JPS6311866A - Direct current sensor - Google Patents

Abstract

PURPOSE:To extend a current detection range by the same magnetic core, by providing a bias magnetic field generating means for generating a bias magnetic field in the magnetic core. CONSTITUTION:A bias magnetic field generating means is constituted of an auxiliary coil 5, a variable resistor 6 and a DC power source 7. In order to generate a magnetic field in the direction opposite to that of a main magnetic field B generated by a current I to be detected and having intensity not entering a saturation region, a current is made to flow to the coil 5 at first from the power source 7 through the resistor 6 in such a state that no current I flows. Then, the current flowing to the coil 5 is changed while the resistor 6 is adjusted and a bias magnetic field D is generated so as to obtain a main magnetic field -B4 generated when the current I is -I3. Since the current generating said magnetic field D is always supplied to the coil 5 even in such a state that the current I flows, the magnetic sensor 3 detected from an output lead 4, for example, the output voltage of a Hall element is not saturated even when the current I changes and output voltage proportional to the current can be obtained.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a DC current sensor using a magnetic field sensor, and more particularly to a DC current sensor that expands the current detection range with the same magnetic core.

[Conventional technology]

Figure 5 is an example of "Sensor Technology (November 1982 issue)"
FIG. 2 is a perspective view showing a conventional current sensor described in FIG. In the figure, 1 is an electric wire through which a detected current 1 (A) flows. A magnetic core 2 surrounds a part of the electric wire 1, and serves as a magnetic conduction path for the main magnetic field B generated by the detected current 1 (A). 3 is an end surface 2a of the magnetic core 2. A magnetic field sensor 4 is an output lead of the magnetic field sensor 3 arranged between the magnetic field sensors 2b and 2b with an air gap G interposed therebetween. The conventional sensor is configured as described above, and when a detected current 1 (A) flows through the electric wire 1, the detected current 1 (A
) is generated and taken out from the output lead 4. FIG. 6 is a characteristic diagram showing the relationship between the detected current I(^) and the output voltage V (V) obtained from the magnetic field sensor 3, for example, a Hall element. v! a
The characteristics are as follows. However, since the B-H characteristic of the magnetic core 2 has a saturation characteristic as shown by the line in FIG.
For example, the output voltage (v) obtained from the Hall element also has a characteristic as shown by line C in FIG. That is, when the detected current I(^) is 11, the main magnetic field B (G) in FIG. 7 is B, and the output voltage V (V) in FIG.
is 1, which is proportional to 11 of the detected current 1 (A), but the detected current! When (A) is 12, the B-H characteristic of the magnetic core 2 shown in Fig. 7b is in the saturation region, so the main magnetic field B (G) becomes B2 instead of B3, and the 8th The output voltage V (V) of the magnetic field sensor 3 shown in the figure, for example a Hall element, is not vl but v2, and therefore an output voltage V m proportional to the detected current + (A) by 1° is obtained. do not have. In this case, in order to prevent the B-H characteristic of the magnetic core 3 from becoming saturated even when the detected current 1 (A) is 12, the material of the magnetic core 3 should be made of a high-performance material, or the magnetic core 3 should be made larger so that the cross-sectional area needs to be made larger.

[Problems to be solved by the invention]

As described above, the conventional current sensor detects the detected current (A)
In order to prevent the B-H characteristics of the magnetic core 2 from being saturated even when the voltage is I2,
Since the size of the magnetic core 2 is increased to increase its cross-sectional area, and the material of the magnetic core 2 is made of a material with good performance, there is a problem in that the cost is high. This invention was made in order to solve the above-mentioned problems, and by constantly applying a magnetic field opposite to the magnetic field generated by the current to be detected I (A) to the magnetic core 2, the current is generated in the same magnetic core 2. The purpose is to expand the detection range.

[Means to solve the problem]

The DC current sensor according to the present invention includes a magnetic core provided with bias magnetic field generating means for generating a bias magnetic field in the magnetic core.

[For use]

In this invention, the bias magnetic field generating means applies a bias magnetic field to the magnetic core that generates a magnetic field in the opposite direction to the magnetic field generated by the current to be detected, and also utilizes the negative region of the B-H characteristic of the magnetic core. By doing so, the direct jafil area is expanded, and the current detection range is expanded using the same magnetic core.

【Example】

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure is a perspective view showing an embodiment of the present invention.
, B and G are similar to conventional current sensors. 5 is an auxiliary coil wound around a part of the magnetic core 2 to generate a bias magnetic field within the magnetic core 2; 6 is a variable resistor connected to one end of the auxiliary coil 5; 7 is a variable resistor between the variable resistor 6 and the auxiliary coil 5. It is a DC power supply inserted between the other end and for exciting the auxiliary coil 5, and the auxiliary coil 5 and the variable resistor 6.
and the DC power supply 7 constitute bias magnetic field generating means. Next, while referring to the characteristic diagrams of the detected current I(^), the main magnetic field B(G), and the output voltage V(V) shown in FIGS. 2 to 4, the operation of the embodiment of the present invention will be explained. I will explain about it. The relationship between the detected current I(^) and the main magnetic field B(G) is the second
It has the characteristic d shown in the figure. Here, the detected current I(
The direction of the main magnetic field B (G) generated by ^) is opposite to that of
In order to generate a magnetic field that does not enter the saturation region, first, a current is caused to flow through the auxiliary coil 5 by the DC power supply 7 via the variable resistor 6 while the current to be detected 1 (A) is not flowing. Then, the current flowing through the auxiliary coil 5 is changed while adjusting the variable resistor 6, and the main magnetic field -84 generated when the detected current 1 (A) is -I, as shown by the broken line e in FIG.
A bias magnetic field is generated to obtain . Due to the bias magnetic field obtained in this way, the detected current I
Even if (^) is I2, the main magnetic field B (G) with the characteristic of f shown in Fig. 3 is not saturated and becomes v6, and similarly the output voltage V (V ) is also the detected current 1
■6 proportional to (A) is obtained. The current that generates this bias magnetic field is the detected current 1
(A) is always supplied to the auxiliary coil 5 even when current is flowing, so the output voltage V (V) of the magnetic field sensor 3, such as a Hall element, detected from the output lead 4 is as shown in Fig. 4. The characteristic is that the detected current 1 (A) is 12
Even if the output voltage V(V)V is proportional to the current, it is possible to obtain the output voltage V(V)V without saturation. Specifically, for example, in the characteristic shown by the broken line C, the detected current I (^) is 12 and the output voltage V (V) is 2
Although it is not proportional to the detected current 1 (A) It,
According to the solid line g where the bias magnetic field is applied, the output voltage V
(V) becomes v6 and is not saturated like v2,
An output voltage V(V)V6 proportional to the current to be detected is obtained.

【Effect of the invention】

As described above, according to the present invention, the bias magnetic field generating means for generating a bias magnetic field in the magnetic core is provided, and the bias magnetic field generating means generates a magnetic field in the opposite direction to the main magnetic field generated by the current to be detected. By applying a bias magnetic field to the magnetic core, the B-H characteristic of the magnetic core is shifted to the right and the linear region is expanded, so the current detection range can be expanded with the same magnetic core. Increasing the size of the magnetic core,
There is no need to use a material with good B-H characteristics, and an inexpensive DC current sensor can be obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention, FIG. 2 is a characteristic diagram of the bias magnetic field of the DC current sensor shown in FIG. 1, and FIG. FIG. 4 is a characteristic diagram showing the relationship between the current detected by the DC current sensor in FIG. 1 and the output voltage. FIG. 5 is a perspective view of the conventional DC current sensor. The figure is a characteristic diagram showing the ideal characteristics of a magnetic field sensor using a conventional DC current sensor. Figure 7 is a characteristic diagram showing the relationship between the detected current and the main magnetic field by a conventional DC current sensor. Figure 8 is a characteristic diagram showing the relationship between the detected current and the main magnetic field using a conventional DC current sensor. FIG. 3 is a characteristic diagram showing the relationship between the current detected by the sensor and the output voltage. 1... Electric wire, 2... Magnetic core, 3... Magnetic field sensor (Hall element), 5... Auxiliary coil, 6... Variable resistance,
7...DC power supply, ■...Detected current, B...Main magnetic field, D...Bias magnetic field. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Daikun Masujj! <2 other people) Figure 1 Nail 11 Official Book (Method) % Formula % ( 1. Indication of the case 2. Name of the invention DC current sensor 3. Person making the amendment. Relationship to the case. Patent applicant 4. Agent 5. Date of amendment order. 1985. September 30th (shipping date)
7. Contents of the amendment ■) The name of the invention in the specification is amended from "DC current sensor" to "DC current sensor."

Claims (2)

[Claims] (1) an electric wire through which at least a current to be detected flows, a magnetic core surrounding a part of the electric wire, a magnetic field sensor arranged in a part of the magnetic core to detect a main magnetic field generated in the magnetic core by the current to be detected; A direct current sensor comprising: bias magnetic field generating means provided on a magnetic core and generating a bias magnetic field having a direction opposite to a main magnetic field generated in the magnetic core by the current to be detected. (2) The bias magnetic field generating means consists of an auxiliary coil wound around a magnetic core, a DC power supply for supplying current to the auxiliary coil, and a variable resistor for adjusting the current supplied from the DC power supply. Claim 1 characterized by
DC current sensor described in section.