JP2013162009A - Mold transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress occurrence of crack due to thermal stress, by maintaining the original insulation performance of an insulation sheet arranged between winding conductors.SOLUTION: A mold transformer includes a core, a secondary winding wound around the core, and a primary winding wound around the secondary winding. An insulation sheet is placed between the layers of winding conductor wound by multiple number of turns in the primary winding and secondary winding, and they are resin molded integrally. A hole is formed in at least a part of the insulation sheet, and filled with the resin.

Description

  The present invention relates to a molded transformer, and more particularly, to a molded transformer suitable for an insulating sheet provided between layers of winding conductors.

  In recent years, demand for electric power has continued to increase, especially in urban areas. As a result, substations and power distribution facilities have been installed at various locations in the city, and demands for disaster prevention and safety for these facilities have increased. Yes.

Under such circumstances, with regard to transformers, instead of oil-filled transformers that have been the mainstream so far, molded transformers using synthetic resin as flame retardant transformers, or SF ₆ as non-flammable transformers. Gas-insulated transformers that contain gas have been installed. In particular, molded transformers are in great demand for buildings, schools, hospitals, etc. because of their small size, and now they occupy the mainstream of indoor distribution transformers.

  The mold resin used in this mold transformer is filled with a large amount of inorganic particles such as silica to prevent cracking due to the difference in thermal expansion coefficient between the winding conductor and the epoxy resin. The thermal expansion coefficient is set close to that of the winding conductor so as to relieve the thermal stress. Furthermore, in order to reduce man-hours and material costs while maintaining insulation between the winding conductors of the molded transformer, an insulating sheet is used for the insulation between the winding conductors.

JP 2000-286134 A

  However, cracks between the winding conductor and the mold resin can be suppressed by filling the mold resin with a large amount of inorganic particles and bringing the thermal expansion coefficient of the mold resin close to that of the winding conductor. The difference between the thermal expansion coefficients of the insulating sheet and the mold resin increases, and a problem has arisen that cracks occur at the boundary between the insulating sheet and the mold resin.

  For such a problem, the creepage distance is increased by making the both side surfaces of the insulating sheet disposed between the primary side winding and the secondary side winding into a corrugated shape, and the adhesion with the mold resin is increased. Patent Document 1 describes that the peeling is suppressed by improving the property.

  However, in Patent Document 1, the end portion of the insulating sheet disposed between the primary side winding and the secondary side winding is formed in a corrugated shape so as to extend parallel to the axial direction of the iron core. A convex shape is formed at the end of the insulating sheet. As a result, the thermal stress between the convex portion of the insulating sheet and the mold resin increases, and cracks are likely to occur. Therefore, in patent document 1, it was difficult to provide the mold transformer which relieved the thermal stress.

  The present invention has been made in view of the above points, and the object of the present invention is to maintain the original insulating performance of the insulating sheet disposed between the winding conductors and to suppress the occurrence of cracks due to thermal stress. It is to provide a mold transformer that can be used.

  In order to achieve the above object, a molded transformer according to the present invention includes an iron core, a secondary winding wound around the iron core, and a primary winding wound around the secondary winding. A molded transformer in which an insulating sheet is disposed between layers of a plurality of wound conductors of the primary side winding and the secondary side winding, and these are integrally molded with a resin In the above, a hole is formed in at least a part of the insulating sheet, and the hole is filled with the resin.

  According to the present invention, since the residual thermal stress of the insulating sheet disposed between the winding conductors is reduced, there is an effect that the generation of cracks due to the thermal stress can be suppressed.

It is the perspective view which shows the whole structure of Example 1 of the molded transformer of this invention, and the fragmentary sectional view which shows the one part. It is a perspective view which expands and shows the coil | winding part in Example 1 of FIG. 1, and the edge part of the coil | winding part. It is a perspective view which expands and shows the winding part in Example 2 of the mold transformer of this invention, and the edge part of the winding part. It is a perspective view which shows the insulating sheet in Example 3 of the mold transformer of this invention. It is the perspective view which shows the whole structure of Example 4 of the mold transformer of this invention, and the fragmentary sectional view which shows the part. It is a front view which shows the mold transformer manufactured by applying any one of Example 1-3 of this invention.

  Hereinafter, the molded transformer of the present invention will be described based on the illustrated embodiments. The same reference numerals are used for the same reference numerals in each embodiment.

  1 and 2 show a first embodiment of the molded transformer of the present invention. FIG. 1 shows an outline of the overall configuration of the molded transformer of the present invention and a partial cross section thereof, and FIG. 2 shows an enlarged view of a winding portion and an end portion of the winding portion.

  As shown in FIG. 1, the molded transformer of this embodiment includes an iron core 1 and a secondary winding 2 formed by winding a plurality of winding conductors wound around the iron core 1 and outputting current. A primary winding 3 wound around the outer periphery of the secondary winding 2 and formed by winding a plurality of winding conductors for inputting a current, and a housing support 4 that supports these windings. Has been.

  As shown in the sectional view of FIG. 1, the primary side winding 3 and the secondary side winding 2 are each provided with an insulating sheet 6 between the winding conductors 5 wound around the outer periphery of the iron core 1. The periphery of the insulating sheet 6 is integrally molded with a mold resin 7 such as an epoxy resin having a different thermal expansion coefficient from that of the insulating sheet 6. The insulating sheet 6 is made of an organic insulating sheet made of, for example, polyethylene terephthalate (PET).

  In the molded transformer configured as described above, when the thermal stress is increased from the curing temperature to room temperature, the winding conductor 5 is not in contact with the portion where the thermal stress increases and the occurrence of cracks is a concern. 5 between the end portion of the insulating sheet 6 extending in parallel with the axial direction of the iron core 1 and the mold resin 7.

  Here, the crack means that a crack is formed in the molded mold resin 7, and the thermal stress is an internal force generated when a thermal change is applied to the constrained object. In the case of an unconstrained object, it freely expands or contracts when a thermal change is applied. However, when the object is constrained, thermal stress is generated to prevent this deformation.

  Therefore, in order to suppress the above-described cracks, Example 1 is intended to reduce thermal stress. The details will be described below with reference to FIG.

  As shown in FIG. 2, in this embodiment, the end of the insulating sheet 6 that is not in contact with the winding conductor 5 and extends parallel to the iron core direction from the winding conductor 5 A shaped through-hole 8 (which may be oval) is provided. By providing the through hole 8 at the end of the insulating sheet 6, the through hole 8 is filled with the mold resin 7, and the thermal stress between the end of the insulating sheet 6 and the mold resin 7 is relieved. be able to.

  The present inventors conducted thermal stress analysis using stress analysis software in order to confirm the reduction in thermal stress between the end portion of the insulating sheet 6 and the mold resin 7. The thermal expansion coefficients of the winding conductor (aluminum, copper, etc.) 5, the mold resin 7 and the insulating sheet 6 were substituted into the analysis conditions.

  As a result, when the temperature history is set from 200 ° C. to 20 ° C., a through hole 8 having an arc shape is provided at the end of the insulating sheet 6, and analysis is performed by filling the through hole 8 with the mold resin 7. From the results, it was found that when the through hole 8 is provided, the thermal stress can be reduced by about 35% compared to the case where the through hole 8 is not provided.

  According to such a present Example, by providing the through-hole 8 in the insulating sheet 6 and filling the through-hole 8 with the mold resin 7, the residual thermal stress can be reduced. Cracks due to thermal stress, which is a problem in the vessel, can be suppressed. Furthermore, by suppressing cracks, it is possible to prevent moisture, dust and the like from entering the windings from the cracks, thereby preventing an insulation breakdown accident.

  FIG. 3 shows a second embodiment of the molded transformer of the present invention.

  In Example 1, the arc-shaped through-hole 8 is provided at the end of the insulating sheet 6, but in this example, the whole including the end of the insulating sheet 6, particularly the iron core axial direction of the insulating sheet 6. A plurality of through-holes 8 (which may be elliptical) are provided in the shape of a circular arc, and the plurality of through-holes 8 are filled with a mold resin 7.

  The effect of the configuration of this example is the same as that of Example 1, but in this example, a plurality of through holes 8 provided in the entire insulating sheet 6 are filled with the mold resin 7. Therefore, the thermal expansion of the insulating sheet 6 is relaxed, and cracks due to thermal stress can be further suppressed.

  FIG. 4 shows a second embodiment of the molded transformer of the present invention. The figure shows an insulating sheet 6 disposed between the winding conductors 5.

  In Example 2, a plurality of through-holes 8 having an arc shape are provided in the insulating sheet 6, but in this example, a plurality of insulating sheets (two in this example) are stacked and perforated. The insulating sheet is formed by preventing the portions (through holes) from overlapping and filling the hole with mold resin.

  In the structure of FIG. 4, the insulating sheet 6A on the side close to the iron core shown on the left side of FIG. 4 is provided with a plurality of arc-shaped through-holes 8A (may be oval) and installed on the back surface thereof. The insulating sheet 6B, that is, the insulating sheet 6B far from the iron core shown on the right side of FIG. 4 is provided with a plurality of arc-shaped through holes 8B (may be oval), and the through holes 8A and 8B are molded. The resin 7 is filled. At this time, the through holes 8A and 8B formed in the insulating sheets 6A and 6B are structured so as not to overlap each other.

  Even in the configuration of this example, the effect is the same as that of Example 2. However, in this example, the through holes 8A and 8B opened in the insulating sheets 6A and 6B do not overlap with each other. There is no need to worry about short-circuiting the winding conductor.

  FIG. 5 shows a fourth embodiment of the molded transformer of the present invention.

  In the present embodiment shown in the figure, the curvature of the winding obtained by winding any one of the insulating sheets 6 described in the above-described embodiments 1 to 3 around the axial direction of the iron core 1 as shown in FIG. This is employed in the corner portion 10 of the small primary winding 3 and secondary winding 2.

  That is, in this embodiment, the insulating sheet 6 provided with the arc-shaped through hole 8 at the axial end described in the first embodiment is used for the corner portion 10, and there is no through hole except for the corner portion 10. The primary side winding 3 and the secondary side winding 2 employ an insulating sheet.

  In addition, the insulating sheet 6 provided with a plurality of arc-shaped through-holes 8 as a whole including the axial ends described in the second embodiment, or the through-holes 8A and 8B described in the third embodiment. Insulating sheets 6A and 6B that do not overlap are used for the corner portion 10, and except for the corner portion 10, the insulating sheet 6 provided with the arc-shaped through-holes 8 at the axial ends described in the first embodiment is used. The primary winding 3 and the secondary winding 2 may be used.

  Even in the configuration of this embodiment, the effect is the same as that of each embodiment described above, but in this embodiment, the present invention is applied to a corner portion where stress is concentrated. The stress is relaxed, and the effect of suppressing cracks can be further expected.

  Next, an example in which at least one of Examples 1 to 3 is applied to produce a mold transformer will be described with reference to FIG.

  FIG. 6 shows a molded transformer in which this embodiment is adopted. As shown in the figure, the insulating sheet of any of Examples 1 to 3 is wound around the primary side winding 3 that is manufactured by winding the insulating sheet of any of Examples 1 to 3 between the winding conductors. After the secondary winding 2 is arranged, the iron core 1 is arranged inside the secondary winding 2 to constitute a molded transformer.

  The molded transformer has a tap for connecting the primary power supply to the terminal connection fitting 11 on the winding start side of the primary winding 3, and a winding connection bar 12 to the terminal connection fitting on the winding end side. A tap connection bar 14 is connected to each switching terminal 13.

  Since the molded transformer produced in this manner uses the insulating sheet of any one of Examples 1 to 3, it is possible to provide a molded transformer that has both maintenance of insulation performance and reduction of thermal stress. It became possible.

  Note that the molded winding to which the insulating sheets of Examples 1 to 3 are applied may be only the primary side winding 3 or only the secondary side winding 2. Moreover, although each Example mentioned above demonstrated by the through-hole, it does not need to be a through-hole.

  DESCRIPTION OF SYMBOLS 1 ... Iron core, 2 ... Secondary side winding, 3 ... Primary side winding, 4 ... Housing support part, 5 ... Winding conductor, 6, 6A, 6B ... Insulation sheet, 7 ... Mold resin, 8, 8A, 8B ... Through hole, 10 ... Corner, 11 ... Terminal fitting on the winding start side, 12 ... Wind connection bar, 13 ... Tap switching terminal, 14 ... Tap connection bar.

Claims (9)

An iron core, a secondary winding wound around the iron core, and a primary winding wound around the secondary winding, wherein the primary winding and the secondary winding are In a molded transformer in which an insulating sheet is disposed between layers of a plurality of wound conductors, each of which is molded integrally with a resin,
A mold transformer, wherein a hole is formed in at least a portion of the insulating sheet, and the hole is filled with the resin. The molded transformer according to claim 1,
The hole is a through hole formed in an end portion of the insulating sheet that is not in contact with the winding conductor and extends in parallel to the iron core axis direction from the winding conductor, and the through hole The mold transformer is filled with the resin. The molded transformer according to claim 1,
The hole is a plurality of through holes formed in the entire insulating sheet, and the resin is filled in the plurality of through holes. The molded transformer according to claim 3,
The insulating sheet in which the plurality of through holes are formed is formed by laminating a plurality of sheets so that the through holes do not overlap with each other, and each through hole is filled with the resin. . The molded transformer according to any one of claims 1 to 4,
The mold transformer, wherein the hole or the through hole is circular or elliptical. The molded transformer according to any one of claims 1 to 5,
The mold transformer is an organic insulating sheet. An iron core, a secondary winding wound around the iron core, and a primary winding wound around the secondary winding, wherein the primary winding and the secondary winding are In a molded transformer in which an insulating sheet is disposed between layers of a plurality of wound conductors, each of which is molded integrally with a resin,
A hole is formed in at least a part of the insulating sheet positioned at a corner portion of at least one of the primary side winding and the secondary side winding with a small curvature of the winding wound around the axial direction of the iron core. The mold transformer is characterized in that the hole is filled with the resin. The molded transformer according to claim 7,
The insulating sheet located at the corner portion is not in contact with the winding conductor, and a through hole is formed at an end portion of the insulating sheet extending in parallel to the core axis direction from the winding conductor. The molded transformer is characterized in that the insulating sheet other than the corner portion is an insulating sheet having no through hole, and the through hole is filled with the resin. The molded transformer according to claim 7,
The insulating sheet located at the corner portion has a plurality of through holes formed in the whole insulating sheet, or the insulating sheet in which the plurality of through holes are formed does not overlap the through holes. And the insulating sheet other than the corner portion is not in contact with the winding conductor and extends in parallel to the core axis direction from the winding conductor. A molded transformer having a through hole formed at an end of the insulating sheet, wherein the resin is filled in the through hole.

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