JP4791431B2 - Non-contact voltage current probe device - Google Patents

Description

  The present invention relates to a contactless voltage / current probe apparatus capable of measuring a voltage in a cable and a current flowing in the cable.

  In information communication devices and electronic / electrical devices, high-density, high-integration, large-capacity, and low-power consumption are progressing with the progress of semiconductor technology. The configuration of the apparatus has also become complicated, and various cables and the like have been connected. Various transmission systems have been devised, and the types of signals used for communication are increasing. Furthermore, inverter technology and the like have been introduced for power saving, and the power harmonics of the power supply system and electromagnetic interference waves generated thereby are increasing.

  In these situations, malfunctions and failures due to signal degradation, malfunctions due to power quality degradation due to power harmonics, and electromagnetic interference generated from various devices are induced to the cable connected to the device and transmitted through the cable. As a result, malfunctions and failures of other devices have occurred. As the capacity of the device increases, the social impact of a single failure is increasing, and a technique for preventing malfunctions and failures due to such causes is required.

  In the above cases, it is necessary to measure the voltage and current of the signal at the same point, the voltage of the harmonic, the current, the voltage of the electromagnetic interference wave, and the current, but at present, the voltage and current are detected. A probe is required separately. Until now, various probes have been developed for measuring voltage and current. For example, in a voltage probe used for normal voltage measurement, it is necessary to contact the conductor of the cable to be measured, and it is necessary to cut the cable and peel off the outer sheath. It was difficult to apply to existing cables. On the other hand, non-contact type voltage probes and current probes using electromagnetic coupling and electrostatic coupling with cables have been developed, but each is a separate probe and should correspond to various cable diameters in the same way. It is necessary to arrange the necessary measurement bandwidth. Due to physical size restrictions and influences during measurement, there were problems in handling such as measurement locations being not the same.

  Furthermore, in the field of EMC (Electoromagnetic Compatibility), it is necessary to measure common-mode conductive electromagnetic interference radiated from the electronic device through the cable. In the case of ordinary electronic devices, Conducted at specific test sites. However, in a large electronic device that cannot be measured at a test site, such as a large display such as a stadium or a system composed of a large number of devices, how to measure the conducted disturbance is a problem. It has become. For example, when voltage and current are measured individually, the common mode impedance of the measurement target is unknown, so voltage measurement when the impedance is low, or measurement of only the current when the impedance is high, etc. In addition, there is a possibility that the phenomenon that occurs is not accurately captured. Therefore, also in this field, a technique for simultaneously measuring voltage and current at the same place is required.

  Note that there are Non-Patent Documents 1 and 2 as documents relating to the non-contact type voltage probe device. In the structures disclosed in these documents, a voltage generated in a cable passing through the inside is detected by a cylindrical internal electrode, and between the internal electrode and an external electrode arranged in a coaxial cylindrical shape and connected to ground. By detecting this voltage, it is possible to measure the voltage generated in the cable. In this structure, the internal electrode plays a role of voltage detection, and the external electrode provides a role of providing a reference potential and shielding the internal electrode.

  Among non-contact type voltage probes, those utilizing electromagnetic coupling have been developed and sold as shown in Non-Patent Document 3. A current probe using electromagnetic coupling as in Non-Patent Document 3 has a structure in which an inner conductor wire wound around a core material is terminated with a low impedance and is housed in a metal shield storage box. The magnetic field generated by the current flowing in the cable is detected by the toroidal coil, and the voltage generated in the terminal impedance by electromagnetic induction is proportional to the current flowing in the cable, so that the current can be measured. In many current probes, a toroidal coil is housed in a shielded metal box in order to eliminate measurement errors caused by electrostatic coupling with the metal body surrounding the measurement and electrostatic coupling with the cable. .

Considering these structures, both have an internal electrode for detection and a toroidal coil that are coaxially configured, and an electrostatic shield for eliminating the influence of disturbance.
R. Kobayashi, Y, Hiroshima, H, Ito, H, Fururu, M. Hattori, and, Y. Tada: “A Novel Non-contact Capacitive Probe for Common-mode Voltage Measurement”, Trans. EB, Vol. E90- B, No.6, Jun, 2007 Hiroshima, Kuwahara, "Effect of side shield on capacitive voltage probe" IEICE Society Conference Proceedings 1999 Communications Society Conference (Proceedings 1), B-4-50,234, 1999/08/16 ETS-EMCO current probe, [online], Internet <URL: http: //www.astechcorp.co.jp/jp/electronics/Electronics/content/EMCO/current.htm>

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a non-contact voltage / current probe apparatus capable of measuring a voltage in a cable and a current flowing in the cable.

  In the present invention, the toroidal coil functions as a coil that captures the magnetic field generated by the cable penetrating the inside by adopting a structure formed by a coaxially configured toroidal coil and an outer conductor that shields it outside. At the same time, it is characterized by functioning as an internal electrode for voltage detection by electrostatic coupling with the cable. Further, the present invention is characterized in that a reference point for voltage measurement can be provided by adopting a structure in which an external conductor attached for the purpose of eliminating the influence of disturbance can be connected to ground. In this structure, the voltage generated by electromagnetic induction and the voltage generated by electrostatic coupling are applied to the terminal resistance of the toroidal coil, so two voltages between both ends of the terminal resistance of the toroidal coil and the ground are A voltage proportional to the voltage and current of the cable can be measured by adding a function of measuring at a high input impedance. Further, in this structure, it is possible to simultaneously measure two physical quantities of voltage and current at the same location in a non-contact manner with a single non-contact voltage / current probe device. As a result, it is possible to measure the voltage and current at the same point, which was the problem described above, and even when the impedance is unknown, the two physical quantities of voltage and current can be measured at the same time, so that accurate evaluation is possible. Furthermore, the inconvenience of handling is eliminated.

  ADVANTAGE OF THE INVENTION According to this invention, the non-contact-type voltage current probe apparatus which can measure the voltage in a cable and the electric current which flows through a cable can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a configuration diagram of a non-contact type voltage / current probe apparatus according to the first embodiment.

  The non-contact type voltage / current probe apparatus is a non-contact type voltage / current probe apparatus for measuring a voltage V with respect to the ground in the cable 6 and a current I flowing through the cable 6, and a space through which the cable 6 passes is formed inside. A cylindrical inner core 1, a toroidal coil 1A having an inner conductor wire 2 wound around the inner core 1, and a cylindrical shape in which a space through which the cable 6 penetrates and the toroidal coil 1A is disposed is formed inside. An outer conductor 3, a fixing jig 4 provided on the inner side of the inner core 1 for fixing the cable 6 and preventing the cable 6 from approaching the inner conductor wire 2 within a predetermined distance; and the inner core 1 Between the inner core 1 and the outer conductor 3, a spacer 5 that makes the distance between the inner core 1 and the outer conductor 3 constant, and a termination resistor inserted between one end and the other end of the inner conductor wire 2. 8 and A metal storage box 10 having a connection terminal 9 which is means for connecting the external conductor 3 to the ground, a voltage detection circuit 11a for detecting a potential difference with respect to the ground at one end of the termination resistor 8, and a ground at the other end of the termination resistor 8 A voltage detection circuit 11b that detects a potential difference with respect to the voltage, an adder 13a that measures the sum of the detected potential differences, and a subtractor 13b that measures the difference between the detected potential differences.

  The inner core 1 is made of a magnetic material selected according to the frequency of the current I. When it is desired to use the toroidal coil 1A as an air core, the inner core 1 is formed of a nonmagnetic material. When the connectivity between the toroidal coil 1A and the cable 6 is increased and the inductance of the toroidal coil 1A is increased, the inner core 1 is formed of a magnetic material having high magnetic permeability, for example, ferrite or amorphous. Thus, the inner core 1 may be formed of a material according to the purpose. Although the inner core 1 has a cylindrical shape, the inner core 1 may have a cylindrical shape in order to form a toroidal coil, and may have a rectangular cross-sectional shape, for example.

  The fixing jig 4 is made of a foaming material such as foamed rubber or foamed urethane, and has plasticity.

  The fixing jig 4 and the spacer 5 are formed of a material (for example, plastic, silicon caulking agent, etc.) that is a low dielectric constant dielectric material and a low magnetic permeability magnetic material or nonmagnetic material. Thereby, the influence of the measurement in the high frequency region can be reduced.

  The spacer 5 is cylindrical, but may be cylindrical as long as the distance between the inner core 1 and the outer conductor 3 can be made constant. The spacer 5 may be filled with the above material between the inner core 1 and the outer conductor 3.

  The metal storage box 10 has electrical conductivity and is electrically and mechanically connected to the external conductor 3 and the connection terminal 9, and stores the voltage detection circuits 11a and 11b, the adder 13a, and the subtractor 13b. Each voltage detection circuit 11a, 11b has a high input impedance.

  By connecting the connection terminal 9 to the ground, the metal storage box 10 and the external conductor 3 become equipotential with the ground, the internal conductor wire 2 and the circuit in the metal storage box 10 are electrostatically shielded, and are influenced by the influence of the surroundings. Measurement error is reduced.

  Both ends of the inner conductor wire 2 are drawn into the metal storage box 10 through the through holes 14, and the termination resistor 8 is disposed in the metal storage box 10. By drawing the inner conductor wire 2 into the metal storage box 10, the influence of the parasitic capacitance due to the coupling between the inner conductor wire 2 and the periphery and the high frequency region can be minimized. In addition, by drawing the inner conductor wire 2 into the metal storage box 10, the length of the drawn portion can be minimized, and the influence of parasitic inductance in the high frequency region can be minimized. Further, by pulling the inner conductor wire 2 into the metal storage box 10, the voltage detection circuits 11a and 11b, the adder 13a, and the subtractor 13b can be easily attached.

  The outputs of the voltage detection circuits 11a and 11b are connected to the inputs of an adder 13a and a subtractor 13b.

  The output of the adder 13 a is connected to an output terminal 12 a that is electrically and mechanically connected to the metal storage box 10. The output of the subtractor 13 b is connected to an output terminal 12 b that is electrically and mechanically connected to the metal storage box 10.

  The voltage detection circuits 11 a and 11 b, the adder 13 a and the subtractor 13 b are supplied with power from the battery 25 stored in the metal storage box 10. For charging the battery 25, for example, a nickel metal hydride battery or a lithium ion battery may be used. In addition, a power supply terminal may be provided in the metal storage box 10 to supply power from the outside.

  Considering the voltage V and current I shown in FIG. 1, a magnetic field 7 based on Ampere's law is generated around the cable 6 at this time. An electromotive force proportional to the current I is generated by electromagnetic induction in the internal conductor wire 2 constituting the toroidal coil 1 </ b> A, and the induced electromotive force is applied to the termination resistor 8.

  The voltage detection circuit 11a detects a potential difference with respect to the ground at one end of the termination resistor 8, the voltage detection circuit 11b detects a potential difference with respect to the ground at the other end of the termination resistor 8, and a subtractor 13b detects the potential difference between the detected potential differences. When the difference is measured, the difference becomes a potential difference between both ends of the termination resistor 8. This potential difference is induced by the current I and is proportional to the current I. That is, an output proportional to the current I is obtained.

  On the other hand, the inner conductor wire 2 is also coupled to the cable 6 by electrostatic induction, and an electrostatic induction voltage is generated between the inner conductor wire 2 and the cable 6. Further, the inner conductor line 2 is coupled to the outer conductor 3 by electrostatic induction, and an electrostatic induction voltage is generated between the inner conductor line 2 and the outer conductor 3. If the outer conductor 3 is connected to the ground, the space between the cable 6, the inner conductor wire 2, and the outer conductor 3 is equivalent to being divided by capacitance. Therefore, the voltage V can be measured by measuring the potential difference between the inner conductor wire 2 and the outer conductor 3. The potential difference between the inner conductor wire 2 and the outer conductor 3 is the average (1/2 of the sum) of the potential difference between one end of the terminating resistor 8 and the ground and the potential difference V2 between the other end of the terminating resistor 8 and the ground. Can be obtained.

  FIG. 2 is a diagram showing an equivalent circuit of the non-contact voltage / current probe apparatus according to the first embodiment.

  The detection part of the cable 6 and the probe includes the inductance L1 of the cable 6, the inductance L2 of the toroidal coil 1A composed of the inner core 1 and the inner conductor wire 2, and the mutual inductance M between them, the inner conductor wire 2 and the cable 6. The coupling capacitances C and C, the coupling capacitances Cs and Cs between the inner conductor line 2 and the outer conductor 3, and the impedance Z of the termination resistor 8 are represented.

  The voltage detection circuit 11a connected to one end of the impedance Z is given by a parallel circuit 20a of a high resistance Rp and a capacitor Cp. The voltage detection circuit 11b connected to the other end of the impedance Z is given by a parallel circuit 20b of a high resistance Rp and a capacitor Cp.

  The high resistance Rp is usually in the range of 100 kΩ to several tens of MΩ, and the capacitor Cp is usually given in the order of several pF to 50 pF.

In FIG. 2, when the impedance jωL1 due to the inductance L1 in the frequency band of the current I and the voltage V is sufficiently small and the impedance 1 / jωC due to the coupling capacitances C and C is sufficiently large, the current I generates in the toroidal coil. The electromagnetic induction voltage does not depend on the coupling capacitances C and C, and if the potential drop of the inductance L1 is sufficiently small, the electrostatic induction voltage generated in the internal conductor line 2 is proportional only to the common mode voltage. Therefore, if the potentials at both ends of the impedance Z are V1 and V2, the potential difference Vd is
Vd = V1-V2 (1)
It is. This is a potential generated by the inductance L1, the inductance L2, and the mutual inductance M, and is proportional to the current I flowing through the cable.

On the other hand, a potential is generated in the inner conductor line 2 due to electrostatic induction. This can be assumed when the potential drop at jωL1 is sufficiently small, and the potential difference V1 between one end of the impedance Z and the ground and the impedance Z Is given by the average of the potential difference V2 between the other end of each and the ground. That is, the average voltage Vc is
Vc = (V1 + V2) / 2 (2)
As given. This Vc is a voltage determined by the coupling capacitances C and C between the cable 6 and the inner conductor line 2, the coupling capacitances Cs and Cs between the inner conductor line 2 and the outer conductor 3, and the impedances 20a and 20b of the voltage detection circuits 11a and 11b. Yes, proportional to the voltage V generated in the cable.

  FIG. 3 is a diagram illustrating the frequency characteristics of voltage and current in the first embodiment. From FIG. 3, it can be confirmed that the voltage and current generated in the cable can be measured in the range of 0.01 MHz to 10 MHz.

  FIG. 4 is a diagram showing sensitivity characteristics obtained by measuring the relationship between voltage input and output in the first embodiment. FIG. 4 is obtained by measuring the relationship between the output voltage and the input voltage at four representative frequencies (10 kHz, 100 kHz, 1 MHz, and 10 MHz).

  FIG. 5 is a diagram showing sensitivity characteristics obtained by measuring the relationship between current input and output in the first embodiment. FIG. 5 is obtained by measuring the relationship between the input current and the output current at four representative frequencies (10 kHz, 100 kHz, 1 MHz, and 10 MHz).

  4 and 5, it can be confirmed that, in this frequency range, the output increases in proportion to the increase in input for both voltage and current.

From the equivalent circuit of FIG.
(A) The impedance jωL1 of the cable inductance L1 is sufficiently smaller than the impedance 1 / jωC of the coupling capacitances C and C.

Since the current I flows only in the cable in the range where is established, the difference between the voltages V1 and V2 across the inductance L2 of the toroidal coil is the voltage Vm generated by electromagnetic induction. Further, the potentials Va and Vb of the coupling capacitances C and C and the contact point of the cable are considered to be equal if the potential drop of the inductance L1 is sufficiently small. For this reason, the voltages V1 and V2 across the toroidal coil inductance L2 are divided by the potential Vc generated by the divided voltages of the coupling capacitances C and C and the parallel circuits 20a and 20b, and the coupling capacitances Cs and Cs of the inner conductor 2 and the outer conductor 3, respectively. Will only be raised. Accordingly, the potentials V1 and V2 at both ends of the inductance L2 of the toroidal coil are V1 = Vm / 2 + Vc (3)
V2 = −Vm / 2 + Vc (4)
By measuring the voltage between both ends of the toroidal coil and the ground by the voltage detection circuits 11a and 11b, and taking the difference (V1-V2), the value proportional to the current, the average of the sum ( When V1 + V2) / 2 is taken, the value is proportional to the voltage. That is, an output proportional to the voltage V and the current I can be obtained within a range where the condition (A) is satisfied. 4 and 5, the input and output of voltage and current are proportional to each frequency. From this, in the first embodiment, the input is proportional to voltage V and current I in this frequency range. It was confirmed that the value could be measured.

[Second Embodiment]
FIG. 6 is a configuration diagram of the non-contact voltage / current probe apparatus according to the second embodiment.

  In the second embodiment, unlike the first embodiment shown in FIG. 1, the adder 13 a and the subtracter 13 b are not housed in the metal storage box 10. In the case of the first embodiment, it is conceivable that the circuit configuration becomes complicated by housing the adder 13a and the subtractor 13b. Therefore, the internal configuration of the metal storage box 10 is simplified by eliminating the adder 13a and the subtractor 13b and individually outputting the voltages detected at both ends of the termination resistor 8 to the output terminals 12a and 12b. Can do. Furthermore, by using a digital oscilloscope or the like that can store digital data in a measuring device connected to the connection terminal and can perform internal arithmetic processing, an advantage that the output of measurement data can be arbitrarily processed can be obtained.

[Third Embodiment]
FIG. 7 is a configuration diagram of a non-contact type voltage / current probe apparatus according to the third embodiment.

  In the third embodiment, a disc-shaped conductive plate 24 is further provided in order to improve the shielding performance from the disturbance existing around the non-contact type voltage / current probe apparatus shown in FIG. The conductive plate 24 is connected to the end face of the outer conductor 3 so as to face the end face of the inner core 1. In the conductive plate 24, an opening through which the cable 6 passes is formed inside.

  In the non-contact type voltage / current probe device of FIG. 1, there is a possibility that the inner conductor wire 2 is coupled with a disturbance factor (metal body, other cable, etc.) around the inner conductor wire 2. Therefore, by providing the conductive plate 24 of the third embodiment, the shielding effect obtained by the external conductor 3 can be enhanced.

  FIG. 8 is a diagram showing an outline thereof.

  As shown in FIG. 8A, the disturbance factor is directly coupled to the inner conductor line 2 and affects the measurement result. However, as shown in FIG. 8B, by providing the conductive plate 24, it is possible to reduce the electrostatic coupling between the internal conductor wire 2 and the disturbance factor and improve the measurement accuracy. In the third embodiment, the conductive plate 24 is formed in a disc shape in accordance with the shape of the outer conductor 3. However, the conductive plate 24 may be provided with an opening through which the cable 6 penetrates, for example, in a rectangular shape.

[Fourth Embodiment]
FIG. 9 is a configuration diagram of a non-contact type voltage / current probe apparatus according to the fourth embodiment.

  In the fourth embodiment, the inner core 1 is divided and the outer conductor 3 is divided with respect to the non-contact voltage / current probe apparatus shown in FIG. A part of the inner conductor wire 2 is wound around one part of the inner core 1 generated by the division, and the other part of the inner conductor wire 2 is wound around the other part of the inner core 1 generated by the division. Has been. As a result, the cable can be easily sandwiched. In the fourth embodiment, the conductive plate 24 is provided and divided, but the conductive plate 24 may not be provided.

  In order to ensure electrical and mechanical connection between the outer conductor 3 and the conductive plate 24 and to improve the mobility, an electrode fixing stopper 26 is attached to one side of the divided outer conductor 3. A hinge 27 is attached to the opposite side. This ensures the mobility and secures the electrical and mechanical connection after the cable is sandwiched. In the present embodiment, the fastener 26 is attached only to the outer conductor 3, but may be added to the conductive plate 24 in order to connect more reliably. With this structure, the non-contact type voltage / current probe device can be easily attached to the cable, and workability can be improved.

It is a block diagram of the non-contact type voltage current probe apparatus which concerns on 1st Embodiment. It is a figure which shows the equivalent circuit of the non-contact-type voltage current probe apparatus which concerns on 1st Embodiment. It is a figure which shows the frequency characteristic of each voltage and electric current in 1st Embodiment. It is a figure which shows the sensitivity characteristic obtained by measuring the relationship of the input / output of the voltage in 1st Embodiment. It is a figure which shows the sensitivity characteristic obtained by measuring the relationship of the input / output of the voltage in 1st Embodiment. It is a block diagram of the non-contact type voltage current probe apparatus which concerns on 1st Embodiment which concerns on 2nd Embodiment. It is a block diagram of the non-contact-type voltage current probe apparatus which concerns on 3rd Embodiment. It is a figure which shows the outline | summary of heightening the shielding effect obtained by the external conductor with a conductive plate. It is a block diagram of the non-contact-type voltage current probe apparatus which concerns on 4th Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal core 1A ... Toroidal coil 2 ... Internal conductor wire 3 ... Outer conductor 4 ... Fixing jig 5 ... Spacer 6 ... Cable 8 ... Terminating resistor 9 ... Connection terminal 10 ... Metal storage box 11a, 11b ... Voltage detection circuit 13a ... Adder 13b ... Subtractor 24 ... Conductive plate

Claims (9)

A non-contact voltage-current probe device for measuring a voltage to ground in a cable and a current flowing in the cable,
A cylindrical inner core in which a space through which the cable passes is formed, a toroidal coil having an inner conductor wire wound around the inner core,
A cylindrical outer conductor in which a space through which the cable passes and the toroidal coil is disposed is formed;
A fixing jig that is provided inside the inner core and fixes the cable and prevents the cable from approaching the inner conductor wire within a predetermined distance;
A spacer which is provided between the inner core and the outer conductor and makes a distance between the inner core and the outer conductor constant;
A terminating resistor inserted between one end and the other end of the inner conductor wire;
Means for connecting the outer conductor to ground;
A voltage detection circuit for detecting a potential difference with respect to ground at one end of the termination resistor;
A voltage detection circuit for detecting a potential difference with respect to ground at the other end of the termination resistor;
An adder that measures the sum of the detected potential differences;
A non-contact type voltage / current probe apparatus comprising: a subtractor that measures a difference between the detected potential differences.   2. The contactless voltage / current probe apparatus according to claim 1, wherein each of the voltage detection circuits has a high input impedance.   The non-contact type voltage / current probe apparatus according to claim 1, wherein the inner core is formed of a magnetic material selected according to the frequency of the current.   4. The non-contact type according to claim 1, further comprising a conductive storage box connected to the outer conductor and storing the voltage detection circuit, the adder, and the subtractor. Voltage current probe device.   The non-contact type voltage / current probe apparatus according to claim 1, wherein the inner core and the outer conductor have a cylindrical shape.   6. The non-contact type jig according to claim 1, wherein the fixing jig is formed of a dielectric material having a low dielectric constant and a magnetic material or non-magnetic material having a low magnetic permeability and having plasticity. Voltage current probe device.   7. The non-contact type voltage current according to claim 1, wherein the spacer is formed of a dielectric material having a low dielectric constant and a magnetic material or a non-magnetic material having a low magnetic permeability. Probe device.   8. The conductive plate according to claim 1, further comprising a conductive plate that is connected to an end surface of the outer conductor so as to face an end surface of the inner core and that has an opening formed on an inner side thereof. Non-contact voltage / current probe device.   9. The non-contact type voltage / current probe apparatus according to claim 1, wherein the inner core is divided and the outer conductor is divided.

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