Current measurement device

Abstract

To easily divide tracking current.SOLUTION: A current measurement device 10 according to the present disclosure measures tracking current. The current measurement device 10 comprises a magnetic core 11 arrangeable to surround the periphery of wiring 100 to be measured, and a first coil L1 and a second coil L2 wound around the magnetic core 11. The number of turns of the second coil L2 is smaller than the number of turns of the first coil L1. The second coil L2 can detect tracking current flowing in the wiring 100.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a current measuring device. [Background technology]

[0002] When dust or other particles accumulate between the electrodes of a plug inserted into an electrical outlet, a current may flow between the electrodes via the dust or other particles. Generally, the current that flows between the electrodes of the plug through the dust or other particles is called a tracking current.

[0003] If the tracking current continues to flow, it may cause a short circuit between the electrodes and result in a fire. As such, since the tracking current can be a cause of fire, it is important to detect the tracking current.

[0004] For example, Patent Document 1 discloses a tracking current detection device that performs calculation processing on a measured load current and compares the calculation result with a predetermined condition to determine whether or not a tracking current is flowing. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2012-8139 A Summary of the Invention [Problem to be solved by the invention]

[0006] An example of a state in which a tracking current flows is shown in Fig. 7. In the example shown in Fig. 7, power is supplied from a distribution board 301 to an outlet 302, and power is supplied from the outlet 302 to a load 303. The load 303 is an electric device or the like.

[0007] 7, a load current I flows through the load 303. A tracking current It flows through the outlet 302.

[0008] In this case, a current I+It, which is the sum of the load current and the tracking current, flows from distribution board 301 to outlet 302 .

[0009] In order to detect the tracking current, for example, it is possible to measure the current flowing from the distribution board 301 to the outlet 302 by the current sensor 304. In this case, the current sensor 304 detects the current I+It which is the sum of the load current and the tracking current.

[0010] Usually, the load current is much larger than the tracking current. For example, when the load current I is 10 A and the tracking current It is 100 mA, the current detected by the current sensor 304 is 10.1 A. This current is almost the same as the load current of 10 A when no tracking current is flowing. Therefore, it is difficult to separate the current of the tracking current from the measurement result of the current sensor 304.

[0011] Therefore, an object of the present disclosure is to provide a current measuring device that can easily separate the tracking current. [Means for solving the problem]

[0012] According to some embodiments, a current measuring device for measuring a tracking current includes a magnetic core that can be arranged to surround a wiring to be measured, and a first coil and a second coil wound around the magnetic core, the number of turns of the second coil being less than the number of turns of the first coil, and the second coil is capable of detecting the tracking current flowing through the wiring. With such a current measuring device, it is possible to easily separate the tracking current.

[0013] In the current measuring device according to one embodiment, the first coil may be capable of detecting a current having a commercial power frequency flowing through the wiring, thereby making it possible to detect a current having a commercial power frequency.

[0014] The current measuring device according to one embodiment may further include a first current measuring circuit that measures the commercial power frequency current detected by the first coil, and a second current measuring circuit that measures the tracking current detected by the second coil, thereby making it possible to measure the commercial power frequency current and the tracking current.

[0015] In one embodiment, the current measuring device further includes a control unit and a display unit, and the control unit may cause the display unit to display the commercial power frequency current measured by the first current measuring circuit and the tracking current measured by the second current measuring circuit, thereby allowing a user to easily check the commercial power frequency current and the tracking current.

[0016] In one embodiment, the current measuring device further includes an amplifier circuit that amplifies the output current of the second coil, and a low-pass filter that outputs a commercial power frequency current from the output current of the amplifier circuit, and the output current of the low-pass filter may be fed back to the first coil, thereby canceling a magnetic field caused by the commercial power frequency current.

[0017] The current measuring device according to one embodiment may further include a first current measuring circuit that measures the output current of the low-pass filter, and a second current measuring circuit that measures the tracking current detected by the second coil, thereby making it possible to measure the commercial power frequency current and the tracking current.

[0018] In one embodiment, the current measuring device further includes a control unit and a display unit, and the control unit may cause the display unit to display the output current of the low-pass filter measured by the first current measuring circuit and the tracking current measured by the second current measuring circuit, thereby allowing a user to easily check the commercial power frequency current and the tracking current.

[0019] In the current measuring device according to one embodiment, the second coil may be capable of detecting the commercial power frequency current as well as the tracking current.

[0020] In one embodiment, the number of turns of the second coil may be equal to or less than 1 / 100 of the number of turns of the first coil, thereby enabling the second coil to detect a tracking current.

[0021] In the current measuring device according to one embodiment, the magnetic core may be ring-shaped.

[0022] In one embodiment of the current measuring device, the magnetic core may be configured to be partially openable and closable, so that the magnetic core can sandwich the wiring to be measured. Effect of the Invention

[0023] According to the present disclosure, it is possible to provide a current measuring device that can easily separate a tracking current. [Brief description of the drawings]

[0024] [Figure 1] 1 is a schematic configuration diagram of a current measuring device according to a first embodiment. [Diagram 2] 1 is a diagram for explaining the principle by which the current measuring device according to the first embodiment detects a current. FIG. [Diagram 3] 1 is a diagram showing an example of the appearance of a current measuring device according to a first embodiment. [Figure 4] FIG. 11 is a schematic diagram of a current measuring device according to a second embodiment. [Diagram 5] FIG. 11 is a schematic configuration diagram of a current measuring device according to a third embodiment. [Figure 6] 13 is a diagram showing an example of the appearance of a current measuring device according to a third embodiment. FIG. [Figure 7] FIG. 1 is a diagram showing an example of conventional tracking current measurement. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0026] (First embodiment) FIG. 1 is a schematic diagram of a current measuring device 10 according to the first embodiment.

[0027] The current measuring device 10 is a device that measures a tracking current. Fig. 1 shows how the current measuring device 10 measures a current I flowing through a wiring 100 that is a measurement target. The wiring 100 may be, for example, a wiring that connects a distribution board and an outlet.

[0028] The current measuring device 10 is able to measure the tracking current by separating the current flowing through the wiring 100 into a current having a commercial power frequency and a tracking current.

[0029] Current at commercial power frequency is current that flows through a load such as an electrical appliance connected to an electrical outlet, and is a current with a low frequency such as 50 Hz or 60 Hz.

[0030] The tracking current is a pulsed current that flows between the electrodes of a plug inserted into an electrical outlet, passing through dust and other particles, and is a high-frequency current. The frequency of the tracking current is, for example, several hundred kHz, which is much higher than the frequency of the commercial power supply current.

[0031] The current measuring device 10 includes a magnetic core 11, a first coil L1, a second coil L2, a first current measuring circuit 12, a second current measuring circuit 13, a control unit 14, and a display unit 15.

[0032] The magnetic core 11 can be disposed so as to surround the wiring 100 to be measured. The magnetic core 11 may be, for example, in a ring shape. The magnetic core 11 may be configured so that a portion of the magnetic core 11 can be opened and closed. When the magnetic core 11 is configured so that a portion of the magnetic core 11 can be opened and closed, the wiring 100 can be sandwiched therebetween.

[0033] The first coil L1 is a coil wound around the magnetic core 11. The first coil L1 can detect a current of commercial power frequency flowing through the wiring 100 sandwiched by the magnetic core 11.

[0034] The second coil L2 is a coil wound around the magnetic core 11. The number of turns of the second coil L2 is smaller than the number of turns of the first coil L1. The second coil L2 can detect a tracking current flowing through the wiring 100 sandwiched by the magnetic core 11.

[0035] The number of turns of the second coil L2 is 1 / 100 or less of the number of turns of the first coil L1. As an example, the number of turns of the first coil L1 may be 4000, and the number of turns of the second coil L2 may be 4. In this case, the number of turns of the second coil L2 is 1 / 1000 of the number of turns of the first coil L1.

[0036] The principle of the first coil L1 detecting a commercial power frequency current flowing through the wiring 100 and the second coil L2 detecting a tracking current flowing through the wiring 100 will be described with reference to FIG.

[0037] 2, a current Io of commercial power frequency and a tracking current It are superimposed and flow through the wiring 100. At this time, a magnetic field M1 is generated around the wiring 100 due to the current Io of commercial power frequency. In addition, a magnetic field M2 is generated around the wiring 100 due to the tracking current It.

[0038] At this time, a current flows through the first coil L1 and the second coil L2 so as to cancel out the magnetic fields M1 and M2.

[0039] First, consider the current for canceling the magnetic field M1 caused by the commercial power frequency current Io. A current for canceling the magnetic field M1 flows through both the first coil L1 and the second coil L2, but since the number of turns in the first coil L1 is much greater than the number of turns in the second coil L2, the current flowing through the second coil L2 is much smaller than the current flowing through the first coil L1. For example, if the number of turns in the second coil L2 is 1 / 1000 of the number of turns in the first coil L1, the current flowing through the second coil L2 is 1 / 1000 of the current flowing through the first coil L1. Therefore, the commercial power frequency current Io can be detected by detecting the current flowing through the first coil L1.

[0040] Next, consider the current for canceling the magnetic field M2 caused by the tracking current It. The tracking current It is a high-frequency current of several hundreds of kHz. Therefore, in order to cancel the magnetic field M2, it is necessary to pass a high-frequency current through the first coil L1 and the second coil L2. However, the first coil L1 has a large number of turns and a large inductance component, so it is almost impossible to pass a high-frequency current through it. On the other hand, the second coil L2 has a small number of turns and a small inductance component, so it is possible to pass a high-frequency current through it.

[0041] Therefore, a current for canceling the magnetic field M2 caused by the tracking current It flows through the second coil L2. Therefore, the tracking current It can be detected by detecting the current flowing through the second coil L2.

[0042] Returning to FIG. 1 again, the explanation will be continued.

[0043] The first current measuring circuit 12 is connected to the first coil L1. The current of the commercial power frequency detected by the first coil L1 is input to the first current measuring circuit 12. This allows the first current measuring circuit 12 to measure the current of the commercial power frequency detected by the first coil L1. The first current measuring circuit 12 outputs a signal corresponding to the measured current of the commercial power frequency to the control unit 14. The first current measuring circuit 12 may output the signal corresponding to the measured current of the commercial power frequency as a current or a voltage.

[0044] The second current measuring circuit 13 is connected to the second coil L2. The tracking current detected by the second coil L2 is input to the second current measuring circuit 13. This allows the second current measuring circuit 13 to measure the tracking current detected by the second coil L2. The second current measuring circuit 13 outputs a signal corresponding to the measured tracking current to the control unit 14. The second current measuring circuit 13 may output the signal corresponding to the measured tracking current as a current or a voltage.

[0045] The control unit 14 controls the entire current measuring device 10 and each block of the current measuring device 10. The control unit 14 includes at least one processor, at least one dedicated circuit, or a combination of these. The processor is a general-purpose processor such as a central processing unit (CPU) or a graphics processing unit (GPU), or a dedicated processor specialized for a specific process. The dedicated circuit is, for example, a field-programmable gate array (FPGA) or an application specific integrated circuit (ASIC).

[0046] The control unit 14 obtains, from the first current measuring circuit 12, a signal corresponding to the current of the commercial power frequency measured by the first current measuring circuit 12. The control unit 14 obtains, from the second current measuring circuit 13, a signal corresponding to the tracking current measured by the second current measuring circuit 13.

[0047] The control unit 14 causes the display unit 15 to display the current of the commercial power frequency measured by the first current measuring circuit 12 and the tracking current measured by the second current measuring circuit 13.

[0048] The display unit 15 can display various types of data and may include, for example, an LCD (Liquid Crystal Display) or an organic EL (Electro Luminescent) display.

[0049] An example of the appearance of the current measuring device 10 according to the first embodiment is shown in Fig. 3. Fig. 3 shows an example in which the current measuring device 10 is a clamp-type current measuring device.

[0050] In the case of the configuration shown in FIG. 3, a portion of the magnetic core 11 can be opened and closed, and the magnetic core 11 can sandwich the wiring 100 to be measured.

[0051] In the example shown in FIG. 3, the display unit 15 displays the following values ​​as the commercial power frequency current and the tracking current: Power frequency current: 11.23A Tracking current: 125.5mA

[0052] According to the current measuring device 10 of the first embodiment as described above, the tracking current can be easily separated. More specifically, the current measuring device 10 includes a first coil L1 and a second coil L2 wound around a magnetic core 11. The number of turns of the second coil L2 is smaller than the number of turns of the first coil L1. As a result, the first coil L1 with the larger number of turns detects the current of the commercial power frequency, and the second coil L2 with the smaller number of turns detects the tracking current. In this way, the first coil L1 with the larger number of turns detects the current of the commercial power frequency, and the second coil L2 with the smaller number of turns detects the tracking current, so that the current measuring device 10 of the first embodiment can easily separate the tracking current.

[0053] Second embodiment FIG. 4 is a schematic diagram of a current measuring device 10a according to the second embodiment.

[0054] Like the current measuring device 10 according to the first embodiment, the current measuring device 10a according to the second embodiment is also a device that measures a tracking current.

[0055] The current measuring device 10a according to the second embodiment includes a magnetic core 11, a first coil L1, a second coil L2, a first current measuring circuit 12, a second current measuring circuit 13, a control unit 14, a display unit 15, an amplifier circuit 16, and a low pass filter (LPF) 17.

[0056] The current measuring device 10a according to the second embodiment differs from the current measuring device 10 according to the first embodiment shown in FIG.

[0057] Regarding the current measuring device 10a of the second embodiment, the differences from the current measuring device 10 of the first embodiment will be mainly described, and descriptions of points in common or similar to the current measuring device 10 of the first embodiment will be omitted as appropriate.

[0058] The first coil L1 is a coil wound around the magnetic core 11.

[0059] The second coil L2 is a coil wound around the magnetic core 11. The number of turns of the second coil L2 is less than the number of turns of the first coil L1. The second coil L2 can detect a tracking current flowing through the wiring 100 sandwiched by the magnetic core 11. In addition to the tracking current, the second coil L2 can also detect a current of commercial power frequency flowing through the wiring 100 sandwiched by the magnetic core 11.

[0060] The amplifier circuit 16 is connected to the second coil L2. The output current of the second coil L2 is input to the amplifier circuit 16. The output current of the second coil L2 includes a current of the commercial power supply frequency detected by the second coil L2 and a tracking current.

[0061] The amplifier circuit 16 amplifies the output current of the second coil L2 and outputs the amplified current to the low-pass filter 17.

[0062] The low-pass filter 17 passes and outputs a low-frequency current out of the output current of the amplifier circuit 16. In other words, the low-pass filter 17 passes a current having a commercial power frequency out of the output current of the amplifier circuit 16, but hardly passes a tracking current out of the output current of the amplifier circuit 16. The low-pass filter 17 may be a low-pass filter of any configuration configured to have such frequency characteristics.

[0063] The output current of the amplifier circuit 16 includes a current having a commercial power supply frequency, which is a low frequency current, and a tracking current, which is a high frequency current. The low-pass filter 17 outputs only the current having the commercial power supply frequency, which is a low frequency current.

[0064] The output current of the low-pass filter 17 is supplied to the first coil L1. That is, the current having the commercial power frequency included in the output current of the low-pass filter 17 is fed back to the first coil L1.

[0065] In this way, when the current of the commercial power frequency is fed back to the first coil L1, the magnetic field generated due to the current of the commercial power frequency flowing through the wiring 100 and the magnetic field generated due to the current of the commercial power frequency fed back to the first coil L1 cancel each other out.

[0066] Then, the magnetic field generated due to the commercial power frequency current flowing through the wiring 100 is greatly reduced, and only the magnetic field generated due to the tracking current flowing through the wiring 100 remains, so that the second coil L2 carries almost only a current for canceling the magnetic field generated due to the tracking current. Therefore, the second coil L2 can detect the tracking current.

[0067] The first current measuring circuit 12 is connected to the low-pass filter 17. The first current measuring circuit 12 can measure the output current of the low-pass filter 17. Since the output current of the low-pass filter 17 includes a current with a commercial power frequency, the first current measuring circuit 12 can measure the current with the commercial power frequency. The first current measuring circuit 12 outputs a signal corresponding to the measured current with the commercial power frequency to the control unit 14. The first current measuring circuit 12 may output the signal corresponding to the measured current with the commercial power frequency as a current or a voltage.

[0068] The second current measuring circuit 13 is connected to the second coil L2. The tracking current detected by the second coil L2 is input to the second current measuring circuit 13. This allows the second current measuring circuit 13 to measure the tracking current detected by the second coil L2. The second current measuring circuit 13 outputs a signal corresponding to the measured tracking current to the control unit 14. The second current measuring circuit 13 may output the signal corresponding to the measured tracking current as a current or a voltage.

[0069] The current measuring device 10a according to the second embodiment as described above can easily separate the tracking current. More specifically, the current measuring device 10a according to the second embodiment includes a first coil L1 and a second coil L2 wound around a magnetic core 11, an amplifier circuit 16 that amplifies the output current of the second coil L2, and a low-pass filter 17 that outputs a current of commercial power frequency from the output current of the amplifier circuit 16. The output current of the low-pass filter 17 is fed back to the first coil L1. This causes a magnetic field generated due to the current of commercial power frequency flowing through the wiring 100 to cancel out a magnetic field generated due to the current of commercial power frequency fed back to the first coil L1. Therefore, the second coil L2 can detect only the tracking current, and the current measuring device 10a according to the second embodiment can easily separate the tracking current.

[0070] Third embodiment FIG. 5 is a schematic diagram of a current measuring device 10b according to the third embodiment.

[0071] Like the current measuring device 10 according to the first embodiment, the current measuring device 10b according to the third embodiment is also a device that measures a tracking current.

[0072] The current measuring device 10b according to the third embodiment includes a magnetic core 11, a first coil L1, a second coil L2, a first current measuring circuit 12, and a second current measuring circuit 13.

[0073] The current measuring device 10b according to the third embodiment differs from the current measuring device 10 according to the first embodiment shown in FIG. 1 mainly in that the current measuring device 10b does not include the control unit 14 and the display unit 15.

[0074] Regarding the current measuring device 10b of the third embodiment, the differences from the current measuring device 10 of the first embodiment will be mainly described, and descriptions of points in common or similar to the current measuring device 10 of the first embodiment will be omitted as appropriate.

[0075] As described above, the current measuring device 10b according to the third embodiment does not include the control unit 14 and the display unit 15. Therefore, the current measuring device 10b according to the third embodiment does not need to supply power to the control unit 14 and the display unit 15, and therefore can have a simple configuration without a power supply unit.

[0076] An example of the appearance of a current measuring device 10b according to the third embodiment is shown in Fig. 6. Fig. 6 shows an example in which the current measuring device 10 is a clamp-type probe.

[0077] In the case of the configuration shown in FIG. 6, a portion of the magnetic core 11 can be opened and closed, and the magnetic core 11 can sandwich the wiring 100 to be measured.

[0078] 3, the current measuring device 10b according to the third embodiment can supply to an external device the L1 output output by the first current measuring circuit 12 and the L2 output output by the second current measuring circuit 13. In this case, the commercial power frequency current and tracking current may be displayed in an external device to which the L1 output and L2 output of the current measuring device 10b according to the third embodiment are connected.

[0079] The current measuring device 10b of the third embodiment is the current measuring device 10 of the first embodiment that does not have the control unit 14 and the display unit 15, but a configuration in which the current measuring device 10a of the second embodiment does not have the control unit 14 and the display unit 15 is also possible.

[0080] It is obvious to those skilled in the art that the present disclosure can be realized in other specific forms other than the above-described embodiments without departing from the spirit or essential characteristics thereof. Therefore, the above description is illustrative and not limiting. The scope of the disclosure is defined by the appended claims, not by the above description. Any modifications within the scope of the equivalents of all modifications are included therein.

[0081] For example, the arrangement and number of each component described above are not limited to the above description and the contents illustrated in the drawings. The arrangement and number of each component may be arbitrarily configured as long as the function can be realized.

[0082] For example, in the above-described embodiment, a configuration in which one first coil L1 is wound around the magnetic core 11 has been shown, but multiple first coils L1 may be wound around the magnetic core 11. For example, if four first coils L1 are wound around the magnetic core 11 at equal intervals, errors due to measurement positions can be reduced, and the first coil L1 can detect the current with even greater accuracy.

[0083] For example, in the above-described embodiment, a configuration in which one second coil L2 is wound around the magnetic core 11 has been shown, but multiple second coils L2 may be wound around the magnetic core 11. For example, if two second coils L2 are wound around the magnetic core 11 at equal intervals, errors due to measurement positions can be reduced, and the second coil L2 can detect the current with even greater accuracy.

[0084] For example, in the above-described embodiment, the first coil L1 and the second coil L2 are wound around the magnetic core 11, but the third coil L3 may be further wound around the magnetic core 11. By adjusting the number of turns of the third coil L3, the third coil L3 may be configured to be able to separate and detect inverter noise and the like.

[0085] For example, in the above-described embodiment, the current measuring devices 10 and 10a are configured to be capable of measuring the commercial power frequency current and the tracking current, but the current measuring devices 10 and 10a may further include a magnetic core and a coil capable of measuring leakage current (Io), resistive component leakage current (Ior), etc.

[0086] For example, in the above-described embodiment, the second coil L2 detects the tracking current, but the number of turns of the second coil L2 may be adjusted so that the second coil L2 can separate and detect harmonics. [Explanation of symbols]

[0087] 10, 10a, 10b current measuring device 11 Magnetic core 12 1st current measurement circuit 13 Second current measurement circuit 14 Control section 15 Display 16 Amplification circuit 17 Low-pass filter (LPF) L1 First coil L2 Second coil 100 Wiring 301 Distribution Board 302 Outlet 303 Load 304 Current Sensor

Claims

1. A current measuring device for measuring a tracking current, comprising: a magnetic core that can be arranged to surround the wiring to be measured; a first coil and a second coil wound around the magnetic core; Equipped with The number of turns of the second coil is less than the number of turns of the first coil, The second coil is capable of detecting a tracking current flowing through the wiring.

2. 2. The current measuring device according to claim 1, The first coil is capable of detecting a current of a commercial power frequency flowing through the wiring.

3. 3. The current measuring device according to claim 2, a first current measuring circuit that measures the current of the commercial power frequency detected by the first coil; a second current measuring circuit for measuring the tracking current detected by the second coil; The current measuring device further comprises:

4. 4. The current measuring device according to claim 3, Further comprising a control unit and a display unit, The control unit causes the display unit to display the current having the commercial power frequency measured by the first current measurement circuit and the tracking current measured by the second current measurement circuit.

5. 2. The current measuring device according to claim 1, an amplifier circuit that amplifies an output current of the second coil; a low-pass filter for outputting a current having a commercial power frequency from the output current of the amplifier circuit; Further equipped with The output current of the low pass filter is fed back to the first coil.

6. 6. The current measuring device according to claim 5, a first current measuring circuit for measuring an output current of the low pass filter; a second current measuring circuit for measuring the tracking current detected by the second coil; The current measuring device further comprises:

7. 7. The current measuring device according to claim 6, Further comprising a control unit and a display unit, The control unit causes the display unit to display the output current of the low-pass filter measured by the first current measuring circuit and the tracking current measured by the second current measuring circuit.

8. 6. The current measuring device according to claim 5, The second coil is capable of detecting the mains frequency current as well as the tracking current.

9. 2. The current measuring device according to claim 1, A current measuring device, wherein the number of turns of the second coil is 1 / 100 or less of the number of turns of the first coil.

10. 2. The current measuring device according to claim 1, The current measuring device, wherein the magnetic core is ring-shaped.

11. 2. The current measuring device according to claim 1, The current measuring device, wherein the magnetic core is configured so that a portion of the magnetic core can be opened and closed.

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