JPH0611009B2 - Resin mold coil - Google Patents

Description

TECHNICAL FIELD The present invention relates to a resin mold coil having high withstand voltage, which is suitable as a high voltage winding for an extra-high voltage power receiving transformer or the like.

[Background of the Invention]

A transformer using a resin mold coil has a smaller stray capacitance to the ground than an oil-filled transformer, so surge impedance becomes large.Therefore, an abnormally large shock voltage may occur when switching the primary side depending on the switching conditions and circuit conditions. May join transformers and threaten insulation. Especially when adopting resin mold coil for high voltage winding such as transformer for extra high power reception,
In order to have an insulation strength sufficient to withstand the above-mentioned shock voltage, the coil has to be large in size and the manufacturing cost must be increased in the conventional technology.

The prior art and its problems will be described in more detail with reference to FIGS.

In the resin molded coil 1 shown in FIGS. 1 and 2, the coil conductor 2 is wound around the interlayer insulator 3 in a multilayer solenoid form, and the winding terminals 4 and 5 are connected from the winding start end and the winding end end. Although the inner and outer circumferences of the drawn single coil are covered with resin-impregnated thin leaf insulators 6 and 7, and the coil ends are covered with a resin layer 8 to form a high voltage winding for one leg of the transformer. The resin mold coil composed of such a single coil can be used for transformers up to 6 kV class.

That is, when an impact voltage such as a switching surge is applied to such a resin mold coil, the initial potential distribution inside the coil becomes as shown by the curve A in FIG. 3, and thereafter, the potential of each part oscillates up and down. And settles into a steady potential distribution indicated by a straight line B. In this transitional period, the voltage sharing ratio between the layers near the winding start end and the winding end end (for example, between the first layer and the second layer) of the coil is between the interlayers of the coil (for example, the fourth layer and the fifth layer).
Since the voltage sharing ratio (between layers) becomes abnormally large, if an interlayer voltage in a steady state is increased, there is a possibility that dielectric breakdown will occur between layers when an impact voltage is applied. Is.

For this reason, in an extra-high voltage power receiving transformer with a high line voltage such as a 20 kV class transformer, the resin mold coil is evenly divided in the coil axis direction and sequentially connected in series to form a high voltage winding for one leg. Therefore, a method of reducing the voltage applied between the coil layers has been conventionally used. FIG. 4 shows an example in which the coil is divided into three equal parts, and the parts other than the winding terminals 4 and 5 corresponding to those in FIG. 2 are shown with the same reference numerals with subscripts a, b and c. 9, 10
Is a connecting conductor between the coils. However, even when the coils are divided in this way, due to the internal potential oscillation as described above, a higher voltage is applied between the layers close to the winding terminals 4 and 5 of the end coils 1a and 1b than the other layers, and insulation is concerned. The reliability is not enough.

As a countermeasure, as shown in FIG. 5, the end coil 1a,
The interlayer insulators 3a and 3b of 1b are made thicker than the interlayer insulator 3c of the intermediate coil 1c to reinforce the insulation. In this way, as shown in FIG. There has been a problem that the sizes of the partial coils 1a and 1b are increased and the manufacturing cost is accordingly increased.

[Object of the Invention]

An object of the present invention is to provide a small resin mold coil having high insulation strength that can withstand high-frequency shock voltage such as switching surges, high reliability, and low manufacturing cost.

[Outline of Invention]

In order to achieve this object, in the present invention, a first end coil and a second end coil each having a winding terminal, and a series connection between the first end coil and the second end coil are provided in the middle of the first end coil and the second end coil. At least one intermediate coil provided, and the first and second end coils and the intermediate coil have the same coil arrangement, and the first and second end coils have one layer. The number of turns is smaller than the number of turns per layer of the intermediate coil.

Example of Invention

 An embodiment of the present invention will be described with reference to FIG.

This embodiment is an example in which the resin mold coil is divided into three pieces, the end coils 1a and 1b and the intermediate coil 1c. The coil conductors 2a, 2b and 2c are individually sandwiched by the interlayer insulators 3a, 3b and 3c. The inner and outer peripheries of the multi-layer solenoid coil obtained by being wound on a glass fiber cloth, a thin fiber insulator 6a, 6b, 6 formed by impregnating a liquid resin such as an epoxy resin into a base material such as a polyester fiber cloth and solidifying the same.
A resin layer 8 which is covered with c, 7a, 7b, and 7c, and a coil end is solidified with liquid resin such as epoxy resin or high-viscosity putty resin.
It is made by covering with a, 8b and 8c, and the end coil 1a, 1
b and the intermediate coil 1c have the same coil arrangement. The winding terminals 4 and 5 are drawn out from the winding start end of the end coil 1a and the winding end end of the end coil 1b, and the winding end end of the end coil 1a and the winding start end of the intermediate coil 1c and the intermediate coil 1 are drawn.
The winding end of c and the winding start of the end coil 1b are connected by connecting conductors 9 and 10, respectively, to form a high voltage winding for one leg of the transformer.

The ratio of the number of windings per layer of the end coils 1a and 1b and the intermediate coil 1c depends on the required insulation strength, but as an example, different values such as 20:60:20 are selected. If the values are the same, the ratio of the number of turns of each coil is the same as above. Thus, if the number of turns per layer of the end coils 1a and 1b is made smaller than that of the middle coil 1c, FIG.
Since the voltage applied between the layers of the end coils 1a and 1b is lower than that when the coils are equally divided as shown in FIG. 5,
Even when an impact voltage is applied to the winding terminals 4 and 5, the voltage sharing ratio between the layers near the winding terminals of the end coils 1a and 1b is significantly reduced, and dielectric breakdown does not occur between the layers. Moreover, as shown in FIG. 5, the inter-layer insulators 3a and 3b of the end coil are formed.
Since it is not necessary to increase the thickness of the coil to reinforce the insulation, it is possible to increase the insulation strength without increasing the size of the coil and increasing the cost.

The number of coil divisions is not limited to three, but if the voltage applied to the coil is high, the number of divisions may be increased if necessary to reduce the interlayer voltage of the coil close to the winding terminals. The feature of the present invention is that the voltage sharing ratio between the layers near the winding terminals can be further reduced with the same number of coil divisions as compared with the case of equal division, and in this sense also the cost reduction effect is great.

Incidentally, the above-mentioned embodiment is a resin mold coil which does not require a die,
Each part coil is individually molded to ensure insulation between each part coil and the connection conductor.However, when casting is performed using a mold, each part coil is positioned via a spacer and integrated with the connection conductor. It is also possible to mold it.

7 to 9 show another embodiment of the present invention.

When the resin mold coil is configured in the coil axial direction, that is, divided into upper and lower parts, the temperature of the upper coil rises larger than that of the lower coil due to convection of the surrounding air when energized.
For example, in FIG. 6, the temperature rise of the bottom coil 1b
If the temperature is 40 ° C., the temperature rise of the uppermost coil 1a will be 100 ° C., which causes a considerable temperature difference. Therefore, it is uneconomical to increase the cost if the materials used and the current densities of the coils are uniformly determined according to the uppermost coil having a large temperature rise.

From such a viewpoint, in the embodiment of FIG. 7, the other coil 1 is used as the interlayer insulator 3'b of the lowermost coil 1b having a low temperature rise.
Cost reduction is achieved by using an inexpensive material having lower heat resistance than the interlayer insulating materials 3a and 3c of a and 1c. , And ordinary kraft paper is used as the interlayer insulator 3'b.

Similarly, in the embodiment shown in FIG. 8, the resin layer 8'b of the lowermost coil 1b is made of an inexpensive material having a lower heat resistance than the resin layers 8a and 8c of the other coils 1a and 1c to reduce the cost. For example, epoxy resin having good heat resistance is used for the resin layers 8a and 8c, and polyester resin having lower heat resistance is used for the resin layer 8'b. Further, also as a thin insulator covering the inner and outer circumference of the coil, other coil 1a other than the lowest coil,
1c is made of thin insulating material 6a, 6c, 7a, 7c made of glass fiber cloth with good heat resistance, and the lowest coil 1b is made of polyester fiber cloth with lower heat resistance. Insulators 6'b and 7'b can be used.

The embodiment shown in FIG. 9 is the bottom coil having a margin for temperature rise.
1b uses a conductor 2'b that is finer than the other coils 1a and 1c,
By increasing the current density, the coil is made smaller and the cost is reduced.

By appropriately using the various cost reduction measures shown in FIGS. 7 to 9, the cost can be further reduced and an economical resin mold coil can be obtained.

FIG. 10 is an external view of a mold transformer using a resin mold coil according to an embodiment of the present invention, in which one leg of the high voltage winding 11 is divided into the low voltage winding 12 as shown in FIG. Combined and attached to the U, V, and W legs of the iron core 13, respectively, to form a molded transformer. Therefore, if the high-voltage winding 11 is downsized, the size of the iron core 13 is also downsized, and the entire transformer can be downsized.

〔The invention's effect〕

According to the present invention, as compared with the conventional evenly-divided resin-molded coil, it is possible to further reduce the voltage sharing ratio between the layers near the winding terminals when the impact voltage is applied with the same number of coil divisions. It is possible to provide sufficient insulation strength to withstand internal potential vibrations due to shock voltage without increasing the thickness of the interlayer insulating material and increasing the high voltage of high voltage transformers. It is possible to obtain a resin mold coil which is suitable for use as a winding wire, has a smaller size, higher reliability, is easy to manufacture, and is inexpensive to manufacture.

[Brief description of drawings]

FIG. 1 is an external view of a conventional resin-molded coil consisting of a single coil, FIG. 2 is a cross-sectional view thereof, FIG. 3 is a diagram showing a potential distribution inside the coil, and FIGS. Sectional views of the divided resin mold coil, FIGS. 6 to 9 are sectional views of the coil showing an embodiment of the present invention, and FIG. 10 is a mold transformer to which the resin mold coil in one embodiment of the present invention is applied. It is an external view. 1a, 1b, 1c ... Split coils 1a, 1b ... End coils 1c ... Intermediate coils 2a, 2b, 2'b, 2c ... Coil conductors 3a, 3b, 3'b, 3c, 6a, 6b, 6'b, 6c, 7a, 7b,
7'b, 7c, 8a, 8b, 8'b, 8c ... Insulator 4, 5 ... Winding terminal 9, 10 ... Connection conductor between coils

Claims (1)

[Claims] 1. A first end coil and a second end coil each having a winding terminal, and at least one middle connected in series between the first and second end coils and the first and second end coils. Partial coil, and the first and second end coils,
The intermediate coil has the same coil arrangement,
A resin mold coil, wherein the number of turns per layer of the first and second end coils is smaller than the number of turns per layer of the intermediate coil.