RU1812513C - Measuring transducer of alternating current - Google Patents

Abstract

Usage: the invention relates to measuring equipment and can be used for non-contact measurement of alternating currents in the circuits of radio and power plants in a wide frequency band, as well as as a measuring organ in emergency control systems of electrotechnological installations. SUMMARY OF THE INVENTION: an AC measuring transducer comprises a magnet wire made of a soft magnet material on which input windings, measuring windings, feedback windings, voltage amplifiers, single-quadrant voltage repeaters, are located. 1 ill.

Description

The invention relates to the field of measurement technology and can be used for non-contact measurement of alternating currents in the circuits of radio and power plants in a wide frequency band. It can also be used as a measuring body in emergency control systems of electrotechnological installations.

The purpose of the invention is to improve the accuracy of measuring the modulus of the sum of the measured currents and to increase the speed.

The introduction of single-quadrant voltage followers, a second measuring winding and a second feedback winding made it possible to create a magnetic flux in the magnetic circuit that is directed counter to the flux generated by the measured currents, regardless of the direction of the resulting magnetic flux. Thus, the introduction of these elements made it possible to obtain the output signal of the current transducer proportional to the modulus of the sum of the measured currents. Since the resulting magnetic flux is close to zero (due to the significant gain of the voltage amplifiers), the error in summing the currents does not exceed a tenth of a percent. Due to the low output impedance of the single-quadrant repeaters, the voltage of the feedback windings functions in the high frequency region as windings of a current transformer, which increases the speed of the device.

The drawing shows a functional diagram of a measuring transformer of alternating current.

The device comprises a magnetic circuit 1 made of a magnet of soft material, on which the input windings 2, 3, 4 ... N + 1, the first and second measuring windings 5, 6, the first and second feedback windings 7, 8, and the first and second voltage amplifiers 9, 10, the first and second single-quadrant voltage repeaters 11 and 12, and the measuring cut w

Yo

crop 13. The findings of the first input winding 2 are connected to the inputs of the devices 17 and 18, the outputs of the second input winding 3 are connected to the inputs of the device 19 and 20, the terminals N of the input winding 4 are connected to the inputs of the devices 21 and 22, to the inverting and non-inverting inputs of the first amplifier, for example 9 are connected, respectively, the leads of the beginning and end of the first measuring winding 5. To the output of the first voltage amplifier 9 is connected the input of the first one-quadrant voltage repeater

11. to the output of the latter is connected the output terminal of the first feedback winding 7, the output terminal of which is connected to the output 23 of the device. To the inverting and non-inverting inputs of the second voltage amplifier 10 are connected respectively the terminals of the end and the beginning of the second measuring winding 6. To the output of the second voltage amplifier 10 is connected the input of the second one-quadrant voltage follower

12. To the output of the latter is connected the output of the end of the second feedback winding 8, the output of which is connected at the beginning to the output 23 of the device. Between the output 23 of the device and its common bus 24 included measuring resistor 13.

The device operates as follows. .

In the absence of supply voltages and the flow of input currents, the latter create magnetic fluxes in magnetic circuit 1. The resulting magnetic flux is equal to the sum of the (algebraic) magnetic flux created by the above currents. In the measurement windings 5 and 6. and also in the feedback windings 7 and 8, the transformer EMF is proportional to the magnitude of the resulting magnetic flux. When the supply voltage is applied, the output signals of the measuring windings 5, b are amplified by voltage amplifiers 9, 10. The output signals of amplifiers 9, 10 are fed to the inputs of single-quadrant voltage repeaters 11, 12, voltage repeaters transmit half-waves of only one polarity. However, the windings 7, 8 are turned on in relation to each other and create magnetic fluxes directed in the opposite direction to the resulting magnetic flux, therefore, at any time in the device, automatic compensation of the resulting magnetic flux is provided. Due to the significant gain KU 1 of the voltage amplifiers 9 and 10, the non-linearity of the transfer characteristics of single-quadrant voltage repeaters

11 and 12 practically does not contribute to the overall error of the device, and the resulting magnetic flux is close to zero, since the resulting magnetic flux is close to zero, the measured currents practically do not affect the processes in inductively coupled circuits, i.e., the operation current summation is performed with high accuracy. As indicated above, the output currents of voltage followers 11 and 12 have the same direction, therefore, the voltage drop created by these currents has only one polarity, i.e. the output signal of the device is proportional to the modulus of the sum of the measured currents.

The device can be used as a measuring body in emergency control systems for low-voltage AC networks, as well as

measuring body differential protection.

Claims (1)

SUMMARY OF THE INVENTION A measuring transducer of alternating current, comprising N input windings, a measuring winding and a feedback winding located on a magnetic core of soft magnetic material, a measuring resistor. two voltage amplifiers, the terminals of the beginning and end of the measuring winding, respectively, are connected to the inverting and non-inverting inputs of the first voltage amplifier, the terminal output of the feedback winding and the first terminal of the measuring resistor are connected to the output of the converter, the second terminal of the measuring resistor is connected to the common bus of the converter, the terminals of N input windings are connected respectively to the inputs of the converter, characterized in that that, in order to improve the accuracy of measuring the modulus of the sum of the measured currents and increase the speed, two single-quadrant voltage followers, a second measuring winding, and a second a feedback winding, wherein the output terminal of the second feedback winding is connected to the output of the converter, the outputs of the first and second one-quadrant voltage repeaters are connected respectively to the output terminal of the first and second end of the second feedback windings, the inputs of the first and second one-quadrant voltage repeaters are connected with the outputs of the first and second voltage amplifiers, respectively, the leads of the beginning and end of the second measuring winding are connected respectively to non-inverting and inverting inputs second voltage amplifier.