JPH0488615A - Manufacture of molded transformer - Google Patents

Abstract

PURPOSE:To prevent the stress added to the structure in resin by properly adjusting the pressure against the resin. CONSTITUTION:A pressure container 1 containing potting jig 6 having a built-in structure 7 is heated up using heaters 5, and as the pressure of the container 1 is transmitted to a pressure medium through the intermediary of a pressure pump 2, resin 8 is uniformly pressed through the medium 3, and the volume shrinkage corresponding to the above-mentioned pressure occurs. Also, when the resin 8 has thermosetting property, it begins to harden by heating by a heater within the suitable temperature range. The pump 2 is stopped after the stop of heating, a cover 1a is opened, and the inside of the container 1 is brought back to the normal pressure, and the resin 8 is expanded from the state of compression hardening. This expansion force acts to a structure 7 as outwardly acting force. As the application of current to the heater 5 is stopped, the resin 8 is brought back to the normal temperature and contracted by cooling. At this time, inward-acting force acts on the structure 7.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is a method for manufacturing a molded transformer having a structure in which an iron core and a coil are integrally molded, which can be applied not only to consumer use but also to industrial transformers. Regarding.

(Prior art) Generally, when manufacturing transformers, thermosetting resin is used to strengthen the insulation and improve environmental resistance of structures such as coils and iron cores, which are the components of the transformer, and to improve reliability. Molding is carried out using methods such as

(11111 to be solved by the invention) In this case, if the coil and the iron core are integrally molded with the same resin at the same time, internal stress is applied to the iron core due to curing shrinkage of the resin during molding, resulting in deterioration of the core characteristics. Due to the difference in expansion coefficient between the resin and the iron core, cracks, peeling, etc. may occur, and wire breakage may occur.To prevent this, a buffer layer must be placed around the iron core to prevent internal stress from being transmitted to the iron core. There was a problem in that it was necessary to take preventive measures such as installing

Further, even with this treatment, the problem of cracks and peeling cannot be solved, and when cracks occur, partial discharge and voltage withstand failure are caused, resulting in a lack of safety.

The present invention has been proposed in view of the above circumstances, and its purpose is to provide a molded transformer that does not cause deterioration of core properties or cracks, and does not require the above-mentioned buffer layer. The objective is to propose a manufacturing method for.

(Means for Solving the Problems) The present invention impregnates an iron core or a coil in a resin whose expansion coefficient is approximately similar to the expansion coefficient of the structure, heats the resin, applies pressure, and heats the resin. After stopping, the pressure is released and the structure is molded with resin,
The above objectives have been achieved.

(Function) In the present invention, when the resin for molding is pressurized, it contracts due to the pressurizing force, and conversely, when the pressure is released, it expands accordingly.

In addition, we focused on the fact that resin has the property of expanding when heated and contracting when heating is stopped and cooled, thereby preventing stress on structures and the occurrence of resin cranking and peeling. That is, the present invention is configured as described above, applies pressure and heat to the resin to cure it, shrinks the resin,
After that, by releasing the pressure, the cured resin is caused to expand, and when the heating is stopped, it contracts.
These contractions and 11 tensions act to cancel each other out, reducing the residual stress that acts on the structure (coils and cores), reducing the properties of the core without providing a guard layer, and preventing the resin from deteriorating. This prevents the occurrence of cracks, etc.

(Example) 1 to 3 show one embodiment of the present invention.

In these figures, (1) is a pressure vessel that has a lid (la) that can be opened and closed and whose interior can be sealed, and a pressure pump (2).
and is filled with a pressure medium (3) made of a working fluid that transmits pressure to the inside. As an example of this connection means, a mode is shown in which the pressurizing pump (2) and the lid (1a) are connected by a connecting pipe (4).
Of course, it is also possible to connect the end of the container to the container body (1b) side. Further, (5) is a heating means such as a heater, which is provided, for example, on the outer periphery of the container body (lb), and by activating the heater (5), the container body (lb) is heated.
), and thus the contents inside the container body (1) can be heated.

(6) is a case or botting jig placed inside the pressure vessel (1), and a coil or iron core tonnage structure (7) as a transformer is placed inside this potting Y odor case (6). In addition, the botting jig (6) is filled with a resin (8) for molding a structure. In this case, the structure (
As for 6), as shown in FIGS. 3(a) and 3(b), a toroidal coil having a donut-like shape will be explained as an example, but it may be other than the donut-like shape. As the resin (8), a high viscosity resin such as epoxy resin having an expansion coefficient almost similar to that of the iron core is used.

Next, a method for manufacturing a molded transformer according to the present invention will be explained.

A. Heating/pressurizing process■ The pressure vessel (1) containing the botting jig (6) having the structure (7) therein as described above is heated via the heater (5), Pressure pump (2)
When high pressure is applied through the pressure medium (3), the pressure is transmitted to the pressure medium (3) as shown by arrow A, so the resin (8) is uniformly pressurized through the pressure medium (3) and the pressure is increased accordingly. volumetric contraction occurs. In addition, in this process, the resin (8) transmits pressure to every corner of the structure (7), and the structure (7) receives pressure evenly according to Pascal's principle, so it will not break and will not break. It can be impregnated with fables.

■ Also, if the resin (8) is thermosetting, the heater (5)
Curing is started by heating at an appropriate temperature range. At this time, the resin (8) hardens and shrinks, although slightly. Although it is not constant when curing begins, the amount of resin that is reduced due to this is replenished by being constantly pressurized.

B. Pressure release/return to normal temperature process ■ After stopping heating, stop the pressurizing pump (2) and open the lid (1a) to return the inside of the pressure vessel (1) to normal pressure (1 atm). As a result, the resin (8) expands from its compressed and hardened state. This expansion force acts on the structure (7) as an outward force, as shown by arrow B.

(2) Moreover, since the electricity supply to the heater (5) is also stopped, the resin (8) is returned to room temperature (for example, 20° C. to 30° C.), thereby cooling and shrinking. At this time, as shown by arrow C, an inward force acts on the structure (7).

(2) In this process, the difference between these outward forces B and inward forces C is reduced, that is, they are canceled out, thereby eliminating stress on the structure (7).

FIG. 4 shows an example of the experimental results of the pressing force applied to the resin (8) and the rate of decrease in the inductance of the iron core at room temperature, and it was found that the inductance value of the iron core differs depending on the magnitude of the pressure.

In addition, Figure 5 shows the characteristics of inductance with respect to temperature, where a shows a case where the pressure on the resin (8) is high, b shows a case where the pressure is the lowest among the three, and a shows a case where a pressure approximately in between them is applied. The experimental results are shown below.

Considering this, it is possible to obtain a transformer with a desired inductance value by appropriately controlling pressure, temperature, etc.

(Effects of the Invention) As described above, according to the present invention, by appropriately adjusting the pressure on the resin, the contraction and expansion of the resin are made to cancel each other out, thereby causing stress applied to the structures in the resin. This has the effect of preventing deterioration of core characteristics.

In addition, since the resin used has a coefficient of expansion similar to that of the iron core, it is possible to prevent cracks and peeling, and since it is pressurized, impregnation properties are improved, and potential voids are also reduced by pressurizing. Alternatively, by dissolving it in a resin, the corona starting voltage is improved, and even structures with simple shapes as well as complex shapes can be pressurized, so they can be reliably molded.

[Brief explanation of the drawing]

Figures 1 and 2 are manufacturing process diagrams of the present invention, Figure 3 is an example of a structure used in the present invention, and Figure 4 shows the relationship between pressurizing force and inductance reduction rate based on experimental results in the present invention. The explanatory diagram, FIG. 5, shows a temperature characteristic diagram of inductance in the present invention. 1... Pressure vessel, 1a. lb...container body, 2゜3...pressure medium, 4...5...heater, 6...botting jig, 7...lI structure 8. . Lid, pressure pump, connecting pipe, resin Fig. 4 Patent applicant: Tamura Manufacturing Co., Ltd. Representative Patent attorney: Michio Takayama (and one other person) Fig. 5 Sano

Claims (1)

[Claims] Impregnating a structure such as an iron core or a coil in a resin whose expansion coefficient is approximately similar to the expansion coefficient of the structure, heating the resin and applying pressure, and releasing the pressure after stopping the heating,
A method of manufacturing a molded transformer, comprising molding the structure with resin.