JP4846194B2 - Transformer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention reduces a transition voltage between windings and protects a device connected to the other winding from a surge even if a lightning surge or a high-frequency surge intrudes into a power electronics device in one winding. About.
[0002]
[Prior art]
FIG. 10 shows a winding of a transformer having a conventional anti-contact plate. The outer winding (high-voltage side winding) 101 and the inner winding (low-voltage side winding) 102 are wound around the iron core 103, and an anti-contact plate 104 is disposed between the two windings 101, 102. ing. The anti-contact plate 104 is made of metal and grounded (see FIG. 10B). Further, the anti-contact plate 104 is formed with a one-turn prevention portion 105 so as to form one turn with respect to the magnetic flux of the iron core 103 and prevent short circuit.
[0003]
Now, the incompatibility prevention plate 104 plays a role of preventing so-called incompatibility that prevents the high-voltage side winding 101 from contacting the low-voltage side winding 102 in an insulation accident. At the time of an insulation failure of the high-voltage side winding 101, since the anti-contact plate 104 is in front of the low-voltage side winding 102, the arc does not reach the low-voltage side winding 102 and is grounded by the anti-contact plate 104. Thereby, even if an insulation accident occurs in the high-voltage side winding 101, it is possible to prevent the accident from expanding such that the potential of the low-voltage side winding 102 becomes the potential of the high-voltage side winding 101.
[0004]
In recent years, the application of power electronics equipment has been expanding. A converter, a UPS (Uninterruptible Power Supply), etc. are used for the power source, and an inverter or the like is used for the motor drive. By the way, a semiconductor switching element represented by an IGBT (Insulated Gate Bipolar Transistor) forms a main circuit of a power electronics device. The semiconductor switching element has low proof strength against overvoltage. This is due to the fact that the withstand voltage of the junction portion of the switching element is small, and sufficient consideration is necessary when using the semiconductor switching element. When a surge such as a lightning surge enters, it is necessary to attenuate the surge below the withstand voltage of the semiconductor switching element.
[0005]
If there is a transformer between the surge intrusion destination (in this case, the high voltage side) and the power electronics device (in this case, the low voltage side), the high voltage side winding 101 is connected if the transformer has the anti-contact plate 104. Since the shield is made of metal, the common mode of surge hardly transfers to the low-voltage side winding 102. Since the surge frequency is also high in the normal mode, the magnetic flux flows to the iron core 103 to the same extent as the outside of the iron core, and the coupling between the high-voltage side winding 101 and the low-voltage side winding 102 is weak. The side shift is very small.
[0006]
As described above, when the transformer has the incompatibility prevention plate 104, a surge transition that causes an overvoltage with respect to the power electronics device can be extremely reduced, and reliability can be ensured.
[0007]
In recent years, high-frequency surges generated by switching operations of power electronics equipment can propagate to the power supply line and cause various malfunctions such as instrument malfunctions. Yes.
[0008]
On the other hand, when a transformer exists between the affected devices, the propagation of high frequency surges to the affected devices can be greatly reduced by installing the anti-contact plate 104. Since the above-mentioned surge and the high-frequency surge generated from the power electronics equipment have a frequency of several tens of kHz to several MHz, the surge transition can be greatly reduced by the same principle.
[0009]
By the way, many harmonic currents and high frequency currents are generated from power electronics equipment. These current flows to the low-voltage side winding 102, thereby harmonics and high-frequency magnetic flux is generated when these are large, incompatible prevention plate 104, the size name current flows because made of metal, to be overheated is there. Dividing the winding in the stack direction in the winding of FIG. 10, the core radial component of the magnetic flux is increased and thereby, current of incompatible prevention plate 104 is further increased, easier to overheat and crossed prevention plate 104 .
[0010]
[Problems to be solved by the invention]
As countermeasures against overheating of the anti-contact plate 104, the insulation around the anti-contact plate 104 is made of high heat resistance, and a large cooling space is secured to enhance cooling performance. There was a drawback that would become larger.
[0011]
The present invention has been made in view of the above circumstances, and an object thereof is to provide a transformer that is compact and has good manufacturability while suppressing the transition of surge.
[0012]
[Means for Solving the Problems]
The transformer according to claim 1 is a resistive conductive film having a specific resistance value of 0.01 to 100 Ω · m and a film thickness of 10 to 100 μm by applying or spraying a resin filled with carbon powder on a peripheral surface of an insulating cylinder. The transition voltage prevention plate formed by applying the transition voltage prevention plate is disposed between the windings, and the resistance conductive film of the transition voltage prevention plate is grounded. The outer peripheral surface or the inner peripheral surface of the insulating cylinder is formed with a gap at both ends in the circumferential direction, and further, the inner peripheral surface or the outer peripheral surface of the insulating cylinder is formed so as to complement the gap. The overlap part is formed in the outer peripheral surface and inner peripheral surface of a cylinder, It is characterized by the above-mentioned.
According to such a configuration, the resistance conductive film of the transition voltage prevention plate has a resistance component, so that the flow of eddy current is suppressed as much as possible, and accordingly, heat resistance and cooling performance are not much considered. This eliminates the need to do this, makes it compact and improves the manufacturability.
And since the transition voltage prevention board is formed by apply | coating or spraying the resin with which carbon powder was filled to the surrounding surface of the insulation cylinder, workability is good and a reliable resistive conductive film is obtained.
Furthermore, since the resistance conductive film can be manufactured with good performance and the short-circuiting with high resistance to the commercial frequency magnetic flux of the iron core is eliminated, loss due to the resistance conductive film can be reduced.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
The first embodiment of the present invention will be described below with reference to FIGS.
As shown in FIG. 1, an outer winding 1 and an inner winding 2 are wound around an iron core 3, and a resistance conductor is provided between two cylindrical windings 1 and 2. A transition voltage prevention plate 4 is inserted. The outer winding 1 is generally a high-voltage side winding, and a surge enters from the power supply system. The inner winding 2 is generally a low voltage side winding, and there is a surge intrusion of power electronics equipment. As shown in FIG. 2, the transition voltage prevention plate 4 is formed by applying or spraying a resistive conductive film 6 over the entire outer periphery of the insulating cylinder 5, and the resistive conductive film 6 is grounded (FIG. 1B). )reference). In this case, the insulating cylinder 5 may be formed integrally with resin in a cylindrical shape, or may be formed by bending a press board into a cylindrical shape.
[0020]
There are various methods for producing the resistive conductive film 6, such as a method of filling metal particles into a resin. However, in order to apply to a transformer, it is required to manufacture a large area efficiently, to have flexibility that does not break even when the insulator is deformed, and to require high reliability. In this embodiment, as shown in FIG. 3, fine carbon powder 7 is filled in resin such as epoxy resin 8, that is, mixed well so as to be uniformly dispersed. The mixed liquid is applied to the insulating cylinder 5 by application or spraying and dried to form the resistive conductive film 6.
[0021]
The carbon powder 7 exists in a state where part of the carbon powder 7 is in contact and part of the carbon powder 7 is separated. However, if the mixing is sufficient, a specified specific resistance value is obtained. The electrical conduction mechanism is that when the carbon powder 7 is in contact with the epoxy resin 8 between the carbon powder 7, the resin layer is extremely thin, causing electrical conduction by the tunnel effect. It is considered to be decided.
[0022]
This resistance conductive film 6 has been confirmed by the inventors' experiments to maintain a specified resistance value even in a high-temperature life test, without causing peeling, and to have high reliability.
[0023]
Hereinafter, the operation and effect of the present embodiment will be described.
FIG. 4 shows a conceptual lumped constant equivalent circuit when a normal mode surge is applied to the outer winding 1. The capacitance between the outer winding 1 and the transition voltage prevention plate 4 is Cs, the capacitance between the transition voltage prevention plate 4 and the inner winding 2 is Cu, and the capacitance between the inner winding 2 and the ground is Ce. Let R be the resistance to ground of the voltage prevention plate 4. In practice, these quantities must be treated as distributed constants, but are treated as a lumped circuit for the sake of simplicity.
[0024]
When the transition voltage prevention plate 4 is not provided, the shared voltage of Ce determined by the capacitances of Cs, Cu, and Ce with respect to the high-frequency component of the surge is the transition voltage. On the other hand, when there is the transition voltage prevention plate 4, the shared voltage on the transition voltage prevention plate 4 is greatly reduced by bypassing the surge current to the ground at R in the middle stage. For this reason, the transition voltage can be greatly reduced.
[0025]
Next, let us consider the behavior of the transition voltage prevention plate 4 with respect to the magnetic flux of the commercial frequency. As described above, the harmonics and high-frequency currents generated by the power electronics equipment also generate magnetic flux in the radial direction of the iron core 3 in some cases. When this magnetic flux penetrates the transition voltage prevention plate 4, an eddy current flows so as to be linked to the magnetic flux. However, this eddy current is extremely small because the transition voltage prevention plate 4 has a resistance component. Therefore, there is almost no loss due to this harmonic.
[0026]
Therefore, transition voltage prevention plate 4 is a resistive conductor not heat generation, such as in the case of using a conventional mixing tactile prevention plate 104, it is necessary to use a heat-resistant insulating material around the transition voltage prevention plate 4 Therefore, there is no need to secure a large cooling space to enhance cooling, and a compact transformer with good manufacturability can be obtained.
[0027]
Therefore, as the configuration of the transition voltage prevention plate 4, it is desirable to form a resistive conductive film on the insulator in order to reduce the space. The film thickness of the resistive conductive film 6 for obtaining a certain resistance value in the transition voltage prevention plate 4 is required to be 10 μm or more in the inventor's experiment, and as an upper limit value that does not cause peeling or cracking. It was found to be 100 μm. Thus, from the viewpoint of reliability, the thickness of the resistive conductive film 6 needs to be in the range of 10 to 100 μm.
[0028]
On the other hand, when the specific resistance of the resistive conductive film 6 was changed in the film thickness in this range, the voltage transfer rate extremely increased when the resistivity became 100 Ω · m or more as shown in FIG. This is because in the equivalent circuit of FIG. 4, R increases and the potential of the resistive conductive film 6 increases. When the resistive conductive film 6 is formed on the entire surface in the circumferential direction of the insulating cylinder 5, the resistive conductive film 6 forms one turn with respect to the magnetic flux of the iron core 3 to form a resistance short circuit. Thereby, a commercial frequency current flows in the circumferential direction of the resistive conductive film 6. In this case, in the experiment of the inventor, if the specific resistance value of the resistive conductive film 6 is set to 0.01 Ω · m or more, the current of the commercial frequency flowing in the circumferential direction becomes as small as possible, thereby ignoring the generated loss. I knew it was possible.
[0029]
In this way, by setting the resistance conductive film 6 to a film thickness of 10 to 100 μm and a specific resistance in the range of 0.01 to 100 Ω · m, it is possible to reduce loss due to a reliable current that makes a round of the resistance conductive film 6. It can be eliminated.
[0030]
(Second embodiment)
The second embodiment of the present invention will be described below with reference to FIG.
In the second embodiment, a transition voltage prevention plate 9 which is a resistive conductor is used instead of the transition voltage prevention plate 4 of the first embodiment, and the other configurations are the same as in the first embodiment. It is the same.
[0031]
As shown in FIG. 6, the transition voltage prevention plate 9 has, for example, two unit prevention plates 10 and 11 each having resistance conductive films, particularly high resistance conductive films 10b and 11b formed on press boards 10a and 11a, for a total of four rounds. Connected in the direction. In this case, the end portions of the press boards 10a and 10a of the unit prevention plates 10 and 10 are in contact with the end portions of the high resistance conductive films 11b and 11b of the unit prevention plates 11 and 11, and thus the high resistance conductive films 10b and 10b. 11b is necessarily present in the radial direction, and a divided portion is formed in which the high-resistance conductive films 10b and 11b are not electrically contacted. The high resistance conductive films 10b and 11b are grounded.
[0032]
As a result, the high resistance conductive films 10b and 11b do not form one turn around the iron core 3 (see FIG. 1). Therefore, the lower limit value of the specific resistance of the resistance conductive film 6 described in the first embodiment is 0. There is no limit of 01Ω · m. In addition, since the unit prevention plates 10 and 11 forming the transition voltage prevention plate 9 are divided and arranged in the circumferential direction around the iron core 3, the manufacturability can be improved.
[0033]
(Third embodiment)
The third embodiment of the present invention will be described below with reference to FIG.
In the third embodiment, a transition voltage prevention plate 12 which is a resistive conductor is used in place of the transition voltage prevention plate 4 of the first embodiment, and other configurations are the same as in the first embodiment. It is the same.
[0034]
As shown in FIG. 7, the transition voltage prevention plate 12 uses a circular insulating cylinder 13 and has a resistance conductive film 14 formed on the outer peripheral surface thereof. The resistance conductive film 14 forms one turn in the circumferential direction. In order to avoid this, the end portions 14a and 14a have ends in the circumferential direction. The resistance conductive film 14, particularly the resistance conductive film 14 is interpolated between the end portions 14 a and 14 a of the resistance conductive film 14 so that the resistance conductive film 14 always exists in the radial direction on the inner peripheral surface of the insulating cylinder 13. A high resistance conductive film 15 is formed. In this case, the high resistance conductive film 15 overlaps the end portions 14 a and 14 a of the resistance conductive film 14 via the insulating cylinder 13.
[0035]
As a result, since the resistive conductive film 14 does not form one turn around the iron core 3, it is limited by the lower limit of 0.01 Ω · m of the specific resistance as in the resistive conductive film 6 described in the first embodiment. There is no.
[0036]
(Fourth embodiment)
Hereinafter, a fourth embodiment of the present invention will be described with reference to FIG.
The fourth embodiment is the same as the first embodiment except for the following configuration.
Since electric power is supplied to the outer winding 1 through the leads 16 and 16, the leads 16 and 16 pass through the upper portion of the transition voltage prevention plate 4 and the vicinity of the lower end thereof.
[0037]
Since the transition voltage prevention plate 4 has a very thin resistance conductive film 6, the electric field concentrates on the lower end portion. Therefore, in this embodiment, shields 17 and 17 are provided on the upper and lower ends of the resistive conductive film 6 to relax the electric field of the resistive conductive film 6 and improve the insulation strength. As the structure of the shield 17, for example, a metal round bar is shaped into an arc shape, and an appropriate one is selected depending on the model and capacity, and has a predetermined width dimension around the lead 16 in the circumferential direction. The shield 17 can be achieved by a structure in which one end or both ends are directly grounded, and by connecting one end or both ends to the resistive conductive film 4.
[0038]
In this way, a structure having a high voltage such as the lead 16 of the outer winding 1 can be disposed close to the transition voltage prevention plate 4, and the transformer can be made compact.
[0039]
(Fifth embodiment)
Hereinafter, a fifth embodiment of the present invention will be described with reference to FIG.
When the transition voltage prevention plate 4 is formed by applying or spraying the resistance conductive film 6 of the first embodiment to the surface of the insulating cylinder 5, the carbon powder 7 on the surface of the resistance conductive film 6 may be Some may come out with so-called stains. The carbon powder 7 is a fine particle, and even if it is slightly present in the transformer, it does not cause a serious accident such as dielectric breakdown. However, if the transformer is operated at a load exceeding its rating, such as when it is in an operating condition that is not taken into account at the time of manufacture, the amount of carbon powder 7 increases, which may be a factor that determines the service life.
[0040]
A transformer is a device that is required to be extremely high quality. Therefore, even in the unlikely event, an insulator is placed on the surface of the resistive conductive film 6 in order to prevent the carbon powder 7 from diffusing into the transformer. For example, it is formed by coating a resin film 18 on the resistive conductive film 6 as shown in FIG. Thereby, scattering of the carbon powder 7 from the resistive conductive film 6 can be prevented, and the transformer can be made more reliable.
[0041]
(Other examples)
Although the resin film is coated on the resistive conductive film 6 in the fifth embodiment, a structure in which insulating films are stacked may be used.
The transition voltage prevention plate as a resistive conductor is configured by a combination of an insulator and a resistive conductive film, but is not limited thereto, and may be configured by a resistive conductor itself having no insulator.
[0042]
【The invention's effect】
As is clear from the above description, the present invention can provide a transformer with low loss, compactness, and good manufacturability by providing a resistance conductor between windings.
[Brief description of the drawings]
FIG. 1 is an overall cross-sectional view (a) showing a first embodiment of the present invention and a cross-sectional view taken along line BB (b).
2 is an enlarged cross-sectional view of a transition voltage prevention plate. FIG. 3 is a structural diagram of a resistive conductive film. FIG. 4 is a lumped circuit diagram. FIG. 5 is a characteristic resistance-voltage transition rate characteristic diagram of a resistive conductive film. FIG. 7 is a cross-sectional view of a transition voltage preventing plate showing a second embodiment of the invention. FIG. 7 is a view corresponding to FIG. 6 showing a third embodiment of the invention. FIG. 8 is an overall view showing the fourth embodiment of the invention. Cross-sectional view (a) and cross-sectional view along line CC (b)
FIG. 9 is a view corresponding to FIG. 2 showing a fifth embodiment of the present invention. FIG. 10 is a cross-sectional view of the entire prior art and FIG.
[Explanation of symbols]
1 is an outer winding, 2 is an inner winding, 3 is an iron core, 4 is a transition voltage prevention plate (resistance conductor), 5 is an insulating cylinder, 6 is a resistance conductive film, 7 is carbon powder, 8 is an epoxy resin, 9 Is a voltage blocking plate (resistance conductor), 10 is a unit prevention plate, 10a is a press board, 10b is a high resistance conductive film, 11 is a unit prevention plate, 11a is a press board, 11b is a high resistance conductive film, and 12 is a transfer A voltage prevention plate (resistance conductor), 13 is an insulating cylinder, 14 is a resistance conductive film, 15 is a high resistance conductive film, 16 is a lead, 17 is a shield, and 18 is a resin film.

Claims (1)

Transition voltage prevention formed by applying or spraying resin filled with carbon powder on the peripheral surface of the insulating cylinder to provide a resistance conductive film having a specific resistance value of 0.01 to 100Ω · m and a film thickness of 10 to 100 μm The plate is arranged between the windings, and the resistance conductive film of the transition voltage prevention plate is grounded.
The resistance conductive film of the transition voltage prevention plate is formed on the outer peripheral surface or inner peripheral surface of the insulating cylinder with a gap at both ends in the circumferential direction, and further, the inner peripheral surface or outer peripheral surface of the insulating cylinder Further, the transformer is formed so as to complement the gap, and an overlap portion is formed on the outer peripheral surface and the inner peripheral surface of the insulating cylinder.

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