JPH03214612A - Molded coil - Google Patents

Abstract

PURPOSE:To obtain a molded coil whose durability is high and which is small- sized and lightweight by a method wherein glass cloths are buried into synthetic- resin layers at the inside and the outside of a raw coil in such a way that their end parts do not protrude from the end part of a finished molded coil. CONSTITUTION:A glass cloth 5 whose width is equal to or larger than the total length from the end part to the end part of one or more windings is buried into a resin layer 6 at the outside of a raw coil 3. A glass cloth 4 whose width is equal to or larger than the total length from the end part to the end part of a bobbin is buried into a synthetic-resin layer at the inside of the raw coil 3. The individual glass cloths 4, 5 are buried in such a way that their end parts do not reach the end part of a finished molded coil. Consequently, the strength of the resin layer 6 against a thermal stress generated between the winding 3 and the resin layer 6 is increased, and the stress can be dispersed to the whole glass-cloth buried part from a part near the winding part. Thereby, even when the thickness of the resin layer 6 around the raw coil 3 is made thin, it is possible to prevent a temperature rise and a crack from being caused at the winding.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a molded coil used in a molded power distribution transformer and the like.

Conventional technology A molded transformer using a molded coil made by forming a synthetic resin layer such as epoxy resin around the winding has characteristics such as excellent insulation and ease of maintenance, and its uses are wide. First of all, it is expanding.

Conventional molded coils are generally manufactured by forming a winding, setting the winding in a mold, vacuum-casting an epoxy resin, and heating and curing the winding.

Problems to be Solved by the Invention In conventional molded coils manufactured in this manner, the temperature of the winding increases due to heat generation due to copper loss during actual load operation, and thermal stress occurs between the winding and the resin layer. occurs. If the thermal stress exceeds the tensile strength of the resin layer, cracks will occur in the resin layer, significantly reducing the insulation performance. To solve this problem, the thickness of the resin layer around the windings should be increased (for example, 5
m ~ 10mm) L, a method is used to relieve stress inside the resin layer, but when the resin layer is made thicker, the thermal resistance increases, the amount of heat dissipated decreases, and the temperature of the winding increases. There was a problem.

On the other hand, if the resin layer is made thinner, the amount of heat dissipated increases, but the effect of stress relaxation inside the resin layer decreases, resulting in the problem that cracks are more likely to occur due to thermal stress.

The present invention solves these conventional problems, and aims to provide an excellent molded coil that can reduce the thickness of the resin layer around the windings and prevent the occurrence of cracks.

Means for Solving the Problems In order to achieve the above object, the present invention provides PR. It is equipped with an elementary coil formed by connecting one or more windings formed on a P bobbin, and a synthetic resin layer sealed around this elementary coil, and one in the synthetic resin layer on the outside of this elementary coil. A glass cloth with a width equal to or greater than the total length of the above windings from end to end is embedded, and the total length of the bobbin from end to end is buried in the synthetic resin layer inside the coil. A glass cloth having a width equal to or greater than that of the molded coil is buried, and the ends of each glass cloth are buried so as not to reach the ends of the completed molded coil.

Effects Since the present invention has such a configuration, it has the following effects. In other words, since the glass cloth is embedded in the resin layers inside and outside the coil, the strength of the resin layer increases against the thermal stress generated between the winding wire and the resin layer, and the stress is absorbed by the glass cloth fibers into the winding wire. Since the resin layer can be dispersed from the vicinity of the part to the entire part where the glass cloth is embedded, even if the thickness of the resin layer around the bare coil is made thin, it is possible to prevent the temperature rise of the winding wire and the occurrence of cracks.

Further, since the ends of the glass cloth embedded in the synthetic resin layer are buried so as not to reach the ends of the completed molded coil, it is possible to prevent cracks from occurring at the ends of the coil.

Embodiment FIG. 1 is a perspective view of a molded coil showing an embodiment of the present invention, and FIG. 2 is a perspective view of a molded coil shown in FIG. FIG. In Figures 1 and 2, 10 indicates the entire molded coil, 1 is a bobbin, 2 is a winding, 3 is an elementary coil produced by winding 2 on bobbin 1, and 4 and 5 are elementary coils 3. Glass cloth arranged inside and outside, 6 is elementary coil 3
This is a synthetic resin layer that seals the glass cloths 4 and 5.

Next, a method for manufacturing this molded coil will be explained.

First, the cross-sectional area is 186 mm x 276 mm, the radius of curvature of one corner is 60 m, and the length is 40 mm.
0mm core, thickness 125μm, width 400m
After winding the PET film of m, the thickness is 0.18 mm,
Four epoxy glass fiber legs with a diameter of 86 mm were made by winding them seven times. Then, on the outside of the epoxy glass pre-reg, a thickness of 125 urn and a width of 400r
After one turn of PET7 ilm of 1.0 nm was made, the core and the wound material were transferred to a dryer, and the straight portion of the wound material was clamped with an iron plate and then heated at 150'C for 5 hours. Then, the evogishi glass pre-leg was cured. After curing the pre-reg 5, remove the PET film, treat the surface of the cured pre-reg with sandpaper, remove the resin that flowed out, and remove the PET film.
A total of four 6 mm bobbins 1 were manufactured. These bobbins 1
After setting it on the core described above, the thickness is 70tim and the width is 7.
0mm aluminum foil, thickness 25am, width 78mm
The winding wire 2 was formed by overlapping two PET films of 1.0 mm in diameter and wound 174 times to produce an elementary coil 3 as shown in FIGS. 3 and 4. In the same way, the remaining 3 pobins 1
A winding 2 was also formed on the top, making a total of four elementary coils 3. The thickness of the winding 2 including the pobbin 1 was 24 mm.

Next, as shown in Figure 5, the cross-sectional area is 180mm x 2
An inner frame 7 with a radius of curvature of 70rrl m and a part of the corner of 57 mm is prepared, and this inner frame 7 has a thickness of 0.18 mm,
After winding the glass cloth 4 with a width of 344 mm twice, the elementary coil 3 is set on the glass cloth 4 of the inner frame 7, and the first elementary coil 3a and the second elementary coil 3b, and the second elementary coil 3b and the third elementary coil 3 are set on the glass cloth 4 of the inner frame 7. The elemental coil 3c'--the third elemental coil 3c and the fourth elemental coil 3d were each connected. After wiring is completed, the thickness is 0.18mm and the width is 344mm.
Two sheets of nrm glass cloth 5 were wound around the outer periphery of these elementary coils 3 and fixed with adhesive tape. However, in order to secure a resin flow path, these two pieces of glass cloth 5 are left with an unwound part of about 12 mm in width at the position (terminal part) where the tap switching lead and the winding start and winding end leads are pulled out. Ta.

Next, inside a bucket-shaped outer frame 8 made of tin with a cross-sectional area of 240 mm x 330 mm and a radius of curvature of a part of 81 mm and a depth of 400 mm, an inner frame 7 with a glass cloth 4 wound thereon and After placing the integrated coil 3 set in the frame 7 and wrapped with the glass cloth 5, the tap switching lead and the winding start and end leads were placed in the outer frame 8 and heated at 80°C. It was dried overnight and preheated.

Next, a bisphenol epoxy resin compound (60% by weight of silica) was vacuum cast into the gap between the inner frame 7 and the outer frame 8.
℃ for 12 hours, 120℃ for 6 hours, 140℃ for 4 hours,
The synthetic resin layer 6 was formed by heating and curing, respectively. After the resin layer 6 has hardened, the tin outer frame 8 and inner frame 7 are removed, and post-processing such as deburring is performed so that the inner and outer resin layers 6 of the element coil 3 have a thickness of 3 mm. A molded coil with a completed coil height of 374 mm was obtained.

Note that the glass transition temperature of the cured resin material used in this example was 130°C. Further, the glass cloths 4 and 5 used in this example are plain woven products for electrical insulation and are treated with silane.

Comparative Example 1 After preparing four bare coils 3 with windings 2 formed on the bobbin 1 in the same manner as in the above embodiment, the four bare coils 3 were set in the inner frame 7 having the same dimensions as in the above embodiment. , first elementary coil 3
A and the second elemental coil 3b, and the second elemental coil 3b and the third elemental coil 3c were successively connected. Thereafter, the molded coil is set in the outer frame 8 having the same dimensions as in the example described above, and subjected to preheating drying, vacuum casting, and curing under the same conditions as in the example described above. I got it.

Comparative Example 2 Four elementary coils 3 were prepared in which the windings 2 were formed on the pobbins 1 in the same manner as in the above embodiment. Next, an inner frame 7 having the same dimensions as in the previous embodiment was provided with a thickness of 0.18 mm. After winding the glass cloth 4 with a diameter of 344 mm twice and fixing it with adhesive tape, the glass cloth 4 was divided into two parts at a width of 172 mm. after that,
Preheating, casting, and curing were performed under the same conditions as in the previous example, and a molded coil was obtained that differed from the example only in that the glass cloth 4 was divided into two parts.

Comparative Example 3 After forming four elementary coils in the same manner as in the above example,
A glass cloth 4 of the same size was fixed to the inner frame 7 of the same size as in the previous example by the same method, and the four element coils were sequentially connected. Next, on the outside of each element coil 3, a thickness of 0.
After fixing a plain weave glass tape of 18 mm and diameter 40 mm from end to end around each elemental coil 3, preheating, casting, and curing were performed under the same conditions as in the previous example to form the glass inside the elemental coil 3. A molded coil was obtained that differs from the example only in that the cross is independent for each elementary coil 3.

Comparative Example 4 A molded coil was manufactured in the same manner as in the above example, but the width of the glass cloths 4 and 5 disposed inside and outside the elementary coil 3 was 30 mm longer than in the example.
A molded coil was obtained that differed from the example only in that the ends of the glass cloths 4 and 5 protruded from the ends of the completed molded coil.

In order to compare the occurrence of cracks due to thermal stress in the molded coils obtained in the above Examples and Comparative Examples, DC current was continued to flow through each coil for a certain period of time, and the winding average when the coil surface temperature was saturated and fixed. Temperature was measured using a microohmmeter. The average winding temperature was measured by increasing the current value in sequence, and the current value was increased until cracks occurred.

The measurement results are shown in the table below.

Sample Winding temperature at the time of crack occurrence (℃) Example
210 Comparative Example 1 130 1 0 Comparative Example 2 135 Comparative Example 3 136 Comparative Example 4 135 As is clear from the above results, the molded coil manufactured according to the above example had a high temperature until cracking occurred, and the molded coil did not crack as much. This indicates that it is unlikely to occur. Furthermore, since the heat dissipation effect is high, the thickness of the synthetic resin layer 6 sealed inside and outside the element coil 3 can be made thinner, and the size and weight can be reduced.

Effects of the Invention As described above, according to the molded coil of the present invention, the glass cloth is embedded in the synthetic resin layers inside and outside the base coil so that its ends do not protrude from the ends of the completed molded coil. , the strength of the synthetic resin layer increases against the thermal stress generated between the winding wire and the resin layer, and the glass cloth fibers can disperse the stress from the vicinity of the winding part to the entire buried glass cloth part, and the surrounding area of the bare coil. Even if the thickness of the synthetic resin layer is made thinner, it is possible to prevent a temperature increase in the winding wire and the occurrence of cracks, and it is possible to realize a compact, lightweight molded coil with high durability.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a molded coil showing an embodiment of the present invention, FIG. 2 is a sectional view taken along line nn in FIG. 1, FIG. 3 is a plan view showing an elementary coil in the same molded coil, and FIG. The figure is a front view of the allotropic coil, and FIG. 5 is an exploded perspective view for explaining the method of manufacturing the same molded coil. 1...Bobbin, 2...Winding wire, 3...Elementary coil, 4
, 5...Glass cloth, 6...Synthetic resin layer, 7...
- Inner frame, 8... Outer frame, 10... Molded coil.

Claims (1)

[Claims] The method includes an elementary coil formed by connecting one or more windings formed on an FRP bobbin impregnated and hardened with a thermosetting resin, and a synthetic resin layer sealed around the elementary coil, and a synthetic resin layer sealed around the elementary coil. A glass cloth having a width equal to or greater than the total length of the one or more windings from end to end is embedded in the outer synthetic resin layer, and a glass cloth is embedded in the inner synthetic resin layer of the elementary coil. A glass cloth having a width equal to or greater than the total length of the bobbin from end to end is embedded in the bobbin,
A molded coil characterized in that the ends of each of the glass cloths are buried so as not to reach the ends of the completed molded coil.