JPH07230922A - High-voltage transformer for x-ray power supply and manufacture of coil for the same - Google Patents

Abstract

PURPOSE:To provide a transformer of small size for a power supply in an X-ray diagnosis system, by shortening an insulation distance in a high-voltage winding without decreasing efficiency in heat radiation at a low-voltage winding and a core. CONSTITUTION:A high-voltage winding 10 impregnated with elastic resin, and a core 2 and a low-voltage winding 11, which are not impregnated with the resin, are assembled to form a transformer. An overall body of the transformer is dipped in a cooling medium. In addition to this way, the high-voltage winding may be impregnated with an oil-resistant resin or a resin in a gel state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high voltage transformer for an X-ray power source, and more particularly to a high voltage transformer for an X-ray diagnostic apparatus power source.
In addition, the present invention relates to a high voltage transformer for an X-ray power source, which is suitable for a transformer having a large load variation range.

[0002]

2. Description of the Related Art In a transformer for high voltage generation, it is important to insulate high voltage windings and to radiate and cool low voltage windings and iron cores.
Generally, for example, as shown in Japanese Patent Laid-Open No. 4-262509, an electric wire is wound around a bobbin of a solid insulating material such as insulating paper and immersed in insulating oil to perform insulation and cooling at the same time. However, a gas insulation method has also been proposed as disclosed in, for example, Japanese Patent Publication No. 1-50091. In addition, JP-A-3-25071
As disclosed in Japanese Patent Laid-Open No. 3-250714 and Japanese Patent Laid-Open No. 3-250714, the entire transformer and winding are impregnated with a solid or gel insulator.
Filled transformers have also been proposed.

[0003]

In the high-voltage transformer for the power supply of the X-ray diagnostic apparatus, the maximum voltage is 150 kV because it is necessary to output the X-ray regardless of the capacity, and the capacity is higher than that of a general power transformer. Although it is small, the insulation distance is large, and the ratio of the space for insulation to the entire transformer is large. For this reason, the constraint of reducing the insulation distance is a major impediment to the miniaturization of transformers. Wind the wire around a bobbin of solid insulation,
In the conventional structure in which a winding insulated with insulating paper or a transformer using it is immersed in insulating oil or sealed in insulating gas, the bobbin and insulating paper itself have large dielectric strength, but gas or liquid Since the charged particles can move relatively freely in the cooling medium, a large insulation distance is required as a countermeasure against creeping dielectric breakdown along the surface of insulating paper or the like. Further, since the cooling medium flows due to heat generation of the winding, foreign matter such as metal pieces may be mixed in the high electric field portion of the high-voltage winding, resulting in dielectric breakdown.

On the other hand, in the method of insulating a transformer or winding by impregnating it with a resin, the heat radiation depends on the heat conduction of the resin, so that the heat radiation efficiency is lower than that of the method using an insulating fluid, resulting in overheating. However, there is a drawback that the transformer becomes large as a result of lowering the current density in order to prevent overheating. As a measure against this, the above-mentioned example of Japanese Patent Laid-Open No. 3-250714 proposes a method of winding a cooling duct around the winding, but there is a drawback that the structure becomes complicated. Further, when a stress such as an electromagnetic force is applied to the resin-impregnated winding, the electric wire and the resin are separated from each other, and a wedge-shaped void is generated, which may reduce the dielectric strength.

The present invention reduces the insulation distance of the high-voltage winding and reduces the size of the transformer without impairing the heat dissipation efficiency of the iron core and the low-voltage winding of the high-voltage transformer for the power source of the X-ray diagnostic apparatus. The purpose is to

[0006]

According to the present invention, a high voltage winding in which an insulating coated electric wire of a high voltage transformer for a power source of an X-ray diagnostic apparatus and an insulating paper or a polymer insulating film are combined is made of rubber or gel. A transformer was constructed by impregnating and filling it with an insulating material, and combining it with a low-voltage winding and an iron core that were not impregnated, together with a cooling medium such as mineral oil in a container. Also, the high-voltage winding is impregnated and filled with a rubber-like or gel-like insulator, and an oil-resistant resin layer is formed on the outside, which is combined with a low-voltage winding or an iron core that has not been impregnated for insulation. A transformer was constructed by putting it in a container together with a cooling medium.

[0007]

The high-voltage winding is wound in multiple layers, but the layers are insulated with insulating paper or polymer insulating film, and the voids between the electric wire and the interlayer insulator are filled with resin so that the dielectric strength is improved. improves. In addition, since the resin layer is filled between the inter-layer insulators at the winding ends, it is possible to prevent the charged particles from moving along the surface of the insulator, and to reduce the insulation distance and insulation compared to the case where no resin layer is provided. The yield strength can be improved. Then, by using a rubber-like or gel-like resin as the filling material, when the winding is subjected to thermal stress or external force, it is flexibly deformed without cracking or peeling.

The oil-resistant resin layer formed around the high-voltage winding impregnated and filled with the resin separates the internal resin from the external cooling medium and prevents the interaction between the two.

On the other hand, since the iron core and the low-voltage winding are not impregnated with resin, the heat generated by the iron loss of the iron core and the copper loss of the low-voltage winding is efficiently radiated to the surrounding cooling medium.

[0010]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of a high voltage transformer for X-ray diagnostic apparatus power supply according to the present invention. The transformer 1 has an iron core 2 and windings 3a, 3
Using b as a main component, the whole is immersed in a medium (not shown) such as mineral oil that also serves as insulation and cooling. In the configuration example of the winding 3a, as shown in the drawing, the low voltage electric wire 11 is wound around the bobbin 21, and the high voltage winding 10 wound around the bobbin 22 is arranged with a predetermined insulating layer 20 therebetween. Here, the high-voltage winding 10 according to the present invention includes the outer layer insulator 23 and the end insulators 24a and 24a.
It is impregnated and filled with a polymer resin together with b.

FIG. 2 shows details of an example of the structure of the high voltage winding 10.
Shown in. The high voltage electric wire 12 and the interlayer insulator 25 are alternately wound around the bobbin 22. An enamel-coated electric wire is often used as the high-voltage electric wire 12, and the total number of windings is usually several thousand, and in many cases, 10,000 or more. Cellulose insulating paper or a polymer film of polyethylene or polyimide is suitable for the interlayer insulator 25, and often has a multi-layer structure in which a plurality of thin strips are wound, rather than a single layer. The high-voltage electric wire 12 and the voids of the respective insulators 23, 24a, 24b, 25 are impregnated and filled with a rubber-like or gel-like polymer low cross-linking density resin 26 according to the present invention. If a mineral oil system is used as the cooling medium in which the transformer 1 is dipped, it is recommended that the low cross-linking density resin 26 has oil resistance.

Looking at the maximum voltage of the high-voltage winding of the transformer for the X-ray diagnostic apparatus power supply, one winding in the configuration example of FIG.
For example, 3a is +75 kV, the other winding 3b is -75 kV, and both are connected in series to obtain 150 kV. In miniaturizing the high voltage winding, it is necessary to secure insulation reliability corresponding to such high voltage.

Next, an example of time-current characteristics of the high voltage winding is shown in FIG. A1, A2, and A3 are photography loads in which a large current flows for a short time, but T1 is 0.1 seconds at maximum, and the interval T2 is 1
The repetition is about 4 times at maximum (about 3 times), and the current value I1 is about 1 A. On the other hand, B is a small current load for a long time, the time T3 is several minutes, and the current value I2 is about several mA. As described above, the load of the high-voltage winding has a small average effective value for a long time that controls temperature rise, but a large current of several hundred times is intermittently applied in a short time. Since the loss related to heat generation is proportional to the square of the current value, the practical temperature rise as a diagnostic device is small, but large heat generation occurs in a short time. On the other hand, since the current in the iron core and the low-voltage winding is mainly controlled by the output voltage, the generated loss does not change as much as the loss in the high-voltage winding, and the cooling efficiency can be increased and the size can be reduced.

Considering the load characteristics of the X-ray diagnostic apparatus power supply transformer as described above, in downsizing the transformer, it is important to ensure insulation of the high voltage winding and improve the cooling efficiency of the iron core and the low voltage winding. I know there is. In the present embodiment shown in FIGS. 1 and 2, the high-voltage winding 10 is impregnated and filled with the resin 26, so that the cooling efficiency is reduced, but the high-voltage winding 10 extends along the surface of the winding bobbin 22 and the interlayer insulator 25. The layer dielectric strength is improved and the insulation distance can be reduced. On the other hand, since the iron core 2 and the low-voltage electric wire 11 are directly surrounded by the cooling medium, the cooling efficiency is good and the size can be reduced. Furthermore, since the fluid cooling medium and the high-voltage electric wire 12 are separated from each other by the resin 26, it is possible to prevent foreign matter such as metal powder floating in the cooling medium from touching the high-voltage electric wire 12, and the insulation reliability is improved. improves.

By using a rubber-like or gel-like low-crosslink density resin having elasticity as a resin for impregnating and filling the high-voltage winding, load conditions peculiar to the high-voltage winding, that is, long-time low-current It can be flexibly deformed even when thermal stress due to steep heat generation due to large load fluctuations or shocking electromagnetic force is applied, such as large current flowing intermittently during the load that causes a large loss for several orders of magnitude. Therefore, there is an effect of preventing the deterioration of the insulation performance such as the occurrence of cracks in the resin layer and the peeling of the winding bobbin and the interlayer insulator from the resin layer.

Among the low cross-linking density resins, the gel-like resin has a particularly high adhesive strength, so that it also adheres well to some polymer insulating films having poor adhesiveness with general high cross-linking density resins and has a dielectric strength. Since it can be improved, there is an effect that the range of selection of the material used as the interlayer insulator is expanded.

The low-crosslink density resin 26 used in this embodiment is most preferably a silicone resin from the standpoints of high dielectric strength and environmental friendliness such as no odor and no harm.

FIG. 4 shows a modification of the present invention. Bobbin 22
Wind the high-voltage wire 12 and the interlayer insulator 25 around the
3, the end insulations 24a and 24b are provided, and the structure impregnated and filled with the low cross-linking density resin 26 is further coated with another resin 27 to form the high voltage winding 10. In this embodiment, the rubber-like or gel-like low cross-linking density resin 26 has the effect of ensuring the dielectric strength and absorbing the thermal stress and electromagnetic force applied to the high voltage wire, while the resin 27 coated on the outer periphery is the resin 26. By separating the cooling medium and the cooling medium in which the high-voltage winding 10 is immersed, there is an effect of preventing the interaction between the cooling medium and the resin. Since no thermal stress or electromagnetic force is applied to the resin 27, it is not necessary that the resin 27 is a low-crosslink density resin having elasticity. When an oil resistant resin such as an epoxy resin or an acrylic resin is used, the transformer can be immersed in a mineral oil cooling medium.

[0019]

As described above, according to the present invention, only the high-voltage winding, which has a large thermal stress and electromagnetic force due to instantaneous heat generation but has a small temperature rise for a long time, has an elastic polymer low crosslink density. The insulation distance is reduced while the reliability is ensured by impregnating and filling with resin, and the iron core and the low-voltage winding, which generate a large amount of heat, are directly immersed in the cooling medium without being impregnated with resin, so the transformer can be made smaller. Is obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a partial cross section of a high voltage transformer for an X-ray power source, which is equipped with a high voltage winding impregnated with and filled with a polymer low cross-linking density resin as an embodiment of the present invention.

FIG. 2 is a cross-sectional view of a high-voltage winding constructed by impregnating and winding a polymer low cross-linking density resin into a wound body of an electric wire and an insulator as one embodiment of the present invention.

FIG. 3 is a diagram showing an example of a time characteristic of a current flowing through a high voltage winding of a high voltage transformer for an X-ray power supply.

FIG. 4 is a high-voltage winding according to another embodiment of the present invention, in which a winding body of an electric wire and an insulator is impregnated with and filled with a polymer low cross-linking density resin, and the outer periphery thereof is further coated with another resin. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Transformer, 2 ... Iron core, 3a, 3b ... Winding, 10 ... High voltage winding, 11 ... Low voltage electric wire, 12 ... High voltage electric wire, 20 ... Insulating layer, 21,22 ... Bobbin, 23 ... Outer layer insulator, 24a ，
24b ... Edge insulator, 25 ... Interlayer insulator, 26 ... Polymer low cross-linking density resin, 27 ... Resin, A1, A2, A3, B ...
Load pattern, i, I1, I2 ... current value, t, T1, T
2, T3 ... time.

Front page continuation (72) Inventor Kazuhiro Sato 7-1-1 Omika-cho, Hitachi City, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Keinobu Hatakeyama 1-1-14 Uchikanda, Chiyoda-ku, Tokyo Hitachi Medical Co., Ltd.

Claims (8)

[Claims] 1. A transformer comprising an iron core wound with a low-voltage winding and a high-voltage winding, wherein only the high-voltage winding is impregnated and filled with a polymer low-crosslink density resin. High voltage transformer. 2. A transformer comprising an iron core wound with a low-voltage winding and a high-voltage winding, wherein only the high-voltage winding is impregnated and filled with an oil-resistant polymer low-crosslink density resin, and the high-voltage winding and the iron core And a high voltage transformer for an X-ray power source, characterized in that the low voltage winding is immersed in a mineral oil type cooling medium. 3. The transformer according to claim 1, wherein:
High voltage transformer for X-ray power supply, characterized in that the high-polymer low-crosslink density resin that impregnates and fills the high-voltage winding is a gel. 4. The transformer according to claim 1, wherein the high-voltage winding impregnated with and filled with a polymer low-crosslink density resin is further coated with another polymer resin. A high-voltage transformer for X-ray power supplies. 5. A step of winding an electric wire around an insulating bobbin,
High voltage transformer winding for X-ray power supply, which comprises a step of impregnating and filling a polymer low cross-linking density resin with this composition, and a step of applying another polymer resin to the surface of the composition. Manufacturing method. 6. A high voltage transformer for an X-ray power source, characterized in that a high voltage winding is impregnated and filled with an elastic insulating material. 7. A high-voltage transformer for an X-ray power supply, characterized in that a high-voltage winding impregnated and filled with a polymer low-crosslink density resin is incorporated into an iron core together with a low-voltage winding, and is immersed in a cooling and insulating medium. 8. A power supply device for an X-ray diagnostic apparatus, characterized in that the high voltage transformer according to claim 1 is incorporated in a circuit.