JPH04262265A - current sensor - Google Patents

Abstract

PURPOSE:To prevent the malfunction of an amplification circuit and measure correctly current by inserting a shield conductor insurated from a measured conductor and grounded, between a current sensor body and the measured conductor. CONSTITUTION:A shield conductor 10 of a rectangular shape insulated from a measured conductor 1 and ground, between a current sensor body 7 and the conductor 1, is inserted. The coupling capacitance of the conductor 1 and a plastic case is formed when current flows in the conductor 1. However, the current by a change of the potential of the conductor 1 flows nearly into the earth passing through a lead wire 13 because the coupling capacitance of the conductor 1 and the conductor 1 is far larger than that. Consequently, an amplification circuit is not nearly affected, the malfunction of the amplification circuit is prevented even if the change of the potential occur in the conductor 1, and the current can correctly be measured.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention provides a gap in a part of the iron core that forms a magnetic path surrounding the conductor, inserts a Hall element into the gap, and utilizes the Hall effect to flow through the conductor. This invention relates to a current sensor that detects current.

0002

2. Description of the Related Art FIG. 4 is a perspective view showing a general schematic structure of a conventional current sensor of this type. In the figure, 1 is a conductor to be measured through which the current to be measured flows, 2 is a magnetic path that surrounds the conductor to be measured 1, and a gap 2 is formed in a part of this magnetic path.
The iron core 3 is a Hall element inserted into the gap 2a, and has two voltage application terminals 3a and two output terminals 3b.

4 is a Hall element 3 connected to the output terminal 3b.
an amplifier circuit that amplifies the output of and outputs it from the output terminal 4a;
5 is a power terminal; 6 is a shield body surrounding the amplifier circuit 4;
Reference numeral 7 designates a current sensor main body, which is constructed by inserting the above 1 to 6 into a plastic case 8, molding and fixing them with resin, and attaching external terminals 9, as shown in FIG.

In the conventional current sensor configured as described above, first, when a current to be measured flows through the conductor 1 to be measured, a voltage of several mV to several tens of mV corresponding to the current to be measured flows from the output terminal 3b of the Hall element 3. A small voltage of mV is output. This small output voltage is amplified by the amplifier circuit 4 and output from the output terminal 4a, and the current to be measured is detected from this output value. Furthermore, since the amplifier circuit 4 is generally composed of electronic components and operates with minute signals, it is susceptible to noise caused by the current and voltage flowing through the conductor 1 to be measured and is susceptible to malfunction. To prevent this, it is surrounded by a shield body 6.

[0005]

[Problems to be Solved by the Invention] Since the conventional current sensor is constructed as described above, if the change in potential of the conductor to be measured 1 dV/dt is large, the coupling between the conductor to be measured 1 and the plastic case 8 will be reduced. Current flows through the capacitance, and because this passes through the amplifier circuit 4, the amplifier circuit 4 malfunctions.
There was a problem that accurate current measurement could not be performed because the correct signal could not be output.

The present invention was made to solve the above-mentioned problems, and it is an object of the present invention to provide a current sensor capable of accurately measuring current by preventing malfunction of the amplifier circuit. .

[0007]

[Means for Solving the Problems] A current sensor according to the present invention has a shield conductor that is insulated from the conductor to be measured and grounded inserted between the current sensor main body and the conductor to be measured. .

[0008]

[Operation] The shield conductor of the current sensor according to the present invention shunts the current due to the change in potential dV/dt of the conductor to be measured to the ground, thereby preventing malfunction of the amplifier circuit.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing the structure of a current sensor according to an embodiment of the present invention, and FIG. 2 is a sectional view showing the structure of main parts of the current sensor in FIG. In the figure, the conductor to be measured 1 and the current sensor main body 7 are similar to those of the conventional current sensor in FIGS. 4 and 5. 10 is a rectangular cylindrical shield conductor inserted between the conductor to be measured 1 and the current sensor body 7; 11 and 12 are the shield conductors 10;
An insulator 13 is a lead wire that grounds the shield conductor 10 to the earth.

In one embodiment of the present invention configured as described above, a current flows through the conductor 1 to be measured and the plastic case 8 is connected to the conductor 1 as in the conventional current sensor.
However, since the coupling capacitance between the conductor under test 1 and the shield conductor 10 is much larger, most of the current due to the change in potential dV/dt of the conductor under test 1 is It flows through the lead wire 13 to the ground.

Therefore, the current can be accurately measured even if there is a change in the potential of the conductor 1 to be measured, with almost no effect on the amplifier circuit 4. Note that although the shield conductor 10 is effective even if it is short, the longer the shield conductor 10 is, the greater the coupling capacitance between the conductor 1 to be measured and the shield conductor 10 becomes, so the effect becomes greater. Furthermore, it is convenient to integrate the shield conductor 10 and both insulators 11 and 12 with the current sensor main body 7 and harden them with a resin mold or the like.

FIG. 3 is a schematic diagram showing the configuration of the main parts of a current sensor in another embodiment of the present invention. In the figure, 14, 15, 16 are shield conductors formed in multiple stages to surround the conductor 1 to be measured, and insulators 17, 16, respectively.
18, 19, and 20 are insulated and independent. A lead wire 21 connects the outermost shield conductor 14 to the ground. The shield conductors 14, 15, 16 and the insulators 17, 18, 19, 20 are formed to be shorter in the longitudinal direction as they are farther away from the conductor 1 to be measured.

Another embodiment of the present invention configured as described above applies a capacitor bushing, and the potential of the conductor 1 to be measured is very high, so it is necessary to strengthen the insulation from the current sensor main body 7. When applied to various cases, the potential gradient becomes uniform and the dielectric strength improves.

[0014]

As described above, according to the present invention, a shield conductor which is insulated from the conductor to be measured and is grounded is inserted between the current sensor main body and the conductor to be measured. This has the effect that it is possible to provide a current sensor that can accurately measure current by shunting current caused by potential changes to the ground to prevent malfunction of the amplifier circuit.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the configuration of a current sensor in an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the configuration of essential parts of the current sensor in FIG. 1;

FIG. 3 is a schematic diagram showing the configuration of main parts of a current sensor in another embodiment of the present invention.

FIG. 4 is a perspective view showing the configuration of a conventional current sensor.

FIG. 5 is a perspective view showing the appearance of the current sensor main body.

[Explanation of symbols]

1 Conductor to be measured 2 Iron core 2a　Void 3 Hall element 4 Amplification circuit 7 Current sensor body 10 Shield conductor

Claims (1)

[Claims] 1. A current sensor consisting of an iron core surrounding a conductor to be measured and having a gap in a part of the magnetic path, a Hall element inserted into the gap, and an amplifier circuit connected to the output side of the Hall element. A current sensor comprising a main body, a shield conductor interposed between the conductor to be measured and the current sensor main body, insulated from the state to be measured, and grounded.