Current measuring device for a three-phase supply line leading to a consumer

Abstract

In a current measuring device for a three-phase power supply line leading to a consumer, the current measuring device comprises a fastening element that can be fixed to the three-phase power supply line, wherein a plurality of magnetic field sensors MFS1, MFS2, MFS3 are fixed to the fastening element and are connected to an evaluation unit.

Description

[0001] European patent EP2369353B1 discloses a current measuring circuit for a three-phase power supply line leading to a consumer. However, this current measuring device requires an intermediate plug in the supply line, which is essential for the measurement.

[0002] The disadvantage here, however, is that an intermediate plug solution for existing three-phase consumers, e.g. machines in industrial plants, can only be implemented with great effort because the supply line has to be cut open for this purpose.

[0003] The object of the invention is to provide a current measuring device for a three-phase supply line leading to a consumer, which can be easily used in existing supply lines and which does not require a separate power supply.

[0004] This object is achieved by a current measuring device for a three-phase supply line leading to a consumer according to claim 1.

[0005] The essential idea of ​​the invention is to provide a self-powered (autonomous) current measuring device powered by the flow of the measuring current through induction current. The sensor and evaluation electronics, as well as a radio module, are powered independently. The data is made available locally or via an NB-IoT or LP-WAN connection to a higher-level evaluation unit. For persistently low measuring currents, another energy harvesting module (vibration, PV, Peltier, etc.) can also be installed.

[0006] The current measuring device can be mounted on a mounting element or as a folding element (folding current transformer). It can be retrofitted to existing systems without disconnecting a cable.

[0007] An antenna connection is advantageous for installation in control cabinets so that the radio signal can reach outside or the range is increased.

[0008] The wireless signal is preferably implemented in the standard IO-Link, IoT core, and, if necessary, with mesh functionality. Especially in mesh mode, it is important for the signal path that as many nodes as possible are operational at the same time. Therefore, an energy storage device is helpful for bridging short periods of powerlessness if no other energy harvesting option is available.

[0009] Advantageous further developments are specified in the subclaims.

[0010] The invention is explained in more detail below using an embodiment shown in the drawing.

[0011] They show: Fig. 1 Three-phase supply line in section Fig. 2 Three-phase supply line according to Fig. 1 with several magnetic field sensors arranged on the jacket Fig. 3 Top view of a fastening element with several magnetic field sensors Fig. 4 Block diagram of a GMR cell Fig. 5 wireless transmission

[0012] Fig. Figure 1 shows a cross-section of a three-phase power supply line with three conductors L1, L2, L3 for transmitting the three-phase current with three phases each delayed by 120°, a neutral conductor N and a protective conductor E. The individual conductors are insulated and all three are enclosed by an insulating sheath M.

[0013] Fig. 2 shows a supply line according to Fig. 1 with several magnetic field sensors, e.g., three magnetic field sensors MFS1, MFS2, MFS3, arranged around the sheath M of the three-phase power line. The number of magnetic field sensors must be selected such that the magnetic field measurement allows conclusions to be drawn about the current flowing in the individual conductors.

[0014] Fig. Figure 3 shows an enlarged top view of a fastening element. The fastening element can be securely attached to the three-phase power supply cable. The magnetic field sensors MFS1, MFS2, and MFS3 are fixed to the fastening element, e.g., a flexible band that can be wrapped around the sheath M and securely fastened to the sheath M, e.g., with a hook-and-loop fastener (indicated in gray). The sensors are connected to an evaluation unit that has an interface to a higher-level unit. The interface can be wireless or wired. An IO-Link interface, commonly used in automation technology, is conceivable as an interface.

[0015] Fig. 4 shows a block diagram for a GMR cell

[0016] Fig. 5 wireless transmission path from the current measuring device to a cloud storage (moneo Cloud)

[0017] The function of the invention is explained in more detail below. Since the GMR cells are spaced at different distances from the individual conductors L1, L2, and L3, the actual magnetic field strength can be determined from the respective differential signals, from which the current in the individual conductors can then be calculated.

[0018] The current measuring device according to the invention can be easily used with existing three-phase power lines leading to consumers. No modification of the three-phase power line is required.

[0019] The invention can also be used with a standard AC line and even a DC line. In addition to GMR cells, AMR cells or Hall sensors are also conceivable as magnetic field sensors.

[0020] The invention offers the following advantages: - Self-fed by the measuring current flow through induction current. An inductive tapping unit is provided for this purpose. - Supplies power to the sensor and evaluation electronics - Contains and operates a radio module that forwards the measurement data locally or via NB-IoT or LP-WAN - Radio signal preferably in standard IO-Link, IoT Core and if required with mesh functionality - For permanently low measuring currents, an energy storage device or another energy harvesting module can be installed (vibration, PV, Peltier, etc.). - Split current transformer, for easy retrofitting and so that no power cables have to be disconnected from systems - Additional antenna connection will be helpful for installation in control cabinets to amplify the radio signal and thus increase the range - more efficient use (tapping) of the measuring current as an energy supplier through induction effects 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 2369353B1

[0001]

Claims

[1] Current measuring device for a three-phase supply line leading to a consumer, characterized by that the current measuring device comprises a fastening element which can be fixed to the three-phase power supply line, wherein a plurality of magnetic field sensors MFS1, MFS2, MFS3 are fixed to the fastening element and are connected to an evaluation unit, wherein the evaluation unit is self-supplied via an inductive tapping unit which is fed by the measuring current. [2] Current measuring device according to claim 1, characterized by , the magnetic field sensors are designed as GMR cells. [3] Current measuring device according to one of the preceding claims, characterized by that at least three magnetic field sensors are provided on the fastening element. [4] Current measuring device according to one of the preceding claims, characterized by that it has a radio module that is also powered by the inductive tapping unit.

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