CS259355B1 - Wiring for real measurements of the AC component - Google Patents

Abstract

The circuit solves the measurement of the real component of alternating current for the needs of automation of technological processes. In the circuit, there is a capacitor after the measuring current transformer, which is charged to a voltage proportional to the real component of the measured current by switching circuits consisting of switching diodes, capacitors and resistors.

Description

259355

The invention solves the measurement of the real component of the electric alternating current by simple passive circuit elements.

Until now, the real component of the current is a meter-based measuring instrument, or a complex electronic device operating on the principle of high-frequency or switched resistivity. The displacement measuring devices are used in automatic control as their output is not an electrical signal. Electronic devices are complex, expensive and expensive. The measurement by dirty resistance pulses is overridden by an error resulting from a linear inductive load.

The above mentioned drawbacks are eliminated by the connection of the invention, the principle being that a current measuring transformer is connected to the circuit of the measured current. This transformer is retracted by a load resistor. The first measuring transformer terminal is connected via a capacitor to the first output terminal of the connection. The second terminal transformer is directly connected to the second output terminal of the connection and simultaneously to the middle terminal of the transformer. The first output terminal of the connection is connected to the first terminal of the voltage transformer via a first switching diode and a parallel second second resistor to a second capacitor. At the same time, the first input terminal of the connection is a switching diode and a parallel connected third resistor through the third capacitor connected to the second terminal of the voltage transformer. Advantages of the connection according to the invention are that the connection is simple and not expensive for the components. The cost of making it is low. By plotting the current at a time when the reactant component of the current is zero, the device does not affect the measurement non-linearity. The simplicity of connection and the good quality of the output signal make it possible to apply wiring in automation and regulation of technological processes.

In the attached drawing, there is a wiring diagram.

The first secondary terminal 11 of the transformer 1 is coupled via the capacitor C3 to the output terminal 16 of the transformer. The second secondary terminal 12 of the measuring transformer 1 is directly connected to the second output terminal 17 of the wiring and simultaneously the center terminal 16 of the voltage transformer 10. The first output terminal 16 of the wiring is via the first switching diode 4 and parallel the second resistor R6 coupled to the second capacitor C8 coupled to the first terminal 14 of the voltage transformer 10. At the same time, the first output terminal 16 of the connection through the types is a switching diode 5 and a parallel third resistor R7 with a third capacitor C9 connected to the second terminal 15 voltage transformer 10.

The measured current transformed by the measurement transformer 1 produces a voltage drop across the measuring resistor R2 connected between the measuring transformer terminals 11, 12, which is a measure of the measured current. The capacitance C3 is charged at the voltage reference voltage across the voltage transformer 10 at this time. The switching circuit for charging the capacitor C3 consists of switching diodes 4, 5, which are opened for a short time by a reference voltage from clamps 13, 14a 14, 15 of the voltage transformer 10. Opening of the switching diodes 4, 5 at the moment of reference reference the tension is provided by the capacitance generated by the capacitors C8, C9. Slow discharge of these capacitors C8, C9 provide resistors R6, R7. The sample voltage to which the capacitor C3 is charged is proportional to the instantaneous value of the measured current at the time of the maximum reference voltage. The accretion voltage is in the phase with the real component of the measured current and the real compound current is sinusoidal, so the unidirectional voltage on capacitor C3 is proportional to the real component of the measured current. An analog-to-digital converter or a control circuit with an input resistor R1S connects to the output terminals 16, 17. In order for the device to function reliably according to the connection, the values of its circumferential elements must satisfy the following conditions: C3 C8C8 = C9R6 = R7 C3. R18> R6. C8> -> C3. R2 ω where ω is the circular frequency of the measured current.

The connection is also suitable for measuring the free vector components of the current and for measuring the vector of the measured current by turning the reference vector of the reference vector.

Claims (1)

SUBJECT Circuit for measuring the real component of an alternating current, characterized in that a measuring transformer (1) having a load resistor (R2) connected in parallel to the secondary winding, is connected between the first secondary terminal (11) of the measuring transformer (1) ) and the first wiring output terminal (16) is a capacitor (C3), the second secondary terminal (12) of the measuring transformer (1) is connected to the middle terminal (14) of the voltage transformer of the invention (10) and the second wiring output terminal (17). wherein the first output terminal of the wiring (16) is connected both through the series-parallel connection of the first switching diode (4), the second capacitor (C8) and the second resistor (R6) to the first terminal (14) of the voltage transformer (10) and a diode (5), a third capacitor (C9) and a third resistor (R7) with a second terminal (16) of the voltage transformer (10).