SU1264086A1 - Contactless current sensing element - Google Patents

Abstract

This invention relates to electrical measuring technology. The purpose of the invention is to simplify the design and increase the reliability of the sensor by the fact that the sensor contains only two electrodes 2 and 3, which are located on the surface of the conductor 1 on dielectric substrates 6. A measure of the measured current is the value of capacitive coupling between electrodes 2 and 3, the value which depends on the current in the conductor 1. 4 Il.

Description

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The invention relates to electrical measuring equipment and can be used for non-contact measurement of large currents.

The purpose of the invention is to simplify the design and increase the reliability of a contactless current sensor due to the location of the transducer electrodes on the surface of the conductor.

FIG. 1 shows a contactless current sensor, open type; in fig. 2 transverse and axial sections of a contactless current sensor with the designation of the conductor conduction region in the absence of a measured current; in fig. 3 shows a transverse and axial section of a contactless current sensor with indication of the conductor conduction region when a measured current passes through it, FIG. 4 shows the dependence of the capacitance between the electrodes on the magnitude and direction of the current in the conductor.

A contactless current sensor (Fig. 1) contains a conductor 1 and two electrodes 2 and 3 connected to the output terminals 4 and 5 of the sensor. The electrodes 2 and 3 are located on the surface of the conductor 1 on the dielectric substrates 6. The longitudinal axis of current flow water 1 is indicated by the position 7, the conductive section of the conductor 1 in the absence of current is indicated by the position 8 (Fig. And the conductive section of the conductor 1 when current passes through the conductor I is indicated by the position 9 (Fig. 3). The contactless current sensor works as follows. When a controlled current flows along the longitudinal axis 7 of the conductor 1 (Fig. 1), a potential difference appears in its cross section between the center and the edges, the sign of which does not depend on the current direction. This is due to the fact that when current flows inside conductor 1 is axially concentrated, causing a negative potential in the center of the cross section of conductor 1 relative to its edges (for conductor 1 with electronic conductivity) Axial current concentration occurs due to the interaction of the current with the internal magnetic field created by the current itself. Axial current compression in This is the result of the distribution of potentials in

its cross-sectional planes do not depend on the direction of the current in the conductor and cause the main current carriers to deplete the extreme surface areas of the conductor 1. At the same time, the conductive section of the conductor 1 decreases with increasing current, i.e. it is compressed to the longitudinal axis 7 and

the depleted zone of the conductor 1 expands from the edges to the axis 7. In the absence of current in the conductor 1 (Fig. 2), the geometric dimensions of its cross section coincide with its dimensions

conductive section 8. At the same time between the electrodes 2 and 3 there is a capacitive coupling, the value of which is determined by the geometric dimensions and the relative position of the electrodes 2 and 3, as well as the distance from the electrodes 2 and 3 to the conductive section 8.

With the passage of current through the conductor 1, axial compression occurs

current (Fig. 3) and the dimensions of the conductive section 9 are smaller than the geometrical dimensions of the section of the conductor 1. At the same time, due to the axial reduction of the dimensions of the conductive section, its effect on the capacitive coupling between electrodes 2 and 3 decreases, and the value of this connection increases (Fig. 4). To increase capacitive coupling, electrodes 2 and 3 can be made in the form of rings and are located on the conductor 1 also on annular dielectric substrates 6, which also insulate the electrodes 2 and 3 from the conductor 1. As the material of the conductor 1, a metal with magnetic permeability of 100-500 or semiconductor, such as germanium or silicon. To measure the current, a measuring device, such as a capacitance meter, is then connected to the output terminals 4 and 5, the scale of which is calibrated when the sensor is pre-calibrated. Another possible way to measure current is to use the capacitance of the sensor as the frequency-response element of an oscillating circuit. For this, the output terminals 4 and 5 are connected to an oscillating circuit and the resonant frequency of this circuit is measured, the value of which in this case is a measure of the measured current.

The electrodes 2 and 3 can also be made in the form of two parallel printed conductors and placed on the surface of the conductor in various ways: along the generatrix of the conductor, in the form of a spiral, etc.

The specific geometrical dimensions of the electrodes, their location, the distance between them, the thickness of the dielectric substrates are determined by the shape and size of the conductor and the requirements for the dynamic range of the measured currents.

When choosing a dynamic range for changing the capacitance of a sensor, the physical properties of a conductor substance — magnetic permeability and conductivity — are essential. The axial compression of the current in the conductor and, accordingly, the increase in capacitive coupling between the sensor electrodes increases with increasing magnetic permeability of the conductor material and decreases with increasing conductivity. Therefore, as a conductor can be used both metals and semiconductors.

The proposed contactless current sensor (as compared to the prototype) has a simple design, high reliability, contains only a few simple structural elements (two electrodes with dielectric substrates and a conductor), which allows its use in various operating conditions.

Claims (1)

Invention Formula A contactless current sensor comprising a conductor for connecting a controlled current to the circuit and a transducer connected to the conductor having two electrodes that are connected to the output terminals of the sensor, characterized in that, in order to simplify and improve reliability, each electrode of the transducer is mounted on the surface of the conductor on the dielectric substrate. eight 126 36 cf3us.2 fig.Z -0 -7