Current measuring 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 Art

[0002] When dust or the like accumulates between the electrodes of a plug inserted into an outlet, a current may flow between the electrodes through the dust or the like. Generally, the current flowing between the electrodes of such a plug through dust or the like is referred to as a tracking current.

[0003] If the state in which the tracking current flows continues, the electrodes may short-circuit and ignite. Thus, since the tracking current may cause a fire, it is important to detect the tracking current.

[0004] For example, Patent Document 1 discloses a tracking current detection device that performs arithmetic processing on a measured load current and compares the arithmetic result with a predetermined condition to determine whether a tracking current is flowing.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] FIG. 7 shows an example of a state in which a tracking current is flowing. 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 electrical device or the like.

[0007] In the example shown in FIG. 7, a load current I flows through the load 303. Further, a tracking current It flows through the outlet 302.

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

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

[0010] Normally, 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 the tracking current is not flowing. Therefore, it is difficult to separate the current corresponding to 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 measurement device capable of easily separating the tracking current.

Means for Solving the Problem

[0012] A current measurement device according to some embodiments is a current measurement device for measuring a tracking current, and includes a magnetic core that can be arranged so as to surround the 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 is less than the number of turns of the first coil, and the second coil can detect the tracking current flowing through the wiring. According to such a current measurement device, it is possible to easily separate the tracking current.

[0013] In the current measurement device according to an embodiment, the first coil may be capable of detecting a current having a commercial power supply frequency flowing through the wiring. Thereby, a current having a commercial power supply frequency can be detected.

[0014] In a current measurement device according to an embodiment, a first current measurement circuit that measures the current of the commercial power supply frequency detected by the first coil, and a second current measurement circuit that measures the tracking current detected by the second coil may be further provided. Thereby, the current of the commercial power supply frequency and the tracking current can be measured.

[0015] In a current measurement device according to an embodiment, a control unit and a display unit are further provided, and the control unit may cause the display unit to display the current of the commercial power supply frequency measured by the first current measurement circuit and the tracking current measured by the second current measurement circuit. Thereby, the user can easily confirm the current of the commercial power supply frequency and the tracking current.

[0016] In a current measurement device according to an embodiment, an amplifier circuit that amplifies the output current of the second coil, and a low-pass filter that outputs the current of the commercial power supply frequency among the output currents of the amplifier circuit are further provided, and the output current of the low-pass filter may be fed back to the first coil. Thereby, the magnetic field caused by the current of the commercial power supply frequency can be canceled out.

[0017] In a current measurement device according to an embodiment, a first current measurement circuit that measures the output current of the low-pass filter, and a second current measurement circuit that measures the tracking current detected by the second coil may be further provided. Thereby, the current of the commercial power supply frequency and the tracking current can be measured.

[0018] In a current measurement device according to an embodiment, a control unit and a display unit are further provided, and the control unit may cause the display unit to display the output current of the low-pass filter measured by the first current measurement circuit and the tracking current measured by the second current measurement circuit. Thereby, the user can easily confirm the current of the commercial power supply frequency and the tracking current.

[0019] In the current measurement device according to an embodiment, the second coil may be capable of detecting a current having a commercial power supply frequency together with the tracking current.

[0020] In the current measurement device according to an embodiment, the number of turns of the second coil may be 1 / 100 or less of the number of turns of the first coil. Thereby, the second coil can detect the tracking current.

[0021] In the current measurement device according to an embodiment, the magnetic core may have a ring shape.

[0022] In the current measurement device according to an embodiment, a part of the magnetic core may be configured to be openable and closable. Thereby, the magnetic core can sandwich the wiring to be measured.

Advantages of the Invention

[0023] According to the present disclosure, it is possible to provide a current measurement device capable of easily separating a tracking current.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

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

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

[0027] The current measurement device 10 is a device that measures a tracking current. FIG. 1 shows a state where the current measurement 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 measurement device 10 can measure the tracking current by separating the current flowing through the wiring 100 into a commercial power frequency current and a tracking current.

[0029] The commercial power frequency current is a current that flows through loads such as electrical devices connected to an outlet, and is a current with a low frequency such as 50 Hz or 60 Hz, for example.

[0030] The tracking current is a pulsed current that flows between the electrodes of a plug inserted into an outlet through dust or the like, and is a current with a high frequency. The frequency of the tracking current is, for example, about several 100 kHz, which is much higher than the frequency of the commercial power frequency current.

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

[0032] The magnetic core 11 can be arranged so as to surround the periphery of the wiring 100 that is the measurement target. The magnetic core 11 may have, for example, a ring shape. The magnetic core 11 may have a configuration in which a part is openable and closable. When the magnetic core 11 has a configuration in which a part is openable and closable, the wiring 100 can be sandwiched.

[0033] The first coil L1 is a coil wound around the magnetic core 11. The first coil L1 can detect a current at the 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 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.

[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, etc. 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] Referring to FIG. 2, the principle by which the first coil L1 detects a current at the commercial power frequency flowing through the wiring 100 and the second coil L2 detects a tracking current flowing through the wiring 100 will be described.

[0037] In the example shown in FIG. 2, a current Io at the commercial power frequency and a tracking current It are superimposed and flowing through the wiring 100. At this time, a magnetic field M1 is generated around the wiring 100 due to the current Io at the commercial power frequency. Also, a magnetic field M2 is generated around the wiring 100 due to the tracking current It.

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

[0039] First, consider the current for canceling the magnetic field M1 caused by the current Io of the commercial power supply frequency. Currents for canceling the magnetic field M1 flow through both the first coil L1 and the second coil L2. However, since the number of turns of the first coil L1 is much larger than that of 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, when the number of turns of the second coil L2 is 1 / 1000 of the number of turns of 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 current Io of the commercial power supply frequency can be detected by detecting the current flowing through the first coil L1.

[0040] Subsequently, consider the current for canceling the magnetic field M2 caused by the tracking current It. The tracking current It is a current with a high frequency such as several 100 kHz. Therefore, in order to cancel the magnetic field M2, it is necessary to flow a high-frequency current through the first coil L1 and the second coil L2. However, since the first coil L1 has a large number of turns and a large inductance component, it can hardly flow a high-frequency current. On the other hand, since the second coil L2 has a small number of turns and a small inductance component, it can flow a high-frequency current.

[0041] Therefore, the 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 description will be continued.

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

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

[0045] The control unit 14 controls the entire current measurement device 10 and each block of the current measurement device 10. The control unit 14 includes at least one processor, at least one dedicated circuit, or a combination thereof. The processor is a general-purpose processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit), or a dedicated processor specialized for specific processing. The dedicated circuit is, for example, an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

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

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

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

[0049] FIG. 3 shows an example of the appearance of the current measurement device 10 according to the first embodiment. FIG. 3 is an example when the current measurement device 10 is a clamp-type current measurement device.

[0050] When configured as shown in FIG. 3, a part of the magnetic core 11 is openable and closable, 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 current at the commercial power supply frequency and the tracking current. Current at commercial power supply frequency: 11.23 A Tracking current: 125.5 mA

[0052] According to the current measurement device 10 according to the first embodiment as described above, the tracking current can be easily separated. More specifically, the current measurement device 10 includes 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 less than the number of turns of the first coil L1. Thereby, the first coil L1 with a large number of turns detects the current at the commercial power supply frequency, and the second coil L2 with a small number of turns detects the tracking current. In this way, since the first coil L1 with a large number of turns detects the current at the commercial power supply frequency and the second coil L2 with a small number of turns detects the tracking current, the current measurement device 10 according to the first embodiment can easily separate the tracking current.

[0053] (Second Embodiment) FIG. 4 is a schematic configuration diagram of a current measurement device 10a according to the second embodiment.

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

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

[0056] The current measurement device 10a according to the second embodiment is different from the current measurement device 10 according to the first embodiment shown in FIG. 1 mainly in that it includes an amplifier circuit 16 and a low-pass filter 17.

[0057] Regarding the current measurement device 10a according to the second embodiment, the differences from the current measurement device 10 according to the first embodiment will be mainly described, and the descriptions of the points common or similar to the current measurement device 10 according to 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 the tracking current flowing through the wiring 100 sandwiched by the magnetic core 11. Also, the second coil L2 can detect the current of the commercial power supply frequency flowing through the wiring 100 sandwiched by the magnetic core 11 together with the tracking current.

[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 the current of the commercial power supply frequency and the tracking current detected by the second coil L2.

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

[0062] The low-pass filter 17 passes and outputs the current of a low frequency among the output currents of the amplifier circuit 16. That is, the low-pass filter 17 passes the current of the commercial power supply frequency among the output currents of the amplifier circuit 16, and hardly passes the tracking current among the output currents 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 the current of the commercial power supply frequency which is a current of a low frequency and the tracking current which is a current of a high frequency. The low-pass filter 17 outputs only the current of the commercial power supply frequency which is a current of a low frequency.

[0064] The output current of the low-pass filter 17 is supplied to the first coil L1. That is, the current of the commercial power supply 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 supply frequency is fed back to the first coil L1, the magnetic field generated due to the current of the commercial power supply frequency flowing through the wiring 100 and the magnetic field generated due to the current of the commercial power supply frequency fed back to the first coil L1 cancel each other out.

[0066] Then, the magnetic field generated due to the current of the commercial power supply frequency flowing through the wiring 100 is greatly reduced, and only the magnetic field generated due to the tracking current flowing through the wiring 100 mainly remains. Therefore, only the current for canceling the magnetic field generated due to the tracking current hardly flows through the second coil L2. Therefore, the second coil L2 can detect the tracking current.

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

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

[0069] Also, with the current measurement device 10a according to the second embodiment as described above, the tracking current can be easily separated. More specifically, the current measurement 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 the current at the commercial power supply frequency among the output currents of the amplifier circuit 16. Then, the output current of the low-pass filter 17 is fed back to the first coil L1. As a result, the magnetic field generated due to the current at the commercial power supply frequency flowing through the wiring 100 and the magnetic field generated due to the current at the commercial power supply frequency fed back to the first coil L1 cancel each other out. Therefore, since the second coil L2 can detect only the tracking current, the current measurement device 10a according to the second embodiment can easily separate the tracking current.

[0070] (Third Embodiment) FIG. 5 is a schematic configuration diagram of the current measurement device 10b according to the third embodiment.

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

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

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

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

[0075] As described above, the current measurement device 10b according to the third embodiment does not include a control unit 14 and a display unit 15. Therefore, since it is not necessary to supply power to the control unit 14 and the display unit 15, it is possible to adopt a simple configuration without a power supply unit.

[0076] FIG. 6 shows an example of the appearance of the current measurement device 10b according to the third embodiment. FIG. 6 is an example when the current measurement device 10 is a clamp-type probe.

[0077] In the case of the configuration shown in FIG. 6, a part of the magnetic core 11 is openable and closable, and the magnetic core 11 can sandwich the wiring 100 to be measured.

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

[0079] The current measurement device 10b according to the third embodiment does not include the control unit 14 and the display unit 15 that the current measurement device 10 according to the first embodiment includes, but a configuration in which the current measurement device 10a according to the second embodiment does not include the control unit 14 and the display unit 15 is similarly possible.

[0080] It is obvious to those skilled in the art that the present disclosure can be realized in other predetermined forms other than the above-described embodiments without departing from its spirit or its essential features. Therefore, the foregoing description is illustrative and not limiting. The scope of the disclosure is defined by the appended claims rather than the foregoing description. Some changes within the scope of equivalents of any change are included therein.

[0081] For example, the arrangement and number of each of the above-described components are not limited to the content shown in the above description and the drawings. The arrangement and number of each component may be arbitrarily configured as long as its 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 is shown, but a plurality of 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, the error due to the measurement position can be reduced, and the first coil L1 can detect the current with higher accuracy.

[0083] For example, in the above-described embodiment, a configuration in which one second coil L2 is wound around the magnetic core 11 is shown. However, a plurality of 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 the measurement position can be reduced, and the second coil L2 can detect the current with higher accuracy.

[0084] For example, in the above-described embodiment, a configuration in which the first coil L1 and the second coil L2 are wound around the magnetic core 11 is shown. However, a 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 or the like.

[0085] For example, in the above-described embodiment, a configuration in which the current measuring devices 10 and 10a can measure the commercial power frequency current and the tracking current is shown. However, 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), and the like.

[0086] For example, in the above-described embodiment, a case where the second coil L2 detects the tracking current is shown. However, by adjusting the number of turns of the second coil L2, the second coil L2 may be configured to be able to separate and detect harmonics.

Explanation of Reference Numerals

[0087] 10, 10a, 10b Current measuring device 11 Magnetic core 12 First current measuring circuit 13 Second current measuring circuit 14 Control unit 15 Display unit 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 measurement 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; Comprising; The number of turns of the second coil is less than the number of turns of the first coil; The first coil can detect a current of commercial power supply frequency flowing through the wiring; The second coil can detect a tracking current flowing through the wiring; A first current measurement circuit for measuring the current of commercial power supply frequency detected by the first coil; A second current measurement circuit for measuring the tracking current detected by the second coil; A current measurement device further comprising.

2. In the current measurement device according to Claim 1, Further comprising a control unit and a display unit; The control unit causes the display unit to display the current of commercial power supply frequency measured by the first current measurement circuit and the tracking current measured by the second current measurement circuit. A current measurement device.

3. A current measurement 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; An amplifier circuit for amplifying the output current of the second coil; A low-pass filter for outputting a current of commercial power supply frequency among the output currents of the amplifier circuit; Comprising; The number of turns of the second coil is less than the number of turns of the first coil; The second coil can detect a tracking current flowing through the wiring; The output current of the low-pass filter is fed back to the first coil. A current measurement device.

4. In the current measurement device according to Claim 3, A first current measurement circuit for measuring the output current of the low-pass filter; A second current measurement circuit for measuring the tracking current detected by the second coil; A current measurement device further comprising.

5. In the current measurement device according to Claim 4, 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 measurement circuit and the tracking current measured by the second current measurement circuit. A current measurement device.

6. In the current measurement device according to Claim 3, The second coil can also detect a current of commercial power supply frequency together with the tracking current. A current measurement device.

7. In the current measurement 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. **Claim 8** In the current measuring device according to claim 1, The magnetic core has a ring shape, a current measuring device. **Claim 9** In the current measuring device according to claim 1, The magnetic core is configured such that a part thereof can be opened and closed, a current measuring device.

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