JPH10135050A - Dry-type transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dry-type transformer, withstanding a high impulse voltage and manufactured at low cost by using minimum amount of resin mold and an inexpressive insulating paper. SOLUTION: A secondary coil 3 is wound around a coil bobbin 2 attached externally to an iron core 1, and a primary coil 4 is wound via an insulation provided at the outside of the secondary coil 3, and an insulation is placed to cover the outside of the primary coil 4. The recessed areas at the exposed ends of the primary coil surrounded by the ends of the both insulations are molded with a synthetic resin 10. Stepped surfaces with one or a plurality of steps formed at the ends of the both insulations surrounding the recessed areas, and an insulating paper contacting intimately with the synthetic resin 10 is used as the insulations forming the stepped surfaces.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-voltage dry-type transformer, and more particularly to a dry-type transformer having a withstand voltage against a high impulse voltage.

[0002]

2. Description of the Related Art In a transformer for electric equipment, even a low-voltage dry-type transformer may be required to withstand a high impulse voltage due to a lightning strike or the like. In such a case, conventionally, the insulation distance between the high voltage coil (primary coil) and other metal parts is increased, or expensive insulating paper with good adhesion is used, and the entire high voltage coil is made of epoxy resin. By molding with, the dielectric strength is increased.

[0003]

However, when the insulation distance between the high-voltage coil and other metal parts is increased, there is a problem that the shape of the transformer becomes large, and the cost is high with good adhesion. Dry type transformers that use insulating paper and have a structure in which the entire high-voltage coil is molded with epoxy resin have a very high manufacturing cost due to an increase in material costs for insulators, the complexity of the resin molding work process, and an increase in the amount of resin material used. There was a problem that became expensive.

Therefore, conventionally, as shown in FIG. 5, use of a dry-type transformer having a simple mold structure in which an epoxy resin 31 is molded only in an upper and lower exposed portion of a high-voltage coil (primary coil) 30 has been studied. However, in this type of dry transformer, the exposed portion of the high-voltage coil 30 is molded (coated) with the resin 31 so that the insulating material (polymerized plural insulating papers) 32 and the adhesive surface of the resin 31 are insulated. Although breakage can be prevented, the insulator 32 is formed by winding insulating paper (including an insulating film), and a slight gap is generated between the insulating papers.

For this reason, when a high impulse voltage is applied, as shown in FIG. 5, when a through dielectric breakdown occurs in the first insulating paper 32a on the high voltage coil side, the first and second sheets are slightly damaged. There is a problem that surface discharge breakdown occurs along a path of a small gap, and dielectric breakdown easily occurs between the high voltage coil 30 and the iron core 33.

Therefore, it has been considered to increase the thickness of the insulating paper of the insulator, to bond the insulating paper to each other, or to mold the end of the insulator with a resin. At the time of winding, there is a problem that the familiarity with the coil is poor, and the workability and workability are deteriorated.
However, there has been a problem that it is difficult to coat the resin around the insulator made of insulating paper satisfactorily from the viewpoint of work steps and the like.

The present invention has been made in view of the above points, and is a dry type transformer which can be manufactured at a low cost using inexpensive insulating paper with a minimum of resin mold and which can withstand a high impulse voltage. The purpose is to provide.

[0008]

In order to achieve the above object, a dry transformer of the present invention has a secondary coil wound around a coil bobbin externally fitted to an iron core, and is disposed outside the secondary coil. The primary coil is wound through the insulator, and the insulator is disposed outside the primary coil so that the concave portion on the exposed end face of the primary coil surrounded by both insulator ends on both sides is formed. In a dry-type transformer molded with synthetic resin,
At the ends of both insulators surrounding the recess, a stepped surface having one or more steps is formed, and the insulator forming the stepped surface is
An insulating paper having good adhesion to a synthetic resin is provided.

Here, the term "insulating paper" is a concept including inexpensive insulating paper made by using pulp, insulating paper made by using polyamide fiber, and the like, and synthetic resin film.

[0010]

[Function / Effect] In a dry transformer having such a configuration, when a high impulse voltage is generated between a primary coil and an iron core due to a lightning strike or the like, a synthetic resin having a high insulating property adheres to the end of the primary coil and an insulator. Therefore, no creeping discharge breakdown occurs on the contact surface. When insulation breakdown occurs, penetration insulation breakdown occurs in the insulation paper closest to the primary coil of the insulator, and creeping discharge breakdown occurs along the inside of the insulation paper.

However, on both sides of the concave portion on the exposed end face of the primary coil surrounded by the ends of both insulators, a step surface having a step portion is formed, and the insulator forming each step portion of the step surface has
Because insulating paper with good adhesion to synthetic resin is used,
In order for the dielectric breakdown to occur, it is necessary to cause a through dielectric breakdown in the insulating paper forming the step surface of each step.

For this reason, the through breakdown voltage can be increased to a value obtained by substantially integrating the through breakdown voltage of the insulating paper of each step, as compared with the conventional dry type transformer, and a good dielectric strength against a high impulse voltage can be obtained. Can be made.

[0013] In addition, since inexpensive insulating paper can be used for insulating paper other than the stair surface where most of the insulating material is formed,
In addition, since the molding of the synthetic resin can be minimized, it is possible to manufacture a dry-type transformer having excellent dielectric strength against a high impulse voltage without increasing the manufacturing cost.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a dry-type transformer to which the present invention is applied. Reference numeral 1 denotes an annular core, and 2 denotes a coil bobbin which is fitted around the core 1. A secondary coil (low-voltage coil) 3 is first wound on the coil bobbin 2, and a first insulator 5 and a second The primary coil (high-voltage coil) 4 is wound via the two insulators 6.

Further, a third insulator 7 and a fourth insulator 8 are disposed outside the primary coil 4 so as to surround them, and an outer peripheral insulating paper 9 is disposed around the outer periphery of the fourth insulator 8.

That is, the first insulator 5 is made of insulating paper such as 1
Eight sheets are formed, that is, formed by winding 18 times around the outer periphery of the secondary coil 3, and a second insulator 6 made of one piece of insulating paper is stacked outside the first insulator 5. The primary coil 4 is wound around the outside of the second insulator 6, and the third insulator 7 made of one piece of ordinary insulating paper is stacked outside the primary coil 4.

Then, a fourth insulator 8 formed by laminating, for example, 18 sheets of insulating paper is placed outside the third insulator 7. Further, an outer peripheral insulating paper 9 is arranged outside the fourth insulator 8 so as to surround the fourth insulator 8.

The insulating paper used for the first insulator 5 and the fourth insulator 8 is mainly inexpensive insulating paper or polyester film. However, as shown in FIG. 2, the insulating paper closest to the primary coil 4 side is used. As the papers 5a and 8a, a polyamide fiber paper or a PEN (polyethylene naphthalate resin) film having good adhesion to a synthetic resin is used. In addition, the insulating paper of the second insulator 6 and the third insulator 7 and the insulating paper 9 for the outer periphery include:
Polyamide fiber paper with good adhesion to synthetic resin or P
An EN (polyethylene naphthalate resin) film is used. The thickness of the insulating papers 5a and 8a, the insulating paper of the second and third insulators 6 and 7, and the insulating paper 9 for the outer periphery are thicker than inexpensive insulating paper, and the through dielectric breakdown voltage is higher. Is getting higher.

The width of the first insulator 5 and the fourth insulator 8 is formed to be larger than the winding width of the primary coil 4, and the width of the second insulator 6
The width of the first and fourth insulators 7 is larger than the winding width of the primary coil 4 and smaller than the first and fourth insulators 5 and 8. As a result, a step is formed near the upper end and the lower end of the second insulator 6 and the third insulator 7, and a recess having a step surface is formed above and below the primary coil 4. Is done.

The stepped portion between the upper end and the lower end of the second insulator 6 and the third insulator 7 covers the recessed portion having such a structure, that is, the upper and lower exposed portions of the primary coil 4. A synthetic resin 10 having good adhesiveness such as an epoxy resin is molded (coated) in the recess so as to cover the step surface. Thereby, the synthetic resin 10 is made of the insulating paper 5 of the first insulator 5.
a, the second insulator 6, the third insulator 7, and the fourth insulator 8 are in good contact with the end surfaces of the upper end and the lower end of the insulating paper 8a.

In the dry-type transformer having such a configuration, for example, even when a high impulse voltage is generated between the primary coil 4 and the iron core 1 due to a lightning strike or the like, the synthetic resin 10 having a high insulating property is used as the first insulator. 5, the insulating paper 5a, the second insulating material 6, the third insulating material 7, and the fourth insulating material 8 are in close contact with the upper and lower end surfaces of the insulating paper 8a. If dielectric breakdown occurs, as shown in FIG. 2, penetrate through the insulating paper 5a of the second insulator 6 and the first insulator 5, or the insulating paper 8a of the third insulator 7 and the fourth insulator 8. Insulation breakdown occurs, and creeping discharge breakdown occurs on the inner surface of the insulating paper 5a of the first insulator 5 or on the outer surface of the insulating paper 8a of the fourth insulator 8.

Therefore, the breakdown voltage of this dry type transformer is improved by the penetration breakdown voltage of one insulating paper having a high insulating property as compared with the conventional one as shown in FIG. Can have dielectric strength.

As described above, since inexpensive insulating paper can be used as the insulating paper of the first insulating material 5 and the fourth insulating material 8 that make up most of the insulating paper, an excellent manufacturing cost can be obtained without increasing the manufacturing cost. A dry type transformer having a dielectric strength against a high impulse voltage can be manufactured.

FIG. 3 shows another embodiment. In this embodiment, the upper end and the lower end of the first to fourth insulators 15 to 18 have a plurality of steps toward the inner primary coil 4. It is formed as follows.

That is, as shown in the enlarged view of the insulator in FIG. 4, the first insulator 15 has a plurality of groups of insulating papers having different widths. A paper group is arranged, and for example, 4
It is formed to have two steps. Similarly, each of the insulating papers of the fourth insulator 18 also has a plurality of insulating paper groups having different widths, and the insulating paper groups are arranged such that the width decreases toward the inside, and the primary coil It is formed to have, for example, four step portions on the concave side of the outer periphery.

The first insulating papers 15a and 18a of each step (each insulating paper group) of the first insulator 15 and the fourth insulator 18 are:
Polyamide fiber paper, which is thicker than insulating paper and has good adhesion to synthetic resin, or PEN (polyethylene naphthalate resin) film is used. Then, the second insulator 16 having the narrowest width and disposed closest to the primary coil 4.
Similarly, the insulating paper of the third insulating material 17 is thicker than inexpensive insulating paper and has good adhesion to synthetic resin, such as polyamide fiber paper or PEN (polyethylene naphthalate resin).
Formed from film.

Thus, a plurality of steps which gradually change at the upper end and the lower end of the first insulator 5 and the second insulator 6 and the third insulator 7 and the fourth insulator 8 are formed. Above and below the primary coil 4, a recess having a stepped surface due to the step is formed. In addition, the predetermined number of insulating papers each having a certain shape are formed such that the width of the insulating papers of the second insulator 16 and the third insulator 17 near the primary coil 4 is the smallest. Then, a synthetic resin 20 having good adhesiveness such as epoxy resin is molded (coated) in the same manner as described above so as to cover the upper and lower exposed portions of the primary coil 4 and to cover the stepped surface of the concave portion.

In the dry-type transformer having such a configuration, for example, when a high impulse voltage is generated between the primary coil 4 and the iron core due to a lightning strike or the like, the synthetic resin 20 having a high insulating property is connected to the first insulator 15 and the second insulating material. Since the object 16, the third insulator 17 and the end face of the upper end and the lower end of the fourth insulator 18 are in close contact with each other, no creeping discharge breakdown occurs there. Since a stepped surface having a plurality of steps is formed in a portion in close contact with the object, most of the insulating paper of the second insulator 16 and the first insulator 15 or the third insulator 17 and the fourth insulator 18 Through insulation breakdown occurs on most insulating papers,
And the inner surface of the innermost insulating paper 15a of the first insulator 15,
Alternatively, creeping discharge breakdown occurs on the outer surface of the outermost insulating paper 18a of the fourth insulator 18.

Therefore, the breakdown voltage of this dry transformer is improved by the penetration breakdown voltage of an extremely large number of insulating papers as compared with the conventional one as shown in FIG. Greater dielectric strength can be provided.

In this type of dry-type transformer, a copper plate or an aluminum plate may be provided with a contact prevention plate to prevent contact between the primary coil and the secondary coil. In this case, the contact prevention plate may be inserted in the insulator between the primary coil 4 and the secondary coil 3, that is, in the first insulators 5 and 15.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a dry transformer showing one embodiment of the present invention.

FIG. 2 is a partially enlarged cross-sectional view of the transformer of FIG.

FIG. 3 is a partial cross-sectional view of a dry transformer according to another embodiment.

FIG. 4 is an explanatory sectional view showing an arrangement of insulators of the transformer.

FIG. 5 is a partial sectional view of a conventional dry-type transformer.

[Explanation of symbols]

 1-iron core 2-coil bobbin 3-secondary coil 4-primary coil 5-first insulator 6-second insulator 7-third insulator 8-fourth insulator

Claims (3)

[Claims] 1. A secondary coil is wound around a coil bobbin externally fitted to an iron core, a primary coil is wound via an insulator disposed outside the secondary coil, and a coil is wound around an outside of the primary coil. A dry type transformer in which an insulator is provided so as to surround it, and a concave portion on an exposed end surface of the primary coil, which is surrounded on both sides by ends of the insulator, is molded with a synthetic resin. A stepped surface having one or a plurality of step portions is formed at the ends of the insulators, and insulating paper having good adhesion to the synthetic resin is disposed on the insulator forming the stepped surface. A dry-type transformer characterized by the following. 2. The insulator inside the primary coil comprises a first insulator having a plurality of insulating papers laminated and a second insulator having one insulating paper, and the width of the second insulator is An insulating paper having good adhesion with the synthetic resin is used for the outermost insulating paper of the first insulator and the insulating paper of the second insulator, which is formed to be smaller than the width of the first insulator. The insulator outside the primary coil comprises a fourth insulator in which a plurality of insulating papers are overlapped and a third insulator having one insulating paper, and the width of the third insulator is equal to that of the fourth insulator. The insulating paper having good adhesion to the synthetic resin is used for the innermost insulating paper of the fourth insulator and the insulating paper of the third insulator, which are formed smaller than the width. The dry transformer according to claim 1. 3. A stepped surface having a plurality of steps is formed at an end of the first insulator and the fourth insulator, and the insulator forming the stepped surface has good adhesion to the synthetic resin. 3. The dry transformer according to claim 2, wherein a suitable insulating paper is provided.