SU1177767A1 - Device for indicating phase quadrature - Google Patents

Abstract

A DEVICE FOR INDICATING PHASE SHIFT 90 °, containing an electrostatic transducer, an electromechanical measuring mechanism of direct current, the movable part of which is fixed on the same axis with the movable part of the electrostatic transducer, characterized in that, in order to improve the accuracy and enhance the functionality, two AC amplifiers with adjustable gain factors, a voltage transformer, an AC measuring resistor, a switching device, a power supply unit Transforming the rotation angle to voltage, a DC amplifier, the primary winding of a voltage transformer is connected to the first input of the device, extreme ends of the secondary winding of the transformer through AC amplifiers with peVynnpyeMbiMH gain factors are connected to fixed electrodes of an electrostatic converter, secondary secondary windings of the secondary windings, and secondary secondary windings are used for secondary secondary windings; with moving. A KOHtaKTOM switch, the first fixed contact of which is connected to the first potential output of an AC measuring resistor, and the second to the second input (Device side, the current outputs of the measuring AC resistor are connected to the third input of the device, the rotation axis of the moving part of the electrostatic converter is optically connected to the input of the unit converting the angle of rotation into voltage M 1, the output of which is connected to the input of a DC amplifier, the output sl of which is connected to an electromechanical Kim with a measuring mechanism and a DC output of the apparatus, the second potential measurement AC output resistor, one terminal of the second input device inputs low-potential usilytopoY; AC with variable gain and a movable electrode of the electrostatic transducer connected to a common bus.

Description

1 1 The invention relates to electrical measuring technique and can be used to construct phase shift indicators between two voltages and a voltage and current used to test and certify the measurement of power and energy. The aim of the invention is to increase the accuracy of the display and enhance the functionality due to the possibility of working with lower levels of input signals and indicating a phase shift not only between two voltages, but also between voltage and current, and also due to the fact that the input circuits may have a common tire. FIG. 1 shows a diagram of the proposed device; in fig. 2 - diagram of the practical implementation of the device. The device contains an electrostatic transducer 1 with a movable part 2, on the same axis with which the mobile part of the electromechanical measuring mechanism 3 of direct current is fixed, alternating current amplifiers 4 and 5, with adjustable gain factors, a voltage transformer 6, a measuring resistor 7. current, switch 8, unit 9 converts the angle of rotation in the voltage, the amplifier 10 direct current, the primary winding of the transformer 6 voltage connected to the first input 11 of the device, the extreme The terminals of the secondary winding of the voltage transformer 6 are connected to stationary electrodes of the electrostatic converter 1 through amplifiers 4 and 5 of alternating current with adjustable voltage coefficients. The middle terminal of the secondary winding of the transformer 6 is connected to the movable contact of the switch 8, the first fixed contact of which is connected to the first potential output of the measuring resistor 7 of the alternating current, and the second to the second input 12 of the device, the current terminals of the measuring resistor 7 of the alternating current are connected to the third input 13 of the device , the axis of rotation of the movable part 2 of the electrostatic converter 1 is optically connected to the input of the angle-to-voltage conversion unit 9, the output of which is connected to the input m amplifier 10 672 DC. The output of which is connected to the electromechanical measuring mechanism 3 DC and output 14 of the device, the second potential output of the measuring resistor 7 AC, one of the terminals of the second input 12 of the device, low-potential inputs of amplifiers 4 and 5 AC with adjustable gain factors and the movable electrode 2 of the electrostatic converter 1 are connected with a common bus. In practical implementation, the upper element 15 of the electrostatic converter 1, together with a divider of resistors 16 and 1 and auxiliary voltage source 18, form an electromechanical measuring mechanism 3 of direct current. The even and odd electrodes 15 and 19 of each element of the electrostatic converter 1 are electrically interconnected. The rotation angle-to-voltage conversion unit 9 consists of an illumination lamp 20, a mirror 21 fixed on the moving part 2, and a differential photoresistance 22 of the power supply 23. As a DC amplifier 10, an operational amplifier with a small zero drift can be used, for example, K544UD2. The nominal output voltage of the AC amplifiers 4 and 5 is 50 V. The frequency range is selected according to the appropriate predetermined frequency range of the indicator. Transformer 6 is made on a permalloy core with a winding with a close inductive connection between the windings. The device works as follows. Previously, after the device is warmed up, a balancing operation is performed. For this, a voltage from the circuit to be measured or an auxiliary alternating voltage is applied to the input of the transformer 6. By varying the gain of the AC amplifier 4 and 5, Ug., Jj at the output 14 is equal to zero. A phase shift 90 is established between current 1 at input 13 and voltage U./v at input 11 or between voltages at output 11 and Uj at output 12 connected by a switch 8. Voltage U at input 11 is supplied to the primary winding of the transformer 6. The voltage on the half windings of the secondary winding of the transformer 6 is geometrically summed with the voltage of the PS, at the potential terminals of the measuring resistor 7 of the alternating current or with the voltage U2 at the input 12, and, changing the transformation ratio of the transformer 6, achieve, for example The secondary windings of the secondary windings of the transformer 6 were of the same order as the voltage drop U or voltage Ts.2l / I; o 12. The sum of voltages is amplified by amplifiers A and 5 AC, one of which has an adjustable factor amplification, and applied to the electrostatic transducer 1 in such a way that the torques arising from the action of these voltages are subtracted. The torque equation of the electrostatic converter is

AM2., + K, X X K, p (, J, or after conversion with

k, 4Ki2, K (1) mi 4KUi (U, /, U,), where K and K 21. The conversion factors of the elements of the electrostatic converter j K and are the gains of amplifiers 4 and 5, respectively;

Ujy is the voltage drop across the measuring resistor 7; K - transfer coefficient of the transformer 6; () is the phase angle between the voltages U-1 and Tsch,

At 4 (oz,) 90 DM 0. If the angle between current 1 at input 12 (voltage U2- at input 12) and voltage and at input 11 differs from 90 °, then the moving part 2 of the measuring transducer 1 equal to the difference of moments, under the action of which the movable part of the rotation is at a certain angle.

The output of block 9 converts the angle of rotation, c. voltage appears voltage proportional to the angle of rotation. The voltage amplified by the DC amplifier 10 is the output of the device. This signal, applied to the DC measuring mechanism 3, serves to create negative feedback on torque. Torque is acting on the moving part 2

LM Curves, where K is the conversion factor. no measuring mechanism 3 dc

The moment dM is directed towards the moment dM2 and compensates for it. Thus, Ugj ,, is proportional to the deviation of the phase shift from 90 °.

In the balancing operation, by changing the K.4 gain of the amplifier 4 or Kyj-AC amplifier 5, the condition (1) is satisfied.

A phase shift indication of 90 ° is performed as follows.

After switching on and warming up the element of the device, the circuit is balanced. The balancing of the circuit is performed to alphaise the conversion coefficients according to expression (1) after switching the device on to the power circuit, changing the parameters of the measuring circuit or changing another measurement limit.

Establishing the phase shift 90 consists in connecting a voltage U to input 11 and current 1 to input 13 (voltage input 12), between which it is necessary to establish a phase shift of 90 °. By varying the phase shift between U and 1 (the voltage Uj / v.), Set the output voltage of the device to zero.

Consider the operation of the proposed device in accordance with the scheme shown in FIG. 2

When the moving part 2 of the electrostatic converter 1 is rotated, the image of the filament of the lamp 20 moves along the differential photoresistance 22. A signal proportional to the angle of rotation of the moving part 2 appears in the diagonal of the bridge formed by the photoresistance 22 and the power source 23

is the output signal of the device at output 14. This signal is fed to a divider on resistors 16 and 17, and the divider's shoulders are equal, where it is summed with the divided-i half of the voltage of the auxiliary voltage source 18. When ua ,,., O

OIL

The elements 15 are applied voltage uBtn 1 I and Vsp I ... 2 -2 -2 created by the elements 15, are balanced, the total moment of the measuring mechanism of direct current 4M 0. At 9, the moving part 2 acts as the torque

. m, chk ,,,,,,,

where K is the conversion factor of the upper element 15. The moment dM is directed towards the moment AM2 and compensates for it. So

thus, Ugji, is proportional to the phase shift from 90 °.

The accuracy of the display, the phase shift in the proposed device is determined by the angular errors of the transformer 6, the measuring resistor 7 of the alternating current, the relative instability of the gain factor of the amplifiers 4 and 5 of the alternating current, the zero drift of the constant current amplifier 10 and does not depend on the value of the constant time of the input circuit measuring mechanism, as its input is shunted by the low output impedance of the AC amplifiers. It is; a; a; it is possible to use the device in chains having a common point. Changing the balancing order allows the display time to be halved and the indicator used in the automatic control system of the 90 ° phase shift.

Claims (1)

DEVICE FOR INDICATING 90 ° PHASE SHIFT, comprising an electrostatic converter, an electromechanical measuring mechanism of direct current, the movable part of which is fixed on the same axis as the movable part of the electrostatic converter, different. the fact that, in order to improve accuracy and expand functionality, it introduced two alternating current amplifiers with adjustable amplification factors, a voltage transformer, an alternating current measuring resistor, a switch, an angle conversion unit for voltage, a direct current amplifier, and the primary the voltage transformer winding is connected to the first input of the device, the extreme terminals of the secondary transformer winding through alternating current amplifiers with adjustable gain connected to the fixed electrodes of the electrostatic converter, the middle terminal of the secondary winding of the transformer is connected to a movable contact of the switch, the first fixed contact of which is connected to the first potential terminal of the measuring AC resistor, and the second to the second input of the device, the current leads of the measuring AC resistor connected to the third input of the device, the axis of rotation of the movable part of the electrostatic converter ι is optically connected to the input of the conversion unit the angle of rotation in the voltage, the output of which is connected to the input of the DC amplifier, the output of which is connected to the electromechanical measuring mechanism of the direct current and the output of the device, the second potential output of the measuring resistor AC, one of the terminals of the second input of the device, low-potential inputs of amplifiers: AC with adjustable gains and a movable electrode of the electrostatic converter are connected to a common bus. SU „„ 1177767