CN1026359C - Magneto-optical current angle comparison method and device - Google Patents

Abstract

The present invention belongs to the field of electric instrument, and is especially suitable for industrial measurement of great current. The method is that the magneto-optical effect is used to make the light polarization plane rotate in the probe placed in the magnetic field to generate a rotation angle theta, the characteristic curve of the emergent light intensity of the probe and theta is established by the detector, the power amplifier and the signal processing system or the microcomputer system, and the ampere-turn number of the comparison winding corresponding to the lowest point of the curve is determined as the measured current value. The probe in the magneto-optical current angle comparator corresponding to the method is composed of a focusing mirror, a sensitive element and an OE double-output prism.

Description

The invention belongs to the category of electrical instruments, and is especially suitable for large current measurement occasions.

Chinese Patent "Multi-Channel Open Type DC Large Current Comparator" "Patent No. 85100829", its structure must ensure that the ampere-turns of the feedback winding are balanced with the ampere-turns in the measured current bus to maintain the zero flux state, and the feedback winding The current tracks the current in the measured current bus, and the current value in the feedback winding is multiplied by a certain variation coefficient to obtain the measured current value. However, due to the influence of the external magnetic field, the basis for the existence of the above invention - the zero magnetic flux will be disturbed, so that the zero magnetic flux that appears in the measurement is not the zero magnetic flux required by the measurement itself. For this reason, the above-mentioned patent provides a whole set of structural measures to reduce the influence of the external magnetic field, such as adopting an independent multi-channel system, each channel is equipped with a feedback winding and an excitation winding, an excitation winding is arranged outside the iron core, and a shielding iron core is also provided. wait. This structure also requires high manufacturing process because the two main core windings must be completely symmetrical, and the additional shielding core makes the structure bloated, large in size and heavy in weight. The implementation effect of the invention is also directly related to the accuracy of the zero magnetic flux, and it is impossible to completely eliminate the interference to the zero magnetic flux.

Aiming at the above-mentioned shortcomings in the prior art, the present invention provides a magneto-optical angle comparison method and device for testing the intensity of a large DC current, which is composed of an open core, a probe, a comparison winding, a signal processing microcomputer and other components.

The present invention is implemented through the following technical measures (Figures 1, 2 and 3), using the current in the comparison group 9 to track the measured current, so that the ratio of the rotation angle θ of the polarization plane generated by the magnetic field of the comparison winding current _to the polarization plane generated by the measured current magnetic field The rotation angle θ _is opposite to the direction and equal in size to form zero magnetism. The measured current value is the ampere-turn number of the comparison winding, that is, i=WI _ratio , where the I _{ratio is} the current of each turn of the coil, and W is the number of turns of the comparison winding. For this reason, the open iron core including the probe 8 is adopted in this method, and its shape depends on the application occasion, and various shapes such as circle, square or rectangle can be adopted. As can be seen from FIG. 2 , the probe 8 is composed of a focusing lens 14 , a polarizer 15 , a sensitive element 16 , a focusing lens 17 , and an analyzer 18 . The incident end of the probe 8 is directly coupled or connected with the light source 2 through the optical fiber 3, and the outgoing end is directly coupled or connected with the detectors 11 and 12 through the optical fiber 10. Since the analyzer 18 in this method adopts an OE double-output prism (GP-5 series), so the detectors 11 and 12 respectively detect the mutually orthogonal OE beams from the analyzer 18 . In order to make the light intensity of O light and E light equal, one of the detectors 11 and 12 is equipped with a power amplifier 13, and the two light beams can be equalized by simple adjustment, thus solving the problem of 45° preset angle adjustment and installation in the dual optical path light path difficulties. According to Marius' law, the light intensity I=I _O cos ² θ coming out from the analyzer 18, where I _O is the output light intensity of the polarizer 15, and I is the output of the analyzer 18 after the polarization plane is rotated by an angle of θ. In this formula, θ has a relationship with COS ² θ as shown in Figure 2. When θ is a certain value, the value of COS ² θ will appear minimum or zero. During the measurement process, the controllable current source 6 can be controlled by using the signal processing circuit 13 or the microcomputer system (including display and printing) to control the current of the comparison winding 9, and the current value of the comparison winding and the rotation angle of the polarization plane generated by it can be controlled. θ ratio, track and _offset the rotation angle θ of the polarization plane generated by the measured current, when the ampere-turns of the comparison winding is equal to the value of the measured current, the light intensity appears zero, that is, the lowest value of the curve shown in Figure 2 appears. Theta value. Due to the influence of magnetic field temperature, external magnetic field and other factors, the coordinates of the curve in Figure 3 will drift, but it will not affect its shape and the appearance of the lowest point, so the reliability and accuracy of the measurement can be well guaranteed.

The outstanding advantages of the present invention are as follows: (1) The OE double-input prism is used as the analyzer in the sensitive element, so that the two beams can be equal with only a simple adjustment, thereby solving the problem of using a 45° preset angle in the dual optical path Difficulties in adjusting and installing the optical path; (2) The iron core in this device adopts a divisible structure, and the iron core is divided into upper and lower parts by using the iron core connector 5, which is convenient for disassembly and maintenance, and can be operated live without affecting production; ( 3) Set up a magnetic shunt 7, which can carry out device maintenance, replacement, and debugging "online", and simply adjust it through the magnetic shunt to achieve the purpose of disconnecting the measured current; It can be used in electrical measurement occasions. (5) Small size, light weight and no interference from external magnetic fields; (6) Microcomputer processing system is used to make the measurement accuracy not affected by temperature, external environment and other factors, and long-term work can be guaranteed; (7) High precision and low price , (8) The device can operate under high voltage through optical fiber connection.

Figure 1 is a schematic diagram of the magneto-optical current comparator. In the figure 1 is the light source driving power, 2 light source, 3 coupler or optical fiber, 4 iron core; 5 Huff surface, 6 controllable current source, 7 magnetic shunt, 8 probe, 9 comparison winding, 10 coupler or optical fiber , 11 detectors, 12 detectors, 13 power amplifiers, 14 signal processing circuits or computer systems (including display, printing).

FIG. 2 is a schematic diagram of the internal structure of the probe 8 .

Fig. 3 is a graph showing the relationship between the light intensity and the rotation angle of the polarization plane.

Figure 4 is the characteristic curve of the stability test.

The magneto-optical current angle comparator provided by the present invention has been tested for stability, and the results of the one-hour continuous test are shown in Table 1 and Figure 4. It should be noted that the accuracy of the test equipment provided in this experiment is 1%.

Standard current (A) Device measurement (A) Reference error (%)

0000 0000

1000 990 -0.10

2000 2030 +0.30

3000 3040 +0.40

4000 4030 +0.30

5000 5050 +0.50

6000 6040 +0.40

7000 7020 +0.20

8000 8020 +0.20

9000 9020 +0.20

10000 10040 +0.40

Claims (3)

1, a kind of Magnetooptic current angle comparison method, it utilizes the tested electric current of current tracking that compares in the winding (9), the plane of polarization rotation angle θ that comparison winding current magnetic field is produced _RatioPlane of polarization rotation angle θ with tested current field generation _QuiltDirection is opposite, and tested current value was for comparing the ampere turns i=WI of winding when equal and opposite in direction formed zero magnetic flux _Ratio, I in the formula _RatioElectric current for every circle coil, W is for comparing the number of turn of winding, for this reason, the concrete measure of this method is for adopting open core, probe (8) is set in the clearance of opening part, (8) shape is decided on the application scenario, can adopt circle, square or rectangular, the direct coupling of incident end of probe (8) or connect with light source (2) by optical fiber (3), the direct coupling of exit end or by optical fiber (10) and detector (11), (12) connect, analyzer (18) adopts OE lose-lose prism, detector (11), (12) each self-monitoring be mutually orthogonal OE light beam from analyzer (18), the light intensity of O light E light is equated, in detector (11), (12) one has power amplifier (13) in, it is equal only to need simple adjustment just can obtain two light beams, according to Malus law, and the light intensity I=I that comes out from analyzer (18) _oCos ²θ, I in the formula _oBe the polarizer (15) output intensity, I is the output intensity of analyzer (18) behind the plane of polarization rotation θ angle, measuring process adopts signal processing circuit (13) or microsystem control controllable current source (6) to get final product the electric current of control ratio than winding (9), control ratio reaches the plane of polarization rotation angle θ ratio that is produced by its than the winding electric flow valuve, follow the tracks of and offset the plane of polarization rotation angle θ quilt that tested electric current produces, when relatively the ampere turns of winding equated with tested current value, null value appearred in light intensity, i.e. θ and cos ²The corresponding θ value of θ family curve minimum.

2, carry out Magnetooptic current angle comparator relatively according to the described method of claim 1, it partly is made up of iron core, comparison winding, controllable current source, signal processing system etc., it is characterized by described iron core is open core (4), opening part is provided with probe (8), probe (8) is made up of focus lamp (14), (17) OE lose-lose prism (15), (18) and sensitive element (16), the incident end connects with light source 2 by optical fiber (3), and exit end connects with detector (11), (12) by optical fiber (10).

3, comparator according to claim 2 is characterized by it and is provided with magnetic shunt (7).

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