Composite magnetic core for three-phase ammeter mutual inductor

Abstract

A composite magnetic core for a three-phase ammeter mutual inductor comprises an annular amorphous magnetic core A, a nanocrystalline magnetic core B is coaxially sleeved in the annular amorphous magnetic core A. A magnetic core C is arranged outside the amorphous magnetic core in one of the following modes: the first mode is that the magnetic core C is directly wound outside the amorphous magnetic core; according to the second mode, the amorphous magnetic core B and the amorphous magnetic core A are arranged in the protective box after being sleeved, the magnetic core C is wound around the peripheral face of the protective box, and the central axis of the magnetic core C is parallel to or coincides with the central axis of the magnetic core A. Through the structure, the consistency of the height of the composite magnetic core for the three-phase ammeter mutual inductor can be realized, and the long-standing problems in the industry are solved.

Description

TECHNICAL FIELD

[0001] The utility model discloses a magnetic core, especially relate to a composite magnetic core for three-phase ammeter mutual inductor belongs to the technical field of electromagnetic device. BACKGROUND

[0002] In the three-phase ammeter, the mutual inductor made of ring-shaped magnetic core is used, and the mutual inductor participates in the metering in the ammeter. Because there are a large number of frequency conversion, switching power supply and rectifier devices in the power grid, these devices increase the direct current component in the power grid, so that the superimposed current of direct current and alternating current passes through the mutual inductor. At present, in order to enable the mutual inductor to resist direct current (i.e. not to be saturated under the condition of direct current, and still have good working curve) and have good comprehensive magnetic properties, the coaxial sleeved composite magnetic core (core) similar to the technical solution disclosed in CN1316521C is widely used. The inner layer adopts nanocrystalline magnetic core (core), and the outer layer adopts amorphous magnetic core (core). The inner layer is sleeved in the outer layer. As the most widely used marketized use at present, the nanocrystalline magnetic core adopted by the inner layer adopts 1K107 nanocrystalline amorphous strip, and the outer layer adopts 1K101 amorphous strip. Because the compositions of the two kinds of strips and the large-scale marketized production, the cost is very competitive. The nanocrystalline material of the inner layer has excellent comprehensive magnetic properties but is basically not resistant to direct current. The amorphous magnetic core of the outer layer has good direct current resistance effect. Domestic three-phase ammeter composite magnetic core manufacturers basically adopt the above-mentioned scheme. The applicant also adopts the above-mentioned scheme in a long time in the past. However, there is a very difficult problem to solve in the scheme, which is the consistency problem of the amorphous magnetic core. The 1K101 amorphous strip is a Fe-based amorphous alloy. The Fe-based amorphous alloy is mainly composed of iron elements, and also contains a small amount of silicon, boron, carbon and other elements. The typical Fe-based amorphous alloy composition is Fe-Si-B system. The addition of silicon and boron elements helps to form an amorphous structure. These elements can prevent the formation of crystals during solidification, so that the alloy presents an amorphous state. In the production of magnetic cores, the outer core needs to be annealed. After annealing, the inductance value under the corresponding current (direct current) needs to meet the size requirements. For example, for the 16*21*10 (nominal size) type, 0.23A (direct current) requires 76-88μH, and 3.24A (direct current) requires 58-62μH. For the 15*21*10 (nominal size) type, 0.23A (direct current) requires 72-84μH, and 3.24A requires 53-59μH.Due to the material itself, the inductance dispersion of the outer magnetic core after annealing is very large. After annealing, the products that cannot meet the inductance requirement are removed, and the inductance dispersion of the products that can meet the inductance requirement is very large. For example, for the 16*21*10 type, although the good products after testing can meet the inductance of 76-88 μH under the requirement of 0.23 A, the values are very scattered, from 76-88 μH, because the inductance of the outer magnetic core is directly related to the angle difference and ratio difference of the transformer after being made into a transformer, that is, if the inductance of the finished magnetic core is greatly different, the angle difference and ratio difference between the transformers made of the finished magnetic core will also be large, and the consistency between the magnetic cores is poor. Because in the three-phase ammeter, a current transformer is needed for each phase, if the inductance of the magnetic cores of the three transformers in the three-phase ammeter is greatly different, the consistency of the three-phase measurement will be poor, and a large error will be generated. In the current smart meter transformation of the power grid, this requirement is becoming more and more strict, so the consistency of the magnetic core is becoming higher and higher. In order to meet this requirement, the current domestic manufacturers adopt the method of strict selection. For example, for the 16*21*10 type, the requirement is 76-88 μH under 0.23 A (DC), in order to meet the consistency requirement, the inductance of the outer amorphous magnetic core is measured after annealing, and the magnetic cores with inductance of 78.5-82.5 μH under 0.23 A are selected for use (or the number of magnetic cores with inductance difference of about 4 in the range of inductance is large). For the 15*21*10 (inner diameter*outer diameter*height) type, the requirement is 72-84 μH under 0.23 A, in order to meet the consistency requirement, the inductance of the outer amorphous magnetic core is measured after annealing, and the magnetic cores with inductance of 76.5-80.5 μH under 0.23 A are selected for use. Although this method can meet the requirement, the relative cost is high, because the number of magnetic cores that can meet such a small dispersion range after one heat treatment is about 5%, and the others that cannot meet the requirement can only be annealed again. Such repeated treatment has a very high cost. Even if the repeated annealing treatment is performed, a large proportion of the magnetic cores still cannot meet the requirement and can only be discarded, which leads to a complicated production process and high cost of such magnetic cores. For the DC-resistant magnetic core, there are many researches in China, such as CN115132479A, which discloses a method for manufacturing a single DC-resistant magnetic core, CN117153549, which discloses a production process of a DC-resistant nanocrystalline double magnetic core current transformer, CN113990604B, which discloses a production process of a DC-resistant nanocrystalline double magnetic core current transformer, and CN1107240491A, which discloses a nanocrystalline alloy double magnetic core current transformer. In the above schemes, either a non-mainstream market material is used or the production process is complex, and there is no scheme that can meet the consistency requirement of the magnetic cores in the three-phase ammeter in terms of the technical problems solved and the performance indicators disclosed. How to ensure the consistency of the magnetic cores used in the three-phase ammeter is a long-standing problem in the industry. SUMMARY

[0003] The utility model discloses a composite magnetic core for three-phase ammeter transformer which meets the requirement of three-phase ammeter to transformer.

[0004] To realize the utility model's purpose, adopted following's technical scheme: a composite magnetic core for three-phase ammeter transformer, including annular amorphous magnetic core A, nanocrystalline magnetic core B is coaxially sleeved in annular amorphous magnetic core A, following one of the following ways is provided with magnetic core C outside amorphous magnetic core, the first way is: magnetic core C is directly wound outside amorphous magnetic core, the second way is: after amorphous magnetic core B, amorphous magnetic core A is sleeved and is loaded into protective box, and magnetic core C is wound on the peripheral surface of protective box, and the central axis of magnetic core C is parallel with or coincides with the central axis of magnetic core A.

[0005] Further, when the second way is adopted, the peripheral surface of the protective box has a groove, and the magnetic core C is wound in the groove.

[0006] Further, the amorphous magnetic core A uses 1K101 amorphous strip, the nanocrystalline magnetic core B uses 1K107 nanocrystalline strip, and the magnetic core C uses 1K107 nanocrystalline strip or uses cobalt-based amorphous strip.

[0007] The utility model discloses a composite magnetic core for three-phase ammeter transformer which meets the requirement of three-phase ammeter to transformer. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 is the schematic diagram of the first embodiment of the utility model.

[0009] Figure 2 is the schematic diagram of the second embodiment of the utility model. DETAILED DESCRIPTION

[0010] In order to more fully explain the implementation of the utility model, the embodiment of the utility model is provided. These embodiment examples are only the elaboration of the utility model, and do not limit the scope of the utility model.

[0011] The utility model is further explained in detail in combination with the drawings, and the various marks in the drawings are as follows: 1: lower half protective box, 2: upper half protective box, 3: magnetic core B, 4: magnetic core A, 5: magnetic core C, 6: groove.

[0012] As shown in the drawings, Figure 1is an embodiment in which the magnetic core C is located outside the magnetic core A, Figure 2 is an embodiment in which the magnetic core C is wound on the protective box. The protective box in the figure is an existing protective box, which is composed of an upper half protective box 2 and a lower half protective box 1. The upper half protective box is inserted into the lower half protective box and buckled to form the protective box.

[0013] In the utility model, 1K101 amorphous strip and 1K107 nanocrystalline strip are existing products, and the heat treatment (annealing) process of the 1K101 amorphous magnetic core (amorphous magnetic core A) is an existing technology. For example, an existing annealing process is as follows: after being placed in the magnetic core A at room temperature, the temperature is raised to 390 degrees Celsius for about 220 minutes, then raised to about 410 degrees Celsius for about 30 minutes, and annealed for about 120 minutes. In order to reduce the inductance of the amorphous magnetic core A, the annealing time at about 410 degrees Celsius can be extended for about 30 minutes.

[0014] A composite magnetic core for a three-phase ammeter transformer includes an annular amorphous magnetic core A4, a nanocrystalline magnetic core B3 coaxially sleeved in the annular amorphous magnetic core A4, and a magnetic core C5 arranged outside the amorphous magnetic core in one of the following modes. In a first mode, the magnetic core C is directly wound outside the amorphous magnetic core B. In a second mode, the nanocrystalline magnetic core B3 and the amorphous magnetic core A4 are sleeved and then placed in a protective box, and the magnetic core C5 is wound on the peripheral surface of the protective box. The central axis of the magnetic core C is parallel to or coincides with the central axis of the magnetic core A. When the second mode is adopted, the peripheral surface of the protective box has a groove 6, and the magnetic core C5 is wound in the groove 6.

[0015] The amorphous magnetic core A adopts an existing 1K101 amorphous strip, the nanocrystalline magnetic core B adopts a 1K107 nanocrystalline strip, and the magnetic core C adopts a 1K107 nanocrystalline strip or a cobalt-based amorphous strip. The cobalt-based amorphous strip is also an existing technology, and a nanocrystalline material strip disclosed in CN101371321B can be used, for example.

[0016] In the utility model, by controlling the annealing process of the magnetic core A, the inductance of the sleeved magnetic core A and magnetic core B can be controlled to be lower than the required value, which is easy to achieve in the process. For example, for a 16*21*10 (inner diameter*outer diameter*height) type, the required inductance is 76-88 μH at 0.23 A (DC), and by extending the annealing time of the corresponding amorphous magnetic core A at the highest annealing temperature, the inductance at 0.23 A (DC) can be reduced to below 76. It is found that after the inductance of the amorphous magnetic core A is reduced by process adjustment, the consistency (dispersion) of the inductance will be improved, which provides a better foundation for adjusting the inductance by the magnetic core C in the next step.

[0017] The following is the magnetic core performance data of the applicant using the present scheme:

[0018] Table I

[0019]

[0020] In Table 1: the nominal specification of the magnetic core is 16*21*10; after being wound into a transformer, the angle difference and the ratio difference are tested, the transformer calibrator device is used for testing, the magnetic core bias current inductance data (unit: μH) is tested by using a ten-turn testing device (32.4 DC corresponding to inductance test of 3.24A, 2.3 DC corresponding to inductance test of 0.23A), and the inductance value under the corresponding bias current is tested. 1 to 10 are ten test magnetic cores.

[0021] The magnetic core is composed of magnetic core B, magnetic core A and magnetic core C from inside to outside. During production, the production process of magnetic core A is adjusted so that the inductance value under direct current 0.23A is lower than 75 μH, magnetic core B and magnetic core A are combined, and then magnetic core C is wound outside magnetic core A to adjust the inductance value to the required range. In the test, the winding turns of magnetic core C are determined according to the inductance value of magnetic core A (with the accumulation of a large amount of production data, the winding turns of magnetic core C required for adjusting from one inductance value to another inductance value can basically form a corresponding relationship, and there is no need to wind according to experience), and the strip material of magnetic core C in the table is 1K107. The strip material 1K107 in the application can be 1K107B.

[0022] Magnetic core C in the above table is located outside magnetic core A. Through tests, it is found that the same effect can be achieved when magnetic core C is wound outside the protective box. As can be seen from Table 1, the dispersion of the bias current data of the magnetic core can be effectively controlled by using the present scheme, and the angle difference and the ratio difference of the ten magnetic cores after being made into transformers are good.

[0023] By using the present scheme, the cost of the strip material is slightly increased, and one more process is added, but basically no waste product can be achieved, so that the overall cost is not increased.

[0024] After the embodiments of the present application are described in detail, those skilled in the art can clearly understand that various changes and modifications can be made without departing from the above patent application range and spirit. Any simple modification, equivalent change and modification made according to the technical essence of the present application to the above embodiments all belong to the scope of the technical scheme of the present application, and the present application is not limited to the implementation modes of the examples described in the specification.

Claims

1. A composite core for a three-phase current meter transformer comprising a ring-shaped amorphous core A in which a nanocrystalline core B is coaxially housed, characterized in that: The magnetic core C is arranged outside the amorphous magnetic core in one of the following modes: in a first mode, the magnetic core C is directly wound outside the amorphous magnetic core B; in a second mode, the nanocrystalline magnetic core B and the amorphous magnetic core A are sleeved and then arranged in a protective box, and the magnetic core C is wound on the peripheral surface of the protective box, with the central axis of the magnetic core C being parallel to or coinciding with the central axis of the magnetic core A.

2. A composite core for a three-phase ammeter transformer according to claim 1, characterized in that: When the second mode is adopted, the peripheral surface of the protective box has a groove, and the magnetic core C is wound in the groove.

3. A composite core for a three-phase ammeter transformer according to claim 1, characterized in that: The amorphous magnetic core A adopts 1K101 amorphous strip material, the nanocrystalline magnetic core B adopts 1K107 nanocrystalline strip material, and the magnetic core C adopts 1K107 nanocrystalline strip material or a cobalt-based amorphous strip material.

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