JP2000068139A - Zero phase current transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zero phase current transformer capable of further reducing leakage fluxes to a core and further reducing a residual voltage. SOLUTION: This transformer is provided with at least two conductors 3a, 3b and 3c, a rectangular core 101 surrounding the conductors 3a, 3b and 3c, a bobbin winding coil 2 inserted to the core 101, a first magnetic shield 7 provided so as to cover the core 101 and the bobbin winding coil 2, and a second magnetic shield 8 further provided inside the first magnetic shield 7 so as to cover the bobbin winding coil 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zero-phase current transformer for detecting a zero-phase current flowing only when a ground fault occurs in a transmission / distribution line or when there is an electric shock.

[0002]

2. Description of the Related Art FIG.
FIG. 6 is a configuration diagram showing a conventional zero-phase current transformer disclosed in Japanese Unexamined Patent Application Publication No. 6-2006. 24, reference numeral 11 denotes an annular core, 21 denotes an output winding (secondary conductor), and 3a and 3b denote primary conductors penetrating the hollow portion of the annular core 11. The material of the annular core 11 is
Permalloy with high magnetic permeability is widely used.
Silicon steel, ferrite, amorphous alloys and the like are also used. The method of molding the annular core 11 differs depending on the material. Ferrite is formed by sintering, but a metal magnetic body such as permalloy or silicon steel is formed by laminating a punched plate or winding it into a toroidal shape.

FIG. 24 shows two primary conductors 3a and 3a.
b is shown, but in the case of three phases, three primary conductors are used by arranging them so as to penetrate the hollow portion of the iron core. Although not shown, the surface of the annular iron core 11 is normally magnetically shielded by a magnetic shield made of a wound iron core such as electromagnetic soft iron or directional silicon steel.

FIG. 25 is a block diagram showing another example of a conventional zero-phase current transformer. In FIG. 25, the annular core 12 is divided into two parts. Other configurations are substantially the same as the conventional example of FIG.

Next, the operation will be described. Conductors 3a and 3
b, when only balanced load currents of opposite directions and equal in magnitude are flowing through the annular core 1
The magnetic flux generated in 1 cancels out and no voltage is induced in the output winding 21. For example, when a ground fault occurs and a difference occurs between the currents of the primary conductors 3a and 3b, that is, when a zero-phase current flows, a voltage is induced in the output winding 21. An earth leakage circuit breaker equipped with a zero-phase current transformer utilizes this principle and has a function of immediately stopping power supply and protecting the circuit in the event of a ground fault or electric shock.

However, in practice, even when only a balanced load current is flowing, a voltage is induced in the output winding due to unevenness of the output winding and asymmetry of the position of the primary conductor with respect to the annular core. Is done. This is called a residual voltage. If this residual voltage is larger than the output for the zero-phase current, it leads to malfunction of the earth leakage breaker. Therefore, the characteristics of the zero-phase current transformer are that the residual voltage generated when only the balanced load current is flowing is small, the output sensitivity to the zero-phase current is high, and in other words, the output for the zero-phase current is Is larger than the residual voltage.

The annular core 11 shown in FIG. 24 has the advantages of high core permeability and high output sensitivity to zero-sequence current, but has an output winding around the entire circumference of the annular core to reduce the residual voltage. It is very difficult to apply lines uniformly. In addition, since the core is annular, it is necessary to use a toroidal winding machine, and the wire storage work for winding is accompanied by the winding work, the winding work takes a long time, and the manufacturing cost increases. There were drawbacks.

Next, the split-type annular core 1 shown in FIG.
2 has the advantage of being able to use a spindle type winding machine because it is divided, and has the advantage that the winding time can be shortened. However, since a small gap having a relative permeability of 1 is formed in two places of the core, the residual voltage is reduced. As a result, the effective magnetic permeability of the core decreases, and the output sensitivity to the zero-phase current decreases.

FIG. 26 is a sectional view showing another example of a conventional zero-phase current transformer. FIG. 27 is a sectional view taken along line XXVII-XXVII of FIG. In the figure, reference numeral 101 denotes a square, rectangular frame-shaped core. Reference numeral 2 denotes a pair of bobbin wound coils inserted through a pair of opposed sides of the core 101, respectively. The bobbin wound type coil 2 is formed by winding a secondary conductor in a coil shape around a bobbin made of resin. The bobbin wound type coil 2 is arranged at approximately the center of the magnetic plate 1d and the magnetic plate 1b, respectively.

Reference numerals 3a, 3b, and 3c denote primary conductors corresponding to three-phase U, V, and W phases. Primary conductors 3a, 3
The b and 3c extend on the same plane perpendicular to the center of the magnetic plate 1d and the magnetic plate 1b. 4 is the primary conductor 3
a, 3b, and 3c are rectangular cylindrical inner circumferential shields provided so as to surround the shields. Reference numeral 5 denotes a rectangular-tube-like outer peripheral shield provided so as to surround the core 101 and the bobbin wound coil 2. Reference numerals 6 and 6 denote a pair of side shields which cover the ends of the inner shield 4 and the outer shield 5 so as to seal them. Each of the shields 4, 5, and 6 is formed by laminating thin sheets of electromagnetic soft iron, silicon steel, or the like, and forms a magnetic shield 7 that covers the core 101 and the bobbin wound coil 2. The primary conductors 3a, 3b, 3c extend so as to penetrate the side shields 6,6.

FIG. 28 shows that when a balanced current having the same magnitude flows in the primary conductor 3a from the top to the bottom in FIG. 28 and the primary conductor 3c from the bottom to the top in FIG. It is a schematic diagram which shows the return magnetic flux (return magnetic flux 9A generated by the primary conductor 3a, the return magnetic flux 9B generated by the primary conductor 3c) which generate | occur | produces in a primary conductor penetration window. A part of the return magnetic flux penetrates into the core 101, and the magnetic flux links the bobbin wound coil 2, and the unbalance is generated as a residual voltage. Factors causing the imbalance include non-uniformity of the magnetic characteristics of the magnetic circuit of the core 101, asymmetry of the conductor position and the magnetic shield position with respect to the magnetic circuit of the core 101, and the like.

FIG. 29 is a diagram schematically showing magnetic flux leakage to the core 101 of the conventional zero-phase current transformer. In the drawing, the outer shield 5 and the side shield 6 of the magnetic shield 7 and the primary conductor 3b (V phase) are omitted. Most of the magnetic flux passing through the window space through which the primary conductor passes is the magnetic flux 10A (ΦA) and 10B (Φ
B). Part of the magnetic flux 11a (Φ
a) and 11 (Φb) leak into the core. The magnetic flux leaks into the core 101 provided with the bobbin wound type coil 2 and (Φa−
A residual voltage proportional to the time derivative of Φb) is induced in the bobbin wound coil 2.

[0013]

The magnetic shield 7 prevents the magnetic flux generated by the load current flowing through the primary conductors 3a, 3b, 3c from entering the core 101 and reduces the residual voltage. However, even if the magnetic shield 7 is provided, the core 10
1 slightly generated magnetic flux leakage.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to further reduce the leakage flux to the core, further reduce the residual voltage, and reduce the cost of winding. The purpose is to obtain a zero-phase current transformer having high output sensitivity to zero-phase current.

[0015]

A zero-phase current transformer according to the present invention comprises a rectangular core, at least two conductors penetrating through a hollow window of the core, at least one side of the core, and a core in a bobbin hole. And a first bobbin wound coil disposed between the core and the conductor so as to cover at least the periphery of the core on the conductor side, and to block leakage magnetic flux from the conductor toward the core. A magnetic shield, provided between the first magnetic shield and the bobbin wound coil on the side of the core where the bobbin wound coil is disposed, and covering at least the periphery of the bobbin wound coil; And a second magnetic shield for blocking a leakage magnetic flux toward the second magnetic shield.

The conductor extends on the same plane, and the bobbin wound coil is a single bobbin wound coil disposed on one side parallel to the plane of the core. The magnetic shield is provided only on one side where the bobbin wound coil is disposed.

Further, the bobbin wound coil is a pair of bobbin wound coils inserted through two opposing sides of the core, and the second magnetic shield is provided with a bobbin wound coil disposed on the core. It is provided only on the side.

The first magnetic shield has a U-shaped cross section with an opening at the outer periphery.

The first magnetic shield comprises an inner peripheral shield and a pair of side shields.

The second magnetic shield has a U-shaped cross section with an opening at the outer periphery.

The second magnetic shield has a rectangular cross section having a slit on the outer periphery.

In the bobbin wound coil, the core insertion hole has a rectangular cross section, and the winding is wound uniformly along the bobbin frame length.

The core is formed by laminating four rectangular magnetic plates with their ends sequentially connected to form a rectangle, and the rectangles are laminated. The joining method is a double wrap joint or a butt wrap joint.

Also, the core is formed by connecting two L-shaped magnetic plates at both ends to form a rectangle, and by stacking rectangles,
The joining method is alternate lamination joining or butt joining.

Further, a rectangular shape is formed by the U-shaped magnetic plate and the strip-shaped magnetic plates connected to both ends of the U-shaped opening side, and the rectangles are formed by lamination. Joining.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a front view showing a cross section of a part of a zero-phase current transformer of the present invention. FIG. 2 shows FIG.
FIG. 2 is a sectional view taken along the line II-II of FIG. FIG. 3 is III-I of FIG.
It is arrow sectional drawing which follows the II line. In the figure, reference numeral 101 denotes a square, rectangular frame-shaped core. The core 101 is a strip-shaped magnetic plate 1a, 1 of the same dimensions and made of a material such as permalloy, silicon steel, iron-based and cobalt-based amorphous alloys.
b, 1c, and 1d are sequentially joined at their ends to form a rectangular frame.

Reference numeral 2 denotes one bobbin wound coil inserted through one side of the core 101. The bobbin wound type coil 2
The secondary conductor is wound in a coil shape around a resin bobbin. Each of the bobbin wound coils 2 has a magnetic plate 1c.
Is arranged at the approximate center.

Reference numerals 3a, 3b, and 3c denote primary conductors made of rectangular copper wires or the like corresponding to the three-phase U, V, and W phases. Generally, in a feed-through type zero-phase current transformer built in an earth leakage breaker,
Since the conductor is connected to the terminal near the entrance of the hollow window 7a, the conductor is bent and comes close to the core.
The primary conductors 3a, 3b, 3c extend on the same plane perpendicular to the center of the magnetic plate 1d and the magnetic plate 1b.

Reference numeral 7 denotes a first magnetic shield 7 using electromagnetic soft iron, silicon steel plate, or the like having a high saturation magnetic flux density and a high magnetic permeability.
The first magnetic shield 7 includes one inner shield 4, one outer shield 5, and a pair of side shields 6.

Reference numeral 8 denotes a second magnetic shield having a U-shaped cross section made of a material such as permalloy, nickel-based or cobalt-based amorphous alloy. The second magnetic shield 8 is disposed with its U-shaped opening facing the outer shield 5, and is covered so as to cover three surfaces of the bobbin wound coil 2.

FIG. 4 shows a bobbin 2a of the bobbin wound type coil 2.
It is a perspective view of. Various resins are used as the material of the bobbin 2a, and the bobbin 2a is manufactured at low cost by injection molding. It is preferable that the bobbin has a terminal (not shown) from the viewpoint of preventing disconnection of the coil. From the viewpoint of reducing the residual voltage, it is desirable that the winding frame length be long and that the windings be wound at a constant pitch.

FIG. 5 is a perspective view of the first magnetic shield 7. FIG. 6 is a perspective view of the inner peripheral shield 4 which is a component of the first magnetic shield 7. FIG. 7 is a perspective view of the outer peripheral shield 5 which is a component of the first magnetic shield 7. FIG. 8 is a perspective view of the side shield 6 which is a component of the first magnetic shield 7. An outer shield 5 is arranged outside the inner shield 4, and a pair of side shields 6 are arranged on both side surfaces so as to be hermetically closed, thereby forming a first magnetic shield 7 having a rectangular passage shape.

The core 10 is provided in the first magnetic shield 7.
1. The bobbin wound type coil 2 is stored. The lead wire of the bobbin wound type coil 2 is provided with a small gap between the outer peripheral shield 5 and one side shield 6, and is led out from this portion. The first magnetic shield 7 prevents the magnetic flux generated by the load current flowing through the primary conductors 3a, 3b, 3c from entering the core 101 and reduces the residual voltage.

When a large current flows through the primary conductors 3a, 3b and 3c, the first magnetic shield 7 must not be magnetically saturated and have a high magnetic shielding effect. High saturation magnetic flux density and high magnetic permeability are required. As a material, a magnetic iron core or a bonded core made of laminated silicon steel sheet is also conceivable. Are suitable.
still. In the wound iron core, Rs are formed at the four corners, but are omitted in the figure. Actually, the shape is as shown in FIG. Since the magnetic flux due to the load current is generated in the winding direction of the wound core, the winding direction is set in the rolling direction of the directional silicon steel having excellent magnetic properties.

In the pair of side shields 6 shown in FIG. 8, punched plates of electromagnetic soft iron and non-directional silicon steel are laminated because they have high saturation magnetic flux density, high magnetic permeability, and can be manufactured at low cost. Things are suitable. When a punched plate of directional silicon steel is used, those in which the rolling direction in the side direction of each laminated plate differs by 90 ° in the vertical direction are alternately laminated.

Since the first magnetic shield 7 is provided so as to surround the core 101, it must be electrically insulated in the circumferential direction so as not to cause a secondary short circuit.
When the above-mentioned silicon steel is used for the side shield 6, the surface coating has an insulating function.

FIG. 10 is a perspective view showing the details of the second magnetic shield 8. The second magnetic shield 8 includes the primary conductor 3
Is arranged via the first magnetic shield 7,
The magnitude of the applied magnetic field is considerably smaller than that of the first magnetic shield. Therefore, there is no worry about magnetic saturation. Therefore, the use of permalloy or a cobalt-based amorphous alloy of the same material as the main core 101 having a lower saturation magnetic flux density but a higher magnetic permeability than the electromagnetic soft iron or silicon steel used for the first magnetic shield member provides an excellent magnetic shielding effect. Is obtained.

FIG. 11 is a side view showing a state in which the bobbin wound type coil 2 is accommodated in a U-shaped second magnetic shield 8. The surface on which the bobbin wound type coil 2 is not shielded is arranged on the outer shield 5 side (the side opposite to the parallel and arranged primary conductors) which is a magnetic shield portion having a small amount of magnetic flux leaking to the main core 101.

FIG. 12 shows that when a balanced current having the same magnitude flows in the primary conductor 3a from the top to the bottom in FIG. 12 and the primary conductor 3c from the bottom to the top in FIG. Return magnetic flux (primary conductor 3
10A is a schematic diagram showing a return magnetic flux 10A generated by a and a return magnetic flux 10B generated by the primary conductor 3c). In the figure, the outer peripheral shield 5, the side shield 6, and the primary conductor 3b (V phase), which are the first magnetic shield members, are omitted.

Most of the magnetic flux passing through the window space through which the primary conductors 3a and 3c pass is the magnetic flux 10A (ΦA) and 10B (ΦB) indicated by solid arrows flowing back through the magnetic shield 7. still,
This magnetic flux is magnetically diffused also into the outer peripheral shield 5 and the pair of side shields 6 having an integral structure, and flows in the same arrow direction. In the present embodiment, the portion of the core 101 where the bobbin wound coil 2 is provided and the first magnetic shield 7
Since the second magnetic shield 8 is provided between the coil 101 and the core 101, the leakage to the core 101 provided with the bobbin wound coil 2 is extremely small. Ignored in the figure, but leaked a little. In order to reduce the leakage magnetic flux, it is convenient to reduce the gap between both ends of the second magnetic shield 8 and the core 101.
This is an effective method. When both ends of the second magnetic shield 8 come into contact with the core 101, the return magnetic flux due to the zero-phase current is bypassed to the second magnetic shield 8, and the output is reduced.
Thus, instead of shielding the entire periphery of the core 101 doubly, only a cylinder having a U-shaped cross section is provided only around the bobbin wound coil 2, and the zero-phase change having excellent residual voltage characteristics is achieved. Sink can be realized at low cost.

Embodiment 2 FIG. 13 is a sectional view showing another example of the zero-phase current transformer of the present invention. In the figure, reference numeral 2 denotes a pair of bobbin wound coils inserted through a pair of opposing sides of the core 101, respectively. The bobbin wound type coil 2
The secondary conductor is wound in a coil shape around a resin bobbin. Each of the bobbin wound coils 2 has a magnetic plate 1a.
And the magnetic plate 1c is disposed substantially at the center. Other configurations are the same as those of the first embodiment.

When two bobbin wound type coils 2 are used as in this embodiment, it is desirable that the shape and the number of turns be the same, the windings be connected in series, and be arranged vertically symmetrically. In order to ensure the required output for the zero-phase current, while taking into account the workability during winding with the spindle type winding machine,
A zero-phase current transformer mounted on an earth leakage circuit breaker having a rated current capacity of several tens to several hundreds of amps has an insulation-covered wire having a winding diameter of about 0.1 mm of about 1000 turns (one bobbin wound type coil). Case) A roll is used.

From the viewpoint of reducing the residual voltage, it is desirable that the primary conductors 3a, 3b and 3c are arranged symmetrically at the center of the core window and the distance between the conductors is made as small as possible. In order to make the current capacity of each conductor the same, generally, the cross-sectional area of each conductor is almost the same. The shape of the conductor may be round or rectangular.

The zero-phase current transformer having such a configuration has a drawback that the number of bobbin-wound coils increases to two, but the number of turns per bobbin-wound coil 2 can be reduced by half, and Has a merit that it is difficult to cause disconnection because the wire diameter can be increased.

Embodiment 3 FIG. 14 is a sectional view showing another example of the zero-phase current transformer of the present invention. In the figure, as is apparent from FIG. 3 of the first embodiment, the outer peripheral shield 5 is farthest from the primary conductors 3a, 3b, 3c. Since the magnetic field generated by the load current decreases as the distance from the primary conductor increases, the magnetic field generated by the outer shield portion 5 among the shield members of the first magnetic shield 7 is the smallest. Therefore, the shielding effect of the outer shield 5 on the core 101 is smaller than that of the inner shield 4 and the side shield 6. The residual voltage increases almost in proportion to the load current. Therefore, the outer shield 5 can be omitted from the zero-phase current transformer mounted on the earth leakage breaker having a small rated capacity (load current) as in the present embodiment. Other configurations are the same as those of the first embodiment.

Embodiment 4 FIG. FIG. 15 is a perspective view of a core showing another example of the zero-phase current transformer of the present invention. The core 101 of the present embodiment includes a plurality of strip-shaped magnetic plates 1a, 1b, 1
c and 1d are joined by a joining method called a double lap joint in which the members are stacked and joined in a generally well-shaped manner. That is, first, two strip-shaped magnetic plates 1
b, 1d are arranged in parallel, and then two strip-shaped magnetic plates 1a, 1c are arranged in parallel so as to be bridged over the respective ends of the two strip-shaped magnetic plates 1b, 1d. This is sequentially repeated, so that a total of eight strip-shaped magnetic plates are stacked in four layers. Each end face of each strip-shaped magnetic plate 1a, 1b, 1c, 1d is flush with the side face so as not to protrude from the side face of the adjacent strip-shaped magnetic plate.

Since the zero-phase current transformer is generally used at a commercial frequency, the thickness of the strip-shaped magnetic plates 1a, 1b, 1c, and 1d is a sufficient number such that deterioration of magnetic characteristics due to eddy current loss does not matter. Millimeters or less are used. This bonding called a double lap joint has an effect that the bonding surfaces can be brought into surface contact even if the thickness of each strip-shaped magnetic plate is slightly different.

In the zero-phase current transformer having such a configuration,
Further, the four strip-shaped magnetic plates 1a, 1b, 1c, 1d are sequentially connected at their ends to form a rectangle, and the rectangles are laminated to be manufactured, so that the material is inexpensive and the cost is reduced. be able to. In addition, each strip-shaped magnetic plate 1
Since the joints at the corners of a, 1b, 1c, and 1d are double wrap joints, even if the thickness of each of the strip-shaped magnetic plates is slightly different, the joining surfaces can be brought into surface contact, and the magnetic permeability decreases. Therefore, the output voltage can be increased.

Embodiment 5 FIG. 16 is a perspective view of a core showing another example of the zero-phase current transformer of the present invention. The core 102 of the present embodiment is joined by a method called a butt wrap joint as shown in FIG. That is, each of the strip-shaped magnetic plates 1a, 1b, 1c, 1d
In the lowermost layer, one end face is abutted to the side face end of the adjacent strip-shaped magnetic plate, while the other side face end is
The end faces of the strip-shaped magnetic plates adjacent to the other side are abutted to form a square-rectangular frame as a whole, and in the next layer, the abutting is performed in the opposite direction, and the layers are stacked. Then, the strip-shaped magnetic plates 1a, 1b, 1
As in the first embodiment, the thicknesses of c and 1d are several millimeters or less, which is sufficient to prevent deterioration of magnetic characteristics due to eddy current loss.

A method of assembling the zero-phase current transformer having such a configuration will be described. First, a pair of bobbin wound coils 2 are placed in parallel at a predetermined distance from each other at a predetermined position on the side shield 6, and are fixed by an adhesive (not shown). Next, the strip-shaped magnetic plates 1b and 1d are inserted into the bobbin wound coils 2, respectively, and the strip-shaped magnetic plates 1a and 1c are
It is arranged by being hung over. This is repeated and FIG.
Are stacked vertically as shown in FIG.

In the zero-phase current transformer having such a configuration,
The core 102 is joined by a butt wrap joint. The butt wrap joint can reduce the height of the core to half as compared with the double wrap joint, and can make the zero-phase current transformer compact.

Embodiment 6 FIG. FIG. 17 is a perspective view of a core showing another example of the zero-phase current transformer of the present invention. The core 103 of the present embodiment is manufactured by forming thin L-shaped magnetic plates 1e and 1f in a rectangular frame shape with their ends joined to each other.
Then, the joining method is alternately laminated joining in which the ends are alternately overlapped. Other configurations are the same as those of the first embodiment.

In the zero-phase current transformer having such a configuration,
Since the L-shaped magnetic plate is used, the first embodiment is used.
However, there is a disadvantage that the cost is slightly higher than that of the strip-shaped magnetic plate, but the number of joints can be two, and the number of joints can be reduced as compared with the case of the strip-shaped magnetic plate. There is an advantage that the effective magnetic permeability can be increased, and thus the output voltage with respect to the zero-phase current can be increased.

Embodiment 7 FIG. FIG. 18 is a perspective view of a core showing another example of the zero-phase current transformer of the present invention. The core 104 of the present embodiment is manufactured by stacking thin L-shaped magnetic plates 1e and 1f in a rectangular frame shape with their ends facing each other. The joining method is butt joining. Other configurations are the same as those of the first embodiment.

In the zero-phase current transformer having such a configuration,
Since the number of joints can be two, and the number of joints can be reduced, the effective magnetic permeability of the core can be increased, the output voltage can be increased, and the height of the core can be halved. The zero-phase current transformer can be made compact.

Embodiment 8 FIG. FIG. 19 is a perspective view of a core showing another example of the zero-phase current transformer of the present invention. In FIG. 19, 1g is a thin U-shaped magnetic plate. The core 105 of the present embodiment includes a U-shaped magnetic plate 1g and a U-shaped magnetic plate 1g.
And a rectangular magnetic plate 1a connected to both ends on the opening side of the rectangular shape, and the rectangular shape is laminated. Then, the joining method is alternately laminated joining. In the present embodiment, a pair of bobbin wound coils 2 are installed on the left side and the right side. Other configurations are the same as those of the first embodiment.

In the zero-phase current transformer having such a configuration,
Since the U-shaped magnetic plate 1g is used, there is a disadvantage that the cost is slightly higher than that of the strip-shaped magnetic plate in Embodiment 1 described above. However, the number of joints is two, which is smaller than that of the strip-shaped magnetic plate. Since the number of joints can be reduced, the effective magnetic permeability of the core can be increased, and therefore, there is an advantage that the output voltage with respect to the zero-phase current can be increased.

Embodiment 9 FIG. FIG. 20 is a perspective view of a second magnetic shield showing another example of the zero-phase current transformer of the present invention.
The second magnetic shield 18 of the present embodiment has a substantially rectangular cylindrical shape, and has a slit 18a formed on one side surface over the entire length. The second magnetic shield 18 is covered so as to cover the bobbin wound coil 2 with the slit 18a facing the outer shield 5 side. Other configurations are the same as those of the first embodiment.

In the zero-phase current transformer having such a configuration,
Although there is a disadvantage that the cost is slightly increased, it is possible to achieve the same or higher magnetic shielding effect. The second magnetic shield 18 is provided so as to surround the core 101. However, when a metal magnetic material having a small specific resistance is used as a material, the second magnetic shield 18
Slit 1 so that the secondary side of the
8a need to be provided.

Embodiment 10 FIG. FIG. 21 is a perspective view of a second magnetic shield showing another example of the zero-phase current transformer of the present invention. The second magnetic shield 28 of the present embodiment has a substantially rectangular cylindrical shape, and has an overlapped portion 28 a
Are formed. Then, the second magnetic shield 28
Is covered so as to cover the bobbin wound coil 2 with the overlapping portion 28a facing the outer peripheral shield 5 side. Other configurations are the same as those of the first embodiment.

In the zero-phase current transformer having such a configuration,
Although there is a disadvantage that the cost is slightly increased, it is possible to achieve the same or higher magnetic shielding effect. The second magnetic shield 28 is provided so as to surround the core 101. However, when a metal magnetic material having a small specific resistance is used as a material, the second magnetic shield 28
So that the secondary side of the
It is necessary to provide a gap 28b in a.

Embodiment 11 FIG. FIG. 22 is a front view partially in section showing another example of the zero-phase current transformer of the present invention. The first magnetic shield 17 according to the present embodiment includes the primary conductor 3
The shape of the hollow window 17a through which a, 3b, and 3c pass is circular. Other configurations are the same as those of the first embodiment. With the zero-phase current transformer having such a configuration, the same effect as in the first embodiment can be obtained.

Embodiment 12 FIG. FIG. 23 is a front view partially in section showing another example of the zero-phase current transformer of the present invention. The first magnetic shield 27 according to the present embodiment includes the primary conductor 3
The shape of the hollow window 27a through which a, 3b, and 3c penetrate is rectangular. The outer peripheral shape of the first magnetic shield 27 is also rectangular. Other configurations are the same as those of the first embodiment.

In the zero-phase current transformer having such a configuration,
There is a disadvantage that the width of the zero-phase current transformer is large, but there is an advantage that the height of the zero-phase current transformer can be reduced, so that the earth leakage breaker incorporating the zero-phase current transformer can be made thin. .

[0065]

The zero-phase current transformer according to the present invention has a rectangular core, at least two conductors penetrating through the hollow window of the core, and a bobbin hole penetrating the core through at least one side of the core. A bobbin wound type coil provided, a first magnetic shield provided between the core and the conductor so as to cover at least a periphery of the conductor side of the core, and blocking a leakage magnetic flux from the conductor toward the core; Leakage magnetic flux provided between the first magnetic shield on the side of the core where the bobbin wound coil is disposed and the bobbin wound coil, covering at least the periphery of the bobbin wound coil and traveling from the conductor to the core And a second magnetic shield for shutting off. Therefore, the leakage flux to the core can be further reduced, and the residual voltage can be further reduced.

The conductor extends on the same plane, and the bobbin wound coil is one bobbin wound coil disposed on one side parallel to the plane of the core. The magnetic shield is provided only on one side where the bobbin wound coil is disposed. Therefore, the second magnetic shield can be easily formed, and the cost can be reduced.

The bobbin wound type coil is a pair of bobbin wound type coils inserted through two opposing sides of the core, and the second magnetic shield is provided with the bobbin wound type coil. It is provided only on the side. Therefore, the number of turns per bobbin wound type coil can be reduced to one half, and the wire diameter of the winding can be increased.
And the cost can be reduced.

The first magnetic shield has a U-shaped cross section with an opening at the outer periphery. Therefore, since the outer peripheral portion is opened and the number of members can be reduced, the cost can be reduced and the creation of the first magnetic shield is facilitated.

The first magnetic shield comprises an inner peripheral shield and a pair of side shields. Therefore, the first
In this case, it is possible to further facilitate the creation of the magnetic shield and reduce the cost.

The second magnetic shield has a U-shaped cross section with an opening at the outer periphery. Therefore, the creation of the second magnetic shield is further facilitated, and the cost can be reduced.

The second magnetic shield has a rectangular cross section having a slit on the outer periphery. Therefore, the leakage flux to the core can be further reduced, and the residual voltage can be further reduced.

In the bobbin wound coil, the core insertion hole has a rectangular cross section, and the winding is wound uniformly along the bobbin frame length. Therefore, the residual voltage can be further reduced.

The core is formed by laminating four rectangular magnetic plates with their ends sequentially connected to form a rectangle, and the rectangles are laminated. The joining method is a double wrap joint or a butt wrap joint. Therefore, the material is inexpensive, and the cost can be reduced.

Further, the core is formed by joining two L-shaped magnetic plates at both ends to form a rectangle, and by stacking rectangles.
The joining method is alternate lamination joining or butt joining. Therefore, the number of joints can be two, and the effective magnetic permeability of the core can be increased, so that the output voltage can be increased.

Further, a rectangular shape is formed by the U-shaped magnetic plate and the strip-shaped magnetic plates connected to both ends of the U-shaped opening side, and the rectangles are formed by lamination. Joining. Therefore, the number of joints can be two, and the effective magnetic permeability of the core can be increased, so that the output voltage can be increased.

[Brief description of the drawings]

FIG. 1 is a front view showing a cross section of a part of a zero-phase current transformer of the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is a sectional view taken along the line III-III in FIG. 2;

FIG. 4 is a perspective view of a bobbin of the bobbin wound coil.

FIG. 5 is a perspective view of a first magnetic shield.

FIG. 6 is a perspective view of an inner peripheral shield that is a component of the first magnetic shield.

FIG. 7 is a perspective view of an outer peripheral shield which is a component of the first magnetic shield.

FIG. 8 is a perspective view of a side shield which is a component of the first magnetic shield.

FIG. 9 is a front view partially in section showing details of the outer shape of the zero-phase current transformer.

FIG. 10 is a perspective view showing details of a second magnetic shield.

FIG. 11 is a side view showing a state in which the bobbin wound coil is accommodated in a U-shaped second magnetic shield.

FIG. 12 is a schematic diagram showing a return magnetic flux generated in the first magnetic shield 7;

FIG. 13 is a sectional view showing another example of the zero-phase current transformer of the present invention.

FIG. 14 is a sectional view showing another example of the zero-phase current transformer of the present invention.

FIG. 15 is a perspective view of a core showing another example of the zero-phase current transformer of the present invention.

FIG. 16 is a perspective view of a core showing another example of the zero-phase current transformer of the present invention.

FIG. 17 is a perspective view of a core showing another example of the zero-phase current transformer of the present invention.

FIG. 18 is a perspective view of a core showing another example of the zero-phase current transformer of the present invention.

FIG. 19 is a perspective view of a core showing another example of the zero-phase current transformer of the present invention.

FIG. 20 is a perspective view of a second magnetic shield showing another example of the zero-phase current transformer of the present invention.

FIG. 21 is a perspective view of a second magnetic shield showing another example of the zero-phase current transformer of the present invention.

FIG. 22 is a front view partially in section showing another example of the zero-phase current transformer of the present invention.

FIG. 23 is a front view partially in section showing another example of the zero-phase current transformer of the present invention.

FIG. 24 is a configuration diagram showing a conventional zero-phase current transformer.

FIG. 25 is a configuration diagram showing another example of a conventional zero-phase current transformer.

FIG. 26 is a sectional view showing another example of a conventional zero-phase current transformer.

FIG. 27 is a sectional view taken along the line XXVII-XXVII of FIG. 26;

FIG. 28 is a schematic diagram showing return magnetic flux generated in a magnetic shield.

FIG. 29 is a diagram schematically showing magnetic flux leakage to a core of a conventional zero-phase current transformer.

[Explanation of symbols]

2 bobbin wound type coil, 3a, 3b, 3c conductor, 4
Inner circumference shield, 5 outer circumference shield, 6 side shield,
7 first magnetic shield, 7a hollow window, 8, 18, 2
8 Second magnetic shield, 18a slit, 101, 1
02, 103, 104, 105 cores.

Claims (11)

[Claims] 1. A rectangular core, at least two conductors penetrating through a hollow window of the core, and a bobbin winding type disposed on at least one side of the core and penetrating the core through a bobbin hole. A coil, a first magnetic shield provided between the core and the conductor so as to cover at least a periphery of the core on the conductor side, and shielding a magnetic flux leaking from the conductor toward the core; Is provided between the first magnetic shield and the bobbin wound coil on the side where the bobbin wound coil is disposed, and covers at least the periphery of the bobbin wound coil, and A zero-phase current transformer, comprising: a second magnetic shield that blocks leakage magnetic flux toward the core. 2. The bobbin wound coil is one bobbin wound coil disposed on one side of the core parallel to the plane, wherein the conductor extends on the same plane. The zero-phase current transformer according to claim 1, wherein the second magnetic shield is provided only on one side of the bobbin wound coil. 3. The bobbin wound coil is a pair of bobbin wound coils inserted into two opposing sides of the core, and the second magnetic shield is provided with the bobbin wound coil. 2. The zero-phase current transformer according to claim 1, wherein the zero-phase current transformer is provided only on the provided two sides. 4. The zero-phase current transformer according to claim 1, wherein the first magnetic shield has a U-shaped cross section having an opening at an outer peripheral portion. 5. The zero phase current transformer according to claim 4, wherein said first magnetic shield comprises an inner peripheral shield and a pair of side shields. 6. The zero-phase current transformer according to claim 1, wherein the second magnetic shield has a U-shaped cross section having an opening at an outer peripheral portion. 7. The zero-phase current transformer according to claim 1, wherein the second magnetic shield has a rectangular cross section having a slit in an outer peripheral portion. 8. The bobbin winding type coil according to claim 1, wherein the core insertion hole has a rectangular cross section, and the winding is wound uniformly along the bobbin bobbin frame length. The zero-phase current transformer according to any of the above. 9. The core has a rectangular shape in which four strip-shaped magnetic plates are sequentially connected at ends thereof, and the rectangular shape is laminated. The joining method is a double wrap joint or a butt wrap joint. Claim 1 characterized by the following:
9. The zero-phase current transformer according to any one of claims 1 to 8. 10. The core is formed by joining two L-shaped magnetic plates at both ends to form a rectangle, and the rectangles are laminated, and the joining method is alternate lamination joining or butt joining. The zero-phase current transformer according to any one of claims 1 to 8, wherein 11. A rectangular shape is formed by a U-shaped magnetic plate and strip-shaped magnetic plates connected to both ends of the U-shaped opening side, and the rectangles are formed by lamination. 9. The zero-phase current transformer according to claim 1, wherein the current transformer is a butt joint.