JP2000058357A - Manufacture of ac current transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a parasitic capacitance component between secondary winding terminals by making a winding method of a secondary winding part winding or bank winding, in an AC current transformer constituted of an iron core using magnetic material and the secondary winding. SOLUTION: In a secondarily converted simple equivalent circuit of an AC current transformer, a resonance circuit is constituted of the respective reactance components due to exciting inductance 6, secondary leakage inductance 8 and a paracitic capacitance 10 between secondary terminals, and the transmission characteristic becomes the resonance frequency fc[=1/2π√(LCp)], if the secondary leakage inductance value of the inductance 8 is L, and the secondary parasitic capacitance value between terminals of the paracitic capacitance 10 is Cp. As a result, frequency characteristic of the AC current transformer is improved by reducing the paracitic capacitance Cp between secondary terminals. The number of layers of a secondary winding is set as two, and capacitance Ce between layers of a part winding which is divided into (n) is sown by the formula. Accordingly the frequency characteristic of the AC current transformer is markedly improved by reducing the paracitic capacitance Ce between the secondary terminals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an AC current transformer for detecting an AC current, and more particularly to a winding method.

[0002]

FIG. 5 is a perspective view of a conventional AC current transformer for detecting an AC current. In FIG. 5, for example, an electric wire or a conductor 12 through which a current to be detected or measured flows is shown.
The winding ratio of the primary winding wound one or more turns around the iron core 13 using a magnetic material and the secondary winding 14 wound around the iron core separately from the primary winding are a: b, respectively. if,
A current having the magnitude of a / b of the current flowing through the primary winding can flow through the secondary winding. Further, by connecting the resistor 15 between the terminals of the secondary winding, the voltage can be converted into a voltage and used for a measurement signal of a current, a detection signal used for control of a power converter, and the like. In particular, when the current is large, the number of turns of the secondary winding is increased and the current transformer ratio is used as small as possible. The winding of the secondary winding in this case was conventionally a lap winding. In recent years, the switching frequency has been increasing with the progress of semiconductor switching devices, and high-performance AC transformers that can accurately detect high frequency components in measurement and control of power converters, and can detect even large currents. Sinks are needed.

[0003]

As described above, the ability to detect large currents and high-frequency components of the current has been required due to the improvement of the switching frequency and the like. The transmission characteristic of the current of the secondary winding 14 is not sufficient with respect to the flowing high-frequency component current, and when a transient response waveform is observed, phenomena such as high-frequency vibration are observed. One of the causes of this phenomenon is a capacitance component parasitic between the terminals of the secondary winding 14, and this parasitic capacitance component is one of the causes of deteriorating the frequency characteristics of the AC current transformer. Particularly, in an AC current transformer for detecting a large current, the number of turns of the secondary winding 14 is large, and furthermore, since the secondary winding 14 is wound in a lap winding, a parasitic capacitance component between the secondary winding terminals becomes extremely large. The frequency characteristics are significantly worse.

Also, the phase of the secondary winding current or the detection signal converted to voltage by the resistor 15 may be shifted with respect to the current flowing to the primary side, so that the voltage is changed by the resistor 15 connected across the secondary terminal. A method of improving the characteristics by phase compensation etc. of the converted signal is also used, but in this case, the frequency band that can be used around the phase compensated frequency band is limited, so it can be used in a wide range from low to high frequencies. May not be used. In addition, the number of circuit components of the AC current transformer increases, which leads to an increase in the cost of the AC current transformer, and further requires circuit adjustment. The present invention has been made in view of the above points, and an object of the present invention is to provide a method for manufacturing an AC current transformer that solves these problems.

[0005]

In order to achieve the object, a secondary winding is divided or wound in an AC current transformer composed of an iron core using a magnetic material and a secondary winding. A method of manufacturing an AC current transformer capable of detecting a large current and a current from a low frequency range to a high frequency range by minimizing a parasitic component between terminals of the secondary winding by bank winding to minimize the parasitic component. is there. That is, it is composed of an iron core using a magnetic material in which an electric wire or a conductor through which a current flows is wound one or more turns, and a secondary winding which is divided or bank-wound.

The effect of this is that in a secondary winding wound around a magnetic material, the secondary winding is divided or bank-wound to form a parasitic component between the secondary winding terminals. And a wide operating frequency band from low frequency to high frequency can be realized. In addition, since it is constituted only by the iron core and the secondary winding, there is no need to adjust a phase compensation circuit and the like, and a simple and highly reliable AC current transformer can be realized. Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a main part of an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an electric wire or conductor through which a main current flows, 2 denotes an iron core made of a magnetic material, and 3 denotes a core. The next winding 4 is a resistor. This will be further described with reference to FIGS. FIG. 2 is a simplified equivalent circuit diagram of the AC current transformer of FIG. 1 converted into a second order, 5 is a current source converted into a second order, 6 is an exciting inductance, 7 is an iron loss resistance, 8
Is a secondary leakage inductance, 9 is a secondary winding resistance, and 10 is a parasitic capacitance between secondary terminals. FIGS. 3A and 3B are explanatory diagrams for explaining a winding method of the secondary winding. FIG. 3A is an explanatory diagram of a lap winding, FIG. 3B is an explanatory diagram of a divided winding, and FIG. 3a, 3b and 3c are secondary windings. FIG. 4 is an explanatory diagram shown for explaining the interlayer distribution capacitance.

In FIG. 2, excitation inductances 6, 2
It can be seen that the resonance circuit is constituted by the reactance components due to the leakage inductance 8 and the parasitic capacitance 10 between the secondary terminals. When the frequency is relatively low, such as a commercial frequency, the impedance of the component of the parasitic capacitance 10 is high and does not significantly affect the transmission characteristics. However, in the high frequency region, the excitation inductance 6 has a sufficiently large impedance and can be ignored. On the other hand, the parasitic capacitance 10 adversely affects the transmission characteristics, and the inductance 8 and the parasitic capacitance 10 form a resonance circuit. 2 of 8
If the secondary leakage inductance value is L and the parasitic capacitance value between the secondary terminals of the parasitic capacitance 10 is Cp, the resonance frequency fc (= 1 /
2π√ (LCp)). Therefore, the frequency characteristic of the AC current transformer is greatly improved by minimizing the parasitic capacitance between the secondary terminals.

Since the parasitic capacitance 10 between the secondary terminals at a high frequency varies depending on the shape of each current transformer, it is difficult to perform an analysis using a simple equation. However, although the parasitic capacitance 10 between the secondary terminals in FIG. 2 represents the parasitic capacitance due to various factors as a lumped constant, the following can be considered as the parasitic capacitance between the secondary terminals of the current transformer.

(1) Inter-turn capacitance (2) Interlayer capacitance (1) is a distributed capacitance between adjacent windings and is a geometric capacitance component determined by the winding length and the wire size of the windings. The capacitance between the lines is small enough to be ignored. Since the interlayer capacitance of (2) accounts for most of the parasitic capacitance between the secondary terminals, the interlayer capacitance is reduced by focusing on the interlayer capacitance.
Can be greatly reduced. For example, when the number of turns of the secondary winding is large, it is necessary to wind the winding in multiple layers. The interlayer capacitance is a parasitic capacitance component between two adjacent layers as shown in FIG. In the following, the interlayer capacitance will be considered. However, since this parasitic capacitance component also changes depending on the geometric factors of the winding and the material of the insulating coating used for the electric wire, a clear analysis is difficult. Therefore, FIG.
It is assumed that the interlayer capacitance Ce of a coil composed of two adjacent layers as shown in FIG. Considering a minute part dx at a distance x measured from a point where one end of the winding moves to another layer, the equivalent length at the distance x is given assuming that the length of the layer is ι and the capacitance per unit length is C. The capacity is indicated as:

[0011]

(Equation 1)

Therefore, by dividing and winding the windings as shown in FIG. 3B, the interlayer capacitance generated in each of the divided windings is reduced, which is equivalent to being connected in series, and thus parasitic. The interlayer capacitance can be greatly reduced. For example, as shown in FIG. 4B, if the number of layers is two and the parasitic capacitance component between the divided windings can be ignored, the interlayer capacitance obtained by the above equation (3) is divided into n. The layer length of each divided winding can be reduced to 1 / n. Since n interlayer capacitors are connected in series, the interlayer capacitance of the divided winding is represented as follows.

[0013]

(Equation 2)

From this equation, the interlayer capacitance can be greatly reduced. Further, as can be seen from the formulas (5) and (6), the interlayer capacity is further reduced by increasing the number of layers. Thus, the distributed capacitance parasitic between the layers can be greatly reduced. That is, by applying this winding method to the secondary winding, the parasitic capacitance 10 between the secondary terminals can be reduced, so that the transmission characteristics of the current transformer can be greatly improved. In addition, the current transformer is more effective for a current transformer requiring a smaller current transformer ratio. Although the split winding has been described as an example, the bank winding of FIG. 3C can also effectively reduce the parasitic capacitance 10 between the secondary winding terminals. Although the toroidal core is used as an example in the configuration diagram of FIG. 1, the present invention is not limited to this, and the winding method of the secondary winding of the present invention can be applied to other types of iron cores.

[0015]

As described above, according to the present invention, the following effects can be obtained. (A) An AC current transformer having transmission characteristics in a wide frequency band can be realized. (B) A highly reliable current transformer composed of few components can be realized.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an embodiment of the present invention.

FIG. 2 is a simplified equivalent circuit illustrating electrical characteristics of the AC current transformer of FIG.

FIG. 3 is an explanatory diagram showing a winding method of a secondary winding of FIG. 1;

FIG. 4 is an explanatory diagram relating to an interlayer capacitance parasitic on a winding;

FIG. 5 is an explanatory diagram showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric wire or conductor 2 Iron core 3 Secondary winding 4 Resistance 5 Current source 6 Excitation inductance 7 Iron loss resistance 8 Secondary leakage inductance 9 Secondary winding resistance 10 Secondary terminal parasitic capacitance 12 Primary winding 13 Iron core 14 2 Secondary winding 15 Resistance L Secondary leakage inductance value Cp Parasitic capacitance value between secondary terminals ι Layer length x Distance measured from the point where the winding moves to another layer dx Small length Ce Interlayer capacitance P terminal N terminal n Number of winding divisions 3a Secondary winding 3b Secondary winding 3c Secondary winding

Claims (1)

[Claims] In an AC current transformer including an iron core using a magnetic material as a material for detecting an AC current and a secondary winding, a winding method of a secondary winding wound around the iron core is divided. A method for manufacturing an AC current transformer, wherein the AC current transformer is wound or bank wound.