JPH01308004A - Current detector - Google Patents

Abstract

PURPOSE:To detect small currents accurately by using a cylindrical core, a composition and heat treatment conditions of which are specified, and connecting a rectifier and a resistor in series with a high-frequency exciting coil. CONSTITUTION:An amorphous alloy, a composition of which is composed of 82.0Co-2.0Ni-4.5Fe-8.5Si-3.0B at wt.% and which is thermally treated at 170-230 deg.C and given linear magnetizing characteristics, is used as a cylindrical core 1a. A primary conductor 2a through which currents to be detected flow is passed through the control hole of the core, and an exciting coil 10 connected to a high-frequency power is wound on the thick section of the core, a rectifier 9 and a resistor 11 are connected in series with the exciting coil, and an output section 14 is connected at both ends of the resistor. Since the core is excited at all times by the voltage of the half wave of high frequency, the change of high-frequency exciting currents by currents to be detected is increased to provide a large output, thus, currents can accurate be detected even when the size of a core section is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a device for electrically non-contact detecting current using the magnetic phenomenon of an iron core.

[Conventional technology]

A current transformer is conventionally known as this type of current detection device, and FIGS. 9 and 10 are schematic diagrams for explaining its operating principle. FIG. 9 shows a cylindrical iron core 1 forming a closed magnetic path with a detected flow 1. The primary winding of the flowing conductor! 2, and when the detected current Il flows, the voltage induced in the secondary winding 3 due to changes in the magnetic flux flowing inside the iron core l causes an ammeter 4, which is a load connected to the conductor of the secondary winding 3, to This is to read the secondary current 12 flowing through the sensor. Fig. 10 is almost the same as Fig. 9, but in Fig. 10, a resistor 5 is connected to the conductor of the secondary winding 3 as a load, and the detected voltage is proportional to the secondary current i3 from the voltage across this resistor 5. The current is 1+8,
Such current transformers are mainly used in control circuits. The iron core 1 is usually made of soft magnetic material such as Fe-
Permalloy, a trade name of Ni alloy, is used.

[Problem to be solved by the invention]

However, these current transformers have the following problems that need to be solved in relation to the magnetization characteristics of the Permalloy alloy used for the iron core I. FIG. 11 shows the magnetization characteristics of this alloy, that is, the shape of the relationship curve between the magnetic field and the magnetic flux density, which has a curved portion as shown in FIG. 11 from the time of rising to reaching the saturation magnetic flux. Therefore, as shown in Figure 10, it is necessary to connect a small resistor 5 to the secondary side, which will reduce the output, so the cross-sectional area of the iron core l is increased, and the secondary winding 3
The number of turns will be increased. Therefore, an increase in the weight and dimensions of the iron core and the winding section is unavoidable.In recent years, various electric devices have become more compact due to electronicization, and as a result, the dimensions and weight of the current detection devices used in these devices have increased. This has become a problem, and reducing the size and weight of the current detection unit is an important issue, especially in control equipment that requires detection of small currents.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a small current detection device that uses a material with linear magnetization characteristics for the iron core and can accurately detect relatively small currents. shall be.

[Means to solve the problem]

To achieve the above object, the present invention has a composition of 82% by weight. OCo-2. ONi-4,5Fe-8,5
5i-3.0B, heat-treated at 170 to 230°C to make the magnetization characteristic linear, is used as the cylindrical core, and the primary conductor through which the current to be detected flows is passed through the center hole of the core. A magnetic dynamic coil connected to a high frequency power source is wound around the thick part, a rectifier and a resistor are connected in series to the magnetic dynamic coil, and an output section is connected to both ends of this resistor.

(Function) The current detection device of the present invention is constructed as described above, in which a half-wave voltage is applied from a high-frequency power source to the high-frequency magneto-dynamic coil, and the iron core is constantly magnetized to the point where it is almost saturated. When a current to be detected flows through the next conductor, the magnetic field changes the magnetic flux density range of the iron core, which is subjected to high-frequency dynamic magnetization, and the actance of the iron core changes.Therefore, the high-frequency magnetic current that changes in response to the detected current is The voltage drop across the resistor connected in series with the magnetic dynamic coil can be taken out and passed through a filter circuit to determine the detected IT current.

In particular, the iron core is made of amorphous alloy with a specific heat treatment.
The magnetization characteristics are designed to maintain a straight line until near the saturation point.
Since this iron core is constantly magnetized by a high-frequency half-wave voltage, the change in the high-frequency magneto-dynamic current due to the detected current is large, so a large output can be obtained, and even if the dimensions of the iron core are reduced, the current can be accurately controlled. can be detected.

〔Example] The present invention will be explained below based on examples.

First, the case of detecting alternating current will be described, and FIG. 1 shows a schematic configuration diagram of the apparatus of the present invention. In FIG. 1, la is a cylindrical iron core, and of the primary conductors 2a and 2b connecting the power source 6 and the load 7, the primary conductor 2a in FIG. 1 is passed through the center hole of the iron core 1a. The case where both of the secondary conductors 2a and 2b are passed through the center hole of the iron core 1a will be described later.

On the other hand, a rectifier 9 connected in series to the high frequency power source 8. Iron core 1a
A high frequency magnetic dynamic coil IO1 resistor 11 formed by winding the
A low-pass filter I2 and a DC remover 13 are connected to both ends of the resistor 11 to form an output section.

The current detection device of the present invention has a major feature in that it has a linear relationship with the magnetization characteristics of the iron core 1a.The present inventor focused on an amorphous magnetic material whose magnetization characteristics can be changed by heat treatment, and We considered the conditions. As a result, amorphous magnetic alloys have various compositions, and among them, 82% of them have excellent magnetic properties. OCo-2.0Ni-4,5Fe-8,55i
- By selecting a 3.0B alloy ribbon, forming it into a cylindrical shape with a diameter of 36 mm, and performing heat treatment under specific temperature conditions in a non-oxidizing atmosphere, magnetization characteristics suitable for the iron core of the device of the present invention can be obtained. I found out that it can be done.

FIG. 2 shows a magnetization characteristic diagram from the rise to near the saturation magnetic flux when this amorphous alloy is subjected to FL treatment at 200°C. From Figure 2, the magnetic flux density is 8 A /
It can be seen that it changes linearly up to around m. The coercive force at this time is about 0.5 A/m.0 The characteristic of the core that is effective in the present invention is its hysteresis curve, and this alloy has a coercive force.

Since the residual magnetic flux density is also extremely small, it can be regarded as the same as the magnetization characteristic line in FIG.

Figure 3 is a diagram showing the change in the residual magnetic flux density with respect to the heat treatment temperature of this alloy.
It becomes low in the range of 70-230'C. The degree to which linearity can be obtained by heat-treating this alloy is better as the residual magnetic flux density of the magnetic hysteresis curve is smaller. That is, 1
Iron core 1a is formed by heat treatment at 70 to 230'C.
It becomes possible to impart linearity to the magnetization characteristics of. Therefore, in the current detection device of the present invention, an amorphous alloy iron core 1a having the above-mentioned composition is used after being heat-treated at 170 to 230°C.

Next, the basic operating principle of the device of the present invention will be described. In FIG. 1, a detected current i flows from the voltage tA6 to the load 7 through the negative conductors 2a and 2b, and from the high frequency power source 8,
The iron core 1a is always magnetized by a half-wave high-frequency current IN flowing through the high-frequency magneto-dynamic coil 10 and the resistor 11 through the IT device 9. The magnetic field state of the iron core 1a at this time is schematically shown in FIG. 4 as a relationship diagram between the magnetic field and magnetic flux density.
When the current to be detected is not flowing through the secondary conductors 2a and 2b, the iron core 1a is magnetized as shown by the thick line in FIG. 4(a) and is a high-frequency type? a t i is playing. Next, when the positive current to be detected 11 flows through the primary conductors 2a and 2b, a magnetic field of ΔH is applied to the iron core 1a as shown by the thick line in FIG. 4(b), and the magnetic flux density is (B
, −ΔB), the reactance of the iron core la and the high-frequency magneto-dynamic coil 10 becomes small, and the high-frequency magneto-dynamic current i increases. Similarly, the primary conductor 2a
When a negative detected current -iH flows through , 2b, a magnetic field of -ΔH is applied to the iron core 1a, and the range of change in magnetic flux density is as shown in Fig. 4 (
As shown by the thick line in C), (B + +ΔB) is obtained, and the reactance of the iron core 1a and the high-frequency magnetic dynamic coil 10 is increased, and the high-frequency excitation VA current lH is reduced. Therefore, the high frequency magnetodynamic current i. increases or decreases in accordance with the detected current 11.

Fig. 5 is a current waveform diagram, and Fig. 5(a) shows the -order conductor 2.
A and 2b show the waveform of the high-frequency excitation VA current iH when the detected current 11 is not flowing, and the peak value is constant, but
When the sinusoidal detected current i of FIG. 5(b) flows,
The waveform of the high-frequency magnetodynamic current i shows that the peak value changes sinusoidally as shown in FIG. 5(C). This high frequency magnetodynamic current is taken out from the voltage drop of the resistor 11 in FIG.
By removing the DC component, an output corresponding to the detected current can be obtained.

Although not shown in FIG. 1, the device of the present invention can detect minute currents, so based on the above-mentioned principle, both primary conductors 2a and 2b are passed through the center hole of iron core 1a, and the difference current is detected. It can be effectively used for detecting leakage current as well as for zero-phase current detection. The rest is exactly the same as in Figure 1. Next, an example of actually fabricating this zero-sequence current detection device will be described.

The iron core 1a is made of the aforementioned amorphous alloy ribbon with an outer diameter of 35.2 mm.
1n[a, inner diameter 35 mm + height 1 m wound core, heat treated at 200°C in nitrogen gas, and reinforced with adhesive. The inner diameter of the iron core 1a is determined by the current capacity of the load, and in this example, the load current is 3 phases, 10
It will be about 0 to 200A. Of course, what is detected is leakage current, so the required range is 15 to 500 mA. The high frequency type B8 is a 50Kilz rectangular wave, and the low frequency ilt
The wave generator 12 has a cutoff frequency of IKHz, and the DC remover 13
used a capacitor. FIG. 6 shows a relationship diagram between detected current and output of this device.

As shown in FIG. 6, the current to be detected has good linearity up to 500 mA and can be detected with high accuracy. This zero-phase current detection device has a core weight that is 1/1 that of the core of conventional devices.
00 or less.

The frequency of the high-frequency magnetodynamic current is determined by the high-frequency component of the current to be detected and the cutoff frequency of the low-pass filter 12, and the frequency characteristic of this embodiment is -3 dB at lK11z, and even with a distorted waveform in current detection at a commercial frequency. This level is sufficient.

Furthermore, when detecting the high frequency side, it is sufficient to increase the frequency of the high frequency magnetodynamic current and the cutoff frequency of the low pass filter 12.
It is possible to do up to about 10 times that of this embodiment. Furthermore, since the high frequency current uses a half wave, the DC current may be cut off at regular intervals to form a rectangular wave, and a general timer IC can be used for the high frequency type tA8, in which case the rectifier 9 is also unnecessary. Therefore, it is advantageous in terms of economy. The voltage of the high frequency power supply 8 can be any waveform such as a sine wave, rectangular wave, or triangular wave.

The detection of alternating current by the device of the present invention has been described above, but when the current to be detected includes a direct current component, the output voltage when the current to be detected is not flowing is canceled on the output side. An example thereof is schematically shown in FIG. 7 as a partial configuration diagram of FIG. 1. Since the input side connected to the resistor 11 is the same as in FIG. 1, illustration thereof is omitted, and only the output side of the resistor 11 is shown here.

In FIG. 7, the output section 14a includes a low-pass filter 12a, a DC reference power source 15. Consisting of a differential amplifier 16, when the current to be detected is not flowing, the filter 12a outputs the DC component of the high frequency magnetic dynamic current, and a DC voltage of the same value is output from the DC reference power source 15. However, by inputting these two voltages to the differential amplifier 16 and connecting the differential amplifier 16 so that the difference between the two voltages is output, the output voltage can be made zero. If the device is set up in this way, the detected objects will be DC,
It is also possible to detect J and Z deviations when alternating current or direct current and alternating current are superimposed.

Figure 8 shows an additional iron core 1b in the device configured as shown in Figure 7.
FIG.

That is, in addition to the iron core 1a, there is also an iron core 1b with the same specifications as this.
It is equipped with two iron cores.

A description of the high frequency magnetic dynamic coil will be omitted here. - The iron cores 1a and tb are arranged so that they are magnetized in opposite directions by the secondary conductor 2a, and the voltage across the resistor 11.113 is applied to the differential amplifier 16 via the low-pass filters 12a, 12b of the output section 14b. The output of the differential amplifier 16 is connected so as to be the difference between the two inputs. In FIG. 8, the DC reference voltage TA15 used in FIG. 7 is unnecessary. When the detected current i does not flow, the voltage across the resistor 11.11a is the same, so the output of the differential amplifier 16 is zero. When the detected current 11 flows, the magnetization directions of the iron cores 1a and lb are opposite to each other, so that the resistance 11. Since the detected current included in the voltage across lla has a phase difference of 180 degrees, the output of the differential amplifier 16 is the sum of both voltages. That is, with this configuration, the output can be doubled compared to the case where there is only one iron core 1a, and the accuracy is also improved. Note that it is also possible to add the iron core 1b using the device shown in Figure 1.
It goes without saying that the device shown in FIG. 8 can detect both direct current and alternating current (DC) superimposed.

〔Effect of the invention〕

Conventional current detection devices connect a resistor because the magnetization characteristics of the iron core have curved parts, and the dimensions of the iron core are measured.

In contrast, in the device of the present invention, as described in the examples, the magnetization characteristics of the iron core are improved by using a CO-based amorphous alloy heat-treated under specific temperature conditions for the iron core. shows good linearity up to the vicinity of saturation magnetic flux, and this iron core is subjected to high-frequency dynamic magnetism, and the magnetic flux density of the iron core changes depending on the magnetic field of the detected current.
The high-frequency magneto-dynamic current that increases or decreases in response to the current to be detected can be extracted as a voltage drop across the resistor connected to the magneto-dynamic coil, and since the high-frequency magneto-dynamic current changes greatly depending on the current to be detected, a large output can be obtained. It will be done. As a result, the device of the present invention not only can significantly reduce the magnetic path cross-sectional area of the iron core per unit weight, but also has the great effect of improving current detection accuracy.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of the device of the present invention, Fig. 2 is a diagram of magnetization characteristics after heat treatment of the iron core used in the device of the present invention, and Fig. 3 is a diagram of the relationship between the heat treatment temperature of the iron core and the residual magnetic flux density. , Fig. 4 is a diagram schematically showing the magnetization state when the iron core is used, Fig. 5 is a current waveform diagram of the high frequency magnetodynamic current and the current to be detected, and Fig. 6 is a diagram showing the current waveform of the high frequency magnetodynamic current and the current to be detected. Figure 7 is a relationship diagram between detected current and output voltage when used in the device.
FIG. 8 is a schematic partial configuration diagram of the device of the present invention which is a different example from the one shown in the figure. FIG. 8 is a schematic diagram of the device of the present invention using two iron cores. FIGS. FIG. 11, which is a schematic explanatory diagram of a flow vessel, is a magnetization characteristic diagram of an iron core of a conventional device. 1, l a, 1 b - iron core, 2a, 2b - primary conductor, 5
, 11. lla...Resistance, 8...High frequency power supply, 9
... Rectifier, 10 ... High frequency dynamic magnetic coil, 12.1
2a, 12b...Low pass filter, 13...DC remover, ■, ■Sat, 14b,... Output section, 15...DC reference power supply, 16...Differential amplifier. 31 Figure Concession (AA) 't62 Figure pIL treatment 1 degree (°C) 153 Figure 34 Figure 'E, 5 Figure Okinryo Kogyo Denteshi Senme f) Value (Process A) Kuzu 6 Figure '87 Figure I58 Figure 11th mouth

Claims (1)

[Claims] 1) i) At least one of the primary conductors through which the current to be detected flows passes through the center hole, and the composition is 82.0 Co-2.
at least one cylindrical iron core formed from an amorphous alloy ribbon having 0Ni-4.5Fe-8.5Si-3.0B and heat-treated at 170-230°C; ii) arranged in series with a high frequency power source; 1. A current detection device comprising: a rectifier having a rectifier, a high-frequency magnetic dynamic coil wound around the thick part of the iron core, and a resistor; iii) an output section connected to both ends of the resistor.