Non-contact voltage measuring device

Abstract

To provide a non-contact voltage measuring device that measures the voltage of a conductor of an electric wire in real time in correspondence with an environmental change with simpler calculation than in a prior art.SOLUTION: A non-contact voltage measuring device 1 comprises: electrodes 11, 12 provided in a grip member 10 for gripping an electric wire 2A; a capacitor C1 and an amplifier circuit 21 connected with the electrode 11; a capacitor C2 and an amplifier circuit 22 connected with the electrode 12; and an operation unit 23. The capacitor C1 is connected with an inverted input terminal 211B of the amplifier circuit 21. The capacitor C2 is connected with an inverted input terminal 221B of the amplifier circuit 22. The amplifier circuits 21, 22 include capacitors C3, C4, respectively. The operation unit 23 calculates the voltage of a conductor 2Aa of the electric wire 2A based on the capacities C1, C2, C3, C4 of the capacitors and the voltages of output terminals 211C, 221C of the amplifier circuits 21, 22.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a non-contact voltage measuring device that measures the voltage of a conductor of an electric wire without coming into contact with the conductor. [Background technology]

[0002] 2. Description of the Related Art A non-contact voltage measuring device is known that includes two electrodes and calculates the voltage of a conductor of an electric wire from the voltage induced in each of the two electrodes.

[0003] However, such a non-contact voltage measurement device cannot accurately calculate the drive voltage supplied to a rotating machine that is inverter-driven, because in order to measure the drive voltage of a rotating machine that is inverter-driven, it is necessary to measure a voltage that includes multiple frequency components.

[0004] Therefore, the non-contact voltage measuring device disclosed in Patent Document 1 includes a first voltage measuring unit connected to the first electrode, a second voltage measuring unit connected to the second electrode, a time domain-to-frequency domain conversion unit that converts data measured by each voltage measuring unit from the time domain to the frequency domain, a frequency-by-frequency voltage value calculation unit that calculates a voltage value for each frequency from the data converted to the frequency domain, a frequency domain-to-time domain conversion unit that converts the data of the voltage value for each frequency from the frequency domain to the time domain, and a conductor voltage calculation unit that calculates the voltage of the conductor from the data converted to the time domain. In other words, the non-contact voltage measuring device disclosed in Patent Document 1 includes a time domain-to-frequency domain conversion unit, a frequency-by-frequency voltage value calculation unit, and a frequency domain-to-time domain conversion unit, so that it is possible to measure a voltage including a plurality of frequency components. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-91209 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the non-contact voltage measuring device disclosed in Patent Document 1, it is necessary to convert the data measured by each voltage measuring unit from the time domain to the frequency domain, calculate the voltage value for each frequency, and convert the data for each frequency from the frequency domain to the time domain. In this case, it is necessary to use a Fourier transform or the like in the calculation process, which makes the calculation complicated.

[0007] Therefore, the object of the present invention is to solve the above-mentioned problems and to provide a non-contact voltage measuring device that can measure the voltage of an electric wire conductor in real time with simpler calculations than conventional technology and in response to environmental changes. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention is configured as follows. A non-contact voltage measuring device according to one aspect of the present invention comprises: a first electrode and a second electrode spaced apart from each other; a first capacitor connected to the first electrode; a first amplifier circuit connected in series with the first capacitor; a second capacitor connected to the second electrode; a second amplifier circuit connected in series with the second capacitor; A calculation unit, each of the first electrode and the second electrode faces a conductor of the electric wire without being in contact with the conductor of the electric wire; the first capacitor is connected to an input terminal of the first amplifier circuit; the second capacitor is connected to an input terminal of the second amplifier circuit; the first amplifier circuit includes a third capacitor connected between an output terminal and an input terminal; the second amplifier circuit includes a fourth capacitor connected between the output terminal and the input terminal; The calculation unit is The voltage of the conductor of the electric wire is calculated based on the capacitance of the first capacitor, the capacitance of the second capacitor, the capacitance of the third capacitor, the capacitance of the fourth capacitor, the voltage of the output terminal of the first amplifier circuit, and the voltage of the output terminal of the second amplifier circuit. Effect of the Invention

[0009] According to the present invention, the voltage of the conductor of the electric wire can be measured in real time with simpler calculations than those of the prior art and in response to environmental changes. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is a side view of a grip member of the non-contact voltage measuring device according to the first embodiment of the present invention. [Diagram 2] FIG. 2 is a perspective view of an arm of the gripping member of FIG. 1; [Diagram 3] 1 is a block diagram of a non-contact voltage measuring device according to a first embodiment of the present invention. [Figure 4] 1 is an equivalent circuit diagram of a non-contact voltage measuring device according to a first embodiment of the present invention. [Diagram 5] 4 is a flowchart showing a process for measuring the voltage of a conductor of an electric wire. [Figure 6] FIG. 11 is a front view of a grip member of a non-contact voltage measuring device according to a second embodiment of the present invention. [Figure 7] FIG. 11 is a perspective view of a gripping member of a non-contact voltage measuring device according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] A non-contact voltage measuring device according to one aspect of the present invention comprises: a first electrode and a second electrode spaced apart from each other; a first capacitor connected to the first electrode; a first amplifier circuit connected in series with the first capacitor; a second capacitor connected to the second electrode; a second amplifier circuit connected in series with the second capacitor; A calculation unit, each of the first electrode and the second electrode faces a conductor of the electric wire without being in contact with the conductor of the electric wire; the first capacitor is connected to an input terminal of the first amplifier circuit; the second capacitor is connected to an input terminal of the second amplifier circuit; the first amplifier circuit includes a third capacitor connected between an output terminal and an input terminal; the second amplifier circuit includes a fourth capacitor connected between the output terminal and the input terminal; The calculation unit is The voltage of the conductor of the electric wire is calculated based on the capacitance of the first capacitor, the capacitance of the second capacitor, the capacitance of the third capacitor, the capacitance of the fourth capacitor, the voltage of the output terminal of the first amplifier circuit, and the voltage of the output terminal of the second amplifier circuit.

[0012] According to this configuration, the frequency term can be eliminated in the process of calculating the voltage of the electric wire conductor by the calculation unit. This makes it possible to calculate the voltage of the electric wire conductor without performing complex calculations such as Fourier transform. In other words, it is possible to measure a voltage including multiple frequency components with simpler calculations than in the prior art.

[0013] According to this configuration, the coupling capacitance between the first electrode and the conductor of the electric wire and the coupling capacitance between the second electrode and the conductor of the electric wire can be constantly calculated, and therefore it is possible to respond in real time to changes in the coupling capacitance due to environmental changes such as changes in temperature and humidity, and deterioration of the electric wire over time.

[0014] In the non-contact voltage measurement device, the calculation unit may further calculate a first coupling capacitance between the first electrode and a conductor of the electric wire, and a second coupling capacitance between the second electrode and a conductor of the electric wire.

[0015] According to this configuration, the calculation unit can calculate the first coupling capacitance and the second coupling capacitance based on the capacitances of the first to fourth capacitors, the voltage of the output terminal of the first amplifier circuit, and the voltage of the output terminal of the second amplifier circuit, in a manner similar to the voltage of the conductor of the electric wire.

[0016] In the non-contact voltage measurement device, the calculation unit may calculate the first coupling capacitance and the second coupling capacitance by assuming that the first coupling capacitance and the second coupling capacitance are equal to each other.

[0017] According to this configuration, the first coupling capacitance and the second coupling capacitance can be calculated by a simple calculation.

[0018] In the non-contact voltage measurement device, the calculation unit may calculate the first coupling capacitance and the second coupling capacitance by assuming that a difference between the first coupling capacitance and the second coupling capacitance is constant.

[0019] According to this configuration, even if the first coupling capacitance and the second coupling capacitance are not equal, it is possible to calculate the first coupling capacitance and the second coupling capacitance.

[0020] In the non-contact voltage measuring device, the calculation unit calculates, using the following equations (1) to (6), Z1=(C L1 +C1) / jωC L1 C1···(1) Z2=(C L2 +C2) / jωC L2 C2···(2) Z3 = 1 / jωC3 (3) Z4 = 1 / jωC4 (4) V1 = -(Z3 / Z1)V L (5) V2 = -(Z4 / Z2)V L (6) Where: C L1 is a first coupling capacitance between the first electrode and a conductor of the wire, C L2is a second coupling capacitance between the second electrode and the wire conductor, C1 is the capacitance of the first capacitor, C2 is the capacitance of the second capacitor, C3 is the capacitance of the third capacitor; C4 is the capacitance of the fourth capacitor; Z1 is a composite impedance of a capacitor storing the first coupling capacitance and the first capacitor, Z2 is a composite impedance of the capacitor storing the second coupling capacitance and the second capacitor, Z3 is the impedance of the third capacitor; Z4 is the impedance of the fourth capacitor, V1 is the voltage at the output terminal of the first amplifier circuit; V2 is the voltage at the output terminal of the second amplifier circuit; V L is the voltage of the conductor of the wire, The voltage of the conductor of the wire may be calculated.

[0021] According to this configuration, C L1 and C. L2 By defining the relationship with, for example, C L1 =C L2 Thus, a simultaneous equation is derived: (5) into which (1) and (3) are substituted, and (6) into which (2) and (4) are substituted. By solving this simultaneous equation, the first coupling capacitance C L1 , second coupling capacitance C L2 , and the voltage of the wire conductor V L In the process of solving the simultaneous equations, the ω term (frequency term) disappears. This makes it possible to solve the simultaneous equations without performing complex calculations such as Fourier transform. In other words, it is possible to measure a voltage containing multiple frequency components with simpler calculations than in the prior art.

[0022] The non-contact voltage measuring device may further include a gripping member that grips the electric wire, the first electrode and the second electrode may be provided on the gripping member, and each of the first electrode and the second electrode may face the conductor of the electric wire when the gripping member grips the electric wire.

[0023] According to this configuration, the gripping member grips the electric wire, so that the voltage of the conductor of the electric wire can be calculated.

[0024] In the non-contact voltage measuring device, the first electrode and the second electrode may be arranged side by side and spaced apart along a longitudinal direction of the electric wire when the gripping member grips the electric wire.

[0025] According to this configuration, the coupling capacitance between the first electrode and the conductor of the electric wire and the coupling capacitance between the second electrode and the conductor of the electric wire can be made the same or approximately the same.

[0026] In the non-contact voltage measuring device, the first electrode and the second electrode may be arranged to face each other across a central axis of the electric wire when the gripping member grips the electric wire.

[0027] According to this configuration, the coupling capacitance between the first electrode and the conductor of the electric wire and the coupling capacitance between the second electrode and the conductor of the electric wire can be made the same or approximately the same.

[0028] First Embodiment Fig. 1 is a side view of a gripping member of a non-contact voltage measuring device according to a first embodiment of the present invention. Fig. 2 is a perspective view of an arm of the gripping member of Fig. 1. Fig. 3 is a block diagram of the non-contact voltage measuring device according to the first embodiment of the present invention.

[0029] The non-contact voltage measuring device 1 measures the voltage of a conductor of an electric wire without contacting the conductor. In the first embodiment, the non-contact voltage measuring device 1 measures the voltage of conductors 2Aa, 2Ba, 2Ca (see FIG. 3) of three-phase electric wires 2A, 2B, 2C connected to a motor 4. A gripping member 10 of the non-contact voltage measuring device 1 grips one of the three-phase electric wires 2A, 2B, 2C. The non-contact voltage measuring device 1 measures the voltage of the conductor of the electric wire gripped by the gripping member 10. In FIG. 1, the gripping member 10 grips the electric wire 2A. In FIG. 3, the non-contact voltage measuring device 1 measures the voltage of the conductor 2Aa of the electric wire 2A. The voltage measured by the non-contact voltage measuring device 1 is displayed on the display unit 3.

[0030] 3, in the first embodiment, the electric wire 2A includes a conductor 2Aa and a covering portion 2Ab that covers the conductor 2Aa. Similarly, the electric wire 2B includes a conductor 2Ba and a covering portion 2Bb that covers the conductor 2Ba, and the electric wire 2C includes a conductor 2Ca and a covering portion 2Cb that covers the conductor 2Ca.

[0031] In the following, a description will be given on the assumption that the non-contact voltage measurement device 1 grips the electric wire 2A out of the three-phase electric wires 2A, 2B, and 2C, and measures the voltage of the conductor 2Aa of the electric wire 2A.

[0032] 1 to 3, the non-contact voltage measuring device 1 includes a holding member 10 and a device body 20. As shown in Fig. 1, the holding member 10 holds an electric wire 2A. As shown in Fig. 3, the device body 20 is connected to the holding member 10.

[0033] 1 and 2, the gripping member 10 includes arms 10A and 10B. The arms 10A and 10B grip the electric wire 2A by clamping the electric wire 2A.

[0034] The arm 10A has a surface 10Aa, and the arm 10B has a surface 10Ba. The surfaces 10Aa and 10Ba face each other.

[0035] As shown in Fig. 1, when the gripping member 10 is viewed in the width direction (hereinafter referred to as the width direction), the surface 10Aa has the shape of an arc of a circle constituting a cross section when the electric wire 2A is cut perpendicular to the longitudinal direction. The width direction is parallel to the longitudinal direction of the electric wire 2A when the gripping member 10 grips the electric wire 2A. The width direction (the longitudinal direction of the electric wire 2A) coincides with the depth direction of the paper in Fig. 1 and coincides with the up-down direction of the paper in Fig. 3.

[0036] As shown in FIG. 1, when viewed in the width direction, the surface 10Ba, like the surface 10Aa, has an arc shape of a circle constituting a cross section when the electric wire 2A is cut perpendicularly to the longitudinal direction.

[0037] As a result, when the arms 10A and 10B grip the electric wire 2A, the surfaces 10Aa and 10Ba come into surface contact with the outer circumferential surface of the coating 2Ab of the electric wire 2A. The arms 10A and 10B can also grip an electric wire having a diameter different from that of the electric wire 2A. In this case, the surfaces 10Aa and 10Ba come into line contact with the outer circumferential surface of the coating of the electric wire.

[0038] 2, the arm 10A has a pair of shaft supports 10Ab that face each other in the width direction. Each of the shaft supports 10Ab has a through hole 10Ac that passes through the shaft support 10Ab in the width direction.

[0039] As shown in FIG. 1, the arm 10B has a pair of shaft support portions 10Bb. The pair of shaft support portions 10Bb face each other in the width direction. In FIG. 1, only one of the pair of shaft support portions 10Bb is shown. The pair of shaft support portions 10Bb sandwich the pair of shaft support portions 10Ab from the outer sides in the width direction. Each of the pair of shaft support portions 10Bb has a recess (not shown). The recess is formed on a surface of the shaft support portion 10Bb facing the shaft support portion 10Ab. The recess is recessed in the width direction. Each through hole 10Ac of the arm 10A and each recess of the arm 10B are aligned in a straight line along the width direction.

[0040] A shaft (not shown) is inserted through each through hole 10Ac of the arm 10A and each recess of the arm 10B. This allows the arms 10A and 10B to be rotatably supported relative to each other. That is, the arm 10A is rotatably supported by the arm 10B, and the arm 10B is rotatably supported by the arm 10A.

[0041] A torsion coil spring (not shown) is disposed between the pair of shaft support portions 10Ab. The torsion coil spring is disposed around the shaft. The arms 10A, 10B are biased by the torsion coil spring in a direction in which the gripping member 10 closes. This causes the electric wire 2A to be held in a state in which it is gripped by the gripping member 10.

[0042] In the first embodiment, the arms 10A and 10B face each other. Therefore, when the tips of the arms 10A and 10B come into contact with each other, the gripping member 10 does not close any further.

[0043] As shown in Figures 1 and 2, two electrodes 11, 12 are provided inside the arm 10A of the gripping member 10. The electrode 11 is an example of a first electrode. The electrode 11 is an example of a second electrode. As shown in Figure 2, the electrodes 11, 12 are arranged side by side and spaced apart from each other in the width direction. The electrodes 11, 12 are disposed on the back side of the surface 10Aa of the arm 10A.

[0044] As shown in FIG. 3, the gripping member 10 includes two capacitors C1 and C2. The capacitor C1 is an example of a first capacitor. The capacitor C2 is an example of a second capacitor. In the first embodiment, the capacitors C1 and C2 are provided inside the arm 10A. The capacitor C1 is connected to the electrode 11. The capacitor C2 is connected to the electrode 12. In the first embodiment, the capacitance of the capacitor C1 is set to several pF to several tens of pF. The capacitance of the capacitor C2 is set to 10 to 100 times the capacitance of the capacitor C1.

[0045] As described above, the electrodes 11 and 12 are disposed inside the arm 10A. Therefore, as shown in FIG. 1, when the gripping member 10 grips the electric wire 2A, the arm 10A is between the electrodes 11 and 12 and the electric wire 2A. Also, as described above, the conductor 2Aa of the electric wire 2A is covered by the covering portion 2Ab. Therefore, when the gripping member 10 grips the electric wire 2A, the covering portion 2Ab of the electric wire 2A is between the electrodes 11 and 12 and the conductor 2Aa of the electric wire 2A. That is, when the gripping member 10 grips the electric wire 2A, the arm 10A and the covering portion 2Ab of the electric wire 2A are between the electrodes 11 and 12 and the conductor 2Aa of the electric wire 2A. That is, when the gripping member 10 grips the electric wire 2A, the electrodes 11 and 12 are not in contact with the conductor 2Aa of the electric wire 2A.

[0046] As described above, the electrodes 11 and 12 are disposed on the rear side of the surface 10Aa of the arm 10A. Therefore, when the gripping member 10 grips the electric wire 2A, the electrodes 11 and 12 face the conductor 2Aa of the electric wire 2A in the radial direction of the electric wire 2A.

[0047] Similarly, when the gripping member 10 grips the electric wire 2B, the electrodes 11, 12 are not in contact with the conductor 2Ba of the electric wire 2B and face the conductor 2Ba of the electric wire 2B in the radial direction of the electric wire 2B. When the gripping member 10 grips the electric wire 2C, the electrodes 11, 12 are not in contact with the conductor 2Ca of the electric wire 2C and face the conductor 2Ca of the electric wire 2C in the radial direction of the electric wire 2C.

[0048] The device main body 20 includes a rectangular parallelepiped housing (not shown), amplifier circuits 21 and 22, and a calculation unit 23. The amplifier circuits 21 and 22 and the calculation unit 23 are disposed inside the housing. The shape of the housing is not limited to a rectangular parallelepiped. The amplifier circuit 21 is an example of a first amplifier circuit. The amplifier circuit 22 is an example of a second amplifier circuit.

[0049] The amplifier circuit 21 is connected to the capacitor C1. The amplifier circuit 21 and the capacitor C1 are connected in series with each other. The amplifier circuit 22 is connected to the capacitor C2. The amplifier circuit 22 and the capacitor C2 are connected in series with each other. The configurations of the amplifier circuits 21 and 22 will be described later.

[0050] The calculation unit 23 performs a calculation, which will be described later. The calculation unit 23 can be realized in various ways. For example, the calculation unit 23 may include a memory and a CPU (Central Processing Unit). In this case, the CPU executes a program stored in the memory to execute a calculation, which will be described later. In addition, for example, the calculation unit 23 may be configured by a circuit capable of executing the calculation, which will be described later. Such a circuit is, for example, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or the like. The calculation unit 23 may be realized by combining the above-mentioned configurations. For example, the calculation unit 23 may include a memory, a CPU, and an ASIC.

[0051] The calculation unit 23 is connected to the display unit 3. The display unit 3 is a known display equipped with a plurality of LEDs, liquid crystals, etc. The display unit 3 receives information indicating the voltage of the conductor of the electric wire 2 from the calculation unit 23, and displays the voltage value of the conductor of the electric wire 2 in a format recognizable by the user (for example, numbers).

[0052] 4 is an equivalent circuit diagram of the non-contact voltage measuring device according to the first embodiment of the present invention. The configurations of the amplifier circuits 21 and 22 and the calculations performed by the calculation unit 23 will be described below.

[0053] The amplifier circuit 21 includes an operational amplifier 211 and a capacitor C3. The capacitor C3 is an example of a third capacitor. The capacitor C1 is connected to an inverting input terminal 211B of the operational amplifier 211. The non-inverting input terminal 211A of the operational amplifier 211 is connected to ground. The capacitor C3 is connected to an inverting input terminal 211B and an output terminal 211C of the operational amplifier 211. In other words, the capacitor C3 is connected between the inverting input terminal 211B and the output terminal 211C of the operational amplifier 211. The output terminal 211C of the amplifier circuit 21 is connected to the calculation unit 23. Between the output terminal 211C of the amplifier circuit 21 and the calculation unit 23 is a detection voltage output point 212. In other words, the voltage of the detection voltage output point 212 is the voltage of the output terminal 211C of the amplifier circuit 21.

[0054] The amplifier circuit 22 includes an operational amplifier 221 and a capacitor C4. The capacitor C4 is an example of a fourth capacitor. The capacitor C2 is connected to the inverting input terminal 221B of the operational amplifier 221. The non-inverting input terminal 221A of the operational amplifier 221 is connected to the ground. The capacitor C4 is connected to the inverting input terminal 221B and the output terminal 221C of the operational amplifier 221. In other words, the capacitor C4 is connected between the inverting input terminal 221B and the output terminal 221C of the operational amplifier 221. The output terminal 221C of the amplifier circuit 22 is connected to the calculation unit 23. Between the output terminal 221C of the amplifier circuit 22 and the calculation unit 23 is a detection voltage output point 222. In other words, the voltage of the detection voltage output point 222 is the voltage of the output terminal 221C of the amplifier circuit 22.

[0055] In the first embodiment, the capacitance of the capacitor C3 is set to, for example, several pF to several tens of pF, similar to the capacitance of the capacitor C1. The capacitance of the capacitor C4 is set to, for example, 10 to 100 times the capacitance of the capacitor C3, similar to the capacitance of the capacitor C2.

[0056] The calculation unit 23 calculates the coupling capacitance and the voltage of the conductor 2Aa of the electric wire 2A based on the voltages obtained from the detection voltage output points 212, 222 and the preset capacitances of the respective capacitors C1 to C4.

[0057] The coupling capacitance exists between the electrode 11 and the conductor 2Aa of the electric wire 2A and between the electrode 12 and the conductor 2Aa of the electric wire 2A among the capacitively coupled portions between the non-contact voltage measuring device 1 and the electric wire 2A. That is, as shown in FIG. 4, a capacitor C L1 are equivalently connected, and a capacitor C is provided between the electrode 12 and the conductor 2Aa of the electric wire 2A. L2 In other words, the coupling capacitance calculated by the calculation unit 23 is the capacitor C L1 The capacitance stored in the capacitor C L2 The capacitance stored in the capacitor C L1 The capacitance stored in the capacitor C is an example of a first coupling capacitance. L2 The capacitance stored in is an example of a second coupling capacitance.

[0058] The calculation unit 23 uses the following formulas (1) to (6) to calculate the coupling capacitance between the electrode 11 and the conductor 2Aa of the electric wire 2A, the coupling capacitance between the electrode 12 and the conductor 2Aa of the electric wire 2A, and the voltage of the conductor 2Aa of the electric wire 2A. It should be noted that the calculation unit 23 does not need to calculate the coupling capacitance. In other words, the calculation unit 23 only needs to calculate at least the voltage of the conductor 2Aa of the electric wire 2A.

[0059] Z1=(C L1 +C1) / jωC L1 C1···(1) Z2=(C L2 +C2) / jωC L2 C2···(2) Z3 = 1 / jωC3 (3) Z4 = 1 / jωC4 (4) V1 = -(Z3 / Z1)V L (5) V2 = -(Z4 / Z2)V L (6)

[0060] In the above formulas (1) to (4), the meanings of the symbols including "C" are as follows: L1 is the coupling capacitance (capacitor CL1 C L2 is the coupling capacitance (capacitor C L2 C1 is the capacitance of capacitor C1. C2 is the capacitance of capacitor C2. C3 is the capacitance of capacitor C3. C4 is the capacitance of capacitor C4.

[0061] In the above formulas (1) to (6), the meanings of the symbols including “Z” are as follows: Z1 is the capacitance of the capacitor C L1 and the combined impedance of capacitor C1. Z2 is the combined impedance of capacitor C L2 and capacitor C2. Z3 is the impedance of capacitor C3. Z4 is the impedance of capacitor C4.

[0062] In the above formulas (5) and (6), the meanings of the symbols including "V" are as follows: V1 is the voltage of the detection voltage output point 212, that is, the voltage of the output terminal 211C of the amplifier circuit 21. V2 is the voltage of the detection voltage output point 222, that is, the voltage of the output terminal 221C of the amplifier circuit 22. V L is the voltage of the conductor 2Aa of the electric wire 2A. Note that the equations (5) and (6) are relational expressions between the input voltage and the output voltage in the amplifier circuits 21 and 22, which are inverting amplifier circuits.

[0063] Equations (1) and (2) are substituted into equation (5), and equations (3) and (4) are substituted into equation (6). L1 =C L2 =C L It is said that. L is the coupling capacitance that exists between the non-contact voltage measuring device 1 and the electric wire 2A. This allows the unknown value C L and V L By solving the two-dimensional simultaneous equations, the following equations (7) and (8) are derived.

[0064] C L=-(C1C2C4V2-C1C2C3V1) / (C1C4V2-C2C3V1) (7) V L =-((C2-C1)C3C4V1V2) / (C1C2C4V2-C1C2C3V1) (8)

[0065] The right-hand sides of equations (7) and (8) are all known values. Therefore, from equation (7), the coupling capacitance C L is calculated, and the voltage V of the conductor 2Aa of the wire 2A is obtained from equation (8). L is calculated.

[0066] 5 is a flowchart showing a process for measuring the voltage of the conductor of the electric wire. Hereinafter, with reference to FIG. 5, the calculation unit 23 calculates the voltage V of the conductor 2Aa of the electric wire 2A. L and a coupling capacitance C between the non-contact voltage measuring device 1 and the electric wire 2A. L The procedure for calculating the above will be described.

[0067] First, the calculation unit 23 measures the voltages V1 and V2 of the amplifier circuits 21 and 22 as follows (S10). When a voltage is applied to the three-phase electric wires 2A, 2B, and 2C to supply power to the motor 4, the capacitor C L1 A voltage V1 is applied to the detection voltage output point 212 via the capacitor C1 and the amplifier circuit 21. L2 A voltage V2 is applied to a detection voltage output point 222 via the capacitor C2 and the amplifier circuit 22. The calculation unit 23 acquires these voltages V1 and V2.

[0068] Next, the calculation unit 23 calculates the coupling capacitance C L Next, the calculation unit 23 calculates the voltage V of the conductor 2Aa of the electric wire 2A by the formula (8). L It should be noted that steps S20 and S30 may be executed in the reverse order, or steps S20 and S30 may be executed in parallel.

[0069] According to the first embodiment, it is possible to eliminate the frequency term in the process of calculating the voltage of the conductor 2Aa of the electric wire 2A by the calculation unit 23. This makes it possible to calculate the voltage of the conductor 2Aa of the electric wire 2A without performing complicated calculations using Fourier transform or the like. In other words, it is possible to measure a voltage including multiple frequency components with simpler calculations than in the conventional technology.

[0070] According to the first embodiment, the coupling capacitance between the electrode 11 and the conductor 2Aa of the electric wire 2A and the coupling capacitance between the electrode 12 and the conductor 2Aa of the electric wire 2A can be constantly obtained. Therefore, it is possible to respond in real time to changes in the coupling capacitance due to environmental changes such as changes in temperature and humidity, and deterioration of the electric wire over time.

[0071] According to the first embodiment, the calculation unit 23 calculates the coupling capacitance C based on the capacitances of the capacitors C1, C2, C3, and C4, the voltage of the output terminal 211C of the amplifier circuit 21, and the voltage of the output terminal 221C of the amplifier circuit 22, in the same manner as the voltage of the conductor 2Aa of the electric wire 2A. L1 ,C L2 can be calculated.

[0072] In the first embodiment, C L1 =C L2 =C L This results in a coupling capacitance C L1 and coupling capacitance C L2 can be calculated by a simple calculation.

[0073] According to the first embodiment, C L1 and C. L2 By defining the relationship with, for example, C L1 =C L2 By defining the above, a simultaneous equation is derived: (5) into which (1) and (3) are substituted, and (6) into which (2) and (4) are substituted. By solving this simultaneous equation, the coupling capacitance C L1 , coupling capacitance C L2 , and the voltage of the wire conductor V LIn the process of solving the simultaneous equations, the ω term (frequency term) disappears. This makes it possible to solve the simultaneous equations without performing complex calculations such as Fourier transform. In other words, it is possible to measure a voltage containing multiple frequency components with simpler calculations than in the prior art.

[0074] According to the first embodiment, the gripping member 10 grips the electric wire 2A, so that the voltage of the conductor 2Aa of the electric wire 2A can be calculated.

[0075] According to the first embodiment, the coupling capacitance C L1 and coupling capacitance C L2 and can be the same or approximately the same.

[0076] In the first embodiment, the electrodes 11, 12 and the capacitors C1, C2 are provided inside the arm 10A of the gripping member 10. However, the electrodes 11, 12 and the capacitors C1, C2 may be provided inside the arm 10B of the gripping member 10. In this case, the electrodes 11, 12 are disposed, for example, on the back side of the surface 10Ba of the arm 10B.

[0077] In the first embodiment, the electric wire 2A includes a conductor 2Aa and a covering portion 2Ab that covers the conductor 2Aa. However, the electric wire 2A may not include the covering portion 2Ab. In this case, the conductor 2Aa of the electric wire 2A is exposed to the outside. However, in the first embodiment, the electrodes 11 and 12 are provided inside the arm 10A of the gripping member 10. Therefore, when the gripping member 10 grips the electric wire 2A, the arm 10A is between the electrodes 11 and 12 and the conductor 2Aa of the electric wire 2A. Therefore, even in this case, when the gripping member 10 grips the electric wire 2A, the electrodes 11 and 12 are not in contact with the conductor 2Aa of the electric wire 2A. Note that the electric wires 2B and 2C may not include the covering portions 2Bb and 2Cb, respectively.

[0078] In the first embodiment, the electrodes 11 and 12 are provided inside the arm 10A of the gripping member 10. However, the electrodes 11 and 12 may be provided outside the arm 10A. For example, the electrodes 11 and 12 may be provided on the surface 10Aa of the arm 10A. In this case, the electrodes 11 and 12 are exposed to the outside. However, in the first embodiment, the electric wires 2A, 2B, and 2C each include a covering portion 2Ab, 2Bb, and 2Cb. Therefore, for example, when the gripping member 10 grips the electric wire 2A, the covering portion 2Ab of the electric wire 2A is between the electrodes 11 and 12 and the conductor 2Aa of the electric wire 2A. Therefore, even in this case, when the gripping member 10 grips the electric wire 2A, the electrodes 11 and 12 are not in contact with the conductor 2Aa of the electric wire 2A.

[0079] The non-contact voltage measuring device 1 does not need to include the gripping member 10. In this case, for example, when the non-contact voltage measuring device 1 measures the voltages of the conductors 2Aa, 2Ba, 2Ca of the electric wires 2A, 2B, 2C, the exposed electrodes 11, 12 are attached to the outer circumferential surfaces of the coatings 2Ab, 2Bb, 2Cb of the electric wires 2A, 2B, 2C.

[0080] In the first embodiment, the non-contact voltage measuring device 1 includes a gripping member 10 and a device body 20, with capacitors C1 and C2 provided inside the gripping member 10, and amplifier circuits 21 and 22 and a calculation unit 23 provided inside the device body 20. However, the non-contact voltage measuring device 1 is not limited to the configuration as described above. For example, the capacitors C1 and C2 may be provided inside the device body 20 instead of inside the gripping member 10. Also, for example, the amplifier circuits 21 and 22 may be provided inside the gripping member 10 instead of inside the device body 20. Also, for example, the gripping member 10 and the device body 20 may be configured as one unit.

[0081] In the first embodiment, the capacitors C1, C2 and the operational amplifiers 211, 221 of the non-contact voltage measuring device 1 have a circuit configuration as shown in FIG. 4, but are not limited to the circuit configuration as shown in FIG.

[0082] For example, the capacitors C1 and C3 may be connected to the non-inverting input terminal 211A, the capacitors C2 and C4 may be connected to the non-inverting input terminal 221A, and the inverting input terminals 211B and 221B may be connected to ground. Alternatively, for example, the capacitors C1 and C3 may be connected to the inverting input terminal 211B, the capacitors C2 and C4 may be connected to the non-inverting input terminal 221A, and the non-inverting input terminal 211A and the inverting input terminal 221B may be connected to ground. Alternatively, for example, the capacitors C1 and C3 may be connected to the non-inverting input terminal 211A, the capacitors C2 and C4 may be connected to the inverting input terminal 221B, and the inverting input terminal 211B and the non-inverting input terminal 221A may be connected to ground.

[0083] In the first embodiment, C L1 =C L2 =C L By defining the above, the simultaneous equations (7) and (8) are derived. However, the coupling capacitance C L1 and coupling capacitance C L2 For example, C may be specified as not being equal to L1 +ΔC L1 =C L2 That is, the calculation unit 23 may calculate the coupling capacitance C L1 and coupling capacitance C L2 Assuming that the difference between the capacitance and the capacitance is constant, L1 and coupling capacitance C L2 In this case, the coupling capacitance C can be calculated by the above formula. L1, C L2 can be calculated.

[0084] In this case, the coupling capacitance C L1 and coupling capacitance C L2 Even if the coupling capacitance C L1 and coupling capacitance C L2 It is possible to calculate:

[0085] <Second embodiment> 6 is a front view of a gripping member of a non-contact voltage measuring device according to a second embodiment of the present invention. The non-contact voltage measuring device according to the second embodiment differs from the non-contact voltage measuring device according to the first embodiment in the arrangement of electrodes 11, 12 on gripping member 101. Below, configurations different from the first embodiment will be described. Configurations common to the non-contact voltage measuring device of the first embodiment are given the same reference numerals, and descriptions thereof will be omitted in principle, and will be described only when necessary. This is also true for a third embodiment described later.

[0086] The gripping member 101 has electrodes 11 and 12 therein, similar to the gripping member 10 of the first embodiment. In the second embodiment, as shown in Fig. 6, the electrode 11 is provided inside the arm 10A, and the electrode 12 is provided inside the arm 10B. When the gripping member 101 grips the electric wire 2A, the electrodes 11 and 12 are disposed in positions facing each other across the central axis AX of the electric wire 2A.

[0087] According to the second embodiment, the coupling capacitance C L1 and coupling capacitance C L2 and can be the same or approximately the same.

[0088] <Third embodiment> 7 is a perspective view of a gripping member of a non-contact voltage measuring device according to a third embodiment of the present invention. The non-contact voltage measuring device according to the third embodiment differs from the non-contact voltage measuring device according to the first embodiment in that arms 10A and 10B do not face each other in gripping member 102. The configurations that differ from the first embodiment will be described below.

[0089] As shown in FIG. 7, the gripping member 102 includes an arm 10C instead of the arm 10B shown in FIG.

[0090] The arm 10C has a pair of protrusions 10CA. The pair of protrusions 10CA face each other in the width direction. The pair of protrusions 10CA are formed at positions sandwiching the arm 10A in the width direction. The arm 10A and the pair of protrusions 10CA hold the electric wire 2A by sandwiching the electric wire 2A. The pair of protrusions 10CA do not face the arm 10A. Each of the pair of protrusions 10CA has a surface 10Ca. The surface 10Ca does not face the surface 10Aa of the arm 10A.

[0091] The arm 10C has a pair of shaft support portions 10Cb. In FIG. 7, only one of the pair of shaft support portions 10Cb is shown. The pair of shaft support portions 10Cb face each other in the width direction. The pair of shaft support portions 10Cb sandwich the pair of shaft support portions 10Ab from the outer sides in the width direction. Each of the pair of shaft support portions 10Cb has a through hole 10Cc. Each of the through holes 10Ac of the arm 10A and each of the through holes 10Cc of the arm 10C are aligned in a straight line along the width direction. As a result, similar to the first embodiment, the arms 10A and 10C are supported so as to be rotatable relative to each other.

[0092] In the first embodiment, the arms 10A and 10B face each other. Therefore, when the tips of the arms 10A and 10B come into contact with each other, the gripping member 10 does not close any further. In contrast, in the third embodiment, the pair of protrusions 10CA do not face the arm 10A. Therefore, the pair of protrusions 10CA of the gripping member 102 can close closer to the arm 10A than the arm 10B of the gripping member 10 in the first embodiment. As a result, the gripping member 102 of the non-contact voltage measuring device according to the third embodiment can grip a thinner electric wire 2 than the gripping member 10 of the non-contact voltage measuring device 1 according to the first embodiment. [Explanation of symbols]

[0093] 1. Non-contact voltage measuring device 2A electric wire 2B electric wire 2C wire 10 Gripping member 11 electrode (1st electrode) 12 electrodes (second electrode) 21 Amplification circuit (first amplifier circuit) 211B Inverting input terminal 211C Output terminal 22 Amplification circuit (second amplification circuit) 221B Inverting input terminal 221C Output terminal 23 Arithmetic section C1 capacitor (first capacitor) C2 capacitor (second capacitor) C3 capacitor (third capacitor) C4 capacitor (fourth capacitor)

Claims

1. a first electrode and a second electrode spaced apart from each other; a first capacitor connected to the first electrode; a first amplifier circuit connected in series with the first capacitor; a second capacitor connected to the second electrode; a second amplifier circuit connected in series with the second capacitor; A calculation unit, each of the first electrode and the second electrode faces a conductor of the electric wire without being in contact with the conductor of the electric wire; the first capacitor is connected to a first input terminal which is an input terminal of the first amplifier circuit; the second capacitor is connected to a second input terminal which is an input terminal of the second amplifier circuit; the first amplifier circuit includes a third capacitor connected between a first output terminal that is an output terminal of the first amplifier circuit and the first input terminal; the second amplifier circuit includes a fourth capacitor connected between a second output terminal that is an output terminal of the second amplifier circuit and the second input terminal; The calculation unit is A non-contact voltage measuring device that calculates the voltage of the conductor of the electric wire based on the capacitance of the first capacitor, the capacitance of the second capacitor, the capacitance of the third capacitor, the capacitance of the fourth capacitor, the voltage of the first output terminal, and the voltage of the second output terminal.

2. The non-contact voltage measurement device according to claim 1 , wherein the calculation unit further calculates a first coupling capacitance between the first electrode and a conductor of the electric wire, and a second coupling capacitance between the second electrode and a conductor of the electric wire.

3. The non-contact voltage measurement device according to claim 2 , wherein the calculation unit calculates the first coupling capacitance and the second coupling capacitance by assuming that the first coupling capacitance and the second coupling capacitance are equal to each other.

4. The non-contact voltage measurement device according to claim 2 , wherein the calculation unit calculates the first coupling capacitance and the second coupling capacitance on the assumption that a difference between the first coupling capacitance and the second coupling capacitance is constant.

5. The calculation unit uses the following formulas (1) to (6): Z １ =(C Ｌ１ +C １ ) / jωC Ｌ１ C １ ・・・(1) Z ２ =(C Ｌ２ +C ２ ) / jωC Ｌ２ C ２ ・・・(2) Z ３ =1 / jωC ３ ・・・(3) Z ４ =1 / jωC ４ ・・・(4) V １ =-(Z ３ / Z １ )V Ｌ ・・・(5) V ２ =-(Z ４ / Z ２ )V Ｌ ・・・(6) Where: C Ｌ１ is a first coupling capacitance between the first electrode and a conductor of the wire; C Ｌ２ is a second coupling capacitance between the second electrode and the wire conductor, C １ is the capacitance of the first capacitor, C ２ is the capacitance of the second capacitor, C ３ is the capacitance of the third capacitor, C ４ is the capacitance of the fourth capacitor, Z １ is a composite impedance of a capacitor storing the first coupling capacitance and the first capacitor, Z ２ is a composite impedance of a capacitor storing the second coupling capacitance and the second capacitor, Z ３ is the impedance of the third capacitor, Z ４ is the impedance of the fourth capacitor, V １ is the voltage at the first output terminal, V ２ is the voltage at the second output terminal, V Ｌ is the voltage of the conductor of the wire, The non-contact voltage measuring device according to claim 1 , further comprising a conductor for calculating a voltage of the electric wire.

6. The non-contact voltage measuring device further includes a gripping member that grips the electric wire, The first electrode and the second electrode are provided on the gripping member, The non-contact voltage measurement device according to claim 1 , wherein each of the first electrode and the second electrode faces a conductor of the electric wire when the gripping member grips the electric wire.

7. The non-contact voltage measurement device according to claim 6 , wherein the first electrode and the second electrode are arranged in parallel and spaced apart from each other along a longitudinal direction of the electric wire when the electric wire is gripped by the gripping member.

8. The non-contact voltage measurement device according to claim 6 , wherein the first electrode and the second electrode are arranged to face each other across a central axis of the electric wire when the gripping member grips the electric wire.

Images