JPH02264870A - Current detector - Google Patents

Abstract

PURPOSE:To enable highly-precise and stable detection of a current flowing through a body to be detected, by providing an electrooptical effect element connecting two detecting terminals and a detecting means of a light transmitted through the element and by inputting a voltage between two points of the test specimen to the detecting terminals. CONSTITUTION:A detecting member 10 detects a current to be detected and outputs a light signal proportional to the current, and a processing member 20 sends a light to the detecting member 10 while receiving an output light from the detecting member 10 and subjecting it to an amplification processing. These detecting member 10 and processing member 20 are connected by an optical fiber 30. An electric field corresponding to a voltage between detecting terminals 16 and 17 to which a voltage between two points of a test specimen is inputted is generated in an electrooptical effect element 13 of the detecting member 10. Thereby an electrooptical effect element 13 of the detecting member 10. Thereby an electrooptical effect is produced in the element 13, a refractive index thereof is changed, and the intensity of a transmitted light in a magnitude proportional to the voltage between the terminals 16 and 17 changes in comparison with a state wherein said effect is not produced. Accordingly, a change in a voltage between transparent electrodes 13a and 13b of the element 13 can be detected by the transmitted light sent from a light-emitting element 21 of the processing member 20 to a light-sensing element 22 through a polarizer 11 and an analyzer 14.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a current detection device, and more specifically, the present invention relates to a current detection device that detects a current flowing through a detected object by using electro-optic effects such as Pockels effect and Kerr effect. This invention relates to a current detection device.

[Prior art] In electric welding, welding is performed while passing an electric current through the workpiece.
If the value of the current flowing through the joint part changes during work, the welding condition will not be uniform, so by detecting the welding current flowing through the workpiece, comparing it with the set value, and feeding back the fluctuation of the current value to the power source, The welding current is controlled so that it is always constant.

Conventionally, as this type of current detection device, a device is known that uses a coil or a Hall effect element as a current detection element and detects a current by measuring the voltage or current generated in the element. However, with this device,
The current detection electric circuit connected to the current detection element is susceptible to electromagnetic induction, and the reliability of the detection results is extremely low.

Therefore, as a device for high-frequency welding that solves these difficulties, an optical Faraday element is installed in a pair of conductor lead structures that supply high-frequency current to both edges of an open pipe. a welding current detection device configured to detect the strength of a magnetic field and transmit an optical signal whose intensity is modulated according to the strength of the magnetic field to a welding current detection section spaced apart from the conductor lead structure via an optical fiber; A device has also been proposed (Japanese Unexamined Patent Application Publication No. 6
3-165083). This device has the advantage of being able to detect welding current with high precision without being affected by electromagnetic induction caused by high frequency large current.

[Problems to be Solved by the Invention] However, since the conventional device measures the welding current by detecting the magnetic field generated by the welding current, if the magnetic field changes due to changes in the ambient temperature, the effect will be on the detected current value. The problem was that the detection results were unstable.

Therefore, this invention has developed a current detection device that can stably detect the current flowing through a detected object with high precision without being affected by electromagnetic induction phenomena caused by the current flowing through the detected object or changes in ambient temperature. The purpose is to provide

[Means to solve the problem]

In order to achieve the above object, the present invention includes an electro-optic effect element having two detection terminals connected to each other, and a means for detecting transmitted light of the electro-optic effect element, and the detection terminal has two detection terminals connected to each other. The device is characterized in that it is configured to input the voltage between points.

A polarizer may be provided on the incident side of the electro-optic effect element, and an optical rotator and an analyzer may be provided on the transmission side.

Further, the electro-optic effect element may be any element that produces an electro-optic effect such as Pockels effect or Kerr effect;
It is preferable to use an element that causes the Pockels effect.

Examples of elements exhibiting the Pockels effect include BSO, L
Examples include N.

In addition, as an element exhibiting the Kerr effect, for example, cobalt (
GdCo), single crystal Gd1 (1,, polycrystalline BiGaYI)
G etc. can be used.

[Function] With the above configuration, an electric field is generated in the electro-optic effect element according to the voltage between the rain detection terminals.

This electric field causes an electro-optic effect within the element,
Since the refractive index of the electro-optic effect element changes, when light is transmitted through the element in this state, the intensity of the transmitted light changes compared to a state where the effect does not occur. The magnitude of this change in transmitted light intensity is proportional to the strength of the electric field, that is, the voltage between the rain detection terminals.

Therefore, by detecting the voltage change applied between the rain detection terminals of the electro-optic effect element, it is possible to detect the current flowing through the object to be detected.

In this invention, since the electric field within the electro-optic effect element is detected, there is no fear of being affected by temperature or by the magnetic field generated by electromagnetic induction.

〔Example〕

Hereinafter, the present invention will be described in detail based on the accompanying drawings.

In FIG. 1, a current detection device (1) of the present invention includes a detection section (10) that detects a current to be detected and outputs an optical signal proportional to the current, and a detection section (10) that sends light to the detection section (10). It is composed of a processing section (20) that receives the output light from the detection section (10), amplifies and processes it, and the detection section (10)
) and the processing section (20) are connected by two optical fibers (30).

The detection section (10) is composed of four optical components, as shown in FIGS. 1 and 2. That is, from the upstream side where the light is sent to the downstream side, the polarizer (11),
A π/4 optical rotator (12), an electro-optic effect element (13), and an analyzer (14) are arranged, and all of these optical components are housed in a ceramic casing (15).

The polarizer (11) allows natural light generated from the light emitting element (21) provided in the processing section (20) to pass through the optical fiber (30).
), and the polarizer (11) functions to convert this natural light into linearly polarized light. This linearly polarized light is then π/
The light is incident on the four optical rotators (12).

The π/4 optical rotator (12) functions to convert the linearly polarized light into circularly polarized light by giving a phase difference of π/4 to the incident linearly polarized light. The circularly polarized light thus converted is incident on the electro-optic effect element (13).

The electro-optic effect element (13) can be any element that exhibits an electro-optic effect, but in this example,
Thin plate-like B50 (Bi+zSiO) exhibiting the Pockels effect
□. ) It is formed from a single crystal, and transparent electrodes (13a) (13b) are formed on both opposing surfaces. Both electrodes (1
Detection terminals (16) and (17) made of metal conductors are connected to 3a) and (13b), respectively, and as shown in Fig. 4, rain detection terminals (16) and (17) are connected to the outside of the casing (15). sticking out.

When detecting current, one of both terminals (16) (17) is in contact with the reference voltage side and the other with the detected current side, and the voltage between both terminals (16) (17) is due to the electro-optic effect. It will be applied between the electrodes (13a) and (13b) of the element (13). This voltage generates an electric field within the element (13).

BSO single crystal has the above-mentioned electrode (1) due to the Pockels effect.
3a) When a voltage is applied between (13b), there is a refractive index difference between the two crystal axes, for example <oii> and <OTl>, and the circularly polarized light incident on this single crystal becomes elliptically polarized light. converted. At this time, since the refractive index difference is proportional to the electric field generated within the single crystal, both electrodes (13a) (1
Converting the voltage change between 3b) into a refractive index change of transmitted light,
This means that it can be detected by light transmitted through the single crystal.

The analyzer (14) functions to convert the elliptically polarized light generated by passing through the electro-optic effect element (13) into light intensity. The transmitted light of the analyzer (I4) is transmitted through the optical fiber (3
0) to the light receiving element (22) of the processing section (20).

When circularly polarized light is converted to elliptically polarized light by the electro-optic effect element (13), the intensity of the light transmitted through the analyzer (14) is based on the intensity when the incident light is circularly polarized light (when the Pockels effect does not occur). Then, the electrode (13a) (
13b) varies in proportion to the magnitude of the voltage between them. Therefore, both electrodes (13a) (1
3b) The intensity of the transmitted light of the analyzer (14) can be modulated by the voltage applied between them, and if this transmitted light intensity is detected, the electro-optic effect element (13)
The voltage between the two electrodes (13a) (13b), that is, the current to be detected can be detected.

When the input voltage is AC, AC light Pac is superimposed on DC light Pdc, and the transmitted light intensity P becomes as shown in FIG. The characteristics of this amplitude modulation are given by the following equation.

P=Po (1+m) m=π・V/Vπ・f (V) f (V) = sin (g (V) ) / g
(V) g (V) [(π・V/Vπ)”+(2θ.・a)2) I/1 Here, Po is the reference light intensity, m is the modulation degree (=Pdc/Pac
), V is the voltage applied to the BSO single crystal, ■π is a material-specific constant called the half-wave voltage, and θ. is the natural optical rotation power, d is B
This is the thickness of SO single crystal.

When light with a wavelength of 0.87 μm is transmitted through a BSO single crystal, ■π is 6800 V and θ. is 10.56/mm.

In the range where the applied voltage V is sufficiently smaller than the half-wavelength voltage Vπ,
The modulation degree m is approximately proportional to the applied voltage ■.

FIG. 6 shows the relationship between the applied voltage (■) and the output voltage.

The processing section (20) is provided with a light emitting element (21) made of a light emitting diode etc. and a light receiving element (22) made of a PIN photodiode etc., and the light generated by the light emitting element (21) is transmitted to one optical fiber (30). ) through the detection unit (1
0) is sent to the polarizer (11). Also, the detection part (10)
The output light from the analyzer (14) is sent to the light receiving element (22) via the other optical fiber (30), where it is converted into an electrical signal. This electrical signal is then amplified by an amplifier (23) and input to a computing unit (24). A computing unit (24) analyzes the electrical signal and converts it into a current value.

The output signal of the arithmetic unit (24) is a CR of an oscilloscope, etc.
It is output to the T display (25) and recorder (26). In this way, the current to be detected can be confirmed and recorded.

The processing unit (20) having the above configuration can be arbitrarily configured using conventionally known devices.

Further, as the optical fiber (30), any known optical fiber can be used, but a multimode step index type quartz fiber is preferable.

Next, the usage state of the current detection device (1) configured as described above will be explained, taking as an example the case where it is applied to an electric welding machine.

In FIGS. 3 and 4, (31) is an electric welding machine in the form of a robot, and a welding torch (33) is attached to the tip of an arm (32). The arm (32) has a mounting member (
34), the detection part (10) of the current detection device (1) is attached. Below the welding torch (33), there are 2
A plate-shaped object to be welded (35) is arranged. A welding rod (37) movably supported on the torch (33) by an insulator (38) passes through the interior of the welding torch (33). This welding rod (37) also serves as a ten electrode. Note that during welding, the object to be welded (35) itself serves as one electrode.

Two terminals (16) and (17) of the detection part (10) have one terminal (16) that passes through a hole (39) provided in the side wall of the welding torch (33) and connects the welding rod (37) inside the welding torch (33). The other terminal (17) is in contact with the surface of the workpiece (35).

In this state, when a voltage is applied between the welding rod (37) and the object to be welded (35) to start welding, the welding rod (37)
is melted and filled into the groove of the workpiece (35), forming a bead (
36) is formed and both objects to be welded (35) are joined.

At this time, the welding current flows between the welding rod (37) and the workpiece (35).
), but due to the voltage drop occurring across the workpiece (35), the voltage is detected from the welding rod (37) through the detection terminal (16) and from the workpiece (35) to the detection terminal (17).
There is a certain difference between the voltages detected through. This voltage is applied to the electro-optic effect element (1) of the detection unit (10).
3) is applied to the electrodes (13a) and (13b) to generate an electro-optic effect in the element (13), and this effect changes the intensity of the light that passes through the element (13).

This change in transmitted light intensity is sent to a processing unit (20), photoelectrically converted and amplified, and then processed by a computing unit (24).

This processing result can be easily confirmed on the display (25). Therefore, changes in welding current during work can be easily and highly accurately known, and can also be recorded with a recorder (26) if necessary.

In the above explanation, the current detection device (1) was applied to an electric welding machine (31), but it can also be applied to any other device as long as it detects changes in current over time. Of course.

(Effects of the Invention) As is clear from the above explanation, the current detection device (1) of the present invention is completely unaffected by electromagnetic induction phenomena caused by fluctuations in the current to be detected and by changes in ambient temperature. , the current of the object to be detected can be detected stably with high accuracy.

[Brief explanation of drawings]

1 and 2 show an embodiment of the current detection device of the present invention, FIG. 1 is a block diagram showing its overall configuration, and FIG. 2 is an explanation showing the internal configuration of the detection section of the device. It is a diagram. Figures 3 and 4 show an example of how the device is applied to welding work, with Figure 3 being a schematic illustration and Figure 4 showing an enlarged view of the vicinity of the welding torch in Figure 3. It is a partially enlarged explanatory diagram. FIG. 5 is a graph showing the relationship between the input voltage to the electro-optic effect element and the transmitted light intensity. . FIG. 6 is a graph showing the relationship between the voltage applied to the electro-optic effect element and the output voltage of the processing section. (1)... Current detection device (10)... Detection unit (12)... π/4 optical rotator (13a) (13b) - Electrode (15)... Casing (20)... Processing Part (22)... Light receiving element (24)... Arithmetic unit (26)... Recorder (31)... Electric welding machine (33)... Welding torch (35)... Target Welding object (11)...Polarizer (13)...Electro-optic effect element (14)...Analyzer (16) (17)...Detection terminal (21)...Light emitting element (23) ... Amplifier (25) ... Display (30) ... Optical fiber (32) ... Arm (34) ... Mounting member (36) ... Bead (37) ... Welding rod ( 38)...Insulator 39)...Hole

Claims (1)

[Claims] 1. An electro-optic effect element having two detection terminals connected thereto, and a means for detecting transmitted light of the electro-optic effect element, the detection terminal being connected to two points on the object to be detected. A current detection device characterized in that it is configured to input a voltage between the two. 2. The current detection device according to claim 1, wherein a polarizer is provided on the incident side of the electro-optic effect element, and an optical rotator and an analyzer are provided on the transmission side. 3. The current detection device according to claim 1 or 2, wherein the electro-optic effect element is a Pockels effect element.