SU706789A1 - Current instantaneous value meter - Google Patents

Description

(54) INSTANT MEASURING CURRENT

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The invention relates to reversible measuring devices of electric current and is intended for generating reverse feedback signals in high-speed automatic control systems.

Current measurement devices are known, consisting of a transformer, a type, a diode bridge, and a source | tte- belt voltage. .

However, such devices measure only the amount of current and do not react to its direction.

The most perfect is the instantaneous Tdka meter, containing a constant voltage source, a KS filter with two inputs M1, a choke, the primary winding of which is connected to the measured current circuit, and the secondary connected between the zero bus and the first input of the RC filter, a transformer current, the primary winding of which is included in the circuit of the measured current, and the secondary - in the output current circuit. The disadvantages of the known meter are the large power losses in the bias circuit of the magnetic amplifier and in the balanced circuit when and, snake. Rheni x large currents .; as many as hundreds of amps, as well as difficulty due to unfertilized; sources of variable t otca.

The aim of the invention is to reduce the loss of potential when measuring large quantities.

To achieve this goal, an instantaneous current meter containing a constant voltage source, an EC filter: with two inputs, a choke, the first 1H winding of which is connected to the DCM circuit, and the secondary is connected between the zero bus and the first RC filter input, The current transformer, the primary winding of which is included s measuring current circuit, and the secondary - in the output current circuit, introduced Two transistor-diode switches and a resistor, one output of which is connected to the zero bus voltage source and the other th entry RC-filter N through the secondary winding of the current transformer - the outputs transitive (ztorno -dnodnyh, kotOrk The control inputs are connected to the inputs pevym dotgolshtelno imposed transformers with current second and third secondary windings, the second vhodal

which are connected respectively to the negative and positive tires of a source of constant voltage.

The drawing shows a functional diagram of the proposed meter.

The meter contains transistor diodes 1, 2, current transformer 3, resistor 4, choke 5, EC-filter b, bus 7, 8 negative and positive potentials of a constant voltage source,

The current meter works as follows.

The measured current 1n enters the meter and flows through the primary 66lNk) Tke current transformer 3 and through the primary winding of the throttles 5. Transistor-diode keys 1 and 2 together with the current transformer 3 form a kind of multivibrator in which the output winding of the current transformer plays the role of primary, and the additional secondary windings play the role of control windings and provide a self-oscillating mode — operation of keys 1 and 2. In this way, the remagnetization of the transformer core 3 is maintained more continuously without the use of special s source AC voltage. In this case, it is possible to transfer (transform) even constant current i from the measurement circuit to the resistor circuit 4.

With the direction of current ± indicated in the drawing, the secondary winding of the Transformer and the resistor 4 causes the current IH to flow for one half-oscillation of the keys, through the switch 2, and for another half-period through the diode of switch 1.

, With a different polarity current. “The current IH will flow into the corresponding half-cycles of key oscillations through the switch 1 transistor 1 and the switch 2 diode.

In a real current meter, due to the imperfection of the hysteresis loop of the material of the core of the transformer 3, they contain interference dips. To obtain a quality signal at the output of the | 5 cell, use an RC filter 6, the input of which is connected to resistor 4, and the output is the output of a current meter, in order to compensate for the delay introduced by filter 6, the secondary winding 5 is connected to its output. The winding produces a voltage proportional to the derivative of the measured current, which provides compensation for the delay introduced by the RC filter 6

In the described current meter circuit, the power losses associated with the current measurement are allocated in the main resistor 4, which plays the role of the measuring shunt. The voltage drop across resistor 4 is small — usually 0.075–1 V. The current flowing through this resistor is usually 1000 times less than the measured current 1c. Therefore, the power loss in the described meter, even when measuring large currents, is substantially less than the power loss in the known reverse current meters.

Claims (1)

Invention Formula Meter; instantaneous current value, -. containing a constant voltage source, an RC filter with two inputs, a choke, the primary winding of which is included in the circuit of the measured current, and the secondary is connected between. . the zero busbar and the first input of the RC filter, the current transformer, the primary winding of which is connected to the measured current circuit, and the secondary one to the output current circuit, characterized in that, in order to reduce power losses when measuring large currents, two a transistor-diode switch and a resistor, one output of which is connected to the zero voltage source bus, and the other to the second input of the RC filter and through the secondary current transformer to the outputs of the transistor diode switches, the control inputs of which connected to the first inputs of the second and third secondary windings additionally introduced into the current transformer, the second inputs of which are connected respectively to a minus and a plus bus of a constant voltage source.