ES2833413T3 - Method of manufacturing a current transformer core - Google Patents

Abstract

A method of manufacturing a current transformer core, comprising: the step of providing a core element formed by winding or layering an amorphous Fe-based alloy ribbon whose thickness is not greater than 15 μm and which can become nanocrystals; a longitudinal field heat treatment step that includes heating the core element to not less than a crystallization temperature and within the range of 510 ° C to 600 ° C for 5 minutes to 24 hours in the presence of a magnetic field of no less than 100 A / m applied in a magnetic path direction of the core element, thus forming a core; and a cross-field heat treatment step that includes, after the longitudinal field heat treatment step, heating the core to a temperature below the crystallization temperature and not less than 200 ° C for 20 minutes to 120 minutes in the presence of a field of not less than 80 kA / m applied in a direction perpendicular to the direction of the magnetic path of the core, thus forming a current transformer core, where μr (25) is adjusted by the field heat treatment step transversal to a value between 0.4 × μr (max) (25) and 0.9 × μr (max) (25) and μr (25)> = 4 × 105 where μr (max) (T) is μr (T) achieved by the longitudinal field heat treatment step, and μr (T) is a core amplitude magnetic permeability measured at a temperature T (ºC) in the presence of an AC magnetic field of frequency f = 50 Hz and amplitude H = 1.0 A / m, in which the composition of the Fe-based nanocrystalline alloy is represented by the following formula ula: (Fe1-aMa) 100-xyz-α-β-γCuxSiyBzM'αM "βXγ (atom%) where M is Co and / or Ni, M 'is at least one element selected from the group consisting of Nb, W , Ta, Zr, Hf, Ti and Mo, M "is at least one element selected from the group consisting of V, Cr, Mn, Al, platinum group elements, Sc, Y, rare earth elements, Au, Zn , Sn and Re, X is at least one element selected from the group consisting of C, Ge, P, Ga, Sb, En, As and Be, and the factors that define the composition, a, x, y, z, α , β and γ, respectively satisfy the following conditions: 0 <= a <0.5 0.1 <= x <= 3 10 <= y <= 20 5 <= z <= 10 0.1 <= α <= 5 0 <= β < = 10 0 <= γ <= 10, and wherein the Fe-based amorphous alloy ribbon is formed from a molten alloy by a liquid quenching method.

Description

DESCRIPTION

Method of manufacturing a current transformer core

Technical field

The present invention relates to the method of manufacturing a current transformer core.

Background of the technique

Current transformers (CTs) are current transforming devices for use in measurement and are used, for example, in current counters and earth leakage circuit breakers. Current transformers have a core of soft magnetic material (magnetic core) that is used for a closed magnetic circuit. Patent Document 1 discloses that, as a current transformer core, a core formed of a ribbon of an Fe-based nanocrystalline alloy is preferred. The Fe-based nanocrystalline alloy exhibits a saturation magnetic flux density higher than Permalloy and Co-based amorphous alloys and has a higher magnetic permeability than Fe-based amorphous alloys.

Typical Fe-based nanocrystalline alloy compositions are disclosed, for example, in Patent Document 2 and Patent Document 3. A typical example of the method of manufacturing a core with the use of a nanocrystalline alloy based on In Fe includes the steps of: quenching an alloy melt of material having a desired composition, thereby producing an amorphous alloy ribbon; winding this amorphous alloy ribbon into a ring-shaped core element; and performing a heat treatment to crystallize the amorphous alloy ribbon, thus obtaining a core having a nanocrystalline organization.

Patent Document 4 discloses a magnetic core that is formed by winding a steel tape of an Fe-based nanocrystalline alloy, whose magnetic permeability is greater than 12,000 and less than 350,000, of which the ratio of the magnetic flux density of Bs saturation and residual magnetic flux density Br (Br / Bs) is small, and of which the temperature dependence of magnetic permeability is small.

In this specification, a ring-shaped structure formed by an Fe-based alloy strip on which a heat treatment in a longitudinal magnetic field has not yet been completed is referred to as a "core element". This is sometimes strictly distinguished from the "core" which is made up of an Fe-based nanocrystalline alloy ribbon on which the heat treatment has been completed.

US 2006/077030 A1 and JP 2859286 B2 disclose Fe-Cu-Si-B-based tapes of <50 pm or 18 pm, respectively, wound on cores and heat treated above the crystallization point in the longitudinal field and below the crystallization point in the cross field.

Appointment list

Patent literature

Patent Document 1: Japanese Patent No. 2501860

Patent Document 2: Examined Japanese Patent Publication No. 4-4393

Patent Document 3: Examined Japanese Patent Publication No. 7-74419

Patent Document 4: Japanese PCT National Phase Open Publication No. 2002-530854

Summary of the invention

Technical problem

As for the current transformer described above, a further improvement in the magnetic permeability of the core has been demanded in order to reduce the size and reduce the costs in a device such as a current meter. This is because the improvement in the magnetic permeability of the core not only leads to a higher sensitivity to the electrical current to be measured, but also allows the reduction of the size of the core and the reduction of the number of turns of a coil. around the core.

A conventional solution to improve the magnetic permeability of the Fe-based nanocrystalline alloy is to apply a magnetic field in a magnetic path direction of the core element in the crystallization step by heat treatment. However, the core produced in such a way has such a problem that magnetic deflection is likely to occur due to high residual magnetic flux density. Br. If the core has a magnetic deviation, the magnetic permeability at the operating point decreases so that the demanded characteristics of the current transformer cannot be obtained.

To accommodate variations in the environment of the device, such as the temperature of use, the current transformer must also have such an excellent temperature characteristic that the high magnetic permeability of the core exhibits a small variation within the temperature range of use.

The embodiments of the present disclosure provide a method of manufacturing a current transformer core that performs features that are necessary, for example, in uses to detect electrical leakage. Solution to the problem

A current transformer core is formed by winding or placing a layer of soft magnetic material, in which

the soft magnetic material layer is made up of an Fe-based nanocrystalline alloy tape whose thickness is not more than 15 jm,

A | jr (100-0) is not more than 0.5 where A jr (100-0) is || jr (100) - | jr (0) | / | jr (0), and jr (T) is a permeability core amplitude magnetic measured at a temperature T (° C) in the presence of an applied AC magnetic field of frequency f = 50 Hz and amplitude H = 1.0 A / m, and

the ratio of a residual magnetic flux density Br and a saturation magnetic flux density Bm, Br / Bm, is less than 0.9 where a magnetic flux density B (80) with a magnetic field H = 80 A / m is defined as the saturation magnetic flux density Bm.

In an example, jir (25) has a value between 0.4 * jir (max) (25) and 0.9 * jr (max) (25) where jir (max) (T) is jir (T) obtained by heating an element core at a minimum crystallization temperature, in the presence of a magnetic field of at least 100 A / m, applied in a direction of magnetic path (longitudinal field heat treatment), the core element being formed by shaping a Fe-based amorphous alloy tape having a substantially identical composition and shape to Fe-based nanocrystalline alloy tape to have a substantially identical core shape.

In one example, jir (25)> 4 * 105 is true.

In one example, jir (100) -jir (0) has a positive value.

A method of manufacturing a current transformer core in accordance with the present disclosure includes the steps of claim 1.

In one embodiment, Ajir (100-0) is no more than 0.5, where Ajir (100-0) is | jir (100) -jir (0) | / jir (0) of a fabricated current transformer core.

A device includes: the core of the current transformer as set forth in any one of the preceding paragraphs; a coil provided around the core of the current transformer; and a detection circuit coupled with the coil.

Advantageous effects of the invention

According to the present disclosure, it is possible to provide a current transformer core which is formed of Fe-based nanocrystalline alloy layer that has high magnetic permeability, but is unlikely to experience magnetic deflection, and has excellent characteristic. Of temperature. Brief description of the drawings

FIG. 1 is a diagram showing the configuration of a measurement system used in magnetic permeability measurement.

FIG. 2A is a graph illustrating the relationship between the temperature of a longitudinal field heat treatment and the magnetic permeability jir (25) of the core in the case where a core element was formed by winding an amorphous Fe-based alloy ribbon (thickness : 18 jim) which had the composition of Fe ⁷⁴ Cu-iNb ³ Sh ⁵ . ⁵ B ⁶ . ⁵ .

FIG. 2B is a graph illustrating the relationship between the temperature of a longitudinal field heat treatment and the magnetic permeability jir (25) of the core in the case where a core element was formed by winding an amorphous Fe-based alloy ribbon (thickness : 13 jim) which had the composition of Fe ⁷⁴ Cu-iNb ³ Sh ⁵ . ⁵ B ⁶ . ⁵ .

FIG. 3 is a graph illustrating the relationship between a longitudinal magnetic field during the longitudinal field heat treatment process and the magnetic permeability jr (25) of the core in the case where a core element was formed by winding an amorphous alloy based on Fe (thickness: 13 | jm) that had the composition of Fe74Cu- | Nb3Sil5.5B6.5.

FIG. 4 is a graph illustrating the temperature characteristic of the core magnetic permeability jr (T) for Sample A where the longitudinal magnetic field illustrated in FIG. 3 was 19 A / m and Sample B where the longitudinal magnetic field was 230 A / m.

FIG. 5 is a graph illustrating an example of the magnetic field intensity and temperature profiles of a cross-field heat treatment in the present embodiment.

FIG. 6 is a graph illustrating the BH curves of the respective samples obtained when the duration during which the heat treatment temperature was maintained at 400 ° C (retention time) was set at 60 minutes, 90 minutes and 120 minutes between the profiles illustrated in FIG. 5 and B-H curves of a sample before a cross-field heat treatment.

FIG. 7 is a graph illustrating the magnetic permeability of the respective samples obtained when the duration during which the heat treatment temperature was maintained at 400 ° C (retention time) was set at 60 minutes, 90 minutes and 120 minutes between the profiles illustrated in FIG. 5.

FIG. 8 is a graph illustrating the dependence of magnetic permeability measurement temperature for one of the samples illustrated in FIG. 7 where the duration during which the heat treatment temperature was kept at 400 ° C (retention time) was set at 90 minutes.

FIG. 9 is a graph illustrating the relationship between magnetic field intensity in cross-field heat treatment and magnetic permeability jr (25).

FIG. 10 is a flow chart illustrating an example of a current transformer core manufacturing method in accordance with the present disclosure.

FIG. 11A is a perspective view showing an example of the basic structure of a current transformer 100 to which the present disclosure is applicable.

FIG. 11B is a perspective view showing an example where the current transformer 100 is applied to a zero phase current transformer.

FIG. 12 is a diagram showing an example circuit configuration of an earth leakage breaker 20 that includes the current transformer 100 shown in FIG. 11B.

Description of achievements

Next, an embodiment of the present disclosure is disclosed in detail with reference to the drawings. Note, however, that overly detailed descriptions are sometimes omitted. For example, objects well known in the art and descriptions of substantially the same items are sometimes omitted. This is in order to avoid making the following descriptions unnecessarily redundant and to help those skilled in the art easily understand the descriptions. Note that the present inventor provides the accompanying drawings and the following descriptions in order to assist one skilled in the art in a sufficient understanding of the present disclosure. However, the present inventor does not intend that these drawings and descriptions limit the object mentioned in the claims.

(Realization)

<Core of current transformer>

The core of the current transformer is a core of the current transformer formed by winding or placing a layer of soft magnetic material. The core of the current transformer can be made by winding a layer of soft magnetic material in the form of a ribbon or by layering a plurality of perforated rings from the layer of soft magnetic material. The layer of soft magnetic material that forms part of the core of the current transformer is formed by a ribbon of Fe-based nanocrystalline alloy whose thickness is in the range of not less than 8 jm and not more than 15 jm (typically approximately 13 jm). As will be described later, it was found from experiments performed by the present inventor that the thickness of Fe-based nanocrystalline alloy tape is a significant factor strongly influencing the characteristics of the core of the current transformer for use in detection of electrical leaks.

<Fe-based Nanocrystalline Alloy Tape>

An Fe-based nanocrystalline alloy used in the core of the current transformer is basically produced by a method that includes the step of rapidly cooling a molten alloy, thus obtaining an amorphous alloy strip having a predetermined composition, and the treatment step thermally heating this amorphous alloy ribbon to form nanocrystalline grains. It is known from the results of X-ray diffraction analysis and a transmission electron microscope, that nanocrystalline grains are Fe in a body-centered cubic structure in which Si or the like is incorporated so that a solid solution is formed. At least 80% by volume of the alloy is occupied by nanocrystalline grains whose average grain diameter measured in the maximum dimension is not greater than 100 nm. The other part of the alloy apart from the nanocrystalline grains is mainly amorphous. The proportion of nanocrystalline grains can be substantially 100% by volume.

The composition of the Fe-based nanocrystalline alloy used in the invention is represented by the following formula:

Formula: (Fei-aMa) i ⁰⁰ -xyzap-YCuxSiyBzMaM "pXY (% in atoms)

Here, M is Co and / or Ni. M 'is at least one element selected from the group consisting of Nb, W, Ta, Zr, Hf, Ti and Mo. M "is at least one element selected from the group consisting of V, Cr, Mn, Al, elements of the platinum group, Sc, Y, rare earth elements, Au, Zn, Sn and Re. X is at least one element selected from the group consisting of C, Ge, P, Ga, Sb, In, As and Be.

The factors that define the composition, a, x, y, z, a, p and y, respectively fulfill the following conditions: 0 <a <0.5

0.1 <x <3

10 <and <20

5 <z <10

0.1 <to <5

0 <p <10

0 <and <10

The Fe-based nanocrystalline alloy used in the embodiment of the present disclosure contains Cu in a proportion of 0.1 to 3 atom%. If Cu is less than 0.1 atom%, the effect of decreasing core loss and the effect of increasing magnetic permeability, which are caused by the addition of Cu, are rarely achieved. On the other hand, if Cu is greater than 3% in atoms, there is a probability that the loss of the nucleus is much greater than that which occurs in an alloy to which Cu is not added. In addition, the magnetic permeability deteriorates. In the present disclosure, the particularly preferred content x of Cu is 0.5 to 2 atom%. Within this range, the core loss is particularly small.

The causes of decreased core loss and increased magnetic permeability by the addition of Cu are not clarified, but can be estimated as follows. The interaction parameter between Cu and Fe is positive, so the solubility of the solid is low, and Cu and Fe have a tendency to separate. Therefore, if an alloy is heated in an amorphous state, the Fe or Cu atoms come together to form a group, causing fluctuations in composition. Thus, a large number of local regions are produced that are likely to undergo crystallization, and these regions serve as nuclei for the generation of nanocrystalline grains. The main component of this crystal is Fe, and Cu is rarely incorporated so that a solid solution does not form. Therefore, by crystallization, Cu is purged from the nanocrystalline grains so that the concentration of Cu increases in a region surrounding the crystal grains. Therefore, crystal grains are considered to be difficult to cultivate.

It is estimated that the effect of reducing the size of the crystal grains that is achieved by the addition of Cu is particularly enhanced in the presence of Nb, Ta, W, Mo, Zr, Hf, Ti or the like. If Nb, Ta, W, Mo, Zr, Hf, Ti or the like is not present, the size of the crystal grains is not reduced as much. The effect of accelerating size reduction is particularly great in the cases of Nb, Ta, Zr, Hf and Mo. From these elements, particularly when Nb is added, an alloy is obtained whose crystal grain size is likely to be reduced and it also has excellent soft magnetic properties. When Nb is added, a nanocrystalline phase is produced whose major constituent is Fe. Consequently, the magnetostriction is small compared to amorphous Fe-based alloys, and the magnetic anisotropy attributed to internal stress-strain decreases. These phenomena are believed to be one of the reasons why soft magnetic properties are improved. These elements are contained in the range of 0.1 to 5 atom%, preferably in the range of 2 to 5 atom%. If it is less than 0.1 atom%, there is a probability that the reduction in the size of the crystal grains is insufficient. If it exceeds 5 atom%, the decrease in saturation magnetic flux density is large.

Si and B are elements that are particularly useful for reducing the size of crystal grains of Fe-based nanocrystalline alloy. Fe-based nanocrystalline alloy is obtained, for example, after obtaining an amorphous alloy due to the effect of the addition of Si and B, carrying out a heat treatment to form nanocrystalline grains. The Si content is in the range of 10 to 20 atom%. A preferred content of Si is in the range of 14 to 20 atom%. If the Si content is less than 10 atom%, the amorphous forming capacity of the alloy is low, so it is difficult to stably produce amorphous matter. Furthermore, the decrease in the crystalline magnetic anisotropy of the alloy is insufficient, and therefore it is difficult to achieve excellent soft magnetic properties (eg, low coercivity). If the Si content exceeds 20 atom%, the decrease in the saturation magnetic flux density of the alloy is large and the resulting alloy is likely to become brittle. Note that the content of B is in the range of 5 to 10 atom%. B is an essential element for the formation of amorphous matter. If the content of B is less than 5 atom%, the amorphous forming capacity is low, so it is difficult to stably produce amorphous matter. If the B content exceeds 10 atom%, the decrease in saturation magnetic flux density is large. A still preferred content of B is not more than 7 atom%. If the Si and B contents are excessively large, the saturation magnetic flux density of the alloy decreases markedly.

The Fe-based nanocrystalline alloy may contain at least one element selected from the group consisting of C, Ge, P, Ga, Sb, In, Be, and As in a proportion of not more than 10 atom%. These elements are useful in converting to amorphous matter in the formation of an amorphous alloy ribbon. When added together with Si and B, these elements aid conversion to amorphous matter and provide the effect of adjusting magnetostriction and Curie temperature.

Elements such as V, Cr, Mn, Al, platinum group elements, Sc, Y, rare earth elements, Au, Zn, Sn, Re and the like have the effect of improving anti-corrosion, the effect of improving magnetic properties and the effect of adjusting magnetostriction. The content of these elements does not exceed 10% in atoms at most. If the content exceeds 10 atom%, the saturation magnetic flux density decreases markedly. A particularly preferred content of these elements is not more than 8 atom%. Of these elements, when at least one element selected from the group consisting of Ru, Rh, Pd, Os, Ir, Pt, Au, Cr and V is added, the resulting core has particularly excellent anticorrosive ability.

The main constituent of the remaining part, excluding impurities, is substantially Fe. Part of Fe can be replaced by Co and / or Ni. The content of M (Co and / or Ni) in the above formula, a, is 0 <a <0.5. If a exceeds 0.3, there is a probability that the core loss will increase. Therefore preferably 0 <to <0.3. Here, to achieve high magnetic permeability, a = 0 is preferred.

Next, an embodiment of the current transformer core manufacturing method according to the present disclosure is disclosed.

First of all, an amorphous alloy ribbon, which should be a layer of soft magnetic material, is formed from a molten alloy, having the composition described above, by a known liquid quenching method (quenching method ) such as single roll method, double roll method and the like. In the present disclosure, the thickness of the amorphous alloy tape is not more than 15 pm. The lower limit of the thickness can be set, for example, at 8 pm from the point of view of mass production. The peripheral speed of a chill roll can be set, for example, to about 15 to 50 m / sec. The chill roll can be made of pure copper which has excellent thermal conductivity or a copper alloy such as Cu-Be, Cu-Cr, Cu-Zr, and Cu-Zr-Cr. In the case of mass production, the chill roll can be water cooled. In the formation of the amorphous alloy ribbon, the temperature variation of the roll is kept small because the formation of the amorphous organization of the alloy can sometimes differ depending on the cooling rate. Note that the thickness of the amorphous alloy strip, t, is a value obtained by a weight conversion method. For example, the weight M of a sample of 2 m (longitudinal direction) * 50 mm (width direction) is measured from a long amorphous alloy strip, and the density d [kg / m3] is determined by the dry density measurement (for example, measurement with an AccuPyc II 1340 series product manufactured by SHIMADZU CORPORATION) according to a constant volume expansion method. With the weight M and the density d, the thickness t [m] = M / ((2 * 50'3) xd) can be calculated.

The length of an amorphous alloy strip manufactured industrially by the liquid quenching method exceeds several kilometers. As such, in a casting process that lasts for a long time, it is important to maintain a sufficient cooling capacity immediately after ejection of a molten alloy to the chill roll. That is, due to the sufficient cooling capacity, an amorphous organization alloy can be stably obtained. Regarding the thickness of the alloy strip to be manufactured, it is estimated that, as the thickness decreases, the cooling is easier and amorphous matter is obtained in a stable way. However, according to the research conducted by the present inventor, it was found that when the thickness of the alloy tape is not more than 15 pm, a high magnetic permeability is stably achieved in a manufactured core. The reasons for this are not clear, but can be estimated as follows. Due to the reduced thickness of the alloy ribbon, an extremely stable amorphous organization is obtained, and furthermore, in the generation of a nanocrystallized organization by heat treatment, the crystal grain diameter of the organization is generally uniform and very small.

The process of producing an amorphous alloy by the liquid quenching method can be carried out in air when this alloy does not include an active metal. When the alloy includes an active metal, the production of the amorphous alloy can be carried out in an inert gas such as Ar or He or in a reduced pressure atmosphere. Rapid cooling can be carried out in an atmosphere that includes a nitrogen gas, a carbon monoxide gas, or a carbon dioxide gas. It is advantageous that the surface roughness of the fast-cooling solidified amorphous alloy is small. The surface roughness of the amorphous alloy tape (arithmetic mean roughness Ra) can be set to, for example, 5 pm or less, preferably 2 pm or less, more preferably 1 pm or less.

A ring-shaped structure can be produced by winding or layering the amorphous alloy tape. The ring-shaped structure thus produced (core element) has a configuration such that a plurality of layers of amorphous alloy are layered. There may be a small gap or some other material between the respective amorphous alloy layers. The volumetric occupancy of the amorphous alloy layers in the core element is, for example, about 70% to 90%.

In the present embodiment, a core element formed by winding the amorphous alloy ribbon is provided. However, the present disclosure is not limited to such an example.

Next, a crystallization heat treatment is carried out as follows. A core element formed by winding or layering the amorphous alloy layer is heated in a non-reactive gas atmosphere. According to the research carried out by the present inventor and his collaborators, sufficient magnetic permeability was achieved when the heat treatment was carried out in a nitrogen gas. Nitrogen gas can be used substantially as a non-reactive gas. An inert gas can also be used as the non-reactive gas. Heat treatment can be carried out under vacuum.

The temperature of the crystallization heat treatment described above is set within the range of 510 ° C to 600 ° C. The temperature of the crystallization heat treatment is preferably set between 550 ° C and 600 ° C. If the heat treatment temperature is lower than 510 ° C or higher than 600 ° C, the magnetostriction is large. The retention time at the heat treatment temperature described above (duration of heat treatment) is set within the range of about 5 minutes to 24 hours. If the duration of the heat treatment is less than 5 minutes, it is difficult to keep the entire core alloy at a uniform temperature, so the magnetic properties are likely to vary. On the other hand, if the duration of the heat treatment is longer than 24 hours, it is likely that not only a deterioration of productivity but also a deterioration of the magnetic properties will occur due to the excessive growth of crystal grains or the generation of grains of crystal in irregular shapes.

In the present embodiment, the crystallization heat treatment is carried out in a DC or AC magnetic field. Said heat treatment carried out in a magnetic field causes a magnetic anisotropy in the alloy used in the core of the current transformer. The magnetic field can be applied during the entire period of the heat treatment or it can be applied during a portion of the period of the heat treatment. The magnetic field is applied in the longitudinal direction of the alloy layer in the core element formed by winding the amorphous alloy layer (the circumferential direction of the ring-shaped core element). The intensity of the applied magnetic field is set to 100 A / m or more, so that the alloy layer reaches magnetic saturation. Such a magnetic field is called a "longitudinal magnetic field". A crystallization heat treatment carried out in the presence of an applied longitudinal magnetic field is called a "longitudinal field heat treatment". As the strength of the longitudinal magnetic field increases, the magnetic permeability pr (T) increases. When the intensity of the longitudinal magnetic field increases to a certain level, pr (T) becomes saturated (see FIG. 3 to be described later).

On the other hand, when a longitudinal magnetic field is applied to the ring-shaped core element to such an extent that the alloy layer reaches magnetic saturation, the residual magnetic flux density Br increases greatly, and the ratio between the residual magnetic flux density Br and saturation magnetic flux density Bm, Br / Bm. In the present application, the saturation magnetic flux density Bm is defined as the magnetic flux density B (80) with the magnetic field H = 80 A / m. Br / Bm is also called the "quadrature ratio".

After longitudinal field heat treatment, a magnetic field is applied in the vertical direction of the core. The heat treatment temperature is not less than 200 ° C. The magnetic field is applied for 20 minutes to 120 minutes at a temperature lower than the crystallization temperature of the amorphous alloy. The intensity of the applied magnetic field is not less than 80 kA / m. Such a magnetic field is called a "transverse magnetic field". A heat treatment carried out in the presence of an applied transverse magnetic field is called a "transverse field heat treatment". The longitudinal magnetic field and the transverse magnetic field can be any of a DC magnetic field, an AC magnetic field, and a pulsed magnetic field. Due to the cross-field heat treatment, the residual magnetic flux density Br decreases, although the magnetic permeability decreases and consequently Br / Bm decreases, resulting in a current transformer core in which it is unlikely that magnetic deviation occurs. Dice that high magnetic permeability is achieved due to longitudinal field heat treatment, the magnetic permeability of the core after cross-field heat treatment is higher than the conventional level, and the high magnetic permeability is kept within the use temperature range, so that the temperature characteristics are excellent.

<Magnetic permeability>

In the present application, the term "magnetic permeability" has the same meaning as "relative magnetic permeability". A magnetic permeability measured at temperature T (° C) in the presence of an applied AC magnetic field of frequency f = 50 Hz and amplitude H = 1.0 ampere / meter (A / m) is called "amplitude magnetic permeability", which is expressed as "magnetic permeability | -ir (T)" or simply "jr (T)". When the measurement temperature is not particularly specified, the magnetic permeability indicates a value measured at 25 ° C, that is, jr (25). For the sake of simplicity, jr (25) is sometimes expressed simply as "| jr" in the drawings.

The magnetic permeability of a core that undergoes longitudinal field heat treatment with a magnetic field intensity such that the variation (increase) of magnetic permeability is no longer found even when the applied longitudinal magnetic field is increased, as " jr (max) (T) ". In the embodiment of the present disclosure, when the longitudinal magnetic field intensity during the crystallization heat treatment is 100 A / m, the variation (increase) of the magnetic permeability is not found at a lower magnetic field intensity (e.g. , 90 A / meter). Therefore, jr (max) (T) of the present application indicates the magnetic permeability of a core that is obtained when the intensity of the longitudinal magnetic field during the crystallization heat treatment is 100 A / m.

FIG. 1 is a diagram showing the configuration of a measurement system used in the measurement of magnetic permeability jr (T). In the configuration shown, the primary side conductor 14 of the current transformer is coupled with a function generator 54 configured to generate an AC voltage signal having an arbitrary frequency and an arbitrary waveform, via a digital multimeter 52 ( DMM) which is capable of measuring DC voltage, direct current, AC voltage and electrical resistance over a wide range and resistance R. Meanwhile, the secondary side conductor 12 of the current transformer is coupled with another 56 digital multimeter (DMM) which is different from the digital multimeter 52 on the primary side driver 14 side. In the measurement of the present application, the value of resistance R was set at 47 ohms, and as the 52 and 56 digital multimeters the 34401A digital multimeter manufactured by Agilent Technologies was used. The multifunction generator WF1973 manufactured by NF CORPORATION was used as the function generator 54 for generating an AC voltage signal.

The magnetic permeability jr (T) is determined by the following formula based on the result of a measurement at temperature T:

where Vo (V) is the voltage value measured by the 56 digital multimeter (DMM), Ae (m2) is the effective cross-sectional area of the core, j0 is the magnetic permeability in vacuum, f (Hz) is the frequency , and H (A / m) is the intensity of an AC magnetic field applied by the primary lateral conductor 14.

In the present embodiment, the heat treatment is divided into two phases, in which magnetic fields of different directions are applied. By performing such a distinctive heat treatment on magnetic fields, a current transformer core can be realized which exhibits excellent magnetic properties. In the first phase of heat treatment in a magnetic field, the magnetic field is formed in the direction of a magnetic path formed in a ring-shaped core element ("longitudinal field heat treatment"). Through this heat treatment, the core element becomes a core. Then, in the second phase of heat treatment in a magnetic field, the magnetic field is formed in a direction perpendicular to the direction of the magnetic path described above and applied to the core ("cross-field heat treatment"). By properly performing such two-phase heat treatment in the magnetic fields, a current transformer core with excellent magnetic properties can be obtained. This aspect is described in detail in the next section.

<Effects of longitudinal field heat treatment on magnetic permeability jr (25)>

As a result of the research conducted by the present inventor, it was found that the magnetic permeability jr (25) after longitudinal field heat treatment varies greatly depending on the thickness of the Fe-based nanocrystalline alloy tape. First, this point outlined below.

FIG. 2A is a graph illustrating the magnetic permeability pr (25) in the case where a core element was formed by winding a ribbon of Fe-based amorphous alloy (thickness: 18 pm, width: 10 mm) having the composition of Fe ⁷⁴ Cu-iNb ³ Sii ⁵ . ⁵ B ⁶ . ⁵ . In this example, the core dimensions were 20mm inside diameter, 30mm outside diameter, and 10mm height. The heat treatment temperature (retention temperature) in the longitudinal field heat treatment process was set at 520 ° C, 540 ° C and 560 ° C. The magnetic permeability pr (25) was evaluated based on four samples for each of the retention temperatures. The retention time at the retention temperature was one hour for each sample. The rate of temperature increase to the retention temperature was 6 ° C / min. The rate of decrease in temperature from the retention temperature was 1.5 ° C / min. The applied magnetic field was 230 A / m. The magnetic field was applied over the entire temperature range. Through this heat treatment process, the Fe-based amorphous alloy tape was crystallized and transformed into an Fe-based nanocrystalline alloy tape.

As seen in FIG. 2A, when the retention temperature of the longitudinal field heat treatment was reduced from 560 ° C to 520 ° C, the average magnetic permeability pr (25) increased from about 4 * 105 to about 5.5 * 105 although there was a large variation . Br / Bm, calculated from the saturation magnetic flux density Bm and the residual magnetic flux density Br, which were determined from the B-H curves, was 0.93 in each sample.

FIG. 2B is a graph illustrating the magnetic permeability pr (25) in the case where a core element was formed by winding a ribbon of Fe-based amorphous alloy (thickness: 13 pm, width: 10 mm) having the composition of Fe ⁷⁴ Cu ¹ Nb ³ Si ¹⁵ . ⁵ B ^6.5 (which was the same as the 18 pm thick Fe-based amorphous alloy tape described above). The dimensions of the core and the heat treatment (annealing) conditions were the same as the core of FIG. 2A. The heat treatment temperature (retention temperature) in the longitudinal field heat treatment process was set at 520 ° C, 540 ° C and 560 ° C. The magnetic permeability pr (25) was evaluated based on four samples for each of the retention temperatures. Through the longitudinal field heat treatment process, the Fe-based amorphous alloy tape was crystallized and transformed into an Fe-based nanocrystalline alloy tape.

As seen in FIG. 2B, the average magnetic permeability pr (25) exhibits a value generally equal to about 9 * 105 regardless of the longitudinal field heat treatment temperature. Br / Bm, calculated from the maximum magnetic flux density Bm and the residual magnetic flux density Br that were determined from the B-H curves, was 0.93 in each sample. Note that Bm is the magnetic flux density B (80) in the magnetic field H = 80 A / m. When a relatively thin 13 µm thick Fe-based amorphous alloy tape was thus used, the magnetic permeability pr (25) increased considerably and, furthermore, the value of the magnetic permeability pr (25) was stabilized. On the other hand, regardless of the thickness of the tape, Br / Bm exceeded 0.9 and was equal to 0.93. The high magnetic permeability pr (25) with a thickness of 13 pm was more than expected. Based on this knowledge, the present disclosure defines Fe-based nanocrystalline alloy tape thickness as one of the means to improve magnetic permeability.

From the samples shown in FIG. 2B, a sample obtained by heat treatment at 560 ° C is hereinafter referred to as "Sample 1". The effects of longitudinal magnetic field strength on magnetic properties were examined using Sample 1.

FIG. 3 is a graph illustrating the variation of the magnetic permeability pr (25) of a core such that the dimensions of the core and the heat treatment conditions were the same as those of Sample 1 except for the intensity of the longitudinal magnetic field. The intensity of the longitudinal magnetic field was adjusted within the range of 6 A / m to 115 A / m by adjusting a longitudinal magnetic field that forms a current flowing through a conductive wire (conductive wire for the formation of a longitudinal magnetic field) that It was arranged such that it penetrates through the central opening of a ring-shaped core element in longitudinal field heat treatment. The value of (25) of the core at a longitudinal magnetic field intensity of not less than 75 A / m as shown in FIG. 3 is approximately 9.5 * 105 This value is large compared to the value of pr (25) from Sample 1 shown in FIG. 2B (about 8.7 * 105). This difference in value is probably attributed to the variation of the core samples.

As seen in FIG. 3, when the longitudinal magnetic field intensity is not less than 80 A / m, the magnetic permeability pr (25) saturates.

FIG. 4 is a graph illustrating the temperature characteristic of the magnetic permeability pr (T) of the core for each sample A where the longitudinal magnetic field during the longitudinal field heat treatment was 19 A / m and Sample B (Sample 1) where the longitudinal magnetic field during the longitudinal field heat treatment was 230 A / m. In the graph, the horizontal axis represents the measurement temperature T and the vertical axis represents the magnetic permeability (T).

As seen in FIG. 4, in Sample A for which the longitudinal magnetic field intensity was relatively small, the magnetic permeability (T) decreased sharply as the measurement temperature T increased. Where the core amplitude magnetic permeability measured at 100 ° C was represented by pr (100), the core amplitude magnetic permeability measured at 0 ° C was represented by pr (0) and | (100) | jr (0) | / | jr (0) was represented by Ajr (100-0), Ajr (100-0) was approximately 0.55. On the other hand, in Sample B (Sample 1) for which the intensity of the longitudinal magnetic field was relatively large and the magnetic permeability jir (25) saturated and exhibited the maximum value, the magnetic permeability (T) decreased as it increased. the measurement temperature T. This trend was the same as that of sample A. However, Ajir (100-0) was a small value, 0.14, and the variation of magnetic permeability within the range of use temperature was suppressed 0 ° C to 100 ° C, resulting in excellent temperature characteristics.

Sample A also exhibited high quadrature as Sample B (Sample 1), that is, Br / Bm was 0.93, consistent with the direct current BH curve and had magnetic properties such that magnetic deflection is likely to occur. .

It was discovered from the results described above that Br / Bm cannot be reduced by changing the longitudinal magnetic field intensity.

As seen from the above, when the thickness of the Fe-based amorphous alloy is not more than 15 jim and the longitudinal magnetic field intensity during the crystallization heat treatment is set so that the alloy has sufficient magnetic anisotropy, permeability and excellent temperature characteristics can be achieved. However, the Br / Bm does not decrease and a magnetic drift is likely to occur. Further improvements are needed for the uses of the current transformer core.

The present inventor enthusiastically carried out extensive research and as a result found that by carrying out a manufacturing process which will be described below, a current transformer core can be made of which a practically sufficiently high magnetic permeability is achieved. stably within the use temperature range, and Br / Bm is greatly reduced, although the magnetic permeability is less than that achieved by longitudinal field heat treatment. That is, firstly, the thickness of the Fe-based amorphous alloy is controlled to be no more than 15 jim, and the longitudinal magnetic field intensity during the longitudinal field heat treatment process is adjusted to such a point that The alloy has a sufficient magnetic anisotropy (for example, not less than 100 A / m), so a core is manufactured in which a relatively high value of the magnetic permeability jr (25) can be realized. Next, an appropriate cross-field heat treatment is performed on the core, whereby the Br / Bm reduction is performed. In the next section, the measurement results are described in detail.

FIG. 5 is a graph illustrating an example of the temperature profiles and magnetic field intensity of the cross-field heat treatment in the present embodiment. In the graph, the temperature profile is represented by a solid line and the magnetic field intensity profile is represented by a dotted line. In this example, a 160 kA / m transverse magnetic field was applied to the core for a period that includes the entire period where the core temperature increased, the period where the core was held at a predetermined heat treatment temperature, and the period where the core temperature decreased (approximately 4 hours). In the example of FIG. 5, the heat treatment temperature was 400 ° C and the retention time was 1 hour and 30 minutes (90 minutes).

FIG. 6 is a graph illustrating the B-H curves of current transformer cores obtained by further applying a transverse magnetic field in accordance with the profile illustrated in FIG. 5 for Sample 1 whose core dimensions were the inner diameter of 20 mm, the outer diameter of 30 mm and the height of 10 mm, being set at 60 minutes, 90 minutes and 120 minutes, the time during which the core was maintained at the heat treatment temperature of 400 ° C (retention time), and the core BH curves of Sample 1 prior to cross-field heat treatment. Samples with a retention time of 60 minutes, 90 minutes, and 120 minutes are Example 1, Example 2, and Example 3, respectively. Table 1 presented below shows, for the respective samples, the values of the maximum magnetic flux density Bm, the residual magnetic flux density Br, the coercivity Hc and the quadrature ratio Br / Bm, which were determined from curves BH of FIG. 6. Bm is the magnetic flux density B (80) in the magnetic field H = 80 A / m.

T l 11

As seen in FIG. 6 and Table 1, by adding cross-field heat treatment, the residual magnetic flux density Br decreases compared to that achieved before heat treatment. Since the variation in Bm is small, Br / Bm can decrease to less than 0.9. By lengthening the retention time of the heat treatment, the residual magnetic flux density Br and Br / Bm is further reduced.

FIG. 7 is a graph illustrating the relationship between the retention time of the cross-field heat treatment (400 ° C) and | -ir (25) in Examples 1 to 3. The magnetic permeability jr (25) after heat treatment of longitudinal field of the measured core (magnetic field intensity: 100 A / m) saturates with respect to the magnetic field intensity and presents the maximum value. This maximum value, jr (max) (25), was 9.5 * 105. For each retention time, jr (25) from two samples were measured. Table 2 shows the relationship between retention time and magnetic permeability jr (25), jr (25) / jr (max) (25).

T l 21

As seen in FIG. 7 and Table 2, the magnetic permeability jr (25) decreased as the retention time of the cross-field heat treatment increased. The magnetic permeability jr (25) decreases monotonic with respect to the retention time. In this example, the magnetic permeability can be estimated using the formula jr (25) = (10.5-0.05 * t) x105 where jr (25) is the magnetic permeability and t is the retention time (min). In other words, the magnetic permeability can be adjusted by controlling the retention time of the cross-field heat treatment.

FIG. 8 is a graph illustrating the dependence of the measurement temperature on the magnetic permeability of the sample of Example 2, which is one of the samples described above, where the duration during which the heat treatment temperature was maintained at 400 ° C (retention time) was set at 90 minutes.

As seen from this graph, over a wide range from about -50 ° C to about 100 ° C, the magnetic permeability generally increases monotonic as the measurement temperature increases, and jr (100) -jr (0) has a positive value. A | jr (100-0) of the core of the current transformer measured at temperature T (° C) in the presence of an applied AC magnetic field having a frequency f = 50 Hz and an amplitude H = 1.0 A / m was about 0.25. Also, also in the samples of Example 1 and Example 3, Ajr (100-0) was not more than 0.5.

FIG. 9 is a graph illustrating the relationship between magnetic field intensity in cross-field heat treatment and magnetic permeability jr (25). An amorphous Fe-based alloy tape (thickness: 13 µm, width: 10 mm) was produced having the same alloy composition of Fe ⁷⁴ Cu-iNb ³ Sh ⁵ . ⁵ B ^6.5 than Sample 1 but was from a different production lot. The alloy tape was wound to form a core element. The core element was subjected to a longitudinal field heat treatment under the same conditions as those of Sample 1. In addition, a cross field heat treatment was performed on the core that had been subjected to the longitudinal field heat treatment. In the heat treatment, the retention temperature was 380 ° C and the retention time was 90 minutes. It is shown in the graph jr (25) of the respective samples in the cases where the intensity of the transversal magnetic field was 80 kA / m (Example 4), 160 kA / m (Example 5) and 320 kA / m (Example 6) . As the intensity of the magnetic field increases, jr (25) decreases in a monotonic way. It is understood that the magnetic permeability of the core can be adjusted by controlling the intensity of the transverse magnetic field in the heat treatment. In each of Examples 4 to 6, the Br / Bm evaluated was less than 0.9. Br / Bm had a tendency to decrease as the intensity of the magnetic field increased. In each of Examples 4 to 6, Ajr (100-0) was not more than 0.5. In Examples 4 to 6, jr (25) / jr (max) was 0.5 to 0.7. Here, the magnetic permeability jr (25) of the core after longitudinal field heat treatment (magnetic field intensity: 100 A / m) was saturated with respect to the magnetic field intensity and presented the maximum value. (max) (25) was 8 * 105.

As understood from the foregoing description, a method of manufacturing a current transformer core in accordance with the present disclosure includes: the step of providing a core element formed by winding or layering an amorphous alloy tape with base in Fe whose thickness is not greater than 15 jm and that can be turned into nanocrystals; a longitudinal field heat treatment step including performing a heat treatment on the core element in the presence of a magnetic field applied in a magnetic path direction of the core element to crystallize the amorphous alloy, thereby obtaining a core; and a cross-field heat treatment step that includes performing a heat treatment on the core obtained after the longitudinal field heat treatment step in the presence of a magnetic field applied in a direction perpendicular to the direction of the magnetic path of the core, thus forming a core of the current transformer. Using the cross-field heat treatment step, jir (25) is set to a value between 0.4 * jir (max) (25) and 0.9 * jir (max) (25) where jir (T) is the amplitude magnetic permeability measured at temperature T (° C) in the presence of an applied AC magnetic field of frequency f = 50 Hz and amplitude H = 1.0 A / m, and jir (max) (T) is jr (T) after the passage of Longitudinal field heat treatment (before cross-field heat treatment). As a result, a current transformer core is obtained that has such excellent temperature characteristics that Ajir (100-0) is not more than 0.5 and Br / Bm is less than 0.9 where Ajir (100-0) is | jir ( 100) -jir (0) | / jir (0) measured after manufacture.

FIG. 10 is a flow chart illustrating an example of a current transformer core manufacturing method in accordance with the present disclosure. As described above, in step S120, a core element is provided which is formed by winding or layering an amorphous Fe-based alloy ribbon whose thickness is not more than 15 µm.

Then, in step S140, longitudinal field heat treatment is performed. The treatment temperature of the longitudinal field heat treatment is set at a temperature not lower than the crystallization temperature, that is, within the range of 510 to 600 ° C. The retention time of the treatment temperature is set within the range of 5 minutes to 24 hours. If it is less than 5 minutes, it is difficult to obtain magnetic properties with small variations between the respective cores. If it is longer than 24 hours, productivity deteriorates enormously. The intensity of an applied longitudinal magnetic field is set within the range of not less than 100 A / m. If the strength of the longitudinal magnetic field is less than 100 A / m, there is a probability that the provision of a magnetic anisotropy is insufficient. If the longitudinal magnetic field intensity exceeds 300 A / m, it is difficult to perform the treatment stably.

Then, in step S160, a cross-field heat treatment is performed. The treatment temperature of the cross-field heat treatment is set at a temperature lower than the crystallization temperature, that is, within the range of not less than 200 ° C and lower than the temperature of the longitudinal field heat treatment. If it is less than 200 ° C, there is a probability that the effects of the magnetic field treatment will be insufficient. If it is not lower than the temperature of the longitudinal field heat treatment, there is a probability that the effects of the longitudinal magnetic field treatment will be greatly diminished and the effects caused by a different magnetic field treatment cannot be achieved, that is, a transverse magnetic field treatment performed after longitudinal magnetic field treatment in the present disclosure. The retention time of the treatment temperature is set within the range of 20 minutes to 120 minutes. If the retention time is less than 20 minutes, there is a probability that the effect of applying the magnetic field (provision of a magnetic anisotropy) is insufficient. If retention time exceeds 120 minutes, productivity decreases. The intensity of the applied transverse magnetic field is set within the range of 80-320 kA / m. If the intensity of the transverse magnetic field is less than 80 kA / m, there is a probability that the provision of a magnetic anisotropy is insufficient. If the transverse magnetic field intensity exceeds 320 kA / m, it is unlikely that a stable magnetic field intensity will be obtained and the treatment becomes difficult.

Between step S140 and step S160, the core can be cooled to about room temperature. Desirably, the application of the transverse magnetic field is continued until the core is sufficiently cooled to a temperature of no more than 200 ° C.

Normally, when used, the core of the current transformer can be housed in a box that is made of resin, or the like, for the purpose of protecting the core of the current transformer and isolating a coil from the other elements of the circuit. A core member formed by winding an alloy tape is formed by an elongated continuous alloy layer in the form of a tape and is therefore advantageous in terms of workability. After the core of the current transformer of the present embodiment is housed in a case that is made of resin or the like, a coil is formed around the core for detection, whereby a current transformer can be manufactured.

<Current transformer>

(Example 7)

FIG. 11A shows an example of the basic structure of a current transformer 100 to which the present disclosure is applicable. Current transformer 100 typically includes a ring-shaped (cylindrical) core 10 and a secondary side conductor 12 (secondary side coil) wound around core 10 as shown in FIG. 11A. The primary side conductor 14, which is the object of current measurement, can be inserted typically such that it extends through the central opening of core 10. Primary side conductor 14 can be wrapped around core 10 to make two or more turns as is secondary side conductor 12. The primary side conductor 14 and the secondary side conductor 12 may be an arbitrary known wire whose surface is covered for insulation.

In the example of FIG. 11A, only a portion of each of the primary side conductor 14 and the secondary side conductor 12 is shown schematically. The primary side conductor 14 shown is in the shape of a linear rod, although the actual shape of the primary side conductor 14 is not limited to such a shape. Both ends of the primary side conductor 14 are electrically coupled with a wire, circuit, voltage source, or current source not shown.

When an electrical current flows through the primary side conductor 14 shown in FIG. 11A, a magnetic field is produced around the primary side conductor 14, and a closed magnetic path is formed in the ring-shaped core 10 having high magnetic permeability. When an alternating current flows through the primary side conductor 14, the magnetic flux density in the core 10 varies periodically so that an AC voltage is produced in the secondary side conductor 12. As a result, an electric current flows through a circuit not shown coupled with the secondary side conductor 12. The electrical current flowing through the secondary side conductor 14 can be measured based on the voltage or current output to the secondary side conductor 12.

FIG. 11B shows an example where the current transformer 100 is applied to a zero phase current transformer (ZCT). In the example of FIG. 11B, the electrical currents flowing through the primary side conductors 14 of a single-phase two-line system are measured. In the case of a single-phase three-line system, three primary side conductors are arranged to extend through the opening in core 10, but are not shown. The zero phase current transformer is capable of detecting a current loss when an abnormal current resulting from electrical leakage flows through the primary side conductors 14. The configuration of the current transformer 100 can be designed so that, when a loss of current of 30 milliamps (mA) flows at the frequency of, for example, 50 Hz through the primary side conductors 14, a voltage of 4 millivolts (mV) is produced in secondary side conductor 12.

<Earth leakage breaker>

(Example 8)

FIG. 12 shows an example circuit configuration of an earth leakage circuit breaker 20 that includes current transformer 100 as shown in FIG. 11B. This earth leakage circuit breaker 20 includes a current transformer core 10, a secondary side conductor 12 wound around core 10, a detection circuit 16 coupled to secondary side conductor 12, and a disconnect device 18 coupled to circuit 16. detection.

In the example of FIG. 12, an alternating current is supplied from a transformer 30 to the earth leakage circuit breaker 20 through wires of a single phase two line system. Transformer 30 is coupled, for example, to a commercial electrical power system or any other AC power source. The earth leakage circuit breaker 20 is located in an electrical path coupled with a load 40. The load 40 can be an electronic device or an electrical machine that is configured to receive AC power for operation. The earth leakage circuit breaker 20 is located, for example, in a switchboard.

In the normal state, the sum of the electric currents flowing through a pair of primary lateral conductors 14 is zero. In this case, the disconnecting device 18 of the earth leakage circuit breaker 20 maintains the electrical path in a conductive state, and the load 40 receives AC power from the transformer 30. When an electrical leakage occurs due to, for example, At deteriorated insulation of the load 40, a ground fault current flows from the load 40. Consequently, the total of the electric currents that flow through the pair of primary lateral conductors 14 exhibits a significant value greater than zero, and as a result, a voltage is produced in the secondary side conductor 12. Describing based on the example described above, the configuration of the current transformer 100 is designed in such a way that when an alternating current of 30 mA flows at the frequency of, for example, 50 Hz as a current loss, a voltage is produced. 4 mV on secondary side conductor 12. In this case, the 30 mA current loss refers to the difference between the currents flowing through the pair of primary side conductors 14, rather than each of the currents flowing through the pair of primary side conductors 14 .

The sensing circuit 16 activates the disconnect device 18 based on the voltage or current produced in the secondary side conductor 12. When the voltage or current produced in the secondary side conductor 12 exceeds a predetermined threshold, the detection circuit 16 activates the disconnect device 18 in order to cut the current flowing from the transformer 30 to the load 40. The circuit breaker 20 of earth leakage circuit is configured in such a way that when an abnormal current is equal to or greater than a predetermined value it flows at through the primary side conductor 14 due to electrical leakage, the earth leakage circuit breaker 20 automatically cuts the current for a short period of time, for example, no more than 0.1 seconds.

The current transformer 100 used in such an earth leakage circuit breaker 20 is required to properly detect the occurrence of a weak current loss. The amplitude of the current loss to be detected is defined by the regulations of the respective countries. If the magnetic permeability of the core 10 is low, the voltage that occurs in the secondary side conductor 12 when a weak current loss occurs is low, so the occurrence of electrical leakage cannot be adequately detected. The upper limit of the magnetic permeability of the core 10 can be appropriately set based on the lower limit of the current loss to be detected. For example, when Br / Bm is less than 0.9, the core 10 has a high magnetic permeability, and therefore the earth leakage circuit breaker 20 can have an excellent leakage cut-off function. Furthermore, since the magnetic permeability variation is small within the temperature range of 0 ° C to 100 ° C as described above, the earth leakage circuit breaker 20 can have excellent leakage cut-off function, which it is stable against temperature variation.

Industrial application capacity

The present disclosure is applicable to a current transformer that can be used in an earth leakage circuit breaker and to a core that is suitable for the current transformer.

Reference signal list

10 core current transformer

12 secondary side conductor (secondary side coil)

14 primary side driver

16 detection circuit

18 disconnect device

20 earth leakage circuit breaker

30 transformer

40 load

100 current transformer

Claims (4)

1. A method of manufacturing a current transformer core, comprising: the step of providing a core element formed by winding or layering an amorphous Fe-based alloy ribbon whose thickness is not greater than 15 µm and which can be converted into nanocrystals; a longitudinal field heat treatment step that includes heating the core element to not less than a crystallization temperature and within the range of 510 ° C to 600 ° C for 5 minutes to 24 hours in the presence of a magnetic field of no less than 100 A / m applied in a magnetic path direction of the core element, thus forming a core; Y a cross-field heat treatment step that includes, after the longitudinal field heat treatment step, heating the core to a temperature below the crystallization temperature and not less than 200 ° C for 20 minutes to 120 minutes in the presence of a field of not less than 80 kA / m applied in a direction perpendicular to the direction of the magnetic path of the core, thus forming a current transformer core, where jr (25) is adjusted by the cross-field heat treatment step to a value between 0.4 * jr (max) (25) and 0.9 * jr (max) (25) and jr (25)> 4 * 105 where jr (max) (T) is jr (T) achieved by the longitudinal field heat treatment step, and jr (T) is a core amplitude magnetic permeability measured at a temperature T (° C) in the presence of a field AC magnetic with frequency f = 50 Hz and amplitude H = 1.0 A / m, in which the composition of the Fe-based nanocrystalline alloy is represented by the following formula: (Fe ¹ -aMa) ¹⁰⁰ -xyzap-YCuxSiyBzM'aM "pXY (% in atoms) where M is Co and / or Ni, M 'is at least one element selected from the group consisting of Nb, W, Ta, Zr, Hf, Ti and Mo, M "is at least one element selected from the group consisting of V , Cr, Mn, Al, elements of the platinum group, Sc, Y, rare earth elements, Au, Zn, Sn and Re, X is at least one element selected from the group consisting of C, Ge, P, Ga, Sb, En, As and Be, and the factors that define the composition, a, x, y, z, a, p and y, respectively fulfill the following conditions: 0 <a <0.5 0.1 <x <3 10 <and <20 5 <z <10 0.1 <to <5 0 <p <10 0 <and <10, and wherein the Fe-based amorphous alloy ribbon is formed from a molten alloy by a liquid quenching method. 2. The method of claim 1, wherein Ajr (100-0) is not more than 0.5 where Ajr (100-0) is | jr (100) -jr (0) | / jr (0) of a kernel of manufactured current transformer. 3. The method of claim 1 or 2, wherein a B-H circuit has a curved shape. 4. The method of claim 1, wherein a = 0.