Device for residual current detection

Abstract

A device for detecting residual currents is proposed. The device comprises a printed circuit board (40), which includes at least one electrically conductive conductor (10, 11, 12, 13). The device also includes a planar transformer (20, 21) that surrounds the conductor (10, 11, 12, 13). The planar transformer (20, 21) serves to receive the electromagnetic field around the conductor (10, 11, 12, 13). For this purpose, the planar transformer (20, 21) has at least one leg surrounded by an electrically conductive conductor coil (30). A measurable electrical voltage is induced in this conductor coil (30) via the electromagnetic field of the planar transformer.

Description

[0001] The present invention relates to a device for detecting fault currents and is suitable for printed circuit boards. In particular, the present invention relates to a method for detecting and / or measuring fault currents in or on a printed circuit board assembly.

[0002] Fault currents are electrical currents that do not flow completely through the intended current paths due to unintended current paths. Such an unintended current path can occur, for example, due to an insulation fault.

[0003] Since fault currents are unwanted and can cause further damage to the entire system, they should be detected as early as possible. Corresponding fault current detection systems have been around for a long time and are well known.

[0004] There are also versions of residual current detection that can be mounted on a circuit board. Circuit boards are flat components on which conductor tracks are arranged to conduct an electrical current. Electronic components are also arranged on this circuit board and can be electrically connected to the conductor tracks.

[0005] Residual current detection devices for these circuit boards are known, for example, from EP 3 314 274 B1. These designs can be used anywhere where current-carrying cables or conductor tracks are routed across a circuit board.

[0006] However, these common residual current detectors require a relatively large amount of installation space. However, as circuit boards and their technology continue to become increasingly miniaturized, residual current detectors for circuit boards must also become smaller accordingly.

[0007] The object of the present invention is therefore to design a fault current detection device for a printed circuit board that is as small as possible, ie that takes up as little installation space as possible.

[0008] This problem is solved by the features of claim 1.

[0009] The planar transformer technology is used, which is known, for example, from EP 2 920 798 B1, but has not been implemented for the present application.

[0010] According to the invention, a device for detecting fault currents is proposed, which comprises a printed circuit board, and the printed circuit board contains at least one conductor track. This conductor track can be routed in different directions on the printed circuit board, and several of these conductor tracks can also be routed on the printed circuit board.

[0011] These tracks are designed to conduct an electrical current. The electrical current then flows through the tracks and is guided through the tracks on the circuit board.

[0012] Typically, these conductor tracks are made of copper or silver. Copper- or silver-containing alloys are also possible. In principle, any electrically conductive material can be used for the conductor tracks.

[0013] When using multiple tracks, these can be routed in different layers of the circuit board. It is also possible to route the tracks on and / or below the circuit board.

[0014] According to the invention, the device includes a planar transformer. Such a planar transformer acts as a field concentrator and enables the electromagnetic fields around one or more conductor tracks to be captured. For this purpose, the planar transformer is made of a material that can conduct electromagnetic fields. It is preferably proposed to manufacture the planar transformer from a ferrite, for example, as a ferrite core.

[0015] The planar transformer is arranged on the circuit board in such a way that it encloses the conductor track. The planar transformer is preferably shaped like a rectangle, with the rectangle having a recess in the center, making it hollow. The conductor track is then routed through this recess.

[0016] The planar transformer has at least one leg, which is preferably arranged on the narrow side of the rectangle. For this purpose, the planar transformer can be designed as a closed component with two legs and two connecting pieces connecting the legs, or as an open component with only one leg and an air gap on the side of the planar transformer opposite the leg. The closed design is preferred because it can conduct magnetic fields better.

[0017] A conductor coil is provided on the leg of the circuit board. This conductor coil can be arranged in several turns around the leg. The conductor coil, like the conductor track, is made of an electrically conductive material.

[0018] The conductor track, together with the conductor coil, forms a transformer, in which the conductor track forms the primary winding and the conductor coil forms the secondary winding. The planar transformer absorbs the electromagnetic field induced in the planar transformer by the current-carrying conductor track and conducts the electromagnetic field to the conductor coil. The electromagnetic flux in the planar transformer induces an electrical voltage in the conductor coil, which causes a current to flow in the conductor coil. This corresponds to the familiar principle of a transformer.

[0019] The voltage or current flow in the conductor coil can now be measured using a suitable measuring device and evaluated using suitable means to detect a fault current.

[0020] Fault currents can be detected by knowing the theoretical current value and comparing it with the detected value. Likewise, with an even number of conductor tracks, the fault current can be detected by determining that the detected value is greater than zero. This requires that the current flow direction in the conductor tracks is different, and that half of the conductor tracks have a current flow direction in one direction and the other half have a current flow direction in the opposite direction. A design with conductor tracks for three-phase current is also possible, as the currents balance out here as well. This also makes it possible to detect the fault current when the detected value is greater than zero.

[0021] The planar transformer is preferably designed as a two-part ferrite core, with the ferrite core having a top and bottom surface. This design allows for easy assembly around the conductor track. The planar transformer is arranged around the conductor track via the top and bottom surfaces and assembled into a single component.

[0022] If only a portion of the circuit board is to be enclosed by the planar transformer, it is recommended to provide at least one recess on the circuit board. The leg of the planar transformer is then inserted into this recess. This design allows the device to be positioned precisely on the circuit board. Furthermore, a precise number of conductor tracks can be routed through the planar transformer.

[0023] With the aforementioned embodiments, it is possible to detect the alternating current component of the conductor track, since only alternating current generates a continuously changing electromagnetic field, which can be absorbed by the planar transformer and induced into the conductor coil.

[0024] However, if a direct current component is to be measured, additional measuring elements must be incorporated into the device. For this purpose, it is recommended to include at least one sensor in the device.

[0025] The sensor is designed as a magnetic field sensor, which can also detect non-constantly changing magnetic fields. The sensor is preferably designed as a Hall sensor.

[0026] It has proven advantageous to insert the sensor into an air gap located in one leg of the planar transformer. For this purpose, the leg of the planar transformer can be provided with a recess, or the planar transformer can be designed as a non-enclosed design, in which the top and bottom sides of one leg do not create a closed design.

[0027] In a special embodiment, two sensors can be accommodated in the recess provided in one leg. The second sensor is also designed as a magnetic field sensor and can serve as a backup to the first sensor.

[0028] Preferably, the sensor is also mounted on the circuit board. This allows the sensor to be directly electrically contacted via conductor tracks on the circuit board, thus transmitting the detected signals to an evaluation unit.

[0029] Particularly preferably, the recess in the legs is adapted to the shape of the sensor. For this purpose, the planar transformer has an end on the top and bottom in the leg area, with these ends forming the recess, which corresponds to the shape of the sensor. This design optimizes the electromagnetic flux within the planar transformer.

[0030] For evaluating the fault current detection, the device can include a microcontroller, which can also be located on the circuit board and can be contacted via conductive tracks. Because all electronic elements of the device are located on the circuit board and can be electrically contacted via conductive tracks, a particularly small and compact design is ensured.

[0031] To maintain a constant conductivity for the electromagnetic field and a constant electromagnetic flux in the planar transformer, the planar transformer must be held in position on the circuit board. This can be achieved by encapsulating the planar transformer on the circuit board using a potting compound.

[0032] Furthermore, in addition to the conductor track, a test conductor track can be routed through the planar transformer. This test conductor track can be used to test the function of the fault current detection device both inside and outside of the circuit board's operation. For this purpose, a current flow is generated through the test conductor track, and the evaluation is performed as if the test conductor track were the conductor track to be detected. For this purpose, the test conductor track can also conduct a current containing alternating and / or direct current components.

[0033] By stacking the conductor tracks as current-carrying lines on top of each other (in different layers of the circuit board), the required installation space is significantly reduced. This enables more efficient use of the available space and can lead to cost savings in the planning and implementation of the inventive solution.

[0034] The ability to evaluate the fault current of the conductive paths and derive appropriate measures from it is a valuable tool for monitoring and controlling the inventive solution. This enables rapid identification and response to faults, thereby improving the overall reliability and safety of the device.

[0035] The planar transducer, shaped to fit the ends of the magnetic field sensor, ensures accurate and reliable measurements. This design feature minimizes interference and ensures the sensor is properly aligned, resulting in more precise and consistent readings.

[0036] By placing the microcontroller on the same circuit board as the traces (and, if applicable, the sensor), the overall complexity of the system is reduced. This simplifies the design and manufacturing process, resulting in cost savings and improved reliability.

[0037] The proximity of the microcontroller to other components on the circuit board enables faster and more efficient communication and data processing. This leads to improved system performance and responsiveness.

[0038] Positioning the microcontroller on the circuit board simplifies maintenance and troubleshooting. It allows easier access to the microcontroller and simplifies the identification and resolution of any problems that may arise.

[0039] Using the test track to operate a test current with AC and DC components provides a versatile testing option. This allows for comprehensive testing of the system under various operating conditions and ensures its reliability and performance.

[0040] The ability to generate both AC and DC components of the test current with the test trace eliminates the need for separate test setups. This simplifies the testing process and reduces the required equipment, resulting in cost savings and improved efficiency.

[0041] The test circuit allows for easy adjustment and control of test current parameters. This flexibility enables precise and accurate testing and ensures that the system meets the required standards and specifications.

[0042] Further features are shown in the attached drawings. They show: Fig. 1: Device according to the invention with a circuit board and 4 conductor tracks; Fig. 2: Position of the conductor tracks and corresponding recesses for mounting the planar transformer; Fig. 3: Schematic representation of a planar transformer; Fig. 4: Device according to Fig. 1 with additional sensor; Fig. 5: Device according to Fig. 4 wherein the sensor is arranged on the circuit board; Fig. 6: Device according to Fig. 1 with two sensors;

[0043] Fig. 1 shows a device according to the invention, wherein the circuit board 40 is shown as a non-drawn background of the Fig. 1 applies. Accordingly, it is assumed that the drawing elements are located on a planar circuit board 40.

[0044] On the circuit board 40 there are four conductor tracks 10, 11, 12, 13. These conductor tracks can carry an electric current and this current can have alternating and / or direct current components.

[0045] Also shown is a planar transformer 20, 21, which consists of a top side 20 and a bottom side 21. For positioning and mounting the planar transformer 20, 21 on the circuit board 40, two recesses 41, 42 are provided on the circuit board, into which the planar transformer 20, 21 can be at least partially received. For this purpose, the planar transformer 20, 21 has legs that are guided through the recesses 41, 42. The legs are part of the bottom side 21 of the planar transformer 20, 21. For mounting, after the legs have been received in the recesses 41, 42, the bottom side 21 is at least partially connected to the top side 20 of the planar transformer 20, 21.

[0046] When assembled, the conductor tracks 10, 11, 12, and 13 extend through the planar transformer 20, 21. Thus, the planar transformer 20, 21 can enclose the conductor tracks 10, 11, 12, and 13.

[0047] Furthermore, the circuit board 40 includes a conductor coil 30, which is arranged around one leg of the planar transformer 20, 21. This arrangement allows the alternating current component of the conductor tracks 10, 11, 12, 13 to generate a continuously changing magnetic field, which is transmitted via the planar transformer 20, 21 to the conductor coil 30. This induces an electrical voltage in the conductor coil, which is an indicator of the level of the alternating current component in the conductor tracks 10, 11, 12, 13. This induced voltage generates a current, which is also measurable and can serve as an indicator of the level of the alternating current component in the conductor tracks 10, 11, 12, 13.

[0048] This embodiment forms a transformer in which the conductor tracks 10, 11, 12, 13 form the primary winding with the number of turns 1 and the conductor coil 30 forms the secondary winding with a number of turns corresponding to the windings of the conductor coil.

[0049] Fig. 2 shows the embodiment of Fig. 1, but without the mounted planar transformer. The recesses 41, 42 arranged in the circuit board 40 for mounting the planar transformer, as well as the conductor tracks 10, 11, 12, 13, and 14, can be seen.

[0050] Also visible is the conductor coil 30, which is arranged around one of the recesses 30. In the assembled state, this conductor coil 30 is then located around one leg of the planar transformer.

[0051] Fig. 3 shows a planar transformer 20, 21 as used in the Fig. 1 in the assembled state. The planar transformer 20, 21 consists of two parts, namely a top side 20 and a bottom side 21, with the bottom side 21 having lateral legs.

[0052] Overall, the planar transformer 20, 21 is rectangular with a recess in the center. Thus, the planar transformer is hollow when assembled. The conductor track(s) to be detected can then be routed through this recess, so that they are enclosed by the planar transformer 20, 21 when assembled. The planar transformer 20, 21 is made of a material that can conduct electromagnetic fields, preferably ferrite.

[0053] Fig. 4 shows a further embodiment of a device according to the invention, but with a sensor 50.

[0054] In the example of Fig. 1, only the alternating current component of the fault current of conductor tracks 10, 11, 12, and 13 can be measured. If a universal current with alternating and / or direct current components is to be measured, an additional component is required to detect the direct current component, namely a sensor 50.

[0055] Sensor 50 is preferably designed as a magnetic field sensor, in particular a Hall sensor. This is suitable for detecting magnetic fields, including and in particular from conductor tracks through which direct current flows.

[0056] At least one leg of the planar transformer 20, 21 is used to position the sensor 50 and is preferably shaped such that the leg forms an air gap into which the sensor 50 is inserted. For this purpose, the bottom 21 and the top 20 of the planar transformer 20, 21 have ends that form the air gap when mounted. The ends preferably correspond to the shape of the sensor 50, so that the sensor 50 fills the air gap as much as possible.

[0057] The sensor 50 can be mounted as an electronic component on the circuit board 40, so that the sensor 50 can be evaluated, for example, via a microcontroller on the same circuit board 40. For this purpose, the sensor 50, the microcontroller, and the conductor coil are preferably electrically connected to the microcontroller, for example, via additional conductor tracks on the circuit board 40.

[0058] Such a connection of the sensor 50 on the circuit board 40 shows the Fig. 5. Here, the arrangement of conductor tracks 10, 11, 12, 13 and planar transformers 20, 21 on the printed circuit board 40 as in Fig. 1. In addition, a sensor 50 as in Fig. 4 is provided.

[0059] Mechanically, the planar transformer 20, 21 should be held in the correct position so that the air gap always remains the same. This can be achieved, for example, by encapsulating the planar transformer, at least partially.

[0060] The current-carrying conductor tracks 10, 11, 12, 13 can be arranged as desired in, on or under the circuit board 40, even in different layers of the circuit board 40.

[0061] For testing purposes, an additional test conductor (not shown) on the circuit board 40 can be routed through the planar transformer 20, 21. A universal test current with an AC and / or DC voltage component can then be driven via this test conductor to test the function of the device in the installed state.

[0062] Fig. 6 shows another embodiment of a device for detecting fault currents, but this time with two sensors 50, 51.

[0063] For functional safety reasons, two sensors 50, 51, also preferably designed as magnetic field sensors, can be arranged in the air gap of the planar transformer 20, 21. Thus, the second sensor 51 is designed as a redundancy to the first sensor 50.

[0064] In this embodiment, the conductor tracks 10, 11, 12, 13 are also routed through the planar transformer 20, 21 in the assembled state. Here, too, the conductor tracks 10, 11, 12, 13 can carry a current with an alternating and / or direct current component.

[0065] The alternating current component can still be used as in Fig. 1 is detected via a conductor coil and the direct current component via the sensors 50, 51. However, the sensors can also detect alternating current components.

[0066] The present invention is not limited to the aforementioned features. Further embodiments are conceivable. For example, an embodiment without a conductor coil is conceivable, in which the AC and DC components of the conductor paths pass exclusively through the sensor. Likewise, an embodiment in which the planar transformer is not completely closed in the assembled state is conceivable. LIST OF REFERENCE SYMBOLS 10 Conductor track 1 11 Conductor track 2 12 Conductor track 3 13 Conductor track 4 20 planar transformers, top side 21 Planar transformer, bottom side 22nd edition, top 23rd edition, bottom 30 conductor coil 40 circuit board 41 First recess 42 Second recess 50 First sensor 51 Second sensor QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 3 314 274 B1

[0005] EP 2 920 798 B1

[0009]

Claims

[1] Device for detecting residual currents, with a printed circuit board (40), wherein the printed circuit board (40) includes at least two conductor tracks (10, 11, 12, 13) which are designed to be electrically conductive, characterized by , that the device includes a planar transformer (20, 21) which encloses the conductor tracks (10, 11, 12, 13) and that the planar transformer (20, 21) has at least one leg on which a differential current measurement is carried out for detecting the fault current. [2] Device according to claim 1, characterized by that the planar transformer (20, 21) is designed as a two-part ferrite core with a top side (20) and a bottom side (21). [3] Device according to claim 1 or 2, characterized by that the planar transformer (20, 21) serves as a field concentrator. [4] Device according to one of claims 1 to 3, characterized bythat the printed circuit board (40) has at least one recess (41, 42) in which the leg of the planar transformer (20, 21) is received. [5] Device according to one of claims 1 to 4, characterized by that the leg of the planar transformer is surrounded by a conductor coil (30) which is electrically conductive and designed for differential current measurement. [6] Device according to one of claims 1 to 5, characterized by that the leg of the planar transformer (20, 21) has an air gap in which at least one sensor (50, 51) is arranged. [7] Device according to claim 6, characterized by that the sensor (50, 51) is designed as a magnetic field sensor. [8] Device according to claim 6 or 7, characterized by that the air gap is formed by one end of the top side (20) and the bottom side (21) of the planar transformer (20, 21), the shape of the ends corresponding to the shape of the sensor (50, 51). [9] Device according to one of claims 6 to 8, characterized by that the sensor (50, 51) is arranged on the circuit board (40). [10] Device according to one of claims 6 to 9, characterized by that the device includes a microcontroller for evaluating the sensor (50, 51). [11] Device according to claim 10, characterized by that the microcontroller is connected to the sensor (50, 51) and / or the conductor coil (30). [12] Device according to claim 10 or 11, characterized by that the microcontroller is arranged on the circuit board (40). [13] Device according to one of claims 1 to 12, characterized by that the planar transformer (20, 21) is held in its position by means of a casting compound. [14] Device according to one of claims 1 to 13, characterized by that a test conductor track is passed through the planar transformer (20, 21). [15] Device according to one of claims 1 to 14, characterized by that several conductor tracks (10, 11, 12, 13) are guided in different layers of the printed circuit board (40). [16] Device according to one of claims 1 to 15, characterized by that the conductor track (10, 11, 12, 13) is traversed by a current with alternating current and direct current components.

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