JP2015188029A - zero-phase current transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact zero-phase current transformer, in which magnetic shield effect is high around the secondary winding.SOLUTION: One flat plate shields 1051, 1061 have shield effect higher than that of the other flat plate shields 1052, 1062. Nevertheless, the shield effect as the whole laminated steel plate is equivalent to that when constituted only of the flat plate shield 1051 or 1061. Consequently, the thickness can be reduced by replacing the other flat plate shields 1052, 1062 with those of different thickness.

Description

  The present invention relates to a zero-phase current transformer used for leakage detection applications and the like.

  Zero-phase current transformers used for earth leakage circuit breakers, etc., do not generate voltage in the secondary winding when the current flowing through multiple primary windings is in a balanced state as a whole. When the flowing current is in an unbalanced state, a voltage is generated in the secondary winding to detect a leakage or the like.

  However, even when the current flowing in the primary winding is in an equilibrium state, the magnetic flux due to the current flowing in the primary winding may not cancel out, and a voltage may be generated in the secondary winding. A soft magnetic shield plate is laminated on the substrate.

  Patent Document 1 discloses a technique for improving magnetic shielding performance by providing a nonmagnetic layer between shield layers laminated around a secondary winding.

Japanese Patent Laid-Open No. 7-83960

  In the zero-phase current transformer having the configuration of Patent Document 1, by providing a nonmagnetic layer between the shield layers, the thickness of the magnetic shield around the secondary winding increases, and the size of the zero-phase current transformer increases. There is a problem of becoming.

  An object of the present invention is to provide a zero-phase current transformer that is small in size and has a high magnetic shielding effect around a secondary winding.

  To solve the above problems, the present invention provides a plurality of primary conductors, one secondary conductor, a soft iron core, a plurality of soft magnetic first plate shields, and a plurality of soft magnetic second plates. The primary conductor penetrates the inside of the annular core, the secondary conductor is wound in a toroidal shape in the circumferential direction of the annular core, and the first plate shield and the second plate The shield is disposed outside the region surrounded by the secondary conductor, and the primary conductor is energized with an equilibrium current that cancels out the magnetic field induced in the circumferential direction of the annular core, and at least the primary conductor When a non-equilibrium current flows due to the passage of an abnormal current that partially changes in time, an induced electromotive force due to a magnetic field induced in the circumferential direction of the annular core without the cancellation occurs. Occurring in the conducting wire, the first plate shield and The second plate-like shields are alternately stacked, and the first plate-like shields are induced by the induced electromotive force to the secondary conductors by energizing the balanced current to the primary conductors rather than the second plate-like shields. This can be solved by a zero-phase current transformer that has a high effect of suppressing the current.

  The first plate shield and the second plate shield preferably have different thicknesses.

  The first plate shield and the second plate shield are preferably silicon steel plates.

  The first plate-shaped shield is preferably a non-oriented electrical steel plate 35A360 defined by JIS (Japanese Industrial Standards) C2552, and the second plate-shaped shield is preferably a non-oriented electrical steel plate 50A350 defined by JIS C2552. .

  The magnetic shield around the secondary winding of the present invention has a configuration in which two types of plate-shaped shields having different magnetic shield effects are alternately stacked, so that only one plate-shaped shield having a high shield effect is stacked. A magnetic shield characteristic equivalent to that of the shield can be obtained, the thickness of the magnetic shield is not increased, and a small zero-phase current transformer having a high magnetic shielding effect around the secondary winding can be obtained.

It is a perspective view which shows the zero phase current transformer which concerns on embodiment in this invention. It is a top view which shows the zero phase current transformer which concerns on embodiment in this invention, and has shown the case where it sees from the primary conducting wire direction in FIG. It is sectional drawing of the zero phase current transformer which concerns on embodiment in this invention, and has shown the cross section of the AA surface in FIG. It is a figure which shows the relationship of the detection voltage in a secondary conducting wire with respect to the sum total of the energization current to a primary conducting wire.

  FIG. 1 is a perspective view showing a zero-phase current transformer according to an embodiment 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 passes through the primary conductors 21, 22, 23, and 24.

  A power source current or the like is supplied to the conducting wires 21 to 24, and the magnetic flux generated by the supplied current cancels out in a normal state, resulting in an equilibrium state. Therefore, no signal is detected by the detection coil.

  However, when a leakage occurs, the current flowing to the primary conductors 21 to 24 is unbalanced, a magnetic flux is generated inside the core, a leakage signal is detected from the detection coil, and is detected from the lead wire 12.

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

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

  FIG. 3 is a cross-sectional view of the zero-phase current transformer according to the 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 secondary conductor 102 is wound, and a shield made of soft magnetic or nonmagnetic metal Housed in case 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 cylindrical shields 1041 and 1042 and the annular flat plate shields 1051, 1052, 1061 and 1062, accommodated in the outer case 11, and poured with the resin 13 and sealed.

  When the inner wall of the housing portion of the outer case 11 is conductive, the cylindrical shields 1041 and 1042, the flat plate shields 1051, 1052, 1061, Electrical insulation is performed as appropriate so that a short ring is not formed by the conductive path through 1062.

  Thereby, in the part close | similar to the above-mentioned primary conducting wire, since the local magnetic flux by conducting wire remains in the cylindrical shield 1041, 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.

  Here, the cylindrical shields 1041 and 1042 and the flat plate shields 1051, 1052, 1061 and 1062 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 having a thickness of 0.3 mm to 0.5 mm are exemplified.

  Even if the energization currents to the conducting wires 21 to 24 are in an equilibrium state, the magnetic flux inside the core 100 may not completely cancel out in practice, so that the cylindrical shield 1041 covering the periphery of the secondary conducting wire 102, 1042 and the flat plate shields 1051, 1052, 1061, and 1062 prevent magnetic flux generation inside the core 100 and signal detection to the secondary conductor 102 in a balanced state.

  Here, the flat plate shields 1051 and 1052 are configured as laminated steel plates that are alternately stacked, and the flat plate shields 1061 and 1062 are configured as laminated steel plates that are alternately stacked.

  One of the flat plate shields 1051 and 1061 and the other flat plate shield 1052 and 1062 have different shielding effects for shielding magnetism from the primary conductors 21 to 24 in an equilibrium state.

  Specifically, one of the flat plate shields 1051 and 1061 has a higher shielding effect than the other flat plate shield 1052 and 1062.

  Nevertheless, as will be described later, the shielding effect of the laminated steel plate as a whole is equivalent to the case where only the flat plate shield 1051 and the flat plate shield 1061 are used.

  As a result, the other flat plate shields 1052 and 1062 can be replaced with, for example, inexpensive ones having a low shielding effect, and the thickness dimension can be reduced by replacing them with ones having different thicknesses.

  The cylindrical shields 1041 and 1042 may be configured by stacking two types of plate-shaped shields having different shielding effects, and winding and stacking them in a cylindrical shape.

(Example)
Based on the above-described embodiment, the zero-phase current transformer of the example is configured as follows.

  The core 100 is obtained by winding a nanocrystalline metal ribbon having a thickness of 0.023 mm, and has an inner diameter of 37.4 mm, an outer diameter of 47.8 mm, and a height of 2 mm.

  The secondary conductor 102 was wound 1100 times.

  As the flat plate shields 1051 and 1061, annealed highlight core (registered trademark) 35H360 manufactured by Nippon Steel & Sumikin Co., Ltd. corresponding to the non-oriented electrical steel sheet 35A360 defined by JISC2552 having a thickness of 0.35 mm was used.

  As the other flat plate shields 1052 and 1062, annealed highlight core (registered trademark) 35H360 manufactured by Nippon Steel & Sumikin Co., Ltd. corresponding to the non-oriented electrical steel sheet 50A350 defined by JISC2552 having a thickness of 0.50 mm was used.

  One flat shield 1051, 1061 and the other flat shield 1052, 1062 were alternately laminated four times.

  The total thickness of the laminated steel plates by the flat plate shields 1051 and 1052 is 3.4 mm, and the total thickness of the laminated steel plates by the flat plate shields 1061 and 1062 is also 3.4 mm.

  Cylindrical shields 1041 and 1042 were manufactured by winding Orient Core HiBee (registered trademark) 23ZH95 manufactured by Nippon Steel & Sumitomo Metal Co., Ltd. 8 times and annealing.

(Comparative Example 1)
The laminated steel plates by the flat plate shields 1051 and 1052 and the laminated steel plates by the flat plate shields 1061 and 1062 according to the configuration of the example are each formed by laminating seven flat plate shields obtained by annealing the electromagnetic steel plate 50H350 having a thickness of 0.50 mm. The zero-phase current transformer of Comparative Example 1 was replaced.

(Comparative Example 2)
The laminated steel plates by the flat plate shields 1051 and 1052 and the laminated steel plates by the flat plate shields 1061 and 1062 according to the configuration of the example are each formed by laminating 10 flat plate shields obtained by annealing the electromagnetic steel plate 35H360 having a thickness of 0.35 mm. The zero-phase current transformer of Comparative Example 2 was replaced.

(Comparative Example 3)
The laminated steel plates by the flat plate shields 1051 and 1052 and the laminated steel plates by the flat plate shields 1061 and 1062 according to the configuration of the example are respectively flat plate shields obtained by annealing an electromagnetic steel plate 35H360 having a thickness of 0.35 mm from the secondary conductor 102 side. A zero-phase current transformer of Comparative Example 3 was obtained by replacing the four flat plate shields obtained by laminating four sheets and further annealing the flat plate shield obtained by annealing the electromagnetic steel sheet 50H350 having a thickness of 0.50 mm.

(Comparative experiment)
About the zero-phase current transformer of the said Example and Comparative Examples 1-3, 50-Hz commercial power supply current _IL1 , _IL2 is energized from the primary conductors 21 and 22 to the primary conductors 23 and 24, and the secondary conductor 102 A potential difference voltage value between both ends of a 680Ω resistor connected to both ends was measured as a detection voltage.

FIG. 4 is a diagram showing the relationship of the detection voltage at the secondary conductor with respect to the total current I _L (= I _L1 + I _L2 ) of the energization current to the primary conductor.

  In FIG. 4, the voltage value detected by the secondary conducting wire 102 of the comparative example 2 and an Example which comprised the laminated electromagnetic steel plate only with the electromagnetic steel plate 35H360 is the lowest, and the magnetic shielding effect in an equilibrium state is the highest.

  From the results of Comparative Example 1 and Comparative Example 2, it is interpreted that the shielding effect of the electromagnetic steel sheet 35H360 is higher than that of the electromagnetic steel sheet 50H350.

  Therefore, when the electromagnetic steel plate 35H360 having a high shielding effect is arranged on the side close to the secondary conducting wire 102 as in Comparative Example 3, the magnetic shielding effect is worse than that in Comparative Examples 1 and 2.

  However, when the electromagnetic steel plates 35H360 and the electromagnetic steel plates 50H350 are laminated as in the embodiment, the same magnetic shielding effect as that of the comparative example 3 is obtained even though the electromagnetic steel plate 50H350 having a low magnetic shielding effect is used. Contrary to the expectation, the magnetic shielding effect equivalent to that of Comparative Example 2 is obtained.

  Moreover, the thickness of the laminated electrical steel sheet in the example is 0.1 mm thinner than that in Comparative Example 2, and the thickness can be reduced.

DESCRIPTION OF SYMBOLS 1 Zero-phase current transformer 11 Exterior case 12 Lead wire 13 Resin 21, 22, 23, 24 Primary conducting wire 100 Core 101 Core case 102 Secondary conducting wire 103 Shield case 1031 Gap 1041, 1042 Cylindrical shield 1051, 1052, 1061, 1062 Flat plate shield current I _L1 , I _L2 , I _L

Claims (3)

A plurality of primary conductors;
One secondary conductor,
An annular core having soft magnetism,
A plurality of first plate-shaped shields having soft magnetism;
A plurality of second plate-shaped shields having soft magnetism;
The primary conducting wire penetrates the inside of the annular core,
The secondary conductor is wound in a toroidal shape in the circumferential direction of the annular core,
The first plate-like shield and the second plate-like shield are arranged outside an area surrounded by the secondary conducting wire,
The primary conductor is energized with an equilibrium current that cancels out the magnetic field induced in the circumferential direction of the annular core,
When a non-equilibrium current flows through at least a part of the primary conducting wire, a non-equilibrium current flows, so that the canceling does not occur and the induction induced by the magnetic field induced in the circumferential direction of the annular core is performed. Power is generated in the secondary conductor,
The first plate-shaped shield and the second plate-shaped shield are alternately stacked,
The first plate-shaped shield has a higher effect of suppressing the induced electromotive force to the secondary conductor due to energization of the balanced current to the primary conductor than the second plate-shaped shield. Current transformer.   The zero-phase current transformer according to claim 1, wherein the first plate-shaped shield and the second plate-shaped shield have different thicknesses.   The zero-phase current transformer according to claim 2, wherein the first plate shield and the second plate shield are silicon steel plates.

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