JPH08115835A - Current transformer - Google Patents

Abstract

PURPOSE: To provide a current transformer which reduce the deformation amount of a primary conductor when an excess current flows and which prevents an insulating covering for the primary conductor from being damaged. CONSTITUTION: A current-transformer body is constituted of a primary conductor 1 which is formed to be a hairpin shape and which is covered with an insulating layer 13 and of a secondary coil unit 2 in which a secondary coil is wound on a core interlinked with the primary conductor 1. The current-transformer body is housed inside a container 10 which is filled with an insulating oil. The primary conductor 1 is formed to be the hairpin shape in such a way that a conductor whose cross-sectional contour shape is noncircular is bent to a side on which its cross-sectional secondary moment is largest. The deformation amount of the primary conductor due to a repulsive force acting across straight parts 1a, 1e is reduced when a current flows to the primary conductor 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current transformer using a hairpin type primary conductor.

[0002]

2. Description of the Related Art This type of current transformer comprises a primary conductor bent into a hairpin shape and a secondary coil wound around an annular iron core arranged so as to interlink with the primary conductor. The current transformer body is housed in a container filled with insulating oil.

FIGS. 5A and 5B show a hairpin type primary conductor 1 used in a conventional current transformer of this type. FIGS. 5A and 5B respectively show the same. A top view and a front view are shown. The primary conductor 1 includes a first straight line portion 1a extending linearly in the vertical direction, an arcuate folded portion 1b having one end connected to a lower end of the first straight portion 1a, and a straight line extending upward from the other end of the folded portion 1b. Rising part 1c
And an inclined portion 1d extending obliquely upward from the upper end of the rising portion 1c so as to gradually approach the first linear portion 1a side, and a curved portion extending from the upper end of the inclined portion 1d along the first linear portion 11a. And a second straight line portion 1e extending linearly upward, and at the boundary portion between the folded portion 1b, the rising portion 1c and the inclined portion 1d, and the boundary portion between the inclined portion 1d and the second linear portion 1e. Curved portions C1, C2 and C3 are formed, respectively.

The primary conductor 1 is covered with an insulating layer (not shown in FIG. 5) made of insulating paper or the like, and a portion of the primary conductor 1 covered with the insulating layer is located near the lower end of the first straight portion 1a. Then, the secondary coil unit 2 is arranged. The secondary coil unit 2 is composed of an annular iron core and a secondary coil wound around the iron core, and the annular iron core of the unit is arranged so as to interlink with the primary conductor 1.

A current transformer body is constituted by the primary conductor and the secondary coil unit, and the current transformer body is housed in a container filled with insulating oil.

[0006]

In the hairpin type current transformer, the hairpin type primary conductor 1 is formed by bending the conductor, but in the conventional current transformer of this type, the primary conductor 1 is formed. A pipe made of a metal having a good conductor such as copper or aluminum is used as a conductor, and the cross-sectional profile of the pipe is elliptical, and the pipe is bent on the minor axis side of the ellipse [see FIG. 5 (A)]. Thus, each curved portion is formed. Also, instead of using a pipe, there is also a conductor using an elliptical cross-section with a void in the center, but in this case as well, by bending the conductor to the minor axis side of the ellipse, the primary conductor Each of the curved portions was formed.

When a primary conductor having an elliptical cross-sectional profile is used and the conductor is bent on the minor axis side of the ellipse, a large force is not required to perform the bending work.
Processing can be facilitated. However, the primary conductor bent to the minor axis side of the ellipse (bent by applying a force in the minor axis direction of the ellipse) has a repulsion generated in the reciprocating conductor portion (especially the straight line portions 1a and 1e) when a current flows. Since the second moment of area, which is a coefficient of deformation with respect to the force F, is small, it is relatively easily deformed. Therefore, when an excessive current flows in the primary conductor, the linear portions 1a and 1e are displaced in the directions in which they are separated from each other, and the insulating layer coating the primary conductor is applied to the container of the current transformer or the iron core of the secondary coil unit 2. There was a risk of strong damage and damage.

The repulsive force F acting on the reciprocating conductor portion (between the linear portions 1a and 1b) by the current flowing through the linear portions 1a and 1e of the primary conductor 1 is given by the following equation.

F = 2 × 10 ⁻⁷ × i ² × L / D [N] (1) where i is the peak value [A], L of the current flowing through the reciprocating conductor.
Is the length [m] of the reciprocating conductor, and D is the distance [m] between the conductors.

When an excessive current flows through the primary conductor, the primary conductor is largely deformed and its insulating coating hits a container or the like and is damaged, so that the insulating performance of the primary conductor is deteriorated. Therefore, the deformation of the primary conductor is suppressed as much as possible. It is necessary to.

If the primary conductor is made of a material having a high rigidity (Young's modulus), it is possible to obtain a primary conductor which is not easily deformed. However, the primary conductor needs to be made of highly conductive copper or aluminum. Since the materials that can be used to form the primary conductor are limited, it is difficult to suppress the deformation by selecting the material.

An object of the present invention is to provide a current transformer which suppresses the deformation of the primary conductor when an excessive current flows and prevents the insulation coating of the primary conductor from being damaged.

[0013]

The present invention relates to a current transformer having a primary conductor bent and formed in a hairpin shape, and a secondary coil wound around an iron core interlinking with the primary conductor. Then, in the present invention, the contour shape of the cross section of the primary conductor is made non-circular, and the curved portion of the primary conductor is formed by bending the conductor to the side having the largest moment of inertia of area.

When the profile of the cross section of the conductor is non-circular, the second moment of area is different depending on how the axis is set.
In the present invention, the conductor is curved by applying a force in the direction having the largest moment of inertia of area to form each curved portion of the primary conductor. For example, when the contour shape of the cross section is an ellipse or an ellipse, a force is applied in the major axis direction of the ellipse or the ellipse to bend the conductor.

[0015]

As described above, when each curved portion of the primary conductor is formed by bending the conductor to the side having the largest moment of inertia of area as described above, the primary conductor is less likely to be deformed. It is possible to reduce the deformation amount of. Therefore, it is possible to prevent the primary conductor from being greatly deformed when an excessive current flows, and the insulating layer coating the primary conductor from abutting on the inner surface of the container or the iron core around which the secondary coil is wound. It is possible to prevent the insulating layer of the primary conductor from being damaged and the insulating function from being deteriorated when a current flows.

[0016]

1 and 2 show the overall structure of an embodiment of the present invention. FIG. 1 is a front vertical cross-sectional view of a current transformer of the same embodiment as viewed from the front. FIG. 2 is a side surface vertical cross-sectional view in which the current transformer is viewed vertically from a side surface. See also FIG.
(A) And (B) is the top view and front view of the primary conductor used in the same Example, respectively.

The primary conductor 1 used in this embodiment is as shown in FIG. 3, but the basic shape of the primary conductor when viewed from the front is the same as the conventional one. That is, as shown in FIG. 3B, the primary conductor 1 used in the present embodiment has one end connected to the first straight line portion 1a extending linearly in the vertical direction and the lower end of the first straight line portion 1a. Arc-shaped turnback portion 1b
And a rising portion 1c that linearly rises upward from the other end of the folded portion 1b, and an inclined portion 1d that extends obliquely upward from the upper end of the rising portion 1c so as to gradually approach the first linear portion 1a side. A second straight line portion 1e, which is bent from the upper end of the inclined portion 1d along the first straight line portion 11a and linearly extends upward to almost the same position as the upper end of the first straight line portion,
Curved portions C1, C2, and C3 are formed at the folded portion 1b, the boundary portion between the rising portion 1c and the inclined portion 1d, and the boundary portion between the inclined portion 1d and the second straight portion 1e, respectively.

In this embodiment, as shown in FIG. 3 (A), the material for forming the primary conductor has an oval cross-sectional profile (a shape in which two sides facing the longitudinal direction of the rectangle are arcuate). Using a flat bar-shaped solid conductor exhibiting the above, the conductor is bent to the side having the largest moment of inertia of section (toward the major axis of the section) to form each curved portion C1, C2, C3, and to form a hairpin shape. The primary conductor 1 is formed.

In FIGS. 1 and 2, reference numeral 10 denotes a current transformer container comprising a lower tank 11 made of metal, and a porcelain tube 12 whose lower end is oil-tightly connected to the upper end of the lower tank 11. The primary conductor 1 is covered with an insulating layer 13 made of insulating paper or the like, and the first linear portion 1a and the third linear portion 1 of the primary conductor 1 are covered.
A shield ring 14 for improving the electric field distribution is attached to the outer peripheral portion of the insulating layer 13 covering e.

A pedestal 1 arranged at the bottom of the lower tank 11.
1a is provided with a groove 15 having inclined surfaces 15a and 15b, and the folded portion 1b at the lower end of the primary conductor 1 covered with an insulating layer is inserted into the groove 11a so that the inclined surfaces 15a and 1b are formed.
It is in contact with 5b.

The first of the primary conductors 1 covered by an insulating layer
The secondary coil unit 2 is attached to the portion of the linear portion 1a of the
Is arranged. The secondary coil unit 2 is formed by winding a secondary coil around a plurality of (four in the illustrated example) annular cores that are coaxially arranged, and in a state where the annular core is linked to the primary conductor 1. It is placed on the pedestal 11a. The secondary coil unit 2 includes a coil retainer 17 arranged at an upper end thereof, a stud bolt 18 having a lower end fixed to the pedestal 11 a and penetrating the coil retainer 17, and a nut 19 screwed to an upper end of the stud bolt 18. By pedestal 1
1a. The current transformer body is composed of the primary conductor 1 and the secondary coil unit 2.

The primary terminal 2 is provided on the side wall of the porcelain insulator 12 near the upper end.
0A and 20B are attached, and one end 1A (upper end of the first straight line portion 1a) and the other end 1B (upper end of the second straight line portion 1b) of the primary conductor 1 are connected to these primary terminals, respectively.

The current transformer container 10 is filled with insulating oil,
An oil amount adjusting device 21 is attached so as to close the upper end of the porcelain bushing 12. The oil amount adjusting device 21 includes a diaphragm that communicates with the inside of the container, and absorbs a change in the volume of the insulating oil inside the container caused by a temperature change.

A secondary terminal box 22 is provided on the side surface of the lower tank 11.
Is attached, and an oil-tight bushing 23 is attached to the side surface of the lower tank located in the secondary terminal box. A secondary terminal 24 is provided in the secondary terminal box 22, and a terminal portion of the secondary coil is connected to the secondary terminal 24 through a through conductor of the bushing 23.

As described above, when the curved portion of the primary conductor is formed by bending the conductor to the side having the largest moment of inertia of area, the primary conductor is less likely to be deformed, so that a repulsive force is applied to the primary conductor due to excessive current. It is possible to reduce the amount of deformation of the primary conductor when it acts. When the Young's modulus of the primary conductor is E, the moment of inertia of area is Iz, the length of the conductor is L, and the coefficients are K1 and K2 (K1 and K2 are different values), the conductor receives concentrated load. The deformation amount δ 1 of is given by the following equation.

Δ1 = K1 (PL ³ / EIz) (2) Further, the deformation amount δ 2 when the conductor receives a distributed load is given by the following formula.

Δ 2 = K 2 (PL ⁴ / EIz) (3) As is clear from the above equations (2) and (3), when the material (Young's modulus) and length of the conductor are the same, the amount of deformation Is inversely proportional to the second moment of area. Therefore, by bending the conductor to the side with a large second moment of area to form a hairpin-shaped primary conductor, a primary conductor that is difficult to deform can be obtained,
It is possible to obtain a strong primary conductor against electromagnetic mechanical force due to excessive current.

As an example, as shown in FIGS. 4A and 4B, consider a case where a force F is applied to a rectangular conductor having a rectangular cross section from the short side direction and the long side direction of the rectangle. Assuming that the length of one side of the rectangle along the direction in which F is applied is b and the length of one side in the direction perpendicular to the direction in which the force F is applied is h, the second moment of area is Iz = (b × h ³ ) / 12 … Given in (4).

Here, assuming that the length of the long side of the rectangle is 4 [cm] and the length of the short side is 1 [cm], the force F is applied from the direction of the short side of the rectangle as shown in FIG. 4 (A). The moment of inertia of area Iz1 when the force is applied and the moment of inertia of area Iz2 when the force F is applied from the long side of the rectangle are Iz1 = 0.3, respectively.
33 and Iz2 = 5.333, and Iz2 / Iz1 = 16. That is, the geometrical moment of inertia Iz2 when a force is applied in the long side direction of the cross section of a conductor having the same rectangular cross section is 16 of the geometrical moment of inertia Iz1 when a force is applied in the short side direction.
The deformation amount when the force is applied in the long side direction is 1/16 of the deformation amount when the force is applied in the short side direction.

In the above description, an elliptical shape and an oval shape are mentioned as the contour shape of the cross section of the primary conductor, but in the present invention, the contour shape of the cross section of the primary conductor is non-circular (the second moment of area depends on the direction in which force is applied) Different shapes) can be applied. As a preferable example of the contour shape of the cross section of the primary conductor, in addition to an elliptical shape and an oval shape, for example, a shape in which each corner portion of a rectangle (rectangle) is rounded is considered.

FIG. 3 shows a preferred shape of the hairpin-shaped primary conductor used in the current transformer. The hairpin-shaped primary conductor used in the current transformer according to the present invention has a curved folded portion in the middle thereof. As long as the one end 1A and the other end 1B are located on the same side, the shape is not limited to the example shown in FIG. For example, a simple U-shape without the inclined portion 1d as shown in FIG. 3 in the vicinity of the folded portion may be used.

In the above embodiments, a solid conductor was used as the conductor material forming the primary conductor, but the present invention can also be applied to the case of using a hollow conductor having a flow path for a cooling medium inside. it can.

Although the primary conductor is formed of a single conductor in the above embodiment, the present invention is also applicable to a case where a plurality of hairpin-shaped conductors are arranged and connected in parallel or in series. Can be applied.

The preferred embodiments of the present invention have been described above. The main aspects of the invention disclosed in this specification are as follows.

(1) In a current transformer having a hairpin-shaped primary conductor and a secondary coil wound around an iron core arranged so as to interlink with the primary conductor, the primary conductor is A current transformer comprising a conductor having a non-circular cross-sectional contour shape, and the conductor being bent to the side having the largest second moment of area in each curved portion of the primary conductor.

(2) A first linear portion 1a extending linearly in the vertical direction, an arcuate folded portion 1b having one end connected to the lower end of the first linear portion 1a, and an upper portion from the other end of the folded portion 1b. A rising portion 1c which linearly rises in the direction of the first straight line portion 1a, and a first straight line portion 1a extending obliquely upward from the upper end of the rising portion 1c.
The inclined portion 1d extending so as to approach the side, and the inclined portion 1d
Has a second straight line portion 1e that bends along the first straight line portion 11a from the upper end and extends linearly upward, and includes a folded portion 1b, a boundary portion between the rising portion 1c and the inclined portion 1d, and an inclination. A hairpin-shaped primary conductor 1 in which curved portions C1, C2 and C3 are formed at boundaries between the portion 1d and the second linear portion 1e, and a portion of the primary conductor near the lower end of the first linear portion 1a. In a current transformer having a secondary coil wound around an iron core arranged so as to interlink with the primary conductor,
The primary conductor is composed of a conductor having a non-circular cross section, and each curved portion C1, C2, and C of the primary conductor.
In 3 is a current transformer in which the conductor is bent to the side with the large second moment of area.

(3) The current transformer according to the above item (1) or (2), wherein the profile of the cross section of the primary conductor is an ellipse.

(4) The current transformer according to the above item (1) or (2), wherein the profile of the cross section of the primary conductor is oval.

(5) The current transformer according to the above item (1) or (2), wherein the contour shape of the cross section of the primary conductor is a rectangle with rounded corners.

[0040]

As described above, according to the present invention, since each curved portion of the primary conductor is formed by bending the conductor to the side having the largest moment of inertia of area, the primary conductor when an excessive current flows. It is possible to reduce the deformation amount of. Therefore, it is necessary to prevent the primary conductor from being greatly deformed when an excessive current flows and the insulating layer covering the primary conductor from abutting on the inner surface of the container or the iron core around which the secondary coil is wound and damaging it. Therefore, it is possible to prevent the insulation function from being deteriorated due to the destruction of the insulation layer and improve the reliability.

[Brief description of drawings]

FIG. 1 is a front vertical sectional view showing an embodiment of the present invention.

FIG. 2 is a side elevational sectional view of the embodiment.

3A and 3B are a top view and a front view of a primary conductor used in the embodiment of FIG. 1, respectively.

4 (A) and 4 (B) are cross-sectional views showing different examples of how to apply a force to a rectangular conductor.

5A and 5B are respectively a top view and a front view of a primary conductor used in a conventional current transformer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Primary conductor 2 Secondary coil unit 10 Current transformer container 11 Lower tank 12 Insulator pipe 21 Oil amount adjusting device

Claims (1)

[Claims] 1. A current transformer comprising a primary conductor bent and formed in a hairpin shape, and a secondary coil wound around an iron core interlinking with the primary conductor, wherein the primary conductor has a non-circular cross-sectional shape. A current transformer, characterized in that the conductor is bent to the side having the largest moment of inertia of area in each curved portion of the primary conductor.