SU130984A1 - Device for measuring the phase difference of two alternating voltages - Google Patents

Description

The basis of the proposed device for measuring the phase difference of two variable voltages is a comparison of the sum of the compared voltages with the double value of one of them.

The peculiarity of the proposed device, which provides the possibility of obtaining higher measurement accuracy, is the use of two synchronously operating electronic switches, one of which is designed to alternately supply comparable voltages to a phase-sensitive circuit, the output of which includes a voltage divider voltages removed from the input and output of the divider, to the input of the amplifier. The latter is fed by a reversible electric motor, whose shaft is mechanically connected to the voltage divider engine, the scale of which is directly calibrated in terms of the angle of phase shifts of the compared voltages.

In order to automatically equalize the amplitudes of the compared voltages, the proposed device uses a two-channel input amplifier equipped with a channel gain control in the form of a potentiometer, the slider of which is mechanically connected to the shaft of the reversing motor and the compared voltages are alternately inputted to the amplifier.

Comparable voltages are supplied to the outputs of a two-channel equalizing conductor (see the circuit diagram) assembled on L- to Jlz lamps, having characteristics with alternatingly; steepness. The gain of each jis of the lamps depends on the magnitude of the displacement and when the lamps are switched on differentially, as shown in the diagram, the amplitude of the output signal depends on the position of the slide bar creating the automatic displacement. The amplified signals are fed to the inputs of the low-frequency electronic switch L,

No. 130984-2 which alternately with a low frequency supplies comparable voltages to the input of a phase-sensitive summing circuit on a lamp L.

The electronic switch is a double triode with a total cathode load, which is powered by an alternating voltage of industrial frequency (50 Hz. One half of the lamp operates during one half-cycle of the power frequency, another half is operated during the other half-cycle. In accordance with this, a cathode load is repeated the one voltage being compared, the other.

The summing phase-sensitive circuit is assembled on a double triode with a common anode load and separated cathode loads.

Alternately, the applied voltages are summed with the reference voltage applied to the second grid of the lamp, directly from the anode of the lamp L. With this choice of reference voltage, the same voltage, or different voltage, is applied to the inputs of the summing cascade.

Thus, due to the periodic switching of the compared voltages by the same phase-sensitive circuit, a graduation in time is produced.

To equalize the amplitudes of the compared voltages, the voltage from the cathode load of the lamp L, on which the compared voltages periodically repeat, is applied to the amplifier Vb and then to the detector D, at the output of which a variable frequency is generated (50 Hz). This voltage is fed through the ultrasonic amplifier to the control winding of the D-1 two-phase reversing motor, the voltage on the excitation winding of which is shifted by 90 ° by the capacitor relative to the control voltage of the electronic switch L. The shaft of the D-1 motor is connected to a grounded rehoord with the help of which the redistribution of bias voltages on the grids of the lamps L and L and, consequently, the equalization of the amplitudes of the compared voltages.

The total voltages obtained at the anode of the lamp L of the phase-sensitive summing circuit are sequentially timed through the cathode follower L to the voltage divider QY. The inputs of the second automatic electronic switch L are supplied with voltage from the cathode load of the repeater L, for which a voltage divider is used. In this case, the voltage applied to the input of the divider is supplied to one input of the switch, and the voltage from the output of the divider is supplied to the other input.

The switch L operates synchronously and in phase with the first switch Ld. Therefore, through each half of the triode, at the moment when it is open, only one of the voltage sums, which in this half-period is formed at the anode of the summing circuit, can pass.

Thus, one total voltage passes without dividing through the switch L, and the other total voltage passes with a certain division factor. By adjusting the dividing ratio of the engine QN, it is possible to equal both amplitudes of the total voltages

signals, i.e., KV J, where K is the division factor of the divider QN.

By knowing the division factor / C, it is possible to determine the ratio of the sum of the voltages, and hence the measured phase angle

..i ,,., Cos | -,

from where

-r 2arccos / S.

To automatically equalize the total voltages (IC and Y. the voltage from the output of the switch L through the amplifier Y is fed to the detector D, which separates the low-frequency envelope. The low-frequency voltage after amplification (Y2) controls the reversing motor D-2, whose shaft with the equalizer divider of the voltage divider. When the phase shift between the compared voltages increases or decreases, the system goes out of balance and changes the division ratio of the divider until the amplitude equalizes. Two successive summed signals With the voltage divider slider, a pen of the registering device RU and a pointer are connected. At the same time as the slider slider moves along the slots graduated to the values of the phase angle, the pointer moves with the pen. A certain value of the division factor DN divider, and, consequently, a certain position of the slider of the divider and the pointer associated with it with a pen. The phase angle is determined by the pointer position, and The mm tape is applied to the curve for changing this angle.

The device is powered from the AC mains through the transformer Tr, and the DC circuits are powered from the rectifier B.

Subject invention

Claims (2)

1. A device for measuring the phase difference of two alternating voltages based on comparing the sum of the compared voltages with a double value of one of them, characterized in that, in order to improve the measurement accuracy, it uses two synchronously operating electronic switches, one of which serves to alternately supply compared voltages to a phase-sensitive circuit, the output of which includes a voltage divider, and the second switch is designed to alternately apply voltages taken from the input and output divides It was connected to the input of an amplifier supplying a reversible electric motor, the shaft of which is mechanically connected to the voltage divider engine, the scale of which is directly graduated in terms of the angle of phase shift of the compared voltages. 2. The device according to claim 1, characterized in that, in order to automatically equalize the amplitudes of the compared voltages, it uses a two-channel input amplifier equipped with a variable gain control channel in the form of variable resistance, the slider of which is mechanically connected to the shaft of the reversible motor, the amplifier input is alternately supplied with comparable voltages. - 3 - № 130984