JPS63243765A - Current detector - Google Patents

Abstract

PURPOSE:To obtain a small-sized inexpensive current detector having extremely high accuracy, by generating a pulse signal in the detection coil of a magnetism- sensitive element at the point of time when the next positive magnetic field acts when the negative magnetic field due to a current to the detected is larger than a bias magnetic field. CONSTITUTION:At first, a constant bias magnetic field HDC is always allowed to act on a magnetism-sensitive element 1. Herein, when the external magnetic field HAC generated by the AC current I to be detected flowing to an exciting coil 3 is smaller than the absolute value of the max. peak value thereof, any special phenomenon is not generated in the element 1. However, when the magnetic field HAC larger than HDC acts, at first, a negative magnetic field HR acts on the element 1 and a part low in coercive force is transformed in a negative direction and again reversed in a positive direction by a positive magnetic field HS acting in succession. This transformation speed is especially rapid. Therefore, since a steep pulse signal VS is induced in a detection coil 2 at the point of time when a limit magnetic field HL necessary for generating transformation acts, by detecting the signal VS, it is discriminated that the prescribed current to be detected is supplied.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a current detector using a magnetically sensitive element made of a specially treated composite magnetic material.

First, an overview of the magnetically sensitive element used in the present invention will be explained.

For example, a wire-shaped ferromagnetic material processed by applying external stress such as twisting has uniaxial magnetic anisotropy in the direction of the wire, and has a thick part with relatively zero magnetic force near the wire core. It becomes a composite magnetic material having a portion with a small coercive force in the outer peripheral portion adjacent to this. Alternatively, a composite magnetic material obtained by laminating a plurality of magnetic layers having different magnetic properties and processing to have uniaxial magnetic anisotropy has the following specificity as a magnetically sensitive element used in the present invention.

In other words, it is possible to shift only the magnetization direction of the portion of the magnetically sensitive element with a relatively small coercive force to either the positive direction or the negative direction in response to the direction of action of the external magnetic field, and furthermore, the transposition speed at that time is equal to the coercive force. It has a unique property that it is particularly rapid in the direction of magnetization in the adjacent region where the magnetization is large.

Therefore, based on the magnetic flux change caused by the rapid dislocation at this time, a steep pulse signal can be induced in the detection coil attached to the magnetic sensing element.

Therefore, by configuring the external magnetic field to interlink negative and positive magnetic fields caused by alternating current and detecting the triggering point of the pulse signal, it becomes possible to detect the current at that time.

However, in a composite magnetic material such as a magnetosensitive element, the magnitude of the external magnetic field for inducing the pulse signal depends on the prior history of how the part with a large coercive force has been magnetized in advance. That is, the alternating current value may not always be constant. Although this is an inevitable phenomenon based on magnetic hysteresis characteristics, some kind of correction means is required in order to use it as a current detector.

On the other hand, the current detector of the present invention has succeeded in achieving this by a simple means as described below. In other words, the outline is that a bias magnetic field of a relatively small constant magnitude that magnetizes the part of the magnetosensitive element with a small coercive force in the positive direction is constantly applied, and a negative When the magnetic field is larger than the bias magnetic field, a pulse signal is generated in the detection coil attached to the magnetically sensitive element at the time of application of the next positive magnetic field.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a basic configuration example, where 1 is the aforementioned magnetic sensing element, and 2 is a detection coil attached to it (for example, wound around it or placed nearby). Further, 3 is an excitation coil that generates an external magnetic field using the AC detected current (2). Reference numeral 4 denotes a bias magnetic field generating coil for always magnetizing only the portion of the magnetically sensitive element 1 with a small coercive force in the positive direction, and 5 is a DC power source thereof.

The operation and effect will be explained based on the time chart illustrated in FIG. 2 as follows. A constant bias magnetic field (Dc) is always applied to the magnetic sensing element 1 in the positive direction as shown by the dotted line 6.

When the absolute value of the maximum peak value is smaller than H[IC, the external magnetic field HAC generated by the AC detected current I flowing through the excitation coil 3 is indicated by the dotted line in Figure (a) -Hpc, the solid line As shown in the composite magnetic field (HDC+HAC
) are all positive magnetic fields, so no special phenomenon occurs in the magnetically sensitive element 1.

However, as shown in (b) in the same figure, when an external magnetic field (ae) (in this case, the absolute value of the maximum peak value is larger than HDC) generated by the detected current () acts, the magnetically sensitive element 1
The composite magnetic field (HDC+HAC) shown by the solid line acts on the .

That is, first, a negative magnetic field H11 acts on the magnetically sensitive element 1, and only the portion with a small coercive force is transposed in the negative direction. This portion of small coercive force is affected by the subsequently acting positive magnetic field 1 (s
is reversed again in the positive direction. However, in this case, since the magnetization is directed in the same positive direction as that of the adjacent portion having a large coercive force, the dislocation speed is particularly rapid as described above.

Therefore, at the time when the critical magnetic field HL required to cause a dislocation acts, a steep pulse signal Vs is induced at both ends of the detection coil 2, as shown in the lower part of the figure. It can be seen that the detected current that had been set has been applied.

In the above embodiments, a direct current was used as a means for constantly applying a constant bias magnetic field, but an effect exactly similar to this effect can be obtained near the magnetically sensitive element 10, as illustrated in FIG. It can also be obtained by arranging permanent magnets 7.

Note that when the current detector of the present invention is installed at the end of an actual wiring, it may be necessary to check whether it is in a normal operating state.

In such a case, for example, as shown in the same figure, a permanent magnet 8 that acts as a positive magnetic field is added, and a closed magnetic circuit compensator 9 (shown with diagonal lines in the diagram), which is normally in contact with the permanent magnet 8, is added. )
are pulled apart using the operating fitting 10 (or push button, etc.). At this time, since the positive magnetic field of the permanent magnet 8 acts on the magnetic sensing element 1, a pulse signal Vs is induced, and by detecting this signal, it can be confirmed that the device is in a normal operating state. In addition to this, an excitation coil for checking (
It is also possible to apply a method such as a method in which a magnetic field (not shown) is installed and a magnetic field is generated by energizing the magnetic field based on a remote command.

Next, as illustrated in FIG. 4, wires or devices that carry large currents, such as the power cable 11, are connected by terminals 12 inside the switchboard, and secondary currents l through the current transformer core 13 are connected. By energizing the excitation coil 14, the same magnetizing effect as described above may be applied to the magnetic sensing element 1.

r is an excitation current adjustment resistor.

In this case as well, it goes without saying that if the pulse signal Vs is generated in the detection coil 2 at the limited current value of the power cable 11, for example, the effect as a current detector can be obtained.

Therefore, in each of the embodiments described above, if the predefined detection current is made to correspond to the limited current of the line, it is possible to operate the overcurrent detector with extremely high accuracy.

As described above, the current detector of the present invention has a relatively simple and compact structure, can set a prescribed current as desired, and operates extremely accurately. Moreover, since it can be provided at a low cost, it can be used as a sensor for various loads at the end portions of a large number of wirings.

Therefore, the pulse signal from a sensor placed so that it can be detected from a large number of loads distributed over a wide area is converted into an optical signal,
It can be used in a variety of ways, such as by configuring an optical fiber cable network for centralized monitoring and control.

[Brief explanation of drawings]

1, 3, and 4 are examples showing the configuration of the current detector of the present invention, and FIG. 2 is an example of a time chart of the working magnetic field and pulse signal to explain the operation. be. 1: Magnetic sensing element, 2: Detection coil, 3: Excitation coil, 4: Bias magnetic field generation 5: DC power supply,
Coil, 6: Bias magnetic field, 7.8: Permanent magnet, 9: Compensator, 11: Electric cable, 12: Terminal,
13: Iron core, 14: Excitation coil

Claims (1)

[Claims] A constant bias magnetic field that magnetizes only the part with small coercive force in the positive direction is constantly applied to the magnetosensitive element made of a composite magnetic material with uniaxial magnetic anisotropy, and this is linked. Current detection characterized in that, when a negative magnetic field caused by an alternating current to be detected is larger than the bias magnetic field, a pulse signal is generated in a detection coil attached to the magnetically sensitive element at the time of application of the next positive magnetic field. vessel