JP2004040932A - Dc high-voltage power supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DC high-voltage power supply device by which a high-DC high voltage is effectively obtained without enlarging the device. <P>SOLUTION: Rectifying circuits of one or more steps are constituted by combining capacitor units 22 and rectifying element units 21 and connected in multi-step series. One end of each of the circuits is driven by a secondary winding of a transformer 2, and a Cockcroft circuit 3 for taking out the DC high voltage from the opposite end is arranged. The height of at least the one-step rectifying circuit among the rectifying circuits is made to correspond to a shared voltage of the one-step circuit and made lower than that of the other circuit. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a DC high-voltage power supply, and more particularly to a DC high-voltage power supply capable of generating a DC high voltage of about 1000 to 5000 kV suitable for applications such as an electron beam irradiation device or a particle beam accelerator.
[0002]
[Prior art]
For example, in a thermal power plant or the like, a technique of irradiating the combustion exhaust gas with an electron beam to remove air pollutants from the combustion exhaust gas is known. In an electron beam irradiation apparatus for such a purpose, a high DC voltage of, for example, 800 kV is applied to an acceleration tube, and an electron beam is emitted into the atmosphere to irradiate combustion exhaust gas. When the irradiation target is a liquid such as water, an acceleration voltage having a transmission capability of about 1000 to 5000 kV is required.
[0003]
Such an electron beam irradiation device requires a power supply device for generating a DC high voltage of 1000 to 5000 kV, and a Cockcroft circuit is generally used as a rectifying and boosting circuit. The Cockcroft circuit is a rectifying and boosting circuit in which a capacitor and a rectifying element are combined and connected in multiple stages in series. One end of the circuit is driven by a secondary winding of a transformer, and a DC high voltage is taken out from the other end. That is, according to the Cockcroft circuit, the AC voltage formed in the secondary winding of the transformer is rectified for each half-wave, and the rectified voltages are sequentially added by a multi-stage series circuit combining a capacitor and a rectifying element. DC high voltage is extracted from the last stage.
[0004]
[Problems to be solved by the invention]
In such a Cockcroft circuit, theoretically, twice the product of the number of stages of the rectifier circuit unit in which the capacitor unit and the rectifier element unit are combined and the rectified voltage (for the peak value) of the secondary winding voltage of the transformer. DC high voltage is obtained. However, there is actually a problem that stray capacitance exists between the stages, and this stray capacitance is connected in parallel to the rectifying element, so that a theoretical high DC voltage cannot be obtained.
[0005]
The present invention has been made in view of the above-described circumstances, and has as its object to provide a DC high-voltage power supply device capable of efficiently obtaining a high DC high voltage without increasing the size of the device.
[0006]
[Means for Solving the Problems]
The DC high-voltage power supply of the present invention comprises a combination of a capacitor unit and a rectifier element unit to form a rectifier circuit of one or more stages, which are connected in multiple stages in series, and one end of which is driven by a secondary winding of a transformer, A cockcroft circuit that takes out a DC high voltage from the opposite end is provided, and the height of at least one rectifier circuit of the rectifier circuit is made lower than the height of the other rectifier circuits in accordance with the shared voltage of the rectifier circuit. Features.
[0007]
According to the present invention described above, even if the rectifier circuits in each stage have the same circuit constant, the fact that the sharing ratio of the rectified voltage decreases as going to the subsequent stage due to the influence of the stray capacitance is used in reverse. By providing an insulation design corresponding to this, the overall height of the rectifying and boosting circuit is reduced, and the cost is reduced. That is, on the input stage side connected to the secondary winding of the transformer, a height corresponding to the calculated rectified voltage per rectifier circuit is required for insulation design on the input stage side. As described above, the rectification voltage per one stage of the rectifier circuit decreases. As for the insulation design, there is a margin as it goes to the subsequent stage, so that the height of this portion per one stage of the rectifier circuit can be reduced, and the number of components connected in series for securing the withstand voltage can be reduced. Therefore, the size of the power supply as a whole can be reduced, and the number of components can be reduced to reduce the cost.
[0008]
According to the concept of the insulating design, the height of one stage of the rectifier circuit can be successively (gradually) reduced as one goes to the subsequent stage. However, it is not always preferable from the viewpoint of component standardization that the height per one stage of the rectifier circuit is continuously and continuously changed, and the above insulation design is applied only to some stages of the rectifier circuit of the multi-stage series connection. Even if applied, it is effective in reducing the overall height. Therefore, the stage in which the height of the one-stage rectifier circuit is reduced can be arranged at the stage of the DC high voltage outlet of the Cockcroft circuit or at a plurality of stages near the stage. Further, each stage of the lockcroft circuit may be divided into a plurality of groups, and the height of the rectifier circuit may be adjusted for each of the plurality of groups in accordance with the ratio of the rectified voltage.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
[0010]
FIG. 1 shows a DC high-voltage power supply device according to an embodiment of the present invention, and FIG. 2 shows a configuration example of a balanced cockcroft circuit. The power supply device is housed inside the pressure vessel 1 together with the acceleration tube 13 and includes a transformer 2, a cockcroft circuit 3, and the like. The inside of the container 1 is filled with an insulating gas such as SF ₆ gas to ensure sufficient insulation. In the Cockcroft circuit 3, a capacitor element unit C is mounted on an insulating plate 6 supported by a support post 5, and a rectifying element unit D (Cs) is connected between upper and lower stages. It is configured to be laminated. A corona shield hoop 7 made of a metal material is arranged around the insulating plate 6 to make the potential gradient around the insulating plate 6 gentle and prevent corona discharge from occurring. In addition, a corona shield cover 4 is arranged around the top DC high-voltage output section of the cockcroft circuit 3 to similarly reduce the potential gradient around the DC high-voltage section and prevent the occurrence of corona discharge.
[0011]
In the balanced Cockcroft circuit shown in FIG. 2, a rectifying element unit 21 composed of a rectifying element D and a protection resistor R connected in series with a capacitor Cs connected in parallel to the rectifying element D is provided in a cross-shaped manner. The capacitor unit 22 including the connected protective resistor r is connected to the rectifier element unit 21 to form a one-stage rectifier circuit, which is cascaded in multiple stages. That is, in the rectifier circuit of each stage, the two rectifier element units 21 and 21 are connected in a crosswise manner, and the two capacitor units 22 and 22 are connected between the connection point to the next stage and the connection point to the previous stage. 22 are connected.
[0012]
The operation of the Cockcroft circuit is such that when an AC high voltage of, for example, about 100 kV is generated in each of the secondary windings 20a and 20b of the transformer, the rectification is performed by the rectifying element units 21 and 21 for each half-wave, and the capacitors of the capacitor units 22 and 22 are turned off. The DC voltage rectified to C is charged. The DC current is supplied from the rectifying element units 21 and 21 connected in a crosswise manner to the capacitors C of the second-stage capacitor units 22 and 22 so as to add to the DC voltage stored in the first-stage capacitor C. Inflow. Therefore, in the second-stage capacitor units 22 and 22, the capacitor C is charged with the same rectified voltage as the first-stage rectified voltage. A DC voltage obtained by multiplying the number of stages N of the rectifying element units connected in series in a cross-like manner by the rectified voltage per stage is theoretically obtained at the DC voltage output terminal of the final stage.
[0013]
Here, the rectifying element unit 21 and the capacitor unit 22 are equivalently illustrated as being constituted by a single rectifying element D and a capacitor C, but actually, a large number of single rectifying elements and capacitors are used. It is a series connection aggregate. Each of the rectifiers and capacitors has a normal withstand voltage of a commercially available product. For example, by connecting several hundred individual rectifiers in series, the required withstand voltage per stage is secured.
[0014]
However, in the Cockcroft circuit, stray capacitance exists at each stage, and this stray capacitance is connected in parallel to the rectifying element, and the DC voltage per stage obtained decreases toward the subsequent stage, and as a whole, As described above, there is a problem that a theoretical DC high voltage cannot be obtained. For example, assuming that the input voltage is 3 kV, the operating frequency is 5 kHz, and the parallel stray capacitance of the rectifying element unit is 25 pF in a balanced Cockcroft circuit in which 15 stages of 0.08 μF capacitors are stacked, for example, when a DC high voltage of 3000 kV is generated. The voltage sharing of each stage is as follows. That is, 270 kV is obtained at the lowest stage, 260 kV, 250 kV, 235 kV, 225 kV, 205 kV, 195 kV, 190 kV, 185 kV, 180 kV, 175 kV, 170 kV, 165 kV as the stage rises, and about 160 kV at the top stage. .
[0015]
In such a case, if the insulation design of each stage is made the same and the design is made at the maximum voltage of 270 kV per stage, there is too much room on the subsequent stage. For this reason, the DC high-voltage power supply device of the present invention is characterized in that an insulation design corresponding to the shared voltage is performed in the latter rectifier circuit having a low voltage sharing. The insulation design of each stage may be changed in accordance with the shared voltage of each stage, but the specifications are different for each stage, which is not preferable from the viewpoint of standardization.
[0016]
For this reason, in the embodiment shown in FIG. 1, it is divided into four groups of A, B, C and D according to the voltage sharing. In the lowermost group D, the shared voltage is three stages from 270 kV to 250 kV, so that 270 kV isolation is adopted. In the next group C, since the shared voltage has four stages from 235 kV to 205 kV, 235 kV isolation is adopted. Then, since the shared voltage of the next group B is three stages from 195 kV to 185 kV, 195 kV insulation is adopted. In the uppermost group A, the shared voltage is from 180 kV to 160 kV, so that 180 kV insulation is adopted for the five stages.
[0017]
The height per each step is about 190 mm in the uppermost group A and about 240 mm in the lowermost group D. Each of the groups B and C has an intermediate value. As a result, the overall dimensions can be reduced overall.
[0018]
One rectifying element unit usually comprises several hundred rectifying elements, and it is easy to change the number of series-connected elements according to the required withstand voltage. Therefore, it is possible to reduce the number of rectifying element units connected in series in accordance with the shared voltage per stage, and to adjust the height in the height direction when there is a restriction in the length direction. Similarly, the capacitor unit is actually configured so that the required withstand voltage can be obtained with dozens of capacitor elements.However, by reducing the withstand voltage per stage, the number of required elements must be reduced. Is possible. Accordingly, by lowering the insulation design per stage, the height per stage constituting the Cockcroft circuit can be reduced, and the overall configuration can be reduced in size and size, and the number of series-connected elements can be reduced. This can reduce costs.
[0019]
In the embodiment shown in FIG. 1, an example has been described in which the withstand voltage is divided into four groups in accordance with the shared voltage of the Cockcroft circuit. However, the group to be divided is divided into two groups, and the first and second stages on the input stage side are made regular. The withstand voltage may be the withstand voltage, and the withstand voltage may be reduced with the other steps reduced, so that the height per step may be reduced and the number of components connected in series may be reduced. Conversely, the one or two stages on the output stage side of the DC high voltage may be reduced in withstand voltage corresponding to the shared voltage, so that the height is reduced and the number of series-connected components is reduced.
[0020]
Although the above description is about a balanced Cockcroft circuit, it is needless to say that the present invention can be similarly applied to other circuit types such as a symmetric Cockcroft circuit.
[0021]
It should be noted that the above-described embodiment describes one mode of the embodiment of the present invention, and it is needless to say that various modifications can be made without departing from the spirit of the present invention.
[0022]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a power supply device capable of efficiently obtaining a high DC high voltage without increasing the size.
[Brief description of the drawings]
FIG. 1A is a plan view and FIG. 1B is an elevation view showing a configuration example of a DC high-voltage power supply device according to an embodiment of the present invention.
FIG. 2 is a circuit diagram of a cockcroft circuit in FIG. 1;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 High-pressure vessel 2 Transformer 3 Cockcroft circuit 4 Corona shield cover 5 Prop 6 Insulating support plate 7 Corona shield hoop 13 Accelerator tube 21 Rectifier element unit 22 Capacitor unit

Claims (2)

A combination of a capacitor unit and a rectifier element unit constitutes a rectifier circuit of one or more stages, which are connected in series in multiple stages, one end of which is driven by a secondary winding of a transformer, and a cockcroft circuit that extracts a high DC voltage from the opposite end. Wherein the height of at least one rectifier circuit of the rectifier circuit is made lower than the heights of the other rectifier circuits in accordance with the shared voltage of the rectifier circuit. 2. The DC high-voltage power supply according to claim 1, wherein each stage of the Cockcroft circuit is divided into a plurality of groups, and the height of the rectifier circuit is adjusted for each of the plurality of groups.

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