SU1253306A1 - Direct current instrument transducer - Google Patents

Description

the style is connected to the second input terminal of the excitation generator, five switch key, connected between the first pole of the power source of the constant Toka and the first input terminal of the excitation generator, the moving contact of the potentiometer is connected to the second output of the signal input of the phase detector, the output of the demodulator is connected to the second input an adder of analog signals, the first and second input pins of the demodulator through the sixth and seventh switches of the switch are connected to the non-interconnected outputs of the signal windings of the magnetic comparator a, the combined output of which is connected to the third input terminal of the demodulator.

2. The Converter according to claim 1, about t -. characterized in that the excitation generator contains a master frequency generator and a double frequency, the double frequency output of which is the same name of the excitation generator, and a power amplifier made in the form of a bridge on transistors, whose collector-emitter transitions are bridged

one

The invention relates to electrical measuring equipment and is intended for use in measuring direct currents of large magnitude.

The aim of the invention is to increase the reliability of the converter in automatic mode.

The drawing shows a functional diagram of the device.

The magnetic comparator 1 consists of magnetic cores 2 and 3, excitation windings 4 and 5, signal windings 6 and 7, working windings 8 and 9 of a magnetic screen 10, compensating 11 and measuring 12 windings. Magnetic conductors 2 and 3 with excitation windings 4 and 5, signal 6 and 7 and working 8 and 9 windings are placed in a magnetic screen 10, on top of which compensatory 11 and diodes are connected, the main circuits are connected to the corresponding outputs of the main frequency of the master oscillator, the combined output of the emitters and the combined volt The lecturers are the first and second input pins, respectively, and the two combined emitters with collectors are the first and second output pins of the excitation generator.

3, The converter according to claim 1, T is characterized by the fact that the demodulator contains four capacitors (Pa connected in series between the output pins of the demodulator and pairwise shunted by resistors, the first and second diodes connected by anodes with extreme in the circuit the plates of the first and fourth capacitors, the other plates of which are connected to the first and second input terminals of the demodulator, and the third diode, the anode of which is connected to the cathodes of the first and second diodes and the third input terminal of the demodulator, and masonry second and third capacitors.

measuring winding. The terminals of the latter are connected to the input terminals 13 and 14 of the converter.

Excitation generator 15 contains predetermined main and doubled frequency generator 16 and a power amplifier, made in the form of a bridge with transistors 17-20, whose collector-emitter transitions are shunted back by diodes 21-24. The base circuits of the transistors 17-20 are connected to the respective outputs of the main frequency of the oscillator 16. The output of the double frequency of the oscillator 16 is the same output of the excitation generator 15. The output terminals of the power amplifier (transistor bridge) are the outputs 25, 26 of the excitation generator 15 and the potentiometer outputs 27.

3

The DC amplifier 28 is designed for the full current of the charge, the compensation winding 11 and the reference resistor 29 are connected to its output in series. The signal terminals of the reference resistor 29 are connected to the output terminals 30 and 131 of the converter.

An operative change in the structure of the converter is carried out using the switch 32, which includes keys 33-39. The switch 32 controls the signals from the control unit 40, the signal outputs of which are connected to the outputs of the sensors 41 and 42 of the magnetic conductor saturation.

The converter also includes an analog signal adder 43, a phase detector 44, a serial LC circuit 45, a DC power supply 46, an electric power gate 47 and a demodulator including diodes 48-50, capacitors 51-54 and resistors 55, 56. The capacitors 51-54 of the demodulator are connected in series, for example, in the circuit, the capacitor 51 is connected to the first output terminal of the demodulator. To this end of the demodulator, the anode of the diode 48 is connected and the non-connected end of resistor 55. The edge of the capacitor 54 circuit is connected to the second output terminal of the demodulator. Anode of diode 50 and non-connected output of resistor 56 are connected to the same demodulator pin.

I

The connected plates of capacitors 51 and 52 are connected to the first input terminal of the demodulator, and the connected plates of capacitors 53 and 54 to its second input terminal. The cathodes of the diodes 48 and 50 and the anode of the diode 49 are connected to the third input terminal of the demodulator. The cathode of the diode 49 is connected to the combined input of resistors 55 and 56, as well as to the connected plates of capacitors 52 and 53.

The excitation windings 4 and 5, signal 6 and 7, and working 8 and 9 windings of the magnetic comparator 1 are wound, respectively, one for each magnetic circuit 2 and 3. In each of these pairs, the windings are connected in series.

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The output terminal 25 of the main frequency of the generator 15 is connected to the non-connected output of the excitation winding 4 via successively 5 sensors for saturation of the magnetic cores 41 and the switch 34 of the switch 32. The output terminal 26 of the main frequency of the generator 15 of the excitation is connected directly to the non-interconnected excitation winding 5 successively connected keys 35 of switch 32 and LC sutur 45 - with an output terminal 25. The combined output of the windings 4 and 5 of the excitation through the key 37 of the switch 32 is connected with the corresponding - Displayed signal input of the phase detector 44. The other terminal of the signal input of the phase detector 44 is connected to the movable contact of the potentiometer 27.

The control input of the phase detector 44 is connected to the output doubled by the NOA frequency of the excitation generator 15. The output of the phase detector 44 is connected to the first input of the adder 43 of analog signals, the second input of which is connected to the output of the demodulator. The output of the adder 43 is connected

20

thirty

to the entrance of the UFT 28.

Unconnected output of the working winding 9 is connected to the first input output of the generator 15 excitation

(with the emitter bus of the transistor bridge), and the uncoupled output of the working winding 8 through the series 33 of the switch 32 and the sensor 42 of the magnetic cores 42 with the corresponding pole of the DC power source 46. The emitter is connected to the same pole of the source 46 through the switch 36 of the switch 32; the transistor bridge is connected to the bus. The collector bus of this bridge, which is the second inlet of the excitation generator 15, is connected via an electric power valve 47 connected to the other pole of the source 46 via a forward-facing electric motor.

The first and second inputs of the demodulator through the switches 38 and 39 of the switch 32 are connected respectively to the unconnected signal outputs.

The windings 6 and 7. The combined output of the windings 6 and 7 is connected to the third input-demodulator.

The device works as follows.

Depending on the mode of the measurement transducer, its structure changes. There are two modes of operation; operating mode and input mode. The sets of elements and connections providing the operating mode, the measuring transducer assigned (for multiplicity) the name structure 1, and the set of elements and connections providing the input mode - structure II.

In operation mode (structure I), khpochi 34, 36 and 37 are closed, the rest are open. The excitation windings 4 and 5 receive the excitation voltage from the output of the excitation generator 15. In this mode, the magnetizing force (NS) acting on the magnetic cores 2 and 3 and the magnetism screen 10, is balanced by NS, where 1 "is the constant component of the measured current, the DC compensation current at the output of the DCF 28,

W.

and W, the number of turns corresponds to the measured current

measuring 12 and compensatory 11 windings.

The equilibrium mode of the magnetic comparator t is maintained by a negative feedback loop. If there is an imbalance, i.e., when permanent magnetisation of magnetic cores 2 and 3 appears, a combined modulation frequency voltage appears on the combined excitation windings 4 and 5, the amplitude and phase of which are determined by the magnitude of the amperages ilW W The double frequency voltage is removed from the specified combined output relative to the moving contact of the potentiometer 27 and through a closed key 37 is fed to the signal input of the phase detector 44. The potentiometer 27 balances ACIA control input of the phase detector with respect to drive voltage. With accurate balancing, the signal of the first harmonic of the excitation frequency is absent at the indicated input.

The doubled frequency signal is detected by the phase detector 44. The constant and the voltage (control voltage) at the output of the phase detector 44 in terms of magnitude and sign depends respectively on the magnitude and sign of the imbalance of the amplitude of the 5th laser. The relationship between the rocks is determined by whether it is permissible to neglect the static mismatch

thirty

As noted above, the constant or, more precisely, the imaginary quantities are rigid

35 remote control that provides a negative circuit As for the variable measured current, the component of the meter

40 ki 12 is transformed into the on-line winding 11, since the presence of a magnetic screen by the windings 12 and 11 of the magnetic connection of the creatures and when small

45 resistance R in the circuit screen 10, windings 11, 12 p transformer alternating (Here Rj. + R; - RK value reference resis

50 R; - output resistance R - active counterparts 11.

According to the set forth

55

P

W. -with 1 „W

 -vM

and

instant

variable component and

for ilW. The control voltage is applied to the first input of the adder 43 of the analog signals. The second signal does not receive a signal at this time, since in the structure I the keys 38 and 39 are open and the input of the demodulator is disconnected from the signal source. Therefore, at the output of the adder 43, the output voltage of the phase detector 44 is reproduced, which is fed to the DC input 28. Under the action of this voltage, the current I in the winding 11 changes and, if 6, the equilibrium mode is restored with an accuracy of the static error (here limiting unbalance value at which the operating point of the magnetic computer20

tutor

mn zero

1 remains in the region of truth. Thus, due to the described action of the contour of the negative

 dit by the measured current

feedback current 1 ,, „strictly followed by the owner of his measure. The relationship between these rocks is described by the relation (if it is permissible to neglect the magnitude of static mismatch):

thirty

(ABOUT

and I.

As noted above, 1 d g, constant or, more precisely, slowly varying values, rigid interconnection between the remote control systems provided by the action of the negative feedback circuit. As for the variable component of the measured current, the specified component is from the measuring winding 40 ki 12 is transformed into a compensation winding 11, because due to the presence of a magnetic screen 10 between windings 12 and 11 there is a direct magnetic connection and with a small total

45 resistance R in the circuit of the winding 11, the screen 10, the windings 11, 12 operate as an AC transformer. (Here Rj. + R; - at - the value of the reference resistor 29,

50 R; - output resistance of the UFD 28, R - active winding resistance 11.

In accordance with the foregoing

55

P

W. -with 1 „W

(2)

 -vM

and

instantaneous values

the variable component of the measurable

and compensating currents correspond. venously, and in view of relation (1)

+ 1

 (I ,.

+ 1

),

or

one.

i, W, / W,

Where

Iw

IKO +

 1io +

Relationship (3) indicates that the instantaneous value of the current in the compensation winding circuit 11 is a measure of the instantaneous value of the measured current in the measuring winding 12, of course, with an accuracy of the error of the following negative feedback loop and the transformer of the alternating current.

Using the reference resistor 29, the current c is converted into a voltage that is applied to the output terminals 30 and 31 of the converter. Note that due to the use of a frequency modulated magnetic modulator with a frequency doubler in the I structure as an unbalance detector, high conversion accuracy 1 is achieved in IKO. Let us consider how the structure I is implemented during the converter operation. The output signal of the magnetic core saturation sensor has a low level the current value in the measuring circuit of the sensor is below a certain threshold value, otherwise the output signal of the sensor is high. Both sensors 41 and 42 devices meet these conditions.

In the operating mode, the magnetic cores 2 and 3 are fully demagnetized, the inductance of the excitation windings 4 and 5 is large and the current in the measuring circuit of the sensor 41 is small. The current in the measuring circuit of the sensor 42 in the operating mode is zero (key 33 is open). Therefore, in the operating mode, both inputs of the control unit 40 receive low level signals. Under this condition, in block 40 of the control, commands are issued that provide the closed state of the keys 34, 36, 37 and the open state of the other keys of the switch 32.

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15

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Disruption of the operating mode leads to the presence of the magnetic cores 2 and 3, the current in the circuit of the excitation windings 4 and 5 (and, accordingly, in the measuring circuit of the sensor 41) increases sharply and a high level signal appears at the output of the sensor 41. When a high level signal O is applied to one of the inputs of the control unit 40, the latter will generate commands that ensure that the keys 33, 35, 38 and 39 are closed and the keys 34, 36 and 37 are open. This state of the switches 32 corresponds to the automatic mode. input magnetic comparator 1 in the work area. Measuring transducer for cable II.

in this mode has a stream

After the converter enters the input mode, the current in the measuring circuit of the saturation sensor 41 becomes zero, which corresponds to a low signal level at its output and: at the corresponding input of control unit 40. However, at the same input of block 40, a high level signal appears at the same time, since a relatively large current of the operating windings 8 and 9 (greater than the threshold value) flows in the measuring circuit of the saturation sensor 42 due to the saturation of the magnetic cores 2 and 3 due to the large unbalance windings 11 and 12. Since one of the inputs of control unit 40 has a high level signal, this unit continues to generate commands that provide preserved structures II.

In the input mode, unipolar current pulses are supplied to the working windings 8 and 9: this winding flows through this winding

CURRENT consumed by a transistor bridge 17-20 from the source of the direct current power supply 46. This current is a sequence of monopolar DCK4 pulses, the repetition frequency of which is two times higher than the fundamental frequency of the excitation generator 15. These current pulses are generated using a series LC circuit 45. This circuit is through a key

35 is connected to the output of the main frequency of the excitation generator 15. In each half-period of the output voltage of the excitation generator 15 (i.e., the output voltage of the transistor

91

bridge 17-20), an oscillatory overcharge of the capacitor of the LC circuit 45 occurs. The duration of the recharge is determined by the parameters of the C-C circuit 45 and is approximately equal to a quarter of the period of the main frequency of the reHepato 15 excitation. The electric vein prevents the discharge of the capacitor of the LC circuit 45 in the pause between two adjacent recharges.

The unbalance-ampere rotation of the windings 11 and 12 is detected in structure II by rectifying the voltage generated on the signal windings 6 and 7 when the single-sided pulses are applied to the working windings 8 and 9. This rectification is carried out by a demodulator including diodes 49-50, capacitors 51-54, and resistors 55-56. With such an imbalance detection, the static characteristic of magnetic comparator 1 does not have false zeroes.

At the moment of transition of the measuring converter to the input mode, the unbalance of the ampere turns of the windings 11 and 12 is large. At the output of the demodulator, a voltage appears that goes to the second input of the adder 43. At the first input of the adder 43;

steps, since keys 34, 36 and 37 are open in structure II and there is no double frequency voltage at the control input of phase detector 44. Therefore, at the output of the adder 43, the output voltage of the demodulator is reproduced, which is supplied to the input of the DCF 28. Under the action of this voltage, the current 1 in the winding 11 changes until the unbalance of the amperages of the windings 11 and 12 decreases to a small value (up to the value of the current resolving; matching of the negative feedback loop). In steady-state mode, the relationship between the compressed currents is described by the relation (1).

6

ten

Thus, the conditions for the transition from the mode of entry into the operating mode are created: the imbalance of the amperages of the windings 11 and 12 of the magnetic Comparator 1 is small; they are observed with a margin of input to the working zone of the comparator 1, which has a static characteristic with false zeroes.

As soon as structure II comes to equilibrium, the current in the measuring circuit of sensor 42 decreases below a threshold value. The signal changes at the output of sensor 42: a high level is replaced by a low one. Now the inputs of the control unit 40 receive low level signals. In block 40, commands are generated to ensure that the keys 34, 36 and 37 are in the closed state, and the rest of the keys of the switch 32 are opened. Structure II is replaced by Structure I, the device is activated.

25

In the proposed technical solution, in comparison with (2), complex electronic components are excluded, namely, an adder of analog signals, a 30-pulse generator and a pulse shaper. The functions of the last two nodes are performed by the terminal stage of the excitation generator 15, equipped with a serial LC circuit 45 and an electric valve 47. In this case, the terminal stage is designed as a transistor bridge. The indicated combination of functions is achieved by introducing into the magnetic comparator 1 two working 8 and 9 and two signal 6 and 7 windings. The introduction of these windings made it possible to reduce the number of keys in the switch 32. In addition, it became possible to significantly simplify the demodulator by eliminating the adder and simplifying the rectifier circuit.

35

40

Claims (3)

1. A DC measuring transducer, comprising a magnetic comparator with a magnetic screen, two magnetic circuits, two field windings connected in series, wound one on each magnetic circuit, a measuring winding connected to the input terminals of the converter, and a compensation winding, a DC power supply, two sensors saturation of the magnetic cores, a DC amplifier, to the output of which the compensation winding of the magnetic comparator and the reference the first resistor connected to the output terminals of the converter, a switch with seven keys, a control unit whose inputs are connected to the outputs of the saturation sensors of the magnetic cores, and the output is connected to the control input of the switch, a demodulator, an excitation generator, the first output terminal of the main frequency of which is connected to the first unconnected the output of the excitation windings of the magnetic comparator through the first saturation sensor of the magnetic cores and the first switch key, a phase detector, a control input otorochno connected to the output of the double frequency of the excitation generator, and the first output of the signal input through the second switch key to the combined output of the excitation windings of the magnetic comparator, an adder of analog signals, the first input of which is connected to the output of the phase detector, characterized in that, in order to increase reliability work, a potentiometer, a serial LC-circuit and a power electric valve are introduced into it, and the magnetic comparator is equipped with two sequentially connected signal windings and two ~ by sequentially connected working windings, wound one on each magnetic circuit, the potentiometer being connected between the output terminals of the main frequency of the generator, excitation, second output. The main frequency clamp of the excitation generator is connected directly to the second unconnected terminal of the excitation windings of the magnetic comparator, and through series-connected third switch key and LC-circuit with the first output terminal of the main frequency, one of the unconnected outputs of the working windings of the magnetic computer the rotor 'is connected to the first input terminal of the excitation generator, and the other through the fourth key and the second saturation sensor of the magnetic circuits connected in series with the first pole of the DC power source, the second pole of which is connected through the forward-connected power electric valve to the second input terminal of the excitation generator , the fifth switch key, is connected between the first pole of the DC power source and the first input terminal of the excitation generator, a movable contact potentiometer and connected to the second output of the signal input of the phase detector, the output of the demodulator is connected to the second input of the adder of analog signals, the first and second input terminals of the demodulator through the sixth and seventh switches of the switch are connected to unconnected outputs of the signal windings of the magnetic comparator, the combined output of which is connected to the third input terminal of the demodulator . 2. The Converter according to claim 1, characterized in that the excitation generator contains a master oscillator of the main and double frequencies, the double frequency output of which is the same output as the excitation generator, and a power amplifier made in the form of a bridge on transistors, whose collector-emitter junctions are are shunted by the back-on diodes, the base circuits are connected to the corresponding outputs of the main frequency of the master oscillator, the combined output of the emitters and the combined output of the collectors are respectively first and second input terminals, and two combined outputs of emitters with collectors - the first and second output terminals of the excitation generator. 3. The converter according to claim 1, characterized in that the demodulator contains four capacitors connected in series between the output terminals of the demodulator and pairwise shunted resistors, the first and second diodes connected by the anodes to the outermost plates of the first and fourth capacitors, the other plates of which connected to the first and second input terminals of the demodulator, and a third diode, the anode of which is connected to the cathodes of the first and second diodes and to the third input terminal of the demodulator, and the cathode with combined plates second and third capacitors.