JPS5974614A - Surface shielding type molded transformer - Google Patents

Abstract

PURPOSE:To suppress a discharge between a resin layer and a shield layer by a method wherein the shield layer formed on the surface of an insulation resin layer is composed of a high conductivity part and a low conductivity part and the low conductivity part is provided to an edge portion of the shield. CONSTITUTION:A masking tape is stuck to an end surface 13, a terminal part 12 and an edge portion 7a of a circumference surface, adjacent to them, of a molded coil 11 and a high conductivity metal film is adhered closely to the outside surface of the coil by a melted metal spray and a central portion 7a of a shield layer 7 is formed. After the central portion 7a is hardened, the masking tape on the edge portion 7b is removed and a masking tape is stuck to the surface of the central portion 7a. At this stage, a low conductivity metal film is adhered closely by the melted metal spray. After the edge portion 7b is hardened, all masking tape is removed. A surface shielded molded coil thus composed is combined with a core to compose a molded transformer and an earth terminal 8b is grounded by a lead wire 9. The potential gradient is relieved and a discharge is suppressed.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a molded transformer in which a shield is formed so that it is safe even if a human body touches the surface of the molded coil during energization, and in particular, it relates to a molded transformer in which a shield layer and a resin layer are formed. Regarding the shield layer structure with total relaxation of the electric field between.

[Prior art]

The surface of the molded coil is covered with an insulating resin layer, but because of the capacitance that exists between the resin layer and the ground, it is generally applied to a 7- to 9-volt transformer.
The surface of the coil has a very high potential and there is a risk of electric shock if touched. As a countermeasure, a shield layer made of a thermally sprayed metal coating of aluminum, zinc, etc., which has good close contact with the resin layer and is chemically stable, is provided on the surface of the resin layer except for the area around the terminals of the molded coil. It is possible to ground the layer.

Figures 1 to 3 show this surface shield type molded transformer, where 1 is the iron core, 2 is the FC upper mold coil combined with this, 2' is the terminal part, 3 is the coil conductor, and 4 is the insulation. Resin layer, 5 and 6 are coil terminals provided in the terminal part 2', 7 is a shield layer consisting of a metal sprayed coating that is broken on the surface of the insulating resin layer 4 except for the periphery of these terminal parts, and 8 is for grounding. It is a ground wire that is lucidly connected to terminal fittings, and the other end of the ground wire 9 is connected to an iron core fastener 10 or the like which is at earth potential, and the shield layer 7 is grounded.

Such a surface shield type transformer is constructed so that the shield layer 7 has a high conductivity throughout and has a potential equal to 7-s.

However, in this structure, one of the shield layers 7 is at a potential of 71, and the surface of the other insulating resin layer is 2'.
4' is at a high potential, and the edge 7' of the shield layer 7 has a sharp shape, so the potential between the resin layer and the shield layer changes rapidly and the electric field concentrates. K becomes. Therefore, there is a risk that a discharge may occur between the two through the air.
In particular, in the terminal portion 2', high voltage is applied to the terminals 5 and 6, so discharge is likely to occur between the terminal and the shield layer 1. When a discharge actually occurs, not only does the resin layer deteriorate, but this discharge current≠2 flows to the ground via the ground terminal 8, which can cause problems with other equipment and equipment, such as communication problems due to corrosion and noise. There is a risk of it happening.

In addition, since the molded coil has a large ground capacitance,
The current to charge this capacity will also flow to the ground, which may cause the above-mentioned trouble +1. There is.

[Purpose of the invention]

An object of the present invention is to provide a surface shield type molded transformer in which the electric field strength between a resin layer and a shield layer is reduced.

[Summary of the invention]

In order to achieve the above object, in the present invention, the shield layer is formed of a central portion consisting of a highly conductive four-electrode film, and this [Results of the Invention b]
Example] The present invention will be described in detail below with reference to the drawings.

In FIGS. 4 to 6, parts that are the same as those of the conventional example are designated by the same reference numerals. Various methods can be considered for forming the shield layer 7 on the surface of the resin layer of the molded coil, such as applying a conductive paint, plating, thermal spraying, etc. Here, conductive thermal spraying will be described as an example.

In the figure, masking tape is pasted on the surface of the resin layer of the molded coil where the molded coil is not provided. Specifically, these are the end face 13 of the molded coil 11 shown in FIG. 4, the terminal part 12, and the edge of the outer circumferential surface of the coil adjacent thereto (portion 7b, which will be described later). In this state, metal spraying equipment #
Spray metal onto the outer surface of the coil to a thickness of 20 to 200 mm.
A high conductivity metal film of approximately μm is formed in close contact to form the central portion 7a of the shield layer 7. After this central portion 7a has hardened, the gate masking tape at a portion 7b (described below) adjacent to the central portion 7aK is peeled off, and masking tape is pasted on the surface of the central portion 7a. In this state, a low conductivity metal is sprayed using a metal spraying device to a thickness of 20 to 200 μm in the same manner as above.
The edge portion 7b of the shield layer is formed by closely molding a solenoid film on the resin surface. This edge 7'M: Peel off the masking tape after it hardens. 7 for a 2μ body with high conductivity! Examples of reminium-zinc compounds with low 4-electricity include nichrome, tungsten, varnish, iron, etc.

If the center part 7a of the shield layer and the green part 7"O border overlap, it is possible to make a complete electrical connection between them. 8b is a grounding terminal, and connect it to either of the center part 1a and the edge 7b. However, in the actual example, the resin surface VCjl, which will become the edge 7b, is injected in advance before the metal is sprayed, and a low-conductivity metal is thermally sprayed on top of the resin surface VCjl, so that it is electrically connected to the edge 7b. I feel delusional.

The molded coil Q with a surface shield constructed as described above is combined with the iron core 1 to form a molded transformer in the same manner as shown in FIG. In this usage condition, the mold □□□
As mentioned above, a considerable suppressing voltage 71 is induced on the surface of the fat layer. According to the configuration of the above-mentioned actual example, the edge 7b at the circumferential edge of the shield layer is formed of a low conductivity metal, so the potential difference between the key point, the terminal 8b, and the surface of the resin layer is the ground terminal 8b-
The voltage is shared between the edge 7b and the edge 7b-resin surface, and the potential difference between the valleys becomes small.

Note that the ground terminal 81) &'i is made of a metal with high conductivity. This is the same even if the ground terminal 8b is connected to the central portion 7aVc.

Therefore, the electric potential gradient between the latter, that is, the edge 7b of the shield layer and the resin surface becomes gentle, and even if they are exposed to air with relatively low insulation strength, a discharge between them will not occur. <7'eru. Also between the terminals 5 and 6 and the shield layer 7, electric field concentration does not occur for the same reason as mentioned above, and the discharge I/bar occurs.

In this example, the ground terminal 8b-; the edge 7b of the shield layer
Since the current flowing from the shield layer to the ground terminal due to the large capacitance of the molded resin coil is limited by this edge 7b, there is little interference with other equipment/equipment ( Become.

In addition, in the area of the edge 7b, the farther from the 1st production area Mizushi becomes the crop resistance and can share the potential H+i1 slope.For example, when the terminal 5 is used as a high potential terminal, this terminal 5
The discharge between the terminal 5 and the shield layer can be reduced by not bringing the lacquered terminal 8b too close to the terminal 5.

If the above practical example is shown as an electric circuit, it will be as shown in Fig. 7. That is, the capacitance formed by the coil wire 3 and the central part 7a of the shield layer, which are connected to the terminals 5 and 6, is defined as the capacitor C1, and the capacitance formed by the coil wire and the edge 7b is defined as the capacitor C1. Let it be the capacitor C2. A molded resin layer 4 is interposed between these capacitor+electronic spaces. From this figure, it can be seen that the electric potential between the shield layer and the surface of the molded resin layer (12, 14) becomes loose due to the edge 7b of the shield layer, and the charging current of the capacitor c1 is limited. The parts that are actually touched are parts 7a and 7b, and the conductivity of 7b should be determined so that there is a potential difference between these parts and the ground terminal so that a person at high altitude will not receive an electric shock.

Figure 8 shows other examples of historical sites. This actual reward example is the previous fruit” sleeve 1
The edge of the shield layer is composed of a first edge 7b' and a second edge 7C having different conductivities, and the 71st edge 7b' is the second edge 7b'.
The conductivity is set higher than that of the edge 7C.

The center portion 7a, first edge portion 7b', and second edge portion 7C are adhered to the surface of the resin layer by conductor spraying using masking tape in the same manner as in the previous example, so that the boundaries of each portion are slightly shaped. The overlapping situation of the boundaries of each part 7a, 7b', and 7C is the 9th
As shown in the figure. In this case, the outermost edge 7C
≠; Since the absolute value of thermal deformation due to the thermal expansion coefficient is large, it is better to choose a conductor that is close to the thermal expansion coefficient of the resin layer. Also, each part 7a, 7b', and 7C has a ground terminal aa@s
b.8C is electrically connected, and any terminal therein is grounded.

Let us consider a case where the terminal 8a of the central portion 7a is grounded. In this case, electric field concentration occurs in six places between the central part 7a, the edge part P, the φ1 river, the edge part C, and the resin layer. Therefore, compared to the previous practical example, the electric field burden at each concentration and Q becomes lighter, and the potential gradient between the sealing layer and the resin layer becomes gentler by that amount, and the discharge suppression 71z of both rl becomes even more effective. Become. Which grounding terminal to ground depends on the characteristics of the transformer, i.e. the ease with which discharge occurs, the magnitude of the charging current for the capacitance,
It is determined by taking into consideration all factors such as the voltage applied to the human body when the human body touches the shield layer. Note that two or more important ground terminals may be configured to be all grounded at the same time.

In the case shown in FIG. 9, the edges of each part 7a, 7b', and 7C are all defined by masking tape, so that the overlapping part of each part is formed in a step-like manner by the thickness of the film. In such a structure, each overlapped part is thicker than the other and the heat capacity increases, so heat generation and heat dissipation due to the heat cycle during use are not uniform, resulting in unbalanced expansion and contraction of the entire conductor. Peeling occurs.

An improved version of this is shown in FIG. That is, each overlapping portion t is configured to have a mutually thinner thickness.

During manufacturing, the amount of thermal spray is reduced when spraying each overlapped part, but specifically, the outlet of the thermal spray nozzle is narrowed down, or a mask etc. is installed between the thermal spray nozzle and the resin surface II to control the thermal spray amount. intervene. Furthermore, it is also conceivable to increase the thermal spraying temperature to make the thermal spray particles finer. With the above configuration, the thickness does not change in the overlapping portions of different types of conductors, so that the heat capacity≠2 is uniform throughout the shield layer, and peeling between the conductors due to heat cycles is prevented. Considering that the electric field is concentrated in the overlapping part of the conductors, this configuration has a step-like shape in this part as shown in Figure 9, but since there is no detail at the corner C, there is no Discharge can be reduced.

The one shown in FIG. 11 is the same as that shown in FIG. 10, but each conductor overlaps and each part is formed in a stepped shape, and the effect is almost the same as that in FIG. 10. The spraying order of the conductors can be reversed as shown in FIG. 12, and the conductors can also be sprayed in any order.

When constructing each conductor by thermal spraying, it becomes necessary to apply masking tape, which may make the work cumbersome if the number of types of conductors increases.

It's easy. When pasting the 4 turtle 7 degrees, it is important to avoid creating a space on the 44th surface of the pasted 44 tape and resin layer that invites electrical discharge.

[Devising the invention]

As is clear from the above description, according to the present invention, the voltage gradient between the shield layer and the surface of the insulating resin layer can be alleviated.
Since discharge during this time can be suppressed, deterioration of the molded coil resin layer and interference with other equipment due to noise and corrosion can be prevented.

[Brief explanation of drawings]

Figures 1 (a) and (b) are front and side views of a surface-shielded molded transformer, Figure 2 is a perspective view of a shielded molded coil according to the prior art, and Figure 3 is an A-A'[
4 is a perspective view of the molded coil according to the present invention, FIG. 5 is a sectional view taken along the line B-E', and FIG. 6 is a plan view thereof.
Figure 1 is its electrical equivalent circuit diagram, Figure 8 is a side view of the molded coil of the second practical example, Figure 9 is its CC' sectional view, and Figure 10 is the third practical example. 11 is a sectional view of the fourth actual example, and FIG. 12 is a sectional view of the fourth actual example. 12: Coil terminal part, 12・1+: Insulating resin layer surface, 7
: Sea I red layer, 7a: High conductivity part (center part), 7b.
7 b'・7C: Low conductivity part (edge), 8a@8b*8
c: Ground terminal. Figure 1 Figure 2 Figure Drying 3 Calculation ε Figure 10 Figure 11 Figure q121 Yu 12 [21]

Claims (1)

[Claims] 1. A surface shield constructed by combining a molded coil with an iron core, which has a shield layer on the surface of the insulating resin layer except for the periphery of the coil terminal portion, and has a ground terminal connected to this shield layer. 1. A surface shield type molded transformer, wherein the shield layer includes a high conductivity part and a low conductivity part, and the low conductivity part is arranged at an edge of the shield layer. 2. The surface shield type molded transformer according to claim 1, wherein the edge of the shield layer is an edge facing around the terminal portion. 3. The surface shield type molded transformer according to claim 1 or 2, wherein the ground terminal is electrically connected to the low conductivity portion of the shield layer. 4. The low conductivity part is made up of a plurality of parts having different conductivities, and each part is arranged from the edge to the center in descending order of conductivity. Surface shield type molded transformer as described in . 5. The surface shield type molded transformer according to claim 4, wherein the ground terminal is electrically connected to any conductive part of the low conductivity part.