JPH0410666Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of a primary coil in a potential transformer.

FIG. 1 shows a simplified circuit diagram of a capacitor-type potential transformer as an example of applying the present invention, in which the circuit voltage V1 is divided by the main capacitor 1 and the voltage dividing capacitor 2, and the primary voltage V2 is transferred to the transformer 3.
In addition to the primary coil 3a, 2 from the secondary coil 3b
The next voltage V3 is obtained.

Figure 2 shows a conventionally used transformer of this type.
11 is the iron core, 12 and 13 are 1
The secondary coil 14 is a secondary coil. In this way, the primary coil is usually divided into two or more pieces, and the figure shows, as an example, the case where it is divided into two pieces.

Here, the primary coils 12 and 13 each have a winding 17 on the winding core 15 using a so-called edge-folded interlayer insulating paper 16 with both ends folded back as shown in FIG. We are trying to prevent it from falling off. In addition, each primary coil is wound with an insulating plate 18 such as a press board to protect the winding.
Next, the surrounding area is covered with an insulating layer 19 formed by winding crepe paper or the like, and this insulating layer 1
The penetration dielectric strength of 9 provides insulation between the primary coils and between the primary coils and the ground, respectively.

Furthermore, an insulating plate 20 such as a press board is inserted between each primary coil and the iron core and between the primary coils to prevent misalignment between the primary coil and the iron core and between the primary coils. fixed,
A predetermined creepage distance is maintained. In addition, in order to increase the dielectric strength between the primary coils 12, 13 and the iron core 11, an insulating plate 21 with both ends bent and having a U-shaped cross section is provided, and the primary coils 12, 13 and 2 Between the next coils 14,
A cylindrical insulator 22 is provided. The secondary coil 14 is a coil wound around a winding core 15, and an insulating plate 18 is wound thereon for protection.

In this way, in the conventional structure, the dielectric strength between the end of the primary coil and the iron core is determined by the dielectric strength of the insulating layer 19 covering each primary coil and the creepage distance extended by the insulating plate 20. It is almost determined by

Therefore, in order to strengthen the dielectric strength between the primary coils 12, 13 and the iron core 11, that is, the ground, it is necessary to increase the number of turns of crepe paper or the like that constitutes the insulating layer 19 covering the primary coil to make the insulating layer thicker. The creepage distance must be increased by increasing the number of insulating plates 20 made of pressboard or the like. Moreover, since the insulating layer 19 and other layers applied to ensure this creepage distance are applied to the same thickness regardless of the magnitude of the ground voltage difference between the primary coils 12, 13 and the iron core 11, parts with a small voltage difference will be overinsulated. In addition to the growing size of transformers,
This increases the amount of labor and materials used, which causes the price to rise.

In view of the above-mentioned points, the present invention is designed to rationalize the structure of the primary coil and strengthen the ground insulation of the primary coil with less labor and materials.Examples will be described in detail below.

In the present invention, as shown in FIG. 4, the primary coil is not divided as in the conventional case, but is constituted by a single multi-layer wound primary coil 31. In addition, as shown in FIG. 5, this primary coil 31 uses insulating paper 32 coated with thermosetting adhesive on both sides in advance as interlayer insulation, and one layer is applied while winding 17 is applied on top of the winding core 33. The insulating paper 32 is inserted between each layer to form the primary coil 31.

In addition, the primary coil 31 has the windings successively reduced from both ends for each layer, so that the winding width is reduced toward the upper layer, and the cross section is made into a symmetrical trapezoidal shape as shown in the figure. The winding start of the layer is set to the low voltage side (ground potential), and the winding end of the top layer is set to the high voltage side, and the interlayer insulating paper 32 has the same width regardless of the winding width of the coil, and the height of the window 11a of the iron core 11 and the height of the window 11a of the iron core 11. The winding 17 is arranged so that the insulation distance between the winding end of the top layer, which has a high voltage to ground, and the iron core 11 is longer than that of the winding end of the first layer, which has a low voltage to ground, which is approximately the same or slightly smaller. After this, an insulating plate 34 is wound around the outside to protect the coil.

Furthermore, this primary coil is heated to an appropriate temperature,
By drying, the thermosetting adhesive of the interlayer insulating paper is cured, and the winding of the primary coil and the interlayer insulating paper are firmly integrated. Further, the secondary coil 35 has a winding 17 on a winding core 33 as in the conventional case, and a protective insulating plate 34 is wound thereon. Alternatively, winding the secondary coil using interlayer insulating paper having thermosetting layers on both sides, in the same way as the primary coil, is also effective in making the coil stronger. In addition,
A spacer such as a rectangular insulating plate (not shown) is provided between the primary coil and the secondary coil to maintain a predetermined distance.

The present invention is characterized in that the coil is constructed as described above, which provides many advantages as follows.

First, the reason why the primary coil has a trapezoidal cross section is as follows. That is, in the primary coil 31,
The first layer, which has a low ground voltage, has a wide coil width, and the iron core 1
1, but the coil width becomes narrower as the upper layer increases.At the top layer, the ground voltage is high, but the coil width is the minimum and the creepage distance with the iron core is the maximum. In this way, by making the coil winding width the widest in the first layer and the narrowest in the top layer, the space factor occupied by the core window of the primary coil is reduced compared to the conventional method with a simple rectangular cross section. It is much improved compared to the previous model, and the shape can be made smaller. In addition, the top layer, that is, the end of the coil on the high voltage side, has an obtuse angle, so the electric field is significantly relaxed, and there is no need to provide a shield for mitigating the electric field at the end of the high voltage side coil. There is no need to cover the area, and the effort of taping for this purpose is unnecessary.

Next, insulating paper coated with a thermosetting adhesive is used as interlayer insulation for the primary coil, and the adhesive is cured by heating, and the windings are firmly integrated through the interlayer insulating paper, so short-circuit currents do not occur. A sufficient effect can be obtained in preventing movement of the windings when excessive electromagnetic force is applied.

Furthermore, by keeping the width of this interlayer insulating paper constant regardless of the winding width of the coil, the distance from the winding end of the coil to the end of the insulating paper becomes longer as the upper layer of the coil, that is, the higher voltage side, becomes longer. Considering creeping insulation, the interlayer insulating paper of each layer acts as through insulation, and is useful for strengthening creeping insulation.

In addition, when looking at the primary coil as a whole, this interlayer insulating paper is wound in multiple layers, so it acts as a spacer, preventing misalignment between the primary coil and the iron core, and keeping the relative position constant. can.

As explained above, when using the present invention, without taking any special measures, (1) the dielectric strength is improved by relaxing the electric field at the end of the primary coil, and (2) the excessive electromagnetic force in the event of a secondary short circuit, etc. On the other hand, it is possible to prevent the winding from moving or falling off, (3) to strengthen the creeping insulation of the primary coil, and to make it more compact.

In addition, major effects such as reduction in material and processing costs can be obtained due to the omission of taping work and the like. Note that the present invention is not limited to capacitor-type voltage transformers, but can be applied to other wound-type voltage transformers to obtain similar effects.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing a capacitor-type voltage transformer as an application example of the present invention, Fig. 2 is a sectional view showing the structure of a conventional transformer of this type, and Fig. 3 is a circuit diagram showing the structure of a conventional transformer of this type. FIG. 4 is a cross-sectional view showing the state of the winding wire, FIG. 4 is a cross-sectional view showing an embodiment of the present invention, and FIG. 5 is a cross-sectional view showing the state of the interlayer insulating paper and the winding wire in the present invention. 11... Iron core, 11a... Window, 17... Winding wire,
31... Primary coil, 32... Insulating paper coated with thermosetting adhesive on both sides, 33... Core, 34...
Insulating plate, 35...Secondary coil.

Claims (1)

[Scope of utility model registration request] In an instrument transformer having a multilayer-wound primary coil with one end at ground potential, the primary coil is constructed using interlayer insulating paper coated with thermosetting adhesive on both sides in advance, and both ends of each layer of the winding are The width of the winding is successively reduced to form a symmetrical trapezoidal cross section, the beginning of the first layer of the winding is set to the ground potential, the end of the top layer is set to the high voltage side, and the interlayer insulating paper is connected to the winding. The insulation distance between the winding end of the top layer where the voltage to the ground is high and the potential to the ground is made longer than the end of the winding of the first layer where the voltage to the ground is low, regardless of the decrease in the line width. An instrument transformer characterized in that the coil is heated to harden the thermosetting adhesive to integrate the winding and interlayer insulating paper.