JP2015012070A - Zero-phase current transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zero-phase current transformer having a magnetic shield of stabilized characteristics.SOLUTION: A zero-phase current transformer includes an annular core 100 having soft magnetism, annular flat plate shields 105, 106 having soft magnetism, a cylindrical shield 104 having soft magnetism, and a detection coil 102. The detection coil 102 is wound toroidally around the core 100, and the core 100 has a permeability higher than those of the flat plate shields 105, 106 and the cylindrical shield 104. The core 100 and detection coil 102 are covered, at least partially, with the flat plate shields 105, 106, and the cylindrical shield 104 is a material continuous in the circumferential direction, and not having a start end and terminal end.

Description

  The present invention relates to a zero-phase current transformer used for an earth leakage breaker or the like.

  A zero-phase current transformer, which is mainly used for earth leakage circuit breakers, has a toroidal core wound around a toroidal core and a detection target wire inserted through the toroidal core. is there.

  Two or more conductors are inserted into the core so that the energization directions are opposite to each other. Under normal conditions, magnetic flux cancels out between the conductors, and almost no magnetic flux is generated in the core.

  However, when leakage occurs, the current of the conducting wire becomes unbalanced, magnetic flux is generated in the core, and leakage is detected by the detection coil.

  Patent Document 1 is an example of such a zero-phase current transformer, and has been devised to configure a magnetic shield from an external magnetic field by surrounding a core and a detection coil with a laminated shield plate and a winding shield. .

Japanese Patent Laid-Open No. 06-290978

  In the winding shield described in Patent Document 1, since internal stress remains by winding a magnetic band, a heat treatment for removing distortion is necessary. However, such a heat treatment causes deformation of the winding shield again, and the winding shield. As a result of correcting the shape of the wire, internal stress is generated again. Eventually, the magnetic properties and shape of the shield are not stable, and there is a problem that the magnetic properties of the winding shield may be detected as noise in the detection coil. .

  Accordingly, an object of the present invention is to provide a zero-phase current transformer having a magnetic shield with stable characteristics.

  The present invention provides an annular core having soft magnetism, an annular flat plate shield having soft magnetism, a cylindrical shield having soft magnetism, and a detection coil, and the detection coil is toroidal to the core. The core is higher in permeability than the flat plate shield and the cylindrical shield, and the core and the detection coil are at least partially covered by the flat plate shield and the cylindrical shield, The cylindrical shield is solved by a zero-phase current transformer made of a material continuous in the circumferential direction.

  The radial thickness of the cylindrical shield is preferably 0.2 mm or more and 3.0 mm or less.

  Further, it is desirable that the cylindrical shield has a cross-sectional shape in which both end portions in the cylindrical axis direction or the vicinity thereof, and at least one of them is bent uniformly toward the inner peripheral side or the outer peripheral side. .

  The present invention can provide a zero-phase current transformer having a magnetic shield with stable characteristics.

It is a perspective view which shows the zero phase current transformer which concerns on Embodiment 1 in this invention. It is a top view which shows the zero phase current transformer which concerns on Embodiment 1 in this invention, and has shown the case where it sees from the conducting wire direction in FIG. It is sectional drawing of the zero phase current transformer which concerns on Embodiment 1 in this invention, and has shown the cross section of the AA surface in FIG. It is explanatory drawing which shows the creation process example of the cylindrical shield which concerns on Embodiment 1 in this invention. It is explanatory drawing which shows the outline of the other example of a production process of the cylindrical shield which concerns on Embodiment 1 in this invention. It is explanatory drawing which shows the first die cutting process of the cylindrical shield which concerns on Embodiment 1 in this invention. FIG. 6A is a perspective view during the process, and FIG. 6B is a cross-sectional view of the A ′ plane in FIG. It is explanatory drawing which shows the drawing process of the cylindrical shield which concerns on Embodiment 1 in this invention. FIG. 7A is a perspective view during the process, and FIG. 7B is a cross-sectional view of the A ″ plane in FIG. 7A. It is explanatory drawing which shows die cutting after the drawing process of the cylindrical shield which concerns on Embodiment 1 in this invention. FIG. 8A is a perspective view during the process, and FIG. 8B is a cross-sectional view of the A ″ ″ plane in FIG. It is sectional drawing of the zero phase current transformer which concerns on Embodiment 2 in this invention, and respond | corresponds to the modification of FIG. It is sectional drawing of the zero phase current transformer which concerns on Embodiment 3 in this invention, and respond | corresponds to the modification of FIG. It is sectional drawing of the zero phase current transformer which concerns on Embodiment 4 in this invention, and respond | corresponds to the modification of FIG. It is sectional drawing of the zero phase current transformer which concerns on Embodiment 5 in this invention, and respond | corresponds to the modification of FIG.

(Embodiment 1)
FIG. 1 is a perspective view showing a zero-phase current transformer according to Embodiment 1 of the present invention.

  The zero-phase current transformer 1 accommodates a magnetic shield, an annular core, and a detection coil wound around the core in a toroidal shape, and a lead wire 12 drawn from both ends of the detection coil. Injected and sealed.

  The zero-phase current transformer 1 has an annular shape, and the conducting wires 21, 22, 23, and 24 are inserted therethrough.

  The conductors 21 to 24 are energized with a power supply current or the like, and since the sum of the energized currents is zero when normal, an alternating current is energized to the conductors 21 to 24. No signal is detected by the detection coil.

  However, when leakage occurs, the balance of the currents supplied to the conductive wires 21 to 24 is lost, magnetic flux is generated inside the core, and a leakage signal is detected from the detection coil and detected from the lead wire 12.

  FIG. 2 is a plan view showing the zero-phase current transformer according to Embodiment 1 of the present invention, and shows a case when viewed from the conducting wire direction in FIG. 1.

  The magnetic shield, core, and detection coil housed in the outer case 11 are covered with a resin 13.

  FIG. 3 is a cross-sectional view of the zero-phase current transformer according to the first embodiment of the present invention, and shows a cross section of the AA plane in FIG.

  A core 100 laminated with a high magnetic permeability soft magnetic metal plate such as permalloy is accommodated in a core case 101 made of an insulating resin or the like, a detection coil 102 is wound, and a shield case made of soft magnetic or nonmagnetic metal 103.

  Here, by providing the gap 1031, the shield case 103 is prevented from becoming a short ring against the magnetic field generated when the balance of the energization current is lost.

  The shield case 103 is sandwiched between the annular shields 105 and 106 together with the cylindrical shield 104, accommodated in the exterior case 11, and poured into the resin 13 to be sealed.

  Here, the cylindrical shield 104 and the flat shields 105 and 106 are made of a material having higher saturation magnetization and lower permeability than the core 100. Specifically, silicon steel, carbon steel, electromagnetic steel and the like are exemplified.

  The flat shields 105 and 106 may be composed of laminated steel plates.

  When the inner wall of the housing portion of the outer case 11 has conductivity, the conductive path through the cylindrical shield 104 and the flat plate shields 105 and 106 against the generated magnetic field when the balance of the energized current is lost. Therefore, electrical insulation is performed as appropriate so as not to form a short ring.

  Thereby, in the part close | similar to the above-mentioned conducting wire, since the local magnetic flux by conducting wire remains in the cylindrical shield 104, it can prevent that the core 100 is magnetically saturated in a normal state.

  Moreover, it has the structure which interrupts | blocks as a noise except the earth-leakage signal by the balance of the energization current of conducting wire breaking.

  FIG. 4 is an explanatory diagram showing an example of a production process of the cylindrical shield according to the first embodiment of the present invention.

  The cylindrical shield 104 can be obtained by cutting the pipe 1040 made of coal bed steel or the like having a saturation magnetization higher than that of the core of the zero-phase current transformer and a low permeability.

  FIG. 5 is an explanatory diagram showing an outline of another example of the manufacturing process of the cylindrical shield according to the first embodiment of the present invention. A punched portion 1041 is formed by die-cutting a single steel sheet, further drawn to be processed into a drawn portion 1042, and further, the cylindrical shield 104 is cut out from the cut-out portion 1043 by die cutting. it can.

  FIG. 6 is an explanatory view showing an initial die cutting process of the cylindrical shield according to the first embodiment of the present invention. FIG. 6A is a perspective view during the process, and FIG. 6B is a cross-sectional view of the A ′ plane in FIG.

  FIG. 6A shows a state in which the punched portion 1041 is formed by a punching die 10411 from one steel plate. Here, the description of the molds other than the punching mold 10411 is omitted.

  FIG. 6B is a cross-sectional view of the A ′ plane in FIG. 6A, and also shows other molds omitted in FIG. 6A.

  The arrow in the figure indicates the direction in which the mold moves. The steel sheet is sandwiched between the support molds 10412 and 10413 and the presser molds 10414 and 10415, and is punched by the punching die 10411 from the portion where the punching process is performed at the center to form a punched portion 1041.

  Here, when the punching hole periphery of the support mold has a cross-sectional shape such as a counterbore or chamfer as shown in the drawing when the punching process is performed by the support molds 10412 and 10413 and the punching mold 10411, The edge part of the extraction part 1041 has a cross-sectional shape that is bent uniformly toward the inner peripheral side.

  Here, the punched portion 1041 can be formed not by punching with a mold but by cutting with a laser or the like. In this case, the edge of the punched portion 1041 has an end surface that is substantially vertical.

  FIG. 7 is an explanatory view showing a drawing process of the cylindrical shield according to the first embodiment of the present invention. FIG. 7A is a perspective view during the process, and FIG. 7B is a cross-sectional view of the A ″ plane in FIG. 7A.

  FIG. 7A shows a state where the drawing part 1042 is formed by further drawing with the drawing die 10421. Here, the description of the molds other than the aperture mold 10421 is omitted.

  FIG. 7B is a cross-sectional view of the A ″ plane in FIG. 7A, and also shows other molds omitted in FIG. 7A.

  The arrow in the figure indicates the direction in which the mold moves. The steel plate is sandwiched between the support dies 10422 and 10423 and the presser dies 10424 and 10425, and is drawn from the center by the drawing die 10421 to form the drawn portion 1042.

  Due to the drawing process, the drawn portion 1042 has a cylindrical shape at the inner peripheral portion.

  In order to perform a smooth drawing process, the edge part around the front end surface of the drawing die facing the steel plate is rounded.

  FIG. 8 is an explanatory diagram showing die cutting after the drawing process of the cylindrical shield according to the first embodiment of the present invention. FIG. 8A is a perspective view during the process, and FIG. 8B is a cross-sectional view of the A ″ ″ plane in FIG.

  FIG. 8A shows a state in which the cylindrical shield 104 is cut out from the punched portion 1043 by punching with the drawing die 10421 after drawing. Here, the description of the molds other than the aperture mold 10421 is omitted.

  FIG. 8B is a cross-sectional view of the A ″ ″ plane in FIG. 8A, and other molds omitted in FIG. 8A are also described.

  The arrow in the figure indicates the direction in which the mold moves. The steel plate is sandwiched between the support molds 10422 and 10423 and the presser molds 10424 and 10425, as in FIG. 7B. Cut out from the cutout 1043.

  Here, in order to perform the above-described drawing process, a counterbore process or a chamfering process or the like is performed on the peripheral edge part of the support mold of the support molds 10422 and 10423. The separated edge portion has a cross-sectional shape that is uniformly bent toward the outer peripheral side.

  That is, the present invention includes an annular core 100 having soft magnetism, an annular flat plate shield 105, 106 having soft magnetism, a cylindrical shield 104 having soft magnetism, and a detection coil 102. The core 100 is wound in a toroidal shape, and the core 100 has higher magnetic permeability than the flat plate shields 105 and 106 and the cylindrical shield 104, and at least a part of the core 100 and the detection coil 102 are flat plate shields 105 and 106 and a cylindrical shape. The cylindrical shield 104 may be an embodiment of the zero-phase current transformer 1 that is made of a continuous material in the circumferential direction.

  As a result, the magnetic shield on the inner peripheral side or outer peripheral side of the core 100 and the detection coil 102 is made of a cylindrical shield 104 made of a continuous material in the circumferential direction and having no start and end portions as in Patent Document 1. By doing so, the shape and magnetic properties can be stabilized.

  In addition, the radial thickness of the cylindrical shield 104 is desirably 0.2 mm or more for stabilizing the shape, and desirably 3.0 mm or less for performing drawing or the like.

  Further, it is desirable that the cylindrical shield 104 has a cross-sectional shape that is at both ends in the cylindrical axis direction or in the vicinity thereof, and at least one of them is bent uniformly toward the inner peripheral side or the outer peripheral side. .

  It becomes such a shape by performing drawing. By drawing, cylindrical shields 104 of various sizes and heights can be created, and various shape changes can be quickly handled.

(Embodiment 2)
FIG. 9 is a cross-sectional view of a zero-phase current transformer according to Embodiment 2 of the present invention, and corresponds to the modification of FIG.

  The point that the cylindrical shield 104 is arranged on the outer peripheral side of the shield case 103 is different from FIG. 3 in the first embodiment.

  This configuration is suitable when the conducting current of the conducting wire is smaller than that of the first embodiment and the disturbance magnetic field is strong.

(Embodiment 3)
FIG. 10 is a cross-sectional view of a zero-phase current transformer according to Embodiment 3 of the present invention, and corresponds to the modification of FIG.

  The point that the cylindrical shield 104 has a two-layer structure is different from FIG. 3 in the first embodiment.

  This configuration is suitable when the conducting current of the conducting wire is larger than that of the first embodiment and the thickness of the cylindrical shield needs to be increased.

(Embodiment 4)
FIG. 11 is a cross-sectional view of a zero-phase current transformer according to Embodiment 4 of the present invention, and corresponds to the modification of FIG.

  The cylindrical shield 104 is not sandwiched between the flat plate shields 105 and 106, and is different from FIG. 3 in the first embodiment in that the cylindrical shield 104 is arranged on the inner peripheral side of the flat plate shields 105 and 106.

  This configuration is suitable when the zero-phase current transformer is downsized or thinned and the bending of the end portion of the cylindrical shield 104 in the circumferential axis direction cannot be ignored in configuring the magnetic shield.

(Embodiment 5)
FIG. 12 is a cross-sectional view of a zero-phase current transformer according to Embodiment 5 of the present invention, and corresponds to the modification of FIG.

  3 is different from FIG. 3 in the first embodiment in that the shield case 103 is not provided and the cylindrical shields 104 are arranged on the inner peripheral side and the outer peripheral side of the shield case 103.

  This configuration is suitable when a magnetic shield is required for both the conducting current of the conducting wire and the strong disturbance magnetic field.

DESCRIPTION OF SYMBOLS 1 Zero phase current transformer 11 Exterior case 12 Lead wire 13 Resin 21, 22, 23, 24 Conductor 100 Core 101 Core case 102 Detection coil 103 Shield case 104 Cylindrical shield 105, 106 Flat plate shield 1031 Clearance 1040 Pipe 1041, 1043 Extraction Part 1042 Aperture part 10411 Extraction mold 10412, 10413, 10422, 10423 Support mold 10414, 10415, 10424, 10425 Presser mold 10421 Aperture mold 10431 Extraction mold part

Claims (3)

An annular core with soft magnetism;
An annular flat plate shield with soft magnetism;
A cylindrical shield with soft magnetism;
Equipped with a detection coil,
The detection coil is wound around the core in a toroidal shape,
The core has a higher magnetic permeability than the flat plate shield and the cylindrical shield,
The core and the detection coil are at least partially covered by the flat plate shield and the cylindrical shield,
The said cylindrical shield is comprised with the material continuous in the circumferential direction, The zero phase current transformer characterized by the above-mentioned.   The zero-phase current transformer according to claim 1, wherein a thickness of the cylindrical shield in a radial direction is 0.2 mm or more and 3.0 mm or less.   The cylindrical shield has a cross-sectional shape in which both end portions in the cylindrical axial direction or the vicinity thereof, and at least one of them is bent uniformly toward the inner peripheral side or the outer peripheral side. The zero-phase current transformer according to claim 1 or 2.

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