement contacts in two directions, firstly towards the outside to the edge end of the resistance area and then back to the other measurement contact, which is also arranged on or near the longitudinal central axis of the busbar. Here, the measurement lines may in each case already reach the reversal point before the edge, or may reach the edge or even go beyond the edge. The path of the measurement lines in the edge and back direction may be at least partially essentially symmetrical with respect to the longitudinal central axis and / or the lateral central axis of the resistance area.

[0041] The central configuration of the installation may, for example, be a course which initially runs in a straight line transverse to the direction of the current flowing along the connecting crosspiece in the resistance area, then runs obliquely to the longitudinal and lateral central axes, continues outward towards the edge areas of the resistance area and returns obliquely inward towards the other measurement contacts, the entire course being essentially symmetrical with respect to the longitudinal and / or lateral central axes.

[0042] In one embodiment of the device, the measurement line spans an essentially closed measurement line area, which in one dimension comprises 70-100 percent of the width of the resistor area and in the dimension perpendicular thereto comprises 70-100 percent of the distance between the measurement contacts, the measurement line preferably running along the connecting crosspiece and outside the overlap area with the recess, and therefore preferably not extending beyond the recess.

[0043] In one embodiment of the device, the measurement line across the measurement line area can be composed of multiple conductor paths running parallel to one another, the individual conductor paths being arranged in the same or different planes of the printed circuit board.

[0044] The measuring line may extend in a polygon, in particular a hexagon, which may have an axis of symmetry extending along a central transverse axis and / or a central longitudinal axis. The width of the polygon may be approximately 70-100% of the width of the resistance area.

[0045] A special installation of the measuring wires allows a significant reduction of frequency- and temperature-dependent phase and amplitude errors in AC current measurements using busbars for measuring currents in the micro-ohm range, a very wide measurement range from milliamps to kiloamps is achieved and an almost linear frequency response is achieved within the range of mains frequencies and beyond, as well as within the range of harmonics of the mains frequencies that are relevant for control purposes.

[0046] In conventional AC current measurements using current measuring busbars with large dimensions, significant phase errors can occur due to the skin effect and induction. Possible phase errors occurring during current measurements are largely avoided by the above-mentioned installation of the measuring line. Here, the skin effect not only causes a frequency- and position-dependent amplitude, but also a frequency- and position-dependent phase, the latter of which is often much more important in applications. If the measuring line including the busbar spreads over a surface through which the time-varying magnetic field of the current to be measured passes, an induced voltage will occur in the measuring line between the busbar and the evaluation unit. The above-mentioned arrangement avoids the busbar spreading over such a surface. Instead, due in particular to the fact that the measuring line spreads over a closed measuring line area oriented parallel to the busbar, the current flows in a substantially closed measuring line due to the voltage induced in the measuring line, which is then compensated for by its ohmic voltage drop, making it significantly less susceptible to interference with external AC magnetic fields. The current measuring device is therefore very suitable for use in fast-switching power semiconductors, such as power converters, where a phase-corrected measurement of the AC current for adjusting harmonics at high frequencies is advantageous.

[0047] In one embodiment of the device, the circuit board comprises a further conductor path, designed as a configurable compensation structure for further compensating for the above-mentioned effects and arranged in the resistance area. The conductor path of the compensation structure is electrically connected in series with one of the measurement lines and extends the measurement line at this point. In particular, the compensation structure can be electrically arranged between the measurement line that extends into the measurement line area and the tapping point or can be connected to an interruption of the measurement line. Due to the series connection of the measurement line and the compensation structure, the voltage induced in the conductor path of the compensation structure overlaps with the voltage induced in the measurement line.

[0048] The compensation structure comprises compensation paths consisting in particular of conductor paths extending over a surface aligned perpendicular to the surface of the busbar and parallel to the direction of current flow, the compensation paths in particular including conductor paths arranged in different planes or layers of the printed circuit board and running essentially parallel to one another, and through contact holes, so-called vias, which interconnect the conductor paths in the different planes.

[0049] The compensation path may consist of two compensation arms pointing in opposite directions. Here, the compensation arm may for example start from the connection point and comprise a first conductor path in a first layer of the printed circuit board, a via from the first layer to the second layer, a second conductor path in the second layer of the printed circuit board running parallel to the first conductor path back to the connection point, and a further via from the second layer of the printed circuit board to the first layer. The other compensation arm of the compensation path may be designed to be mirror-inverted with respect to the first compensation arm, i.e. to run in the opposite direction to the first compensation arm and also parallel to the longitudinal axis of the resistive area. Using an electrical connector such as a wire bridge connecting one or the other of the compensation arms to the measurement line allows the selection of which compensation arm is added to the measurement line, and compensation with different signs may be realized by a mirror image structure of the compensation arms. Alternatively, the entire compensation path may be bridged with a wire bridge.

[0050] In one embodiment of the device, multiple compensation paths can be arranged spatially parallel to each other and can be electrically connected in series. Here, the compensation paths preferably have different lengths and therefore span different sized surfaces resulting in different compensation contributions. A further electrical connector allows the selection of which compensation arm of which compensation path is connected to the measurement line, and the individual compensation paths are bridgeable by appropriate connectors and inactive to that extent. This allows various combinations with different stacked spread surfaces, resulting in compensation contributions from zero (no compensation arm connected) to some intermediate values ​​(one or more compensation arms connected in the same or opposite orientation) to a maximum value (all compensation paths connected in the same orientation).

[0051] It will be understood that the device for determining the current has a busbar and a printed circuit board for acquiring the measurement values, and that a printed circuit board having the above-mentioned configuration can essentially be arranged on a busbar having resistive areas and voltage taps, in particular, where the printed circuit board with the compensation structure is largely independent of the specific shape of the busbar or the specific realization of the resistive areas in the busbar.

[0052] In a power converter with current carrying lines for conducting direct and / or alternating currents processed by the power converter, at least one of the current carrying lines has a current determining device, which bridges the interruption of the at least one current carrying line or is integrated in the at least one current carrying line, the power converter is configured to determine the current flowing in the current carrying line during operation of the power converter by using a voltage difference along a resistive area of ​​the busbar detected by measuring contacts, the power converter being designed for a nominal power of more than 10 kW, preferably more than 100 kW, particularly preferably more than 1000 kW.

[0053] The high measurement accuracy achievable with the busbars of the present application allows for a reduced amount of hardware reserve to be maintained in the power converter and / or allows for a higher nominal power to be achieved using other hardware present in the power converter.

[0054] In one embodiment, the power converter comprises a multi-channel device for determining a current, the multi-channel device comprising a multi-channel busbar having at least two individual connection areas for connecting a plurality of conductive lines on a first side and a common busbar on a second side as a common connection area, where each individual connection area is assigned a resistive area arranged between the respective individual connection area and the busbar.

[0055] Here, the multi-channel busbar essentially comprises a parallel circuit of resistive areas of the same or different dimensions through which different currents flow, which are measured via respective voltage drops between the measuring contacts of the respective resistive areas. Here, each of the resistive areas has an optimized current shadow shape as described above. The multi-channel busbar comprises first connection areas electrically isolated from each other on one side and respective resistive areas electrically and mechanically connected to each other on the other side of the multi-channel busbar, such that a common second connection area is formed. Such a multi-channel busbar can be used, for example, in the DC input section of a central inverter of a PV system (photovoltaic power system) to, on the one hand, measure the PV input currents of several strings of photovoltaic modules individually and, on the other hand, supply them as a combined total PV current to the PV busbar.

[0056] The use of multi-channel busbars can realize material cost savings compared to multiple single-channel busbars. Manufacturing and assembly can be simplified, and logistics efforts can be reduced.

[0057] In one embodiment of the power converter, a printed circuit board for measurement acquisition is arranged plane-parallel to the busbar, in particular arranged plane-parallel on the busbar, the printed circuit board covering the multiple resistive areas and connected to the measurement contacts of the multiple resistive areas. By using a common printed circuit board for the multi-channel busbar, various components can be omitted, since various components such as power supplies, microprocessors, analog-to-digital converters, communication drivers, wiring, etc. only need to be realized individually instead of multiple times.

[0058] In one embodiment of the power converter, the circuit board has an evaluation unit for preprocessing the measured voltages and optionally the temperatures of the individual resistance areas, and a galvanic isolation, the evaluation unit being connected to the control unit of the power converter via a galvanic isolation. The use of a common printed circuit board for the measurement electronics with galvanic isolation from the communication means or the surrounding electronics has the advantage that the galvanic isolation has to be provided only once for several measurement channels, which allows cost advantages. This is particularly advantageous when the measurement electronics must be galvanically isolated from the surroundings, for example when high DC voltages occur at the DC input of the PV inverter. Here, this isolation can be set only once, rather than individually for each single-channel busbar.

[0059] In a further embodiment, the printed circuit board of the multi-channel busbar has slots, which are arranged between the resistor areas and extend parallel to the longitudinal center axis from one edge of the printed circuit board over at least half the length of the printed circuit board. These slots can also be arranged next to each other in pairs starting from the opposite edge. They divide the printed circuit board into individual sub-areas that are movable relative to each other and are individually assigned to the respective resistor areas. As a result, the printed circuit board can follow the mutual deformations of the individual resistor areas or connection areas of the multi-channel busbar, thus preventing not only twisting of the printed circuit board but also partial lifting of the printed circuit board from the surface of the busbar in the event of such deformations.

[0060] The power converter has current carrying lines for carrying direct and / or alternating currents processed by the power converter. At least one of the current carrying lines comprises a device for determining the current according to the previous description, which device bridges the interruption of the current carrying line or is integrated in the current carrying line. The power converter is set to determine the current flowing through the current carrying lines during operation of the power converter from the voltage difference along the resistive area detected by the measuring contacts and the resistance value of the resistive area. Here, the resistance value used for the corresponding calculation of the current intensity can be a function of the temperature detected by the temperature sensor.

[0061] In a preferred embodiment, the power converter is designed for a nominal power of more than 10 kW, preferably more than 100 kW, particularly preferably more than 1000 kW. In these power classes, the determination of the direct and / or alternating currents processed by the power converter is particularly demanding due to their correspondingly large amplitudes and can be performed particularly accurately with the described current determination device, which can be particularly easily integrated into the structure of the power converter. [Brief description of the drawings]

[0062] The subject matter of the present application will be further explained and described below with reference to the embodiments illustrated in the drawings.

[0063] [Figure 1] 1a to 1c show schematic diagrams of embodiments of busbars for measuring current. [Diagram 2] 2a and 2b show diagrammatically further embodiments of busbars for measuring current. [Diagram 3] Figure 3a shows a further embodiment of a busbar for measuring current, and Figure 3b shows a schematic representation of an embodiment of a device for measuring current. [Figure 4] FIG. 4 illustrates a schematic of one embodiment of a multi-channel device for determining current. [Diagram 5] 5a to 5c show a schematic representation of an embodiment of a printed circuit board of a device for determining an electric current.

[0064] In the drawings, the same or similar elements are given the same reference numbers. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0065] 1a to 1c show diagrammatically a busbar 11 for measuring current according to the present application.

[0066] The busbar 11 shown in FIG. 1a has two connection areas 11a opposite each other and a resistive area 11b arranged between the connection areas 11a, where the cross-sectional area of ​​the busbar 11 is reduced compared to the connection areas 11a. The reduction in the cross-sectional area is brought about in the illustrated busbar 11 by a reduction in the width of the busbar 11 in the resistive area 11b, alternatively or additionally the thickness of the busbar 11 in the resistive area 11b can be reduced compared to the connection areas 11a. The busbar is integrally formed and is preferably made from a single material, for example copper or aluminum. By connecting a current-carrying conductor (not shown) to one connection area 11a and continuing the conductor in the other connection area 11a, the busbar 11 bridges the interruption of the conductor. When a current flows in the conductor, the same current also flows in the busbar 11, i.e. from one connection area 11a through the resistive area 11b to the other connection area 11a.

[0067] The illustrated busbar 11 is structured essentially symmetrically with respect to the longitudinal central axis LA and the transverse central axis QA. Two measuring contacts 12 are arranged in the region of the longitudinal central axis LA. The two measuring contacts 12 are arranged essentially symmetrically with respect to the transverse central axis QA. A voltage or potential difference between the measuring contacts 12 can be detected via the measuring contacts 12. From this voltage difference, the value of the current flowing in the busbar 11 can be determined by utilizing the electrical resistance of the material of the resistive area 11b connecting the two measuring contacts 12.

[0068] The measurement contacts 12 are preferably designed as press-fit pins, which offers manufacturing advantages, e.g. in terms of precision. The above statements apply analogously to the busbars 11 shown in figures 1b and 1c.

[0069] The busbar 11 shown in FIG. 1a has recesses 4 adjacent to each of the measurement contacts 12 and each spaced slightly apart from the measurement contacts 12 in the direction of the longitudinal central axis LA. The recesses 4 are arranged in such a way that they generate a so-called current shadow at the measurement contacts 12, which means that the current essentially flows around the recesses 4 and thus the measurement contacts 12 barely pass any current because they are arranged in close proximity to the recesses 4. This allows to increase the measurement accuracy of the voltage drop between the measurement contacts 12. Here, the recesses 4 are arranged laterally, in particular perpendicularly to the longitudinal central axis LA. The measurement contacts 12 are arranged between the recesses 4, since they are also essentially symmetrical with respect to the longitudinal central axis LA and essentially symmetrical with respect to each other with respect to the transverse central axis QA. In an alternative embodiment (not shown), the measurement contacts 12 can also be arranged opposite the respective recesses 4, such that the recesses 4 are arranged between the measurement contacts 12.

[0070] The busbar 11 shown in FIG. 1b has two recesses 4 adjacent to each of the measurement contacts 12, which are arranged on opposite sides of the measurement points 12 as seen in the direction of the longitudinal central axis LA and extend substantially laterally, in particular perpendicularly to the longitudinal central axis LA. The recesses 4 are arranged in such a way that they generate a so-called current shadow at the measurement contacts. This means that the current essentially flows around the recesses 4 arranged in pairs and does not reach the measurement contacts 12. Due to the arrangement of the recesses 4, a large part of the area of ​​the measurement contacts 12 is therefore free of current. In comparison with the busbar 11 in FIG. 1a, the effect of this current shadow can be further improved by arranging the recesses 4 in pairs for each measurement contact 12, which can further improve the measurement accuracy. Here, the recesses 4 can be formed essentially symmetrically with respect to the longitudinal central axis LA. The two recesses 4 in the area of ​​the measurement contacts 12 are also essentially symmetrical, in particular essentially point-symmetrically with respect to the measurement contacts 12. At the same time, the two recesses 4 arranged in the area of ​​the measurement contacts 12 can be essentially axially symmetrical with respect to one another with respect to an axis passing through the measurement contacts 12. The recesses 4 of the measurement contacts 12 may also be arranged substantially symmetrically with respect to the central lateral axis QA with respect to the recesses 4 of the other measurement contacts 12 .

[0071] The busbar 11 shown in FIG. 1c has recesses 4 adjacent to each of the measurement contacts 12. Here, the recesses 4 are arranged laterally, in particular perpendicular to the longitudinal central axis LA. They are also formed essentially symmetrically with respect to the longitudinal central axis LA. The two recesses 4 are also arranged substantially symmetrically with respect to one another with respect to the transverse central axis QA. The busbar 11 also has a further recess 4a between the two measurement contacts 12. The further recess 4a is here arranged in the region of the longitudinal central axis LA and / or the transverse central axis QA. The further recess 4a can, for example, be formed essentially symmetrically with respect to the longitudinal central axis LA and / or the transverse central axis QA and in particular can be directly adjacent to both measurement contacts 12.

[0072] The recesses 4 and 4a are arranged in such a way that they form a so-called current shadow at the measurement contact 12, which means that the current essentially flows around the recesses 4, 4a arranged along the longitudinal central axis LA and is essentially conducted to the current-carrying area on the side of the recesses 4, 4a, so that in particular the measurement contact 12 is mainly current-free due to the arrangement of the recesses 4, 4a. The further recess 4a results in an even lower current density in the area of ​​the measurement contact 12 and a more uniform current density in the current-carrying area of ​​the resistance area 11b. This allows the measurement precision to be further increased.

[0073] Figures 2a and 2b show diagrammatically a busbar 11 for measuring current according to the present application.

[0074] The busbar 11 shown in FIG. 2a has two connection regions 11a opposite each other and a resistive region 11b arranged between the connection regions 11a, resulting in a reduced cross-sectional area of ​​the busbar 11 compared to the connection regions 11a. In the illustrated busbar 11, the reduction in the cross-sectional area is achieved by reducing the width of the busbar 11 in the resistive region 11b, but can also be achieved by reducing the thickness of the busbar 11 in the resistive region 11b. The busbar is integrally formed and is preferably made from a single material, for example copper or aluminum. When the busbar 11 bridges an interruption in a current-carrying conductor (not shown), a current flows through the busbar 11 from one connection region 11a through the resistive region 11b to the other connection region 11a.

[0075] The illustrated busbar 11 is structured essentially symmetrically with respect to the longitudinal central axis LA and the transverse central axis QA. The two measuring contacts 12 are arranged in the region of the longitudinal central axis LA. The two measuring contacts 12 are arranged essentially symmetrically with respect to the transverse central axis QA. A voltage or potential difference between the measuring contacts 12 can be detected via the measuring contacts 12. By utilizing the electrical resistance of the material of the resistive area 11b connecting the two measuring contacts 12, the value of the current flowing in the busbar 11 can be determined from this voltage difference. The measuring contacts 12 are preferably designed as press-fit pins, which offers manufacturing advantages, for example in terms of precision.

[0076] The connection areas 11a of the embodiment according to Fig. 2a and 2b have edge-side extensions in the direction of the busbar centre, which run in a taper as protrusions 21 or lugs. The protrusions 21 extending towards each other from opposite connection areas 11a are separated from each other by gaps at the edge of the busbar 11 so that the current flows only through the resistive areas 11b. Fasteners, for example in the form of pins 15 (preferably press-in pins), can preferably be provided on the protrusions 21, by means of which the busbar 11 can be fixed to other components and / or to printed circuit boards 2, 20 (see Fig. 3b-4) for making electrical contacts, if required, on the busbar 11. The pins 15 are preferably of the same design as the measurement contacts 12. This allows further simplifying the manufacture. The above description applies analogously to the busbar 11 shown in Fig. 2b.

[0077] The busbar 11 shown in FIG. 2a has a recess 4 around each of the two measurement contacts 12, which recess surrounds the respective measurement contact 12 on three sides, the "open" faces preferably facing each other. The recesses 4 are arranged in such a way that the current essentially flows around the recesses 4 and does not reach the measurement contacts 12, so that the area of ​​the measurement contacts 12 is almost current-free. The recesses 4 can have the curvature of at least a partially circular segment or consist of three or more straight segments. The two recesses 4 can preferably be arranged essentially symmetrically with respect to one another with respect to the transverse central axis QA. Each of the recesses 4 can itself be formed essentially symmetrically with respect to the longitudinal central axis LA. The above explanations apply analogously to the busbar 11 shown in FIG. 2b.

[0078] The busbar shown in FIG. 2b also has two further recesses 4, which are arranged in the region of the longitudinal central axis LA so as to intersect the longitudinal central axis LA in the longitudinal center and extend from the respective measurement contact 12 to just before the transverse central axis QA. The two further recesses 4 are also arranged essentially symmetrically with respect to each other with respect to the transverse central axis QA, so that only a narrow crosspiece remains in the region of the transverse central axis QA, where further measurement points, such as for example temperature sensors, can be arranged. The current flows essentially around the recesses 4 arranged along the longitudinal central axis LA and essentially in the current-carrying areas to the sides of the recesses 4. This further improves the current shadow of the measurement contacts 12 and further improves the uniformity of the current density in the current-carrying areas of the resistor areas 11b remaining to the sides of the recesses 4.

[0079] 3a shows a schematic representation of an embodiment of a busbar 11 for measuring electrical current according to the present application. The busbar 11 has four recesses 4, each of which semicircularly surrounds a measurement contact 12. The temperature sensor 3 is arranged between two recesses 4 which are central with respect to the longitudinal central axis LA.

[0080] The busbar 11 according to Fig. 3a, like the busbar 11 described above in Figs. 1a, 1b, 1c, 2a, 2b, has two connection areas 11a opposite each other and a resistive area 11b arranged between the connection areas 11a, which reduces the cross-sectional area of ​​the busbar 11 compared to the connection areas 11a. In the illustrated busbar 11, the reduction in the cross-sectional area is achieved by a reduction in the width of that resistive area 11b of the busbar 11, which may alternatively or additionally include a reduction in the thickness. The busbar is integrally formed and is preferably made from a single material, for example copper or aluminium. When the busbar 11 bridges an interruption of a current carrying conductor (not shown) connected to the connection areas 11a, a current flows through the busbar 11 and is conducted from one connection area 11a via the resistive area 11b to the other connection area 11a.

[0081] The busbar 11 is essentially symmetrical with respect to a longitudinal center axis LA, which runs in the longitudinal direction of the busbar 11 from one connection area 11a to the opposite connection area 11a through the resistance area 11b. The measurement contacts 12 are preferably arranged in the area of ​​the longitudinal center axis LA. The illustrated busbar 11 can also be structured essentially symmetrically with respect to a transverse center axis QA. The two measurement contacts 12 can be arranged essentially symmetrically with respect to the transverse center axis QA. A voltage or potential difference between the measurement contacts 12 can be detected via the measurement contacts 12. By utilizing the electrical resistance of the material of the resistance area 11b connecting the two measurement contacts 12, the value of the current flowing in the busbar 11 can be determined from this voltage difference. The measurement contacts 12 are preferably designed as press-fit pins, which offers manufacturing advantages, for example in terms of precision.

[0082] The connection area 11a has an edge-side extension in the direction of the busbar centre, which extends as a lug into a protrusion 21 or taper. The protrusions 21 extending towards each other from opposite connection areas are separated from each other by gaps at the edge of the busbar 11, so that the current flows exclusively through the resistance area 11b. Preferably, fasteners can be provided, for example in the form of pins 15 (not shown, see Fig. 2a, 2b) (preferably press-fit pins), by which the busbar 11 can be fastened to other components and / or, for example, to a printed circuit board 2, 20 (see Fig. 3b, 4) on the busbar 11 and optionally electrically contacted thereto. The pins 15 can be of the same design as the measurement contacts 12.

[0083] In the region of each of the two measurement contacts 12, the busbar 11 shown in FIG. 3a has a measurement point flat 5 on which the measurement contacts 12 are arranged. On the two opposite sides of each measurement point flat 5, a recess 4 is located in each case, which recess 4 partially surrounds the measurement point flat 5 in the form of a circular arc. The recess 4 can have an at least partially circular cross-sectional curvature on the side facing the respective measurement point flat 5. Here, the recess 4 of a measurement contact 12 is preferably arranged substantially symmetrically with respect to the recess 4 of the other measurement contact with respect to the transverse central axis QA, so that the measurement point flats 5 are also symmetrical with respect to one another with respect to the transverse central axis QA.

[0084] Each of the recesses 4 extends laterally, in particular perpendicularly to the longitudinal central axis LA, and can itself be formed essentially symmetrically with respect to the longitudinal central axis LA. The recesses 4 can each have a width of 2 to 10 millimeters in the direction of the longitudinal central axis. The two recesses 4 arranged in the region of the measurement contacts 12 can be formed essentially symmetrically with respect to the measurement contacts 12, in particular essentially point-symmetrically with respect to the measurement contacts 12 and / or essentially axially symmetrically with respect to an axis extending through the measurement contacts 12.

[0085] Since the current flows around the recess 4 and does not reach the measuring point flat 5, there is essentially no current through the recess 4 at the measuring point flat. The measuring point flat 5 is then connected in each case only via two connecting crosspieces 9 to the current-carrying area of ​​the resistance area 11b. The connecting crosspieces 9 can extend laterally, in particular perpendicularly to the longitudinal central axis LA, so that the current flowing essentially parallel to the longitudinal central axis LA does not penetrate the connecting crosspieces 5 or only to a very small extent. Via the connecting crosspieces 5, the associated measuring point flat 5 is at a potential corresponding to the potential of the interface between the connecting crosspiece 5 and the current-carrying area of ​​the resistance area 11b, so that the voltage difference between the measuring contacts 12 essentially corresponds to the voltage difference between these interfaces.

[0086] The connecting crosspieces 9 can have a width, i.e. an extension in the direction of the longitudinal central axis LA, of 2 to 5 millimeters. The measuring point flats 5 can have a longitudinal extent, i.e. an extent in the direction of the longitudinal central axis LA and / or the transverse central axis QA, of 5 to 12 millimeters. Thus, the busbar 11 shown in FIG. 3a can be produced, for example, in a low-cost stamping process, since it has a minimum size of dimensions and structures (recesses 4 and the remaining crosspieces) of 3 mm.

[0087] The temperature sensor 3 can be positioned in the middle of the resistance area 11b and in the middle between the measurement contacts 12, so that the temperature is measured exactly in the middle area of ​​the voltage drop between the measurement contacts 12. As a result, temperature-induced changes in the resistance of the material of the busbar 11 in the resistance area 11b of the busbar 11 can be optimally compensated in connection with the determination of the current flowing through the busbar 11. The average value of the corresponding voltage or temperature from the respective adjacent and oppositely located current-carrying areas of the busbar 11 is available to the temperature sensor 3 as well as to the measurement contacts 12. Thus, non-uniform current or temperature distributions in the opposite current-carrying areas of the busbar 11 do not lead to falsification of the measured values.

[0088] In one embodiment (not shown), two temperature sensors can be arranged in the current carrying area of ​​the busbar. This is particularly useful if mutually facing recesses 4 are joined together to form a common recess 4a, with no material remaining along the longitudinal center axis LA between the measurement point flats (see FIG. 1c). The two temperature sensors are preferably arranged on the transverse center axis and essentially symmetrically with respect to the longitudinal center axis, i.e. in particular in the current carrying areas to the sides of the recess 4. This improves the response behavior of the current measurement in case of sudden changes in the current intensity to be measured, since the measurement is performed directly at the point where heat is generated, i.e. essentially in the current carrying area of ​​the resistive area.

[0089] Figure 3b shows a device 10 for determining electric currents with the busbar 11 of Figure 3a and the printed circuit board 2. The printed circuit board 2 can be arranged on the busbar and fixed on the busbar 11, in particular on the projections 21, by means of pins 15 (see Figures 2a, 2b), which can for example be of the same design as the measuring contacts 12.

[0090] The printed circuit board 2 can be arranged on the surface of the resistance area 11b with almost no space. Thus, the conductor paths in the printed circuit board 2 connecting the measurement contacts 12 as measurement lines 6a, 6b, 7a, 7b to an evaluation unit 18 (not shown) for determining the voltage drop between the measurement contacts 12 are also located close to the surface of the resistance area 11b, and conductor loops during voltage measurements are largely prevented. The shape of the arrangement of the measurement lines 7a, 7b on the printed circuit board 2 can be largely independent of the shape of the busbar and the shape of the current shadow, but it is advantageous if the measurement lines 7a, 7b do not extend through the recess 4 but over the remaining material of the resistance area 11b. Thus, the printed circuit board 2 as shown in FIG. 3b can also be used in conjunction with other busbars 11, for example of FIGS. 1a, 1b, 1c, 2a, 2b. The arrangement of the measurement lines 7a, 7b can be adapted accordingly.

[0091] The measurement lines 7a, 7b are therefore installed as conductor paths in the printed circuit board 2 in such a way that the frequency-dependent phase measurement errors are reduced. The measurement lines 7a, 7b for connecting the measurement contacts 12 to an evaluation unit 18 (not shown) can be installed as conductor paths in the printed circuit board 2 along paths on the surface of the busbar 11 such that the phase errors are significantly reduced compared to a less optimized installation of the measurement lines 7a, 7b. In the example of the device 10 shown in FIG. 3b, the measurement lines 7a, 7b start from the measurement contacts 12, spread over a polygonal shaped measurement line area 8 and are gathered at a common tapping point 6 via measurement tapping lines 6a, 6b. A suitable evaluation unit 18 (not shown) can acquire the potential of the two measurement contacts 12 at the tapping point 6. The measurement lines 7a, 7b can run essentially partially symmetrically with respect to the longitudinal and / or lateral central axes of the resistance area.

[0092] The measuring line area 8 can in particular extend in the shape of a polygon, for example a hexagon, which can have an axis of symmetry running along the central transverse and / or longitudinal axis. The width of the polygon can be approximately 70-100% or 70-85% of the width of the resistive area. The sides of the polygon can also be formed by a number of conductor paths running in parallel.

[0093] In one embodiment of the device 10 , the temperature sensor 3 and the evaluation unit 18 (not shown) may be arranged on the side of the printed circuit board 2 opposite the busbar 11 .

[0094] FIG. 4 shows a multi-channel device 13 for determining electrical current having a multi-channel busbar 14 with a printed circuit board 20 disposed thereon.

[0095] The multi-channel busbar 14 has on a first side four individual connection areas 11a with connection elements 22 for connecting a plurality of current-carrying wires. 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 wire. Each of the individual connection areas 11a is assigned a resistance area 11b arranged between the respective individual connection area 11a and the common busbar 16. Here, the multi-channel busbar 14 essentially has a parallel circuit of resistance areas 11b of identical or different dimensions through which different currents flow, which currents are measured via respective voltage drops between the measuring contacts 12 of the respective resistance areas 11b. The resistance areas 11b have the optimized current shadow shape described above. The multi-channel busbar 14 has first connection areas 11a electrically isolated from one another on one side and respective resistance areas 11b electrically and mechanically connected to one another on the other side of the multi-channel busbar, such that a common second connection area is formed in the form of a common busbar 16.

[0096] In the illustrated example, the shape of the respective resistance area 11b corresponds to the shape of the busbar 11 of FIG. 3a. The resistance area 11b has one or more temperature sensors 3 corresponding to the busbar 11 of FIG. 3a, the measuring contacts 12 are located on the measuring point flats 5 corresponding to the busbar 11 of FIG. 3a and are connected to the current carrying areas of the resistance area 11b by means of the connecting crosspieces 9. The arrangement and shape of the recesses 4 can also correspond to the arrangement and shape of FIG. 3a, the transverse central axis QA and the longitudinal central axis LA being shown corresponding to FIG. 4. It is also possible to build a multi-channel busbar from individual busbar shapes, for example corresponding to the busbars 11 of FIG. 1a, 1b, 1c, 2a, 2b.

[0097] A printed circuit board 20 for measurement acquisition is arranged in a plane parallel to the busbar 14, the printed circuit board 20 covering the multiple resistive areas 11b and connected to the measurement contacts 12 of the multiple resistive areas 11b. Measurement lines are arranged in the printed circuit board 20 and can be formed in a similar manner to the one shown in FIG. 3a, in particular wired as conductor paths in the printed circuit board 20. Measurement values ​​are transmitted from the measurement contacts 12 to the evaluation unit 18 via the measurement lines. Various components, such as, for example, galvanic isolation 17, power supply, evaluation unit 18, A / D converter, communication drivers, wiring, etc., can be omitted by using a common printed circuit board 20 for the multi-channel busbar 14, since they only have to be realized singly and not severally.

[0098] For the reasons already mentioned, it is desirable to arrange the printed circuit board 20 on the multi-channel busbar 14 as flush as possible with the surface. During operation of the busbar 14 in the power converter, thermal and electromechanical effects acting on the multi-channel busbar 14, especially at high operating currents, can lead to deformations of the individual resistor areas 11b relative to the multi-channel busbar 14, in particular relative to each other, and / or deformations of the printed circuit board 20. Such deformations can lead to at least partial lifting of the printed circuit board 20 away from the multi-channel busbar 14. The lifting of the printed circuit board 20 from the surface of the multi-channel busbar 14 can be compensated by slots 19 in the printed circuit board 20, which are respectively arranged between the resistor areas 11b and extend from one edge of the printed circuit board 20 parallel to the longitudinal centerline LA over at least half the length of the printed circuit board 20. The slots 19 allow a slight "twisting" of the sections of the printed circuit board 20 assigned to the individual resistor areas 11b relative to each other. As a result, the printed circuit board 20 is able to follow on a cross-sectional basis the deformations of the individual resistive areas 11b or connecting areas 11a relative to one another, thus reducing the mechanical stress on the device 13.

[0099] 5a-5c show an embodiment of a printed circuit board of a device for determining electric current in different views. FIG. 5a shows a printed circuit board 2 which can be arranged on a busbar 11 (not shown here) in a similar manner to FIG. 3b and which can capture the voltage drop across the resistive area 11b of the busbar 11 by means of a measuring contact 12. For this purpose, the printed circuit board 2 has measuring lines 7a, 7b which extend into the measuring line area 8 and connect the measuring contact 12 to the measuring tapping lines 6a, 6b and the tapping point 6. The printed circuit board 2 also has a compensation structure 30 which is preferably arranged in the resistive area of ​​the busbar 11 and which is electrically connected in series with the measuring line 7b via a further measuring tapping line 6c.

[0100] A compensation structure 30 with a particular configuration is shown enlarged in FIG. 5b. Here, solid lines represent conductor paths 31 in the first layer (layer #1) of the printed circuit board 2, dashed lines represent conductor paths 32, and dotted lines represent conductor paths 33 in the second layer (layer #2) or the third layer (layer #3) 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 a number of compensation paths 40a, 40b, 40c, 40d, which are arranged parallel to each other and parallel to the longitudinal axis of the busbar 11 when the printed circuit board 2 is placed on the busbar 11. Each of the compensation paths 40a, 40b, 40c, 40d has two oppositely directed compensation arms, which will be described in more detail below in connection with FIG. 5c.

[0101] In the exemplary specific configuration according to Fig. 5b, only one compensation arm of the second compensation path 40b is connected to the measurement line 7b. Starting from the measurement tapping line 6c, the circuit described below arises as an extension of the measurement line 7b. The conductor path 31 in layer #1 ends along the horizontal central axis of the compensation structure 33, initially at a soldering point 34 associated with the compensation path 40a. By means of an electrical connector, here for example by means of a bridge 41, this soldering point 34 is connected to another soldering point 34 on the central axis, so that the compensation path 40a is bridged, i.e. in this example the compensation path 40a is not used. Going further, the conductor path 31 reaches the next soldering point 34 associated with the compensation path 40b. A further bridge 41 connects the conductor path 31 to a soldering point 34 associated with the upper compensation arm of the compensation path 40b and coinciding with a via 35 between layers #1 and #2, so that the conductor path 31 is connected to the conductor path 32 in layer #2 via the bridge 41 and the via 35. At the outer end point of the compensation arm, the conductor path 32 is connected to a conductor path 33 in layer #3 of the printed circuit board 2 via a via 36 between layers #2 and #3, which returns to the via 36 at the central axis of the compensation structure 30. From there, the conductor path 32, the via 35 and the conductor path 31 in layer #2 lead to the soldering point 34 associated with the compensation path 40c. In this example, the compensation paths 40c and 40d are also not used and are in any case bypassed by the bridge 41. Finally, the conductor paths 32 on both sides of the central axis of the compensation structure return to the measurement tapping wire 6c, where they are joined.

[0102] It will be understood that the number of the four compensation paths 40a-40d, as well as their respective lengths and order, should be understood as merely an example, and a compensation structure 30 having any number of further compensation paths is contemplated, each of which may be used by connecting one of the respective compensation arms to the measurement line 7b, or may be bridged and not used.

[0103] Figure 5c shows a detailed view of the compensation path 40b of Figure 5b. The conductor path 31, which according to Figure 5b is finally connected to the measurement tapping line 6c, is connected by a bridge 41 to a conductor path 32 belonging to one of the two compensation arms of the compensation path 40b. This compensation arm is formed by the respective section of the conductor path 32 in layer #2, the via 36 between layers #2 and #3, the section of the conductor path 33 in layer #3 and a further via 36, ​​so that the compensation arm forms an approximately closed conductor loop oriented perpendicular to the surface of the printed circuit board (and therefore perpendicular to the busbar 11) and parallel to the longitudinal central axis LA of the busbar. Due to the absence of a correspondingly arranged bridge, the other compensation arm of the compensation path 40b is not connected to the measurement line 7b and is therefore not used.

[0104] Instead of the upper compensation arm of the compensation path 40b, if necessary, the lower compensation arm of the compensation path 40b can be connected to the measurement line 7b by a correspondingly arranged bridge 41, or the compensation path 40b is not used and is bridged by a correspondingly arranged bridge 41. Also, individual or several compensation arms of the other compensation paths 40a, 40c and / or 40d can be connected to the measurement line by suitably arranged bridges 41. It should be noted that the compensation arms of the compensation paths directed in opposite directions cause compensation effects of different signs but the same magnitude.

[0105] The compensation paths 40a-40d preferably span surfaces having different cross-sectional areas. For this purpose, both the length of the arms, i.e. the width of the respective spread surface, and the distance between the opposing conductor paths, i.e. the height of the spread area, can be appropriately selected. Furthermore, the compensation arms can be composed of several loops, whereby the spread surface increases accordingly.

[0106] In a particular embodiment, the length of the compensation arm is at least 1 millimeter and at most 20 millimeters. The distance between the conductor paths of the compensation arm in different planes of the printed circuit board is limited by the thickness of the printed circuit board and the number of planes in the printed circuit board, and is about 0.2 millimeters to about 10 mm.

[0107] As a result of the differently sized extended surfaces of the compensation paths 40a-40d, a large number of combination options are obtained with different compensation effects in each case. In the particular example according to Fig. 5b, a total of 15 different combinations can be created by using the upper compensation arm, a further 15 different combinations of the lower compensation arm, and several mixed forms using lower and upper compensation arms, which have different compensation effects with different amplitudes and possibly different signs, especially when the extended surface increases with a power of two.

[0108] In the particular application of the printed circuit board 2 according to FIG. 5a, for example in a device 10 according to FIG. 3b, in a particular embodiment, a calibration measurement can be used to determine which effects influence the measurement result and to what extent. For this purpose, for example a defined current can be applied to the busbar 11 and the voltage signal detected at the tapping point 6 can be evaluated, while all compensation paths 40a-40b are bridged and in so far the compensation structure is inactive. Depending on a detected falsification of the measurement value, which may for example include a non-linearity of the voltage signal with respect 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 measurement line 7b in order to minimize undesirable effects of the measured current on the measurement lines 7a, 7b and thus on the measurement result. As a result, a configuration of the compensation structure is defined which permanently ensures an optimal compensation of undesirable effects and minimizes measurement errors, in particular of the frequency-dependent phase and amplitude. In the case of a multi-channel busbar 14 according to FIG. 4, this configuration can be defined individually for the measurement of the individual channels in order to optimize the measurement of the individual channels individually. [Explanation of symbols]

[0109] 2. Printed Circuit Board 3 Temperature Sensor 4, 4a Recess 5 Measurement point flat area 6a, 6b, 6c Measuring tapping wire 7a, 7b measurement line 8 Measuring line area 9 Connecting crosspiece 10. Apparatus for determining electric current 11 Busbar 11a Connection area 11b Resistance area 12 Measurement junction 13 Multichannel device for determining electrical current 14 Multi-Channel Busbars 15-pin 16 Common busbar 17 Galvanic isolation 18 Evaluation Units 19 Slots 20 Printed Circuit Board 21 Convex 22 Connection elements 30 Compensation structure 31 Conductor path in layer #1 32 Conductor path in layer #2 33 Conductor path in layer #3 34 Soldering points 35 Via between layer #1 and layer #2 36 Via between layer #2 and layer #3 40a~d Compensation route 41 Bridge LA Longitudinal central axis QA lateral center axis

Claims

1. A busbar (11, 14) for measuring direct and / or alternating currents, in particular of current strengths above 100 Amperes, comprising connection areas (11a) and at least one resistance area (11b) arranged between said connection areas (11a) and with two measurement contacts (12) arranged in said resistance area (11b), the busbars (11, 14) have a shape such that essentially no current flows in the area of ​​the measurement contacts (12) during operation of the busbars (11); The busbars (11, 14) are integrally formed.

2. The busbar (11, 14) according to claim 1, wherein the resistance region (11b) is essentially formed by a taper of its cross section relative to the cross section of the connection region (11a) of the busbar (11, 14), said taper being formed in particular by reducing 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. 3. The busbar (11, 14) according to claim 1 or 2, wherein the busbar (11, 14) has a central longitudinal axis (LA) extending in the longitudinal direction of the busbar (11, 14) from one of the connection areas (11a) to the opposite connection area (11a) through the resistance area (11b), the measurement contacts (12) being arranged in the area of ​​the central longitudinal axis (LA), and the busbar (11, 14) is essentially symmetrical about the central longitudinal axis (LA) at least between the associated connection areas.

4. 3. The busbar (11, 14) according to claim 1 or 2, wherein the busbars (11, 14) are essentially symmetrical, at least between associated connection areas (11a), about respective transverse central axes (QA) extending transversely of the busbars (11, 14) centrally between the respective connection areas (11a), and the measurement contacts (12) are arranged essentially symmetrically about the transverse central axes (QA).

5. 3. The busbar (11, 14) according to claim 1 or 2, wherein the shape of the resistance region (11b) has at least two recesses (4, 4a), which are arranged in the region of the measurement contacts (12) and are spaced apart in the longitudinal direction from the measurement contacts (12), in particular one of the recesses (4, 4a) being arranged in the region of each measurement contact (12).

6. 3. The busbar (11, 14) according to claim 1 or 2, wherein at least one temperature sensor (3) is arranged between the measurement contacts (12), in particular in the region of the longitudinal central axis (LA) and / or the transverse central axis (QA).

7. 3. The busbar (11, 14) according to claim 1 or 2, wherein recesses (4a) are arranged between the measurement contacts (12), the recesses (4a) being essentially symmetrical with respect to the longitudinal centre axis (LA) and / or the transverse centre axis (QA), in particular intersecting the transverse centre axis (QA).

8. 3. The busbar (11, 14) according to claim 1 or 2, wherein the longitudinal central axis (LA) forms an axis of symmetry of one or more recesses (4, 4a) and / or at least two recesses (4, 4a) are arranged essentially symmetrically with respect to a transverse central axis (QA).

9. 3. The busbar (11, 14) according to claim 1 or 2, wherein a recess (4, 4a) is arranged on either side of each measurement contact (12), the recesses (4, 4a) being formed essentially symmetrically with respect to the respective measurement contact (12) along the longitudinal central axis (LA) and / or the transverse central axis (QA).

10. 3. The busbar (11, 14) according to claim 1 or 2, wherein the areas of the measurement contacts (12) each have a measurement point flat (5) and a respective connecting crosspiece (9), the measurement contacts (12) being arranged on the respective measurement point flat (5) and each measurement point flat (5) being connected to a current-carrying area of ​​the resistance area (11b) via the respective connecting crosspiece (9), the connecting crosspiece (9) preferably extending transversely to the longitudinal central axis (LA).

11. 11. The busbar (11, 14) according to claim 10, wherein the connecting crosspiece (9) has a width of 2 to 5 mm and the longitudinal extent of the measuring point flat (5) is 5 to 12 mm.

12. 11. The busbar (11, 14) according to claim 10, wherein recesses (4, 4a) are arranged on both sides of the measuring point flat (5) and the connecting crosspiece (9), said recesses (4, 4a) being preferably intersected in the middle by a central longitudinal axis (LA) and having a width in the direction of said central longitudinal axis (LA) of 2 to 10 millimeters.

13. The busbar (11, 14) according to claim 1 or 2, wherein the material thickness of the resistance area (11b) and / or the connection area (11a) is between 2 and 6 millimeters.

14. The busbar (11, 14) according to claim 1 or 2, wherein the busbar (11, 14) is made of copper or aluminium and / or at least the recesses (4, 4a) are stamped.

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

16. A current determination device (10) comprising a busbar (11, 14) according to claim 1 or 2 and a printed circuit board (2, 20) arranged in a plane parallel to the busbar (11, 14) for obtaining measured values, The current determining device (10), wherein said measurement acquisition comprises acquisition of a voltage difference between two measurement contacts (12) of a resistive area (11b) and, optionally, acquisition of a temperature via at least one temperature sensor (3) of the associated resistive area (11b).

17. 17. The device according to claim 16, wherein the measurement acquisition is performed via measurement lines (7a, 7b) which connect the measurement contacts (12) to a common tapping point (6) and are installed as conductor paths in the printed circuit board (2, 20) such that frequency-dependent phase and amplitude measurement errors are reduced.

18. 18. The device according to claim 17, wherein the measuring lines (7a, 7b) extend within a plane of the printed circuit board (2, 20) arranged as an outermost inner layer of the guide plate (2, 20) on a side of the printed circuit board (2, 20) facing the resistance area (11b).

19. 18. The device according to claim 17, wherein the measurement lines (7a, 7b) are routed from at least one of the measurement contacts (12) of the resistance area (11b) and are gathered at a common tapping point (6) such that the measurement lines (7a, 7b) start from the measurement contacts (12) and extend in two directions away from the measurement contacts (12) to the edges of the resistance area (11b), in particular at least in part, essentially symmetrically with respect to the longitudinal central axis (LA) and / or the lateral central axis (QA) of the resistance area (11b).

20. 18. The device according to claim 17, wherein the measurement lines (7a, 7b) span an essentially closed measurement line area (8) which in one dimension comprises 70-100 percent of the width of the resistance area (11b) and in a dimension perpendicular to said dimension comprises 70-100 percent of the distance between the measurement contacts (12), and wherein the measurement lines (7a, 7b) preferably extend along a connecting crosspiece (9) and outside the overlap area with the recesses (4, 4a).

21. 18. The device according to claim 17, wherein the printed circuit board (2, 20) has a compensation structure (30) comprising a plurality of compensation paths (40a, 40b, 40c, 40d) arranged spatially parallel to one another and capable of being electrically connected in series to one of the measurement lines (7a, 7b), the compensation paths (40a, 40b, 40c, 40d) consisting of conductor paths (31, 32, 33) in different planes of the printed circuit board (2, 20) and in each case extending over a surface oriented perpendicular to the busbars (11, 14) and parallel to the longitudinal central axis (LA).

22. 22. The device according to claim 21, wherein each of the compensation paths (40a, 40b, 40c, 40d) has two opposite compensation arms, which can be connected to the measurement lines (7a, 7b) by the respective compensation paths (40a, 40b, 40c, 40d).

23. 22. Apparatus according to claim 21, wherein the compensation paths (40a, 40b, 40c, 40d) are each bridged or connected to the measurement lines (7a, 7b) by means of matable electrical connectors (41).

24. 17. A power converter comprising current carrying lines for carrying the DC current and / or the AC current processed by the power converter, at least one of the current carrying lines comprising a current determination device (10) according to claim 16, said device bridging an interruption of the at least one current carrying line or being integrated in the at least one current carrying line, the power converter being designed to determine the current flowing through the current carrying line during operation of the power converter using a voltage difference detected by the measuring contacts (12) along the resistive areas (11b) of the busbars (11, 14), the power converter being designed to have a nominal power of more than 10 kW, preferably more than 100 kW, particularly preferably more than 1000 kW.

25. 25. A power converter according to claim 24, comprising a multi-channel device (13) for determining a current, the multi-channel device (13) having a multi-channel busbar (14) comprising, on a first side, at least two individual connection areas (11 a) for connecting a plurality of current-carrying wires and, on a second side, a common busbar (16) as a common connection area (11 a), and wherein a resistive area (11 b) arranged between each of the individual connection areas (11 a) and the common busbar (16) is associated in each case with the individual connection area (11 a).

26. 26. The power converter of claim 25, wherein a printed circuit board (20) for acquiring measurements is arranged in a plane parallel to the busbar (14), the printed circuit board (20) covering the plurality of resistance areas (11 b) and connected to the measurement contacts (12) of the plurality of resistance areas (11 b).

27. 27. The power converter according to claim 26, wherein the printed circuit board (20) comprises a galvanic isolation (17) as well as an evaluation unit (18) for preprocessing the measured voltages and optionally temperatures of the individual resistance areas (11b), the evaluation unit (18) being connected to a control unit of the power converter via the galvanic isolation (17).

28. 26. The power converter of claim 25, wherein the printed circuit board (20) has a slot (19) disposed between the resistor areas (11 b) and extending parallel to the longitudinal central axis (LA) from an edge of the printed circuit board (20) for at least half of the length of the printed circuit board (20).

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