JP2001307931A - Transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mixture contact preventing plate without additionally providing a support structure and to improve a transformer in corona discharge- resistant properties in a withstand voltage test between a mixture contact preventing plate and a low-voltage coil. SOLUTION: A hollow insulator 4 is provided around a low-voltage coil 2, and a mixture contact preventing plate 7 is provided around the hollow insulator 4. The hollow insulator 4 is formed of a large number of rectangular glass chopped strands 5, where the chopped strands 5 are bonded together with insulating adhesive agents 6 so as to produce a large number of voids among them, and the total volume of the voids amounts to nine times or above as large as that of the glass chopped glass strands themselves.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transformer in which an anti-contact plate is disposed between a low-voltage coil and a high-voltage coil.

[0002]

2. Description of the Related Art Some transformers to which a computer, a semiconductor element or the like is connected as a load have a contact prevention plate formed of a conductive material between a high voltage coil and a low voltage coil. When an abnormal voltage such as an external lightning surge or a switching surge on the same bus enters the high-voltage coil from the high-voltage line, the contact prevention plate has a high frequency. It is provided to prevent a voltage from being induced to cause harm such as dielectric breakdown to various electronic devices connected as a load. That is, the contact prevention plate is provided to increase the impedance (= 1 / (ω · c)) between the coils with respect to the high-frequency surge voltage and to reduce the electrostatic induction.

Conventionally, in such a molded transformer, as shown in FIG. 6, an insulator 4b is wound on the outer periphery of the low-voltage coil 2, and then a contact prevention plate 7b is wound on the outer periphery.
As the insulator 4b wound around the outer periphery of the low-voltage coil 2, an insulating film, a glass substrate impregnated with an epoxy resin, or the like is generally used.

[0004] In addition, as shown in FIG.
And a high-voltage coil 3 are arranged at predetermined intervals from each other, and a contact prevention plate 7c sandwiched between prepreg insulators 4c, 4c is disposed.
In some cases, the insulation between the contact prevention plate 7c and the high-voltage coil 3 is ensured by air.

[0005]

However, in the former prior art, for example, in a withstand voltage test between a contact prevention plate (earth) and a low-voltage coil, a voltage of 2 to 4 kV is normally applied. Therefore, when 10 to 22 kV is applied between the contact prevention plate and the low-voltage coil, there is a problem that an audible sound may be generated by corona discharge during application of the test voltage. Such a test with a very high voltage may be performed by the user at the installation site, and the generation of discharge noise itself does not reduce the performance of the transformer, and although there is no problem in actual use,
When the discharge noise is generated, the user may mistakenly think that the performance is inferior.

Further, in the latter conventional technique, the contact preventing plate is used.
Because air with a low dielectric constant is interposed between the low-voltage coils, even if the test is performed at a very high voltage as described above,
Although the discharge noise can be suppressed, a separate support structure for the contact prevention plate is required to fix the contact prevention plate between the high-voltage coil and the low-voltage coil, resulting in a large transformer. In addition, there is a problem that the manufacturing cost increases.

The present invention has been made in view of the above-mentioned conventional problems, and provides a transformer capable of suppressing generation of discharge noise even when a withstand voltage test is performed at a very high voltage while suppressing an increase in size and cost. It is to be.

[0008]

According to a transformer for achieving the above object, a hollow insulator made of an insulating material is provided on the outer peripheral surface of a low-voltage coil, and a contact prevention plate is provided on the outer periphery of the hollow insulator. Is provided, the hollow insulator is formed as a structure having a number of voids in the insulating material, the total volume of the number of the voids is equal to or more than the volume of the insulating material itself,
It is characterized by the following.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a transformer according to the present invention will be described with reference to the drawings.

As shown in FIG. 1, a transformer according to the present embodiment has a low-voltage coil 2 outside a core 1 and a high-voltage coil 3 outside the core.

[0011] Between the low voltage coil 2 and the high voltage coil 3,
As shown in FIG. 2, a hollow insulator 4 and a contact prevention plate 7 formed of a copper plate are arranged. The low-voltage coil 2 includes a plurality of stacked conductors 2a, insulators 2b and 2b disposed at both ends of the conductor 2a in the stacking direction, and an insulating resin 2c that forms an end surface of the coil 2. It is formed. The high-voltage coil 3 also has a plurality of stacked conductors 3a.
And insulators 3b, 3b provided at both ends of the conductor 3a in the stacking direction, and an insulating resin 3c forming an end face of the coil 3. The hollow insulator 4 is wound around the outer periphery of the low-voltage coil 2, and the contact prevention plate 7 is wound around the outer periphery of the hollow insulator 4.

As shown in FIG. 3, the hollow insulator 4 is made of a number of strip-shaped glass chopped strands 5, and the glass chopped strands are bonded to each other with an insulating adhesive 6 so that a gap is formed between them. Things.

The glass chopped strand 5 forming the hollow insulator 4 has an average length of 20 to 50 mm and an average diameter of 5 to 20 μm. As the insulating adhesive, a saturated polyester resin or a bisphenol-based epoxy resin is used. The total volume of the many voids in the structure formed by the glass chopped strand 5 is at least 9 times the total volume of the glass chopped strand itself.

As shown in FIGS. 3 and 4, the edge 8 of the contact prevention plate 7 is bent by 180 °, and a solder 9 is provided at a step between the end 8 and the contact prevention plate main body. It is piled up, and it is finished smoothly with a grinder. That is, the end of the contact prevention plate 7 is formed so as not to have an acute angle portion and to have a certain curvature or more.

As described above, in the present embodiment, since the hollow insulator 4 is wound around the outer periphery of the low-voltage coil 2 and the contact prevention plate 7 is wound around the outer periphery, a special support structure is separately provided. Even if not provided, the contact prevention plate 7 can be easily provided, and the size and cost of the transformer can be reduced. Further, since the hollow insulator 4 has a very large amount of voids in the entire volume, the dielectric constant of the hollow insulator 4 is almost the same as that of air and a small value close to 1, so that the low-voltage coils 2 to
In addition to the increase in impedance between the contact prevention plates 7 and the lack of sharp edges at the ends of the contact prevention plates 7 where corona discharge is likely to occur, the concentration of electric field is reduced, and the corona discharge during the withstand voltage test is achieved. The characteristics are improved. As a result, even if a withstand voltage test is performed at a very high voltage, the occurrence of corona discharge can be suppressed.

Note that CAE (Computer Aided Enginee)
According to the electric field analysis by ring), assuming that the electric field strength at the end of the contact prevention plate 7b of the conventional transformer shown in FIG. 6 is 100%, the edge 8 of the contact prevention plate 7 is not bent in the present embodiment. Even in this state, it has been confirmed that the electric field intensity at the end of the contact prevention plate 7 is reduced to 70%, and the electric field intensity at the portion is reduced to 25% when the end 8 of the contact prevention plate 7 is bent. .

Next, a second embodiment of the hollow insulator will be described with reference to FIG.

The hollow insulator 4a of this embodiment is an insulating sheet formed of a three-dimensional woven fabric of glass fiber or a molded product such as a polyethylene terephthalate resin or a polyamide resin, and has a honeycomb structure. As described above, even with the honeycomb structure, the strength for winding the contact prevention plate can be ensured, and since a large number of voids are formed inside, the dielectric constant can be reduced, and the first embodiment The same effect as described above can be obtained.

Here, although the structure is such that the side surfaces of a number of regular hexagonal cylinders are adjacent to each other, the shape of the rectangular cylinders does not need to be a regular hexagonal cylinder shape. , Or a rhombic cylindrical shape. In these square tube structures, the height direction of the square tube is oriented in the stacking direction of the conductor forming the coil, and the strength against the load applied in this stacking direction is secured.

[0020]

As described above, according to the present invention, since the hollow insulator is wound around the outer periphery of the low-voltage coil and the contact prevention plate is wound around the outer periphery, a special support structure is separately provided. Even without providing, it is possible to easily provide the anti-contact plate,
The size and cost of the transformer can be reduced. Moreover, since the hollow insulator has a large amount of voids in the whole volume, the dielectric constant of the hollow insulator is almost the same as that of air and is 1
, And the impedance between the low-voltage coil and the contact prevention plate increases, so that the electric field concentration can be reduced, and the corona discharge phenomenon can be suppressed even when a withstand voltage test is performed at a very high voltage.

[Brief description of the drawings]

FIG. 1 is a cutaway perspective view of a main part of a transformer according to a first embodiment of the present invention.

FIG. 2 is a sectional view between a high-voltage coil and a low-voltage coil of the transformer according to the first embodiment of the present invention.

FIG. 3 is an enlarged view of a part III in FIG. 2;

FIG. 4 is a developed plan view of a contact prevention plate according to the first embodiment of the present invention.

FIG. 5 is a perspective view of a hollow insulator according to a second embodiment of the present invention.

FIG. 6 is a cross-sectional view (part 1) between a high-voltage coil and a low-voltage coil of a conventional transformer.

FIG. 7 is a cross-sectional view (part 2) between a high-voltage coil and a low-voltage coil of a conventional transformer.

[Explanation of symbols]

1: Iron core, 2: Low voltage coil, 3: High voltage coil, 4, 4a
... hollow insulator, 5 ... glass chopped strand, 6 ...
Insulating adhesive, 7, 7b, 7c: anti-contact plate, 8: edge.

Claims (4)

[Claims] 1. A transformer in which an anti-contact plate is disposed between a low-voltage coil and a high-voltage coil, wherein a hollow insulator made of an insulating material is provided on an outer peripheral surface of the low-voltage coil. The contact prevention plate is provided on the outer periphery of the insulator, and the hollow insulator is formed as a structure having a large number of voids in the insulating material, and the total volume of the large number of voids is the insulating material itself. A volume greater than or equal to the volume of the transformer. 2. The transformer according to claim 1, wherein the insulating material of the hollow insulator has a plurality of strip-shaped glass chopped strands and a gap formed between the plurality of glass chopped strands. And an insulating adhesive for bonding the plurality of glass chopped strands. The total volume of the plurality of voids formed between the plurality of glass chopped strands is 9% of the volume of the insulating material itself.
A transformer that is at least twice as large. 3. The transformer according to claim 1, wherein the hollow insulator has a structure in which a plurality of square tubes having the same height are adjacent to each other by an insulating sheet as the insulating material. Wherein the total volume of the voids in the large number of the rectangular cylinders is at least 9 times the volume of the insulating sheet itself. 4. The transformer according to claim 1, wherein each of the edges of the contact prevention plate is turned 180 °.