JP7365277B2 - Current transformers, iron cores for current transformers - Google Patents

Description

Embodiments of the present invention relate to a current transformer and an iron core for a current transformer.

Conventionally, as disclosed in Patent Document 1, for example, a current transformer is known in which a toroidal secondary coil is provided on an annular or rectangular iron core and a cable to be measured is passed through the iron core. ing.

Japanese Patent Application Publication No. 2010-62419

In the case of such conventional current transformers, in order to arrange the cable so as to pass through the iron core, it is necessary to once disconnect or cut the cable.

However, in actual cable installation sites, there are cases where it is difficult to disconnect or where it is impossible to cut the cables, such as when there are long-distance cables of several hundred meters or several kilometers. In other words, it may be difficult to process the cable.

Therefore, the present invention provides a current transformer and an iron core for the current transformer that can measure the current flowing through the cable even when it is difficult to process the cable.

The current transformer of the embodiment includes an iron core having four U-shaped or C-shaped semi-annular parts, and a plurality of secondary coils that are provided on the iron core and whose inner circumferential side is penetrated by the iron core. , the iron core has a pair of semi-annular sections arranged parallel to each other, each of which has ends located on the same side connected to the other half-annular sections, and four semi-annular sections connected in series. It consists of two magnetic circuits.

A diagram schematically showing the configuration of a current transformer according to the first embodiment Diagram schematically showing the manufacturing process of a current transformer Diagram schematically showing an example of cable installation Diagram to explain the measurement principle of current transformers Diagram schematically showing multiple arrangement modes of cables Diagram showing an example of measurement results using a current transformer A diagram schematically showing the configuration of a current transformer according to the second embodiment Diagram schematically showing an example of cable installation Diagram 1 schematically showing the configuration of a current transformer according to the third embodiment Diagram 2 schematically showing the configuration of a current transformer Diagram showing an example of measurement results using a current transformer Diagram 3 schematically showing the configuration of a current transformer Diagram 4 schematically showing the configuration of a current transformer Diagram 5 schematically showing the configuration of a current transformer Diagram 6 schematically showing the configuration of a current transformer

Hereinafter, a plurality of embodiments will be described with reference to the drawings. In order to simplify the explanation, parts that are substantially the same or have common functions in each embodiment will be described with the same reference numerals.

(First embodiment)
The first embodiment will be described below. As shown in FIG. 1, the current transformer 1 includes an iron core 2 and four secondary coils 3 through which the iron core 2 passes. The iron core 2 is made of a magnetic material with high magnetic permeability, such as ferrite or iron-nickel alloy, and has four semi-annular parts 4 formed in a U-shape in this embodiment. The iron core 2 includes a pair of semi-annular sections 4 arranged parallel to each other such that the ends of the semi-annular sections 4 arranged parallel to each other are arranged in such a manner that the arrangement directions are different by 90 degrees. By connecting the four semi-annular portions 4 in series, each of which is connected to the end portions, constitutes one magnetic circuit that is a so-called closed circuit.

Hereinafter, for the sake of explanation, when explaining the individual semi-annular parts 4, the first semi-annular part 4a, the second semi-annular part 4b, the third semi-annular part 4c, and the fourth semi-annular part 4d are used. shall be indicated. In addition, in this embodiment, the four semi-annular parts 4 are joined by, for example, welding or adhesive, and are connected to each other inseparably, as will be described later.

More specifically, in the case of the iron core 2, a pair of first semi-annular parts 4a and a second semi-annular part 4b are arranged parallel to each other with a predetermined interval, and a set of third semi-annular parts 4c and the fourth semi-annular part 4d are parallel to each other with a predetermined interval, and the arrangement directions are different from each other by 90 degrees with respect to the first semi-annular part 4a and the second semi-annular part 4b. It is located.

The iron core 2 connects one end located on the same side of the first half annular part 4a and the second half annular part 4b with a third half annular part 4c, and connects the other end with a fourth half annular part 4c. By connecting through the annular portion 4d, the four semi-annular portions 4 are connected in series and constitute one continuous magnetic circuit. In other words, the iron core 2 has a generally frame-like shape in which eight of the twelve sides constituting the rectangular parallelepiped can be traced with a single stroke. It is formed in a shape that has a space that allows access to the inside. Note that the inside of the magnetic circuit corresponds to a space located between the valleys of the iron core 2 that constitutes the magnetic circuit.

The secondary coil 3 has an iron core 2 passing through its inner peripheral side, and is provided in each of the semi-annular parts 4 in this embodiment. That is, the iron core 2 is provided with four secondary coils 3. These four secondary coils 3 are provided at positions divided into four equal parts in the longitudinal direction of the iron core 2, and are connected to wiring and resistors (not shown).

The current transformer 1 having such a configuration is manufactured as follows. As shown in FIG. 2, first, two annular cores 5 having a generally rectangular shape with curved corners and a square cross section are prepared, and each is divided into two. Two U-shaped core pieces 6 are formed. Subsequently, by joining the ends of each core piece 6 while changing the direction of the iron core pieces 6 by 90 degrees, each half-annular part 4 is continuous like a single stroke, as described above, and each half-annular part 4 is Iron cores 2 are formed that are connected to each other and constitute one magnetic circuit.

At this time, the ends of the semi-annular parts 4 are joined together, that is, they are inseparably connected to each other. However, in cases where it is not possible to provide a joint part, such as when detecting a minute current, the iron core 2 is integrally molded with a structure in which the semi-annular part 4 is formed in advance, rather than combining the semi-annular parts 4. You can also do that. Therefore, in this embodiment, the semi-annular part 4 includes a configuration in which the semi-annular part 4 is formed by joining the iron core pieces 6, and a configuration in which the semi-annular part 4 is integrally molded including the semi-annular part 4. We have adopted the statement that there is.

Next, the operation of the above configuration will be explained.
For example, as shown in FIG. 3, it is assumed that the cable 8 connecting the device 7A and the device 7B is the object to be measured by the current transformer 1. However, the cable 8 is not limited to the device, and may be connected to a terminal block. Further, as a reference example, as shown in a perspective view in FIG. 4, a conventional current transformer 102 including a frame-shaped conventional iron core 100 and a secondary coil 101 is assumed. This conventional current transformer 102 is also referred to as a so-called zero-phase CT.

Now, in order to measure with the conventional current transformer 102, it is necessary to pass the three-phase cable 103 through the conventional iron core 100. In that case, disconnect the three-phase cable 103 and insert the end. Or, it is necessary to cut the three-phase cable 103. However, in actual installation sites, there are cases where it is difficult to disconnect, such as long-distance cables of several hundred meters or several kilometers, or where it is impossible or not allowed to disconnect. In other words, it may be difficult to process the three-phase cable 103.

In that case, it may be possible to measure using a split core current transformer. Note that the split core current transformer referred to herein means one in which measurements are made by combining a plurality of cores in a ring shape in a disassembled state. However, in the case of split-core current transformers, the contact status of the parts where the cores are combined changes each time measurements are repeated, and the assembly accuracy decreases due to deterioration of the mechanical parts that hold each core in an annular shape. This may cause errors in measurements. Furthermore, when it is necessary to measure large currents, the size of the device including its mechanical parts increases, making it difficult to handle, which is a serious problem in the field.

Therefore, in this embodiment, even if it is difficult to process the cable 8 to be measured, the measurement can be performed as follows.

First, the measurement principle of the current transformer 1 of this embodiment will be explained. The current transformer 1 of this embodiment detects the current flowing through the cable 8 by inversely utilizing the residual voltage that causes an error in the conventional current transformer 102 equipped with the conventional iron core 100. There is. This residual voltage is an event that occurs due to a shift in the position of the cable 8 that passes through the zero-phase CT.

For example, as shown in the front view in FIG. 4, residual voltage occurs when the position of the three-phase cable 8 is shifted from the center of the conventional iron core 100, or when the position of one wire is separated. This is because if the cable 8 were located at the center, the magnetic field interlinking with the conventional iron core 100 should be balanced and canceled out by the three phases, but for example, one phase is emphasized or attenuated, causing a secondary effect. This is because a voltage is induced in the side coil 101 and is detected as if a zero phase is flowing.

In other words, focusing on this residual voltage, if the cable 8 can be placed inside the magnetic circuit without necessarily passing through the conventional iron core 100 as in the conventional current transformer 102, the cable 8 can be placed inside the magnetic circuit. It is believed that the effect of the current flowing through 8 can be measured. As described above, the measurement principle of the current transformer 1 of this embodiment is to perform measurement using the residual voltage, which has conventionally caused errors.

Now, as schematically shown in FIG. 3, the cable 8 generally does not connect the device 7A and the device 7B over the shortest distance, but rather has a length with some margin. It is arranged. Therefore, the cable 8 is considered to be arranged in such a way that it can be bent and routed to some extent. Although the cable 8 and the above-mentioned three-phase cable 103 are shown with different symbols for the sake of explanation, it is assumed that the cable 8 is also for three-phase use.

As shown in FIG. 1, the iron core 2 is provided between the first semi-annular part 4a and the second semi-annular part 4b to block the third semi-annular part 4c side and the fourth semi-annular part 4d side. Moreover, there is no obstruction between the third semi-annular part 4c and the fourth semi-annular part 4d side, and there is no obstruction to the first semi-annular part 4a side and the second semi-annular part 4b side. . In other words, the iron core 2 can be accessed from between the first semi-annular part 4a and the second semi-annular part 4b and between the third semi-annular part 4c and the fourth semi-annular part 4d to the inside of the magnetic circuit. It has a possible structure.

Therefore, for example, as shown in the perspective view in wiring example 1 in FIG. 5, it is possible to arrange the cable 8 inside the magnetic circuit in such a manner that it is wrapped around the iron core 2. Note that although this perspective view shows a cross section of the cable 8 for simplicity, the cable 8 is not cut. In other words, if the illustrated cross section of the cable 8 is referred to as the A end surface 8a and the B end surface 8b for convenience, the cable 8 is not cut at the A end surface 8a and the B end surface 8b, but as shown in the installation mode. It is in a connected state. In other words, the shape of the current transformer 1 allows the cable 8, which remains connected, to be placed inside the magnetic circuit formed by the iron core 2.

Specifically, the cable 8 is arranged near the center of the iron core 2 from between the first semi-annular portion 4a and the second semi-annular portion 4b on the A end surface 8a side. The cable 8 is routed so as to be hooked onto the connecting portion between the first semi-annular portion 4a and the third semi-annular portion 4c, and is connected to the third semi-annular portion 4c and the fourth semi-annular portion on the B end surface 8b side. 4d side and near the center of the iron core 2. In other words, the cable 8 is arranged so as to be wrapped around the current transformer 1 using its extra length.

As a result, as shown in the installation mode, when the current transformer 1 is installed on the side of the wiring route of the cable 8, for example, the cable 8 can be is placed inside the magnetic circuit, making it possible to perform measurements with the current transformer 1. That is, even if it is difficult to process the cable 8, measurement using the current transformer 1 is possible. Furthermore, the current transformer 1 can be easily attached to the existing cable 8.

For example, as shown in a perspective view in wiring example No. 2 of FIG. It can also be placed nearby. Then, the cable 8 is routed so as to be hooked on the connecting portion between the first semi-annular portion 4a and the third semi-annular portion 4c, and then is routed between the third semi-annular portion 4c and the fourth semi-annular portion 4d. It is arranged near the center of the iron core 2, and the A end face 8a is drawn out to the opposite side.

As a result, as shown in the installation mode of wiring example 2, when the current transformer 1 is installed on the wiring path of the cable 8, for example, the cable can be connected without disconnecting or cutting the cable 8. 8 can be placed inside the magnetic circuit, and measurement can be performed using the current transformer 1. Furthermore, the current transformer 1 can be easily attached to the existing cable 8.

Then, when measurements were performed using the arrangement of wiring example 1, it was found that, for example, when a sinusoidal target current is flowing through the cable 8 as shown in FIG. ), and it was confirmed that it is possible to measure a measurement current having an amplitude (W10) that is proportional to the amplitude (W1) of the target current. Further, it was similarly confirmed that the measurement current can be measured in a state where the period and amplitude follow the target current with respect to the results of measurements performed in the arrangement mode shown in wiring example No. 2 shown in FIG. 5.

In this way, the current transformer 1 of this embodiment allows the cable 8 to be placed inside a magnetic circuit where current can be measured without the need for processing the cable 8 due to the characteristic shape of the iron core 2. I have to. However, the cable 8 can also be arranged differently from the wiring example 1 and wiring example 2 described above.

According to the embodiment described above, the following effects can be obtained.
The current transformer 1 includes an iron core 2 having four U-shaped semi-annular parts 4, and a plurality of secondary coils 3, which are provided on the iron core 2 and whose inner circumferential side is penetrated by the iron core 2. There is. Then, the iron core 2 connects the ends of one set of semi-annular parts 4, which are arranged parallel to each other, located on the same side, with another set of semi-annular parts 4, which are arranged parallel to each other. However, the four semi-annular parts 4 are connected in series to constitute one continuous magnetic circuit.

Thereby, in the iron core 2, a space portion that is accessible to the center of the iron core 2 is formed between the semi-annular portions 4 arranged in parallel. As a result, the connected cable 8 can be placed in the center side of the iron core 2, that is, in the space inside the magnetic circuit, without disconnecting or cutting the cable 8.

If the cable 8 can be placed inside the magnetic circuit, it becomes possible to measure the target current flowing through the cable 8 based on the residual voltage as described above. Therefore, even if it is difficult to process the cable 8, the target current flowing through the cable 8 can be measured.

Moreover, the secondary coil 3 is provided in each of the four semi-annular parts 4. Thereby, it becomes possible to arrange each secondary coil 3 so that the relative positional relationship in a magnetic circuit may be equalized, and it is possible to reduce the possibility that measurement accuracy will be adversely affected.
Moreover, since each half-annular part 4 can be connected by combining and joining the core pieces 6 obtained by dividing the annular core 5, the core 2 can be easily formed.

Moreover, it has four semi-annular parts 4 in a U-shape, and the ends of one set of semi-annular parts 4 arranged in parallel are arranged parallel to each other with the arrangement directions different by 90 degrees. The cable 8 is also processed by the iron core 2 for the current transformer 1, which is directly connected to the ends of one set of semi-annular parts 4 and constitutes a magnetic circuit including the four semi-annular parts 4. Even if it is difficult to measure the target current flowing through the cable 8.

(Second embodiment)
The second embodiment will be described below. This second embodiment differs from the first embodiment in that an annular portion is provided between the ends of each semi-annular portion 4. Furthermore, the principle of measurement by the current transformer 1 is the same as in the first embodiment.

As shown as an exploded perspective view and a perspective view in FIG. It is provided with a plurality of secondary coils 3 having an inner peripheral side through which an iron core 2 passes. Of these, the configuration of the semi-annular portion 4 is the same as in the first embodiment. Further, the secondary coils 3 are provided on each of the four sides of the annular portion 10.

The annular part 10 is made of the same material as the semi-annular part 4, and is formed into a rectangular frame shape that is approximately equal in width to the end of the semi-annular part 4. They are connected to each other. At this time, the ends of a pair of semi-annular parts 4 arranged in parallel are connected to one side of the annular part 10, and the arrangement direction is 90 degrees to the other side. The ends of another set of semi-annular parts 4 which are arranged in parallel in different states are respectively connected. That is, the iron core 2 according to the second embodiment has a structure in which the annular part 10 is arranged between the ends of the iron core 2 according to the first embodiment, and a magnetic circuit is formed by the annular part 10 and the semi-annular part 4. It becomes.

In other words, the current transformer 1 of this embodiment has a structure that can be called a hybrid type, which has both the characteristics of the conventional through-type in which the cable 8 is passed through, and the characteristics of the so-called non-through type in which the cable 8 is not penetrated. The characteristic shape of the core 2 makes it possible to place the cable 8, which remains connected, inside the magnetic circuit formed by the core 2. Furthermore, by providing the secondary coil 3 in the annular portion 10, the area in which the cable 8 can be installed in the iron core 2 is expanded, making it possible to apply it to large diameter cables. It becomes possible to wind the wire around, making it possible to measure minute currents.

Specifically, as shown in FIG. 8, for example, the cable 8 has a first semi-annular portion 4a and a second semi-annular portion on the A end surface 8a side, similar to the wiring example 1 of FIG. 5 of the first embodiment. 4b, near the center of the iron core 2 and closer to the first semi-annular part 4a than the annular part 10, so as to be hooked on the connecting part between the first semi-annular part 4a and the third semi-annular part 4c. After being routed to the B end face 8b side, from between the third semi-annular part 4c and the fourth semi-annular part 4d side, to the vicinity of the center of the iron core 2 and closer to the third semi-annular part 4c than the annular part 10. can be placed in Of course, the cable 8 can also be arranged in the same manner as the second wiring example in FIG. 5 of the first embodiment or in another arrangement.

When measurements were performed using this current transformer 1, it was found that, similar to the measurement results shown in FIG. It was confirmed that the current meter 1 could measure the target current. That is, it was confirmed that the current transformer 1 of this embodiment can measure the target current flowing through the cable 8 without the need to process the cable 8 due to the shape of the iron core 2.

In this way, the current transformer 1 of the present embodiment is provided with an iron core 2 having an annular annular portion 10 and four U-shaped semi-annular portions 4, and an iron core 2 having an inner peripheral side penetrated through the iron core 2. A plurality of secondary coils 3 are provided. In the iron core 2, the ends of a pair of semi-annular parts 4 arranged in parallel are connected to one surface of the annular part 10, and the ends of the semi-annular parts 4 arranged in parallel are connected to the other surface of the annular part 10. In this embodiment, the end portions of the other set of semi-annular portions 4 are connected with their arrangement directions different by 90 degrees, thereby forming a magnetic circuit including the four semi-annular portions 4.

Thereby, in the iron core 2, a space portion that is accessible to the center of the iron core 2 is formed between the semi-annular portions 4 arranged in parallel. As a result, the connected cable 8 can be placed in the center side of the iron core 2, that is, in the space inside the magnetic circuit, without disconnecting or cutting the cable 8. Therefore, even if it is difficult to process the cable 8, the target current flowing through the cable 8 can be measured.

Further, the secondary coil 3 is provided in the annular portion 10. This expands the area in which the cable 8 can be installed with respect to the iron core 2, making it possible to apply it to large-diameter cables and winding the cable 8 multiple times, thereby increasing the detection current.

Moreover, it has four semi-annular parts 4 in a U-shape, and the ends of one set of semi-annular parts 4 arranged in parallel are arranged parallel to each other with the arrangement directions different by 90 degrees. The ends of one set of semi-annular parts 4 are indirectly connected via the annular part 10, and the iron core 2 for the current transformer 1 constitutes a magnetic circuit including the four semi-annular parts 4. Even if it is difficult to process the cable 8, the target current flowing through the cable 8 can be measured.

(Third embodiment)
The third embodiment will be described below. In this third embodiment, modified examples and expanded examples of the current transformer 1 described in the first embodiment and the second embodiment will be divided into several aspects and explained.

<A mode of forming a gap between the ends>
For example, as shown in FIG. 9, the current transformer 1 may include a gap member 20 that is disposed between the ends of the semi-annular portion 4 and forms a gap between the ends. In the case of FIG. 9, gap members 20 are provided between the ends of the semi-annular portions 4 in the iron core 2 described in the first embodiment.

The gap material 20 alleviates magnetic saturation by forming a gap between the ends of the semi-annular portion 4, that is, at the joint where magnetic flux density is concentrated and magnetic saturation may occur. Moreover, the gap material 20 is joined to the end portion. This allows the current range to be measured to be wider. Of course, as described in the first embodiment, the cable 8 can also be placed in the current transformer 1 without processing the cable 8.

Alternatively, as shown in FIG. 10, in the iron core 2 described in the second embodiment, gap members 20 may be provided at the joints between the semi-annular portion 4 and the annular portion 10, respectively. In this case as well, by forming a gap at the junction where the magnetic flux density is concentrated and magnetic saturation is likely to occur, magnetic saturation is alleviated and a wider current range can be detected. Of course, as described in the second embodiment, the cable 8 can also be placed in the current transformer 1 without processing the cable 8.

When the target current flowing through the cable 8 was measured using the current transformer 1 shown in FIG. 9 or 10, as shown in FIG. A measured current with an amplitude (W20) that has a period (T20) that matches the period (T2) and has a peak value proportional to the amplitude (W2) of the target current due to the relaxation of magnetic saturation is detected, and the current is tracked to the target current. It was confirmed that measurement could be performed with greatly improved performance.

<A mode of extending the distance between the ends>
For example, as shown in FIG. 12 as an exploded perspective view and an exploded view, the current transformer 1 is configured to include an extension member 30 that is disposed between the ends of the semi-annular part 4 and extends the distance between the ends. Can be done. As shown in an exploded perspective view, the core 2 is constructed by inserting an extension member 30 having a predetermined length and having the same cross-sectional shape as each core piece 6 between the ends of the core pieces 6 which are obtained by dividing the annular core 5 into two. It is formed by bonding them together.

The extension member 30 is made of the same material as the semi-annular part 4 and extends the distance between the ends of the semi-annular part 4. As a result, as shown in the perspective view, the structure is similar to that of the iron core 2 described in the first embodiment, and the ends of the first semi-annular part 4a and the second semi-annular part 4b and the third semi-annular part 4c and the end of the fourth semi-annular portion 4d, an iron core can be manufactured in which the extension member 30 is extended.

In this case, since the area in which the cable 8 can be arranged is expanded, it becomes possible to apply the method to a large-diameter cable and to wind the cable 8 multiple times, making it possible to measure minute currents. Of course, as described in the first embodiment, the cable 8 can also be placed in the current transformer 1 without processing the cable 8.

Alternatively, as shown in FIG. 13, in the iron core 2 described in the second embodiment, between the ends of each semi-annular part 4, more precisely, the joint between each semi-annular part 4 and annular part 10 An extension member 30 may be provided at the location. This makes it possible to expand the area in which the cable 8 can be placed, making it possible to apply it to large-diameter cables and winding the cable 8 multiple times, making it possible to cope with the measurement of minute currents. Of course, as described in the second embodiment, the cable 8 can also be placed in the current transformer 1 without processing the cable 8.

However, the extension member 30 does not necessarily need to be provided between all ends. For example, in the case of FIG. 13, the extension member 30 may be provided on one side of the annular portion 10, and the extension member 30 may not be provided on the other side.

Moreover, the current transformer can be configured to include the gap material 20 and the extension member 30 described above. In that case, the gap material 20 and the extension member 30 may be provided between all the ends, the gap material 20 and the extension member 30 may be provided between some of the ends, or the gap material 20 and the extension member 30 may be provided between some of the ends. It is also possible to mix the end portions with only the extension member 30 provided.

<A mode in which the secondary coil 3 is arranged at a position corresponding to between the ends>
The current transformer 1 may have a configuration in which the secondary coil 3 is provided at a location other than the semi-annular portion 4. For example, as shown in FIG. 14, one end of the first half-annular part 4a and the second half-annular part 4b located on the same side is connected to the third half-annular part 4c, and the other end is connected to the third half-annular part 4c. In the iron core 2 formed by connecting with the fourth semi-annular portion 4d, the secondary coil 3 may be provided at a portion where the semi-annular portions 4 are connected to each other.

In other words, the secondary coil 3 can be arranged at a position corresponding to between the ends. Even with such a configuration, a space can be formed between the semi-annular parts 4 that allows access to the center of the iron core 2, and the cables 8 can be connected without disconnecting or cutting them. 8 can be placed on the center side of the iron core 2, that is, in the space inside the magnetic circuit.

Alternatively, as shown in an exploded perspective view in FIG. 15, an extension member 30 formed to have a predetermined length equal to the cross-sectional shape of each core piece 6 is installed between the ends of the core pieces 6 that are obtained by dividing the annular core 5 into two. In the configuration in which they are inserted and joined together, the extension member 30 may be provided with the secondary coil 3.

As a result, as shown in the exploded view, the distance between the ends of the first semi-annular part 4a and the second semi-annular part 4b and the ends of the third semi-annular part 4c and the fourth semi-annular part 4d is extended. In the iron core 2, it is possible to form a current transformer 1 in which each of the extension members 30 is provided with a secondary coil 3.

Even with such a configuration, a space can be formed between the semi-annular parts 4 that allows access to the center of the iron core 2, and the cables 8 can be connected without disconnecting or cutting them. 8 can be placed on the center side of the iron core 2, that is, in the space inside the magnetic circuit. In addition, the area in which the cable 8 can be arranged can be expanded, making it possible to apply the present invention to large-diameter cables and winding the cable 8 multiple times, making it possible to measure minute currents.

Moreover, in the embodiment in which the secondary coil 3 is arranged between the end parts, a configuration may also be adopted in which a gap material 20 is provided between the end parts. Furthermore, the gap material 20 and the extension member 30 may be provided between all the ends, the gap material 20 and the extension member 30 may be provided between some of the ends, or the gap material 20 and the extension member 30 may be provided between the end portions where only the gap material 20 is provided. It is also possible to mix the end portions with only the extension member 30 provided.

Furthermore, although not shown, the current transformer 1 can be modified or expanded as follows. For example, in each embodiment, the iron core 2 having a square cross section is illustrated, but the iron core 2 having a circular cross section may also be used. Moreover, when the iron core 2 is integrally molded, the iron core 2 having a rectangular or flat cross section can be used.

In each embodiment, the iron core 2 having a U-shaped semi-annular portion 4 is illustrated, but a configuration having a C-shaped semi-annular portion 4 is also possible. In this case, the C-shaped semi-annular portion 4 is formed by dividing the annular annular core 5 into two in the circumferential direction, and the C-shaped semi-annular portion 4 is formed by dividing the annular iron core 5 into two in the circumferential direction. By joining them together, an iron core 2 having a C-shaped semi-annular portion 4 can be formed. Further, if detection of minute current is required, the iron core 2 having the C-shaped semi-annular portion 4 can be integrally molded.

Further, as in the embodiment, a step of dividing each of the two annularly formed iron cores 2 in the circumferential direction to form iron core pieces 6 that become four U-shaped or C-shaped semi-annular parts 4; The formed four core pieces 6 are arranged in parallel with one set of core pieces 6, and the ends of each core piece 6 are placed directly with the ends of other iron core pieces 6 arranged in parallel, or with extensions or Even in the case where it is difficult to process the cable 8, the current transformer 1 using the iron core 2 manufactured by the manufacturing method including the step of indirectly joining the cable 8 through the gap material 20 can be used. Effects similar to those of the embodiment can be obtained, such as being able to measure the flowing target current. That is, the method of manufacturing the current transformer 1 and the method of manufacturing the iron core 2 described in the embodiment, as well as the method of manufacturing the iron core 2 by integral molding, are also included within the equivalent scope of the present invention.

Although several embodiments of the invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention, as well as within the scope of the invention described in the claims and its equivalents.

In the drawings, 1 is a current transformer, 2 is an iron core, 3 is a secondary coil, 4 is a semi-annular part, 8 is a cable, 10 is an annular part, 20 is a gap material, and 30 is an extension member.

Claims (8)

an iron core having four semi-annular parts in a U-shape or C-shape;
a plurality of secondary coils provided on the iron core, the inner circumferential side of which the iron core penetrates;
In the iron core, each of the other semi-annular parts is connected between the ends of a pair of semi-annular parts located on the same side that are arranged parallel to each other, and the four semi-annular parts are connected in series. A current transformer that constitutes one magnetic circuit. An iron core having an annular annular part and four U-shaped or C-shaped semi-annular parts,
a plurality of secondary coils provided on the iron core, the inner circumferential side of which the iron core penetrates;
The iron core has ends of a pair of semi-annular parts arranged in parallel connected to one side of the annular part, and ends of the semi-annular parts arranged parallel to each other on the other side of the annular part. A current transformer in which the end portions of the other set of semi-annular portions are connected in different arrangement directions to constitute a magnetic circuit including the four semi-annular portions. The current transformer according to claim 1 or 2, wherein the secondary coil is provided in the semi-annular portion. The current transformer according to claim 2, wherein the secondary coil is provided in the annular portion. 3. The current transformer according to claim 1, wherein the secondary coil is provided at a portion where the semi-annular portions are connected to each other. The current transformer according to any one of claims 1 to 5, further comprising a gap member disposed between the ends of the semi-annular portion to form a gap between the ends. The current transformer according to any one of claims 1 to 6, further comprising an extension member disposed between the ends of the semi-annular portion to extend the distance between the ends. A pair of semi-annular parts having four U-shaped or C-shaped semi-annular parts arranged parallel to each other is directly connected between the ends located on the same side with another semi-annular part. Or an iron core for a current transformer that is indirectly connected to each other and constitutes a magnetic circuit including the four semi-annular parts.