JP3673224B2 - Current transformer - Google Patents

Description

【００１３】
となる。
【００１４】
電気機器の消費電力を測定する等の目的において、その電源周波数は５０および６０Ｈｚであり、その付近の周波数帯における一般的な演算増幅器のオープンループゲインは通常１０⁵程度あるため、数１からも明らかなように、電流の変換誤差が０．０１％程度の電流トランスを比較的簡単に実現することができる。
【００１５】
もちろん、この出願の発明は以上の実施形態に限定されるものではなく、細部については様々な態様が可能である。
【００１６】
【発明の効果】
以上詳しく説明したとおり、この出願の発明によって、ホール素子を用いることなくコア磁束を能動的に零に保つことができ、それによる入出力特性の直線化改善が実現された、新しい磁束零方式の電流トランスが提供される。
【００１７】
この電流トランスは当然、ホール素子に起因する温度変動はなく、また磁気コアに対する加工も必要ないので理想的な形状の磁気回路を使用することができる。また、バイファイラ方式の巻き線を採用しているので二次巻線と三次巻線の巻数比が必ず１：１になり、簡易な巻線装置を用いてもその比率が保証され、コストダウンを図ることができる。また、安価なコア材を用いても高い変換精度を維持でき、回路構成も機械的構造も非常に単純である。これらのことから、安価に高精度な電流トランスの製造が可能となる。
【図面の簡単な説明】
【図１】この出願の発明の一実施形態を示した回路構成図である。
【図２】図１の等価回路を示した図である。[0001]
BACKGROUND OF THE INVENTION
The invention of this application relates to a current transformer. More specifically, the invention of this application relates to a new zero-flux-type current transformer capable of actively keeping the core magnetic flux at zero without using a Hall element.
[0002]
[Prior art]
Conventionally, in a current transformer, in order to linearize and improve the input / output characteristics by keeping the core magnetic flux at zero, it is often performed to detect the magnetic flux using a Hall element and keep it at zero. .
[0003]
[Problems to be solved by the invention]
However, a zero-flux current transformer using a Hall element has a large detection error due to a temperature change. Therefore, there is a problem that a complicated correction circuit is required to correct it in order to achieve high-precision detection. It was.
[0004]
In addition, since the Hall element needs to create a gap in a part or all of the core and insert it into the gap, the magnetic circuit is disturbed and a structural conversion error occurs.
[0005]
The invention of this application has been made in view of the circumstances as described above, and solves the problems of the prior art, and a new magnetic flux that can keep the core magnetic flux at zero without using a Hall element. It is an object to provide a zero-type current transformer.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the invention of this application is firstly a current transformer in which winding is performed by a bifilar system in which two electric wires are bundled with respect to a toroidal core. One is the secondary winding, the other is the tertiary winding, the secondary winding is connected to the input of the operational amplifier, the tertiary winding is connected to the output of the operational amplifier, and the voltage generated across the secondary winding Provided is a current transformer characterized in that the current flowing in the tertiary winding is controlled so that is always zero.
[0007]
Moreover, 2ndly, the primary winding is further comprised by letting the electric wire different from the said electric wire of a bifilar system winding pass through the hole of a toroidal core, or to wind to a toroidal core several times, It is further characterized by the above-mentioned. A current transformer, and third, the current transformer is further characterized in that it is of a servo type.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a circuit configuration diagram showing an embodiment of the invention of this application having the features as described above, which is a servo-type current transformer.
[0009]
In the embodiment of FIG. 1, a toroidal core, which is a donut-shaped magnetic core, is wound by a bifilar system in which two electric wires are bundled, and one and the other of the electric wires are wound in a secondary winding with a turns ratio of 1: 1. A wire 2nd and a tertiary winding 3rd are used, and the primary winding 1st is configured by penetrating a hole in the toroidal core with a separate electric wire or by being wound around the toroidal core multiple times. Then, an operational amplifier is provided, and the secondary winding 2nd is connected to the input, and the tertiary winding 3rd is connected to the output, so that the voltage generated at both ends of the secondary winding 2nd is always zero. It operates while controlling the current flowing through the winding 3rd.
[0010]
As a result, the magnetic flux induced by the current flowing in the primary winding 1st to be measured is canceled by the magnetic flux induced by the tertiary winding 3rd, and as a result, the magnetic flux inside the core is kept at zero. Further, since a current proportional to the primary current to be measured flows through the tertiary winding 3rd, the primary current can be known by measuring this current.
[0011]
Here, when the circuit of FIG. 1 is converted into an equivalent circuit, it is as shown in FIG. The transfer function by the first order approximation in FIG.
[0012]
[Expression 1]

[0013]
It becomes.
[0014]
For the purpose of measuring the power consumption of electric equipment, the power supply frequency is 50 and 60 Hz, and the open loop gain of a general operational amplifier in the frequency band in the vicinity thereof is usually about 10 ^5. As is apparent, a current transformer having a current conversion error of about 0.01% can be realized relatively easily.
[0015]
Of course, the invention of this application is not limited to the above embodiments, and various aspects are possible for details.
[0016]
【The invention's effect】
As described above in detail, the invention of this application enables the core magnetic flux to be actively maintained at zero without using a Hall element, thereby improving the linearization of input / output characteristics. A current transformer is provided.
[0017]
Naturally, this current transformer has no temperature fluctuation caused by the Hall element and does not require any processing on the magnetic core, so that an ideally shaped magnetic circuit can be used. In addition, since the bifilar winding is adopted, the turn ratio of the secondary winding and the tertiary winding is always 1: 1, and even if a simple winding device is used, the ratio is guaranteed and the cost is reduced. Can be planned. Moreover, even if an inexpensive core material is used, high conversion accuracy can be maintained, and the circuit configuration and mechanical structure are very simple. For these reasons, it is possible to manufacture a current transformer with high accuracy at low cost.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram showing an embodiment of the invention of this application.
2 is a diagram showing an equivalent circuit of FIG. 1. FIG.

Claims (3)

A current transformer in which two wires are wound on a toroidal core and wound by a bifilar method, one of the wires being a secondary winding and the other being a tertiary winding, The tertiary winding is connected to the output of the operational amplifier at the input of the operational amplifier, and the current flowing through the tertiary winding is controlled so that the voltage generated at both ends of the secondary winding is always zero. And current transformer. The current transformer according to claim 1, wherein the primary winding is configured by passing an electric wire different from the electric wire of the bifilar winding through the hole of the toroidal core or by winding the electric wire around the toroidal core a plurality of times. 3. The current transformer according to claim 1, wherein the current transformer is a servo type.

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