JP2727882B2 - DC bias detection method of transformer and polarity determination method of DC bias - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of detecting DC bias of a transformer and a method of determining the polarity of DC bias. If the transformer is subjected to DC bias, the transformer may overheat, increase vibration noise, or adversely affect the equipment on the load side.Therefore, it may be necessary to detect DC bias for the purpose of prevention. is there. For example, in a vehicle transformer, a DC voltage may be generated due to the disconnection of a pantograph, and in a cycloconverter transformer, a DC component may be included in a load current at a specific operation frequency. In some cases, a DC voltage may be generated due to a magnetic storm or the like.

[0002]

2. Description of the Related Art FIG. 6 is a cross-sectional view showing an example of a conventional DC bias detection method, in which 4 is a steel plate tank of a transformer, 5 is a transformer core (hereinafter simply referred to as a core), 6 And 7 are a primary coil and a secondary coil wound around the iron core 5, respectively, 9 is a high-resistance non-magnetic material which is close to the iron core 5 and forms a part of the steel plate tank 4, and 8 is this high-resistance non-magnetic material. An air-core search coil placed outside the body 9. The cross section of the transformer shown in the figure is an example of a shell-type transformer in which the iron core 5 and the steel plate tank 4 are close to each other.

Next, the operation will be described. When the transformer is subjected to DC bias, the magnetic flux density of the iron core 5 is biased to one side and exceeds the saturation magnetic flux density of the iron core 5 around the peak of the magnetic flux density. At this time, the main magnetic flux to pass through the inside of the iron core 5 leaks to the outside. And reaches the steel plate tank 4. In the normal steel tank 4, most of the magnetic flux leaked from the iron core 5 is shielded by the skin effect, and almost no leakage to the outside of the tank. In the conventional example shown in FIG. 6, a part of the steel plate tank 4 close to the iron core 5 is made of a high-resistance non-magnetic material 9 such as stainless steel, for example, and the main magnetic flux leaked out of the iron core 5 due to DC bias. Is transmitted through the high resistance non-magnetic material 9 and leaks out of the tank, and is linked to the air-core search coil 8. A voltage is induced at the terminal of the air-core search coil 8 by a temporal change of the magnetic flux φ linked to the air-core search coil 8, and the voltage is induced as a signal to detect DC bias.

[0004]

The conventional DC bias detection method has the above-described configuration. In a general transformer of a steel plate tank 4, a part of the steel plate tank 4 close to the iron core 5 is raised. There is a problem that the resistive non-magnetic material 9 must be used, and the tank structure needs to be specially designed for DC bias detection.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is a general steel plate tank transformer that does not have a special tank structure for DC bias detection. An object of the present invention is to provide a DC bias detection method capable of detecting magnetism and a DC bias polarity discrimination method.

[0006]

A DC bias detection method for a transformer according to the present invention is directed to a DC bias detection unit configured by winding a search coil around a permanent magnet or a magnetic core comprising a permanent magnet and a yoke. Is installed on the outer surface of a steel plate tank close to the transformer core, and the presence or absence of a DC bias is detected from an output signal of the magnetic flux linking the search coil.

Further, according to a method of determining the polarity of DC bias of a transformer according to the present invention, a DC bias detection unit configured by winding a search coil around a permanent magnet or a magnetic core including a permanent magnet and a yoke is provided. It is installed on the outer surface of a steel plate tank close to the transformer core, and determines the polarity of the DC bias according to the pattern of the appearance order of ripples appearing in the output signal due to the linkage magnetic flux linking the search coil.

[0008]

According to the present invention, there is provided a method for detecting a DC bias of a transformer.
A magnetic circuit is composed of a permanent magnet or permanent magnet and a yoke that constitute the DC bias detection unit, and a part of the steel plate tank on the transformer side. The permeance of the magnetic circuit changes, the operating point on the demagnetization curve of the permanent magnet changes, the amount of interlinkage magnetic flux of the search coil wound therearound changes, and a voltage signal is induced at the search coil terminal. . Based on this signal, the degree of DC bias is detected. In the method for determining the polarity of the DC bias of the transformer according to the present invention, the polarity of the DC bias is determined based on the pattern of the appearance order of ripples appearing in the output signal of the search coil.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. Note that, as the transformer, a core type transformer in which an iron core and a tank are close to each other will be described as an example. FIG. 1 is a perspective view showing an example of a DC bias detecting unit according to the present invention, in which a permanent magnet 1 having a U-shaped N pole and an S pole and a search coil 3 wound therearound are shown.
It consists of. FIG. 2 is a perspective view showing another example of the DC bias detection unit, which is composed of two rod-shaped permanent magnets 1 having N poles and S poles, a yoke 2 connecting them, and a search coil 3 wound therearound. Be composed. FIG. 3 is a cross-sectional view illustrating an example in which the DC bias detection unit in FIG. 1 is installed in a steel plate tank of a transformer. In FIG. 3, 1 is a permanent magnet, 3 is a search coil, and 4 to 7 are components of a transformer to be detected.
Is a steel plate tank, 5 is an iron core, 6 is a primary coil, and 7 is a secondary coil.

Next, the DC bias detection method and the DC bias polarity determination method of the present invention will be described. As shown in FIG. 3, it is assumed that the transformer is subjected to DC bias and the magnetic flux density inside the iron core 5 is biased in the direction of a or b. At the moment when the core 5 is magnetically saturated by the magnetic polarization, the main magnetic flux leaks out of the iron core 5, and the steel plate tank 4 adjacent to the iron core 5 has the direction of the magnetic polarization a.
Or a magnetic flux flows in the direction of b. On the other hand, in the DC bias detection unit, a magnetic circuit is formed by the permanent magnet 1 and a part of the steel plate tank 4, and the permeance thereof causes the permanent magnet 1
The operating point is determined, and a DC magnetic flux based on the operating point is always flowing through the magnetic circuit, and the DC magnetic flux due to it is always linked to the search coil 3 of the detecting section. Where a or b
When the magnetic flux φ of a part of the main magnetic flux flows into the steel plate tank 4 due to the DC bias in the direction, the permeance of the magnetic circuit of the DC bias detection unit changes, and as shown in FIG. The operating point also changes in the direction of a or b. Accordingly, it changes the magnetic flux density from B ₀ in the direction of B _a or B _b.

FIG. 5 shows the change of the interlinkage magnetic flux of the search coil 3 at this time and the pattern of the output voltage signal of the search coil 3 together with the phase relationship with the transformer excitation voltage. As shown in FIG. 5, when there is no DC bias and there is no change in the permeance of the magnetic circuit of the detection unit, there is no change in the flux linkage of the search coil 3 and no output signal appears, but when the DC bias occurs in the a direction. Shows a mountain-like change in the linkage magnetic flux of the search coil 3, and a ripple appears in the output signal in the order of + and-. Further, when the magnetic flux is DC-polarized in the direction b, a valley-like change appears in the linkage magnetic flux of the search coil 3, and a ripple appears in the output signal in the order of-and +. The position of the ripple appearing in the output signal of the search coil 3 is shifted by 180 ° when the direction of the DC bias is a and b.

As described above, the DC bias can be detected, and the polarity of the bias can be determined by the pattern of the appearance order of the + and-ripples appearing as the output signal of the search coil 3.
Further, the degree of the intensity of the DC bias corresponds to the magnitude of the ripple.

[0013]

As described above, according to the DC bias detection method for a transformer according to the present invention, the DC bias bias is formed by winding a search coil around a permanent magnet or a magnetic core comprising a permanent magnet and a yoke. A magnetic detection unit is installed on the outer surface of the steel plate tank close to the transformer core, and the degree of DC bias is determined from the magnitude of the output signal due to the linkage magnetic flux that links the search coil, and the DC bias of the present invention. In the method of determining the polarity of the magnetic polarization, the polarity of the DC magnetic polarization is detected from the pattern of the appearance order of the + and-of the ripple of the output signal. If the transformer has a tank, the degree and polarity of DC bias can be easily detected. In addition, since the DC bias detection unit provided outside the steel plate tank is based on magnetic attraction, there is an effect that attachment and detachment can be easily performed.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating an example of a configuration of a DC bias detection unit.

FIG. 2 is a perspective view showing another configuration example of the DC bias detection unit.

FIG. 3 is a diagram illustrating an embodiment in which a DC bias detection unit is installed in a transformer.

FIG. 4 is a diagram showing demagnetization characteristics and operating points of a permanent magnet.

FIG. 5 is a diagram illustrating a change in linkage magnetic flux of a search coil of a DC bias detection unit and a pattern of an output voltage signal.

FIG. 6 is a diagram for explaining a conventional DC bias detection method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Permanent magnet 2 Yoke 3 Search coil 4 Steel plate coil 5 Transformer core 6 Primary coil 7 Secondary coil

Claims (2)

(57) [Claims] 1. A method for detecting DC bias of a transformer in which a primary coil and a secondary coil are wound around a transformer core in a steel plate tank, wherein the magnetic core comprises a permanent magnet or a permanent magnet and a yoke. To form a DC bias detection unit by winding a search coil, the DC bias detection unit is installed on the outer surface of the steel plate tank, and the magnetic flux leaked by the DC bias is detected by the DC bias detection unit. A DC bias detection method for a transformer, comprising: detecting a DC bias of the transformer from a magnitude of an output signal of the search coil due to a magnetic flux interlinking the search coil through an iron core. 2. A method for detecting DC bias of a transformer in which a primary coil and a secondary coil are wound around a transformer core in a steel plate tank, wherein the magnetic core comprises a permanent magnet or a permanent magnet and a yoke. A DC bias detection unit is formed by winding a search coil, and the DC bias detection unit is installed on the outer surface of the steel plate tank, and the magnetic flux leaked due to the DC bias is detected by the DC bias detection unit. Determining the polarity of the DC bias based on the pattern of the order of appearance of ripples appearing in the output signal of the search coil due to the linkage magnetic flux passing through the iron core and linking the search coil; Method.