SU737842A1 - Device for comparing output voltage of objects operating with ac - Google Patents

Description

one

The invention relates to a pulse technique, namely to the field of high-precision measurements on alternating current, and can be used in comparative measurements to identify 5 magnitude and sign of electrical errors of a precision rotary transformer compared to a reference. Measurement of the magnitude and sign of the EMF inequality can also be obtained 10 also for other objects similar to the operating transformer operating on alternating current at a fixed excitation frequency.

Devices are known for comparing the 5 output voltages of objects operating on alternating current, containing compared objects, synchronous detectors, compensating channels, InTapTpa and blocks for setting the limits 20 of the integration 1.

The purpose of the invention is to enable direct comparison of modules of unphased voltages, increase noise immunity from quadrature and higher components, and increase speed.

This is achieved in that in the device for comparing the output voltages of objects operating at

alternating current containing compared objects, synchronous detectors, compensating channels, integrator and integration limit setting blocks, Comparison inputs are connected in parallel, the synchronous detectors, integration limit setting blocks and Koltsantsi channels are connected to the outputs of their respective comparison objects, the outputs of both synchronous detectors, interconnected in series, connected to the first input of the integrator, the outputs of the compensating channels consisting of each of the following no included bandpass filter, phase shifter, amplifier and rectifier fazochuvsgtvitelnogo are connected to second and third inputs inte17ratora, and outputs setting integration limits blocks are connected to the control inputs of the synchronous detectors sootvetstvuyu1tsih them.

FIG. Figure 1 shows the structural electrical circuit of the proposed device for comparing the output voltages of objects operating on alternating current; in fig. 2 - view of the EMF.

The device consists of compared objects 1 and 2, representing, for example, a rotating transformer and a reference voltage divider, two synchronous detectors 3 and 4, compensating channels 5 and b, each of which contains respectively a band-pass filter 7 (8), a phase shifter 9 (10), amplifier 11 (12) with a transformer output and a phase-sensitive rectifier 13 (14), as well as units 15 and 16 of setting the integration limits and integrator 1

The device works in the following way.

When a variable voltage is applied from the source C {, the compared objects 1 and 2 are supplied to two synchronous detectors 3 and 4 with secondary electromotive forces, whose modules must be compared. Exactly at the time of the zero emf of the second secondary winding of the compared object 1 / representing a rotating transformer, the integration limit setting unit 15 switches the detector 3 to reverse polarity of the EMF (the EMF of the second secondary winding of the rotating transformer in idle mode always coincides in phase with the measured EMF of the first secondary winding). Similarly, switching of the EMF taken from the reference voltage divider with the help of the second detector 4, the switching in which is carried out exactly at the moment of zero transitions of this EMF. During the siihrbnnom detection of signals of each of the sources separately in the measuring circuit, the difference of the detected EMF of the first and highest harmonics, as well as quadrature emf, the type of these emf is shown nafig, 2,

The measuring circuit is connected to the input of the integrator 17,

The integrato output voltage is proportional to the integral of the input voltage, namely

. it | i I.x

for all the components of the emf voltage at the input. It is clear from the mathematical analysis and the imprint from FIG. 2 that with precise switching of the detectors separately for: each of the sources and within the limits of integration

,) t

 , Tia + vf

eb ,, tj,,. oV

where s is the phase difference, t, e, the output voltage after the integrator 17:

-: The quadrature component is zero; - the second and all even G is zero;

- a third Harmonica acts its

the third part, n ta - n ta (and so on), i.e. not equal to zero.

In the absence of odd harmonics in the input signal (except for the first), the output of the integrator 17 shields a voltage proportional to the difference of the integrals of the first harmonics of the equalized electromotive force, the same is true if there is a phase shift between the emf and the reference source. In the latter case, at the input of the integrator 17 (at the input of its adder) there is a signal in the form of cosine-wave segments even with exact equality of the modules, but the integral of this voltage over a period is zero. For correct operation of the circuit, it is only important that this signal does not exceed the dynamic range of the first cascade of the adder. In reality, odd harmonics (interferer) may be present in the EMF. To improve the noise immunity of the circuit using compensation channels, the third harmonic vectors are extracted from the common signal of the secondary winding of the rotating transformer of the object 1, amplified to the transmission coefficient, multiplied by the phase coefficient so that the resulting voltage vector of the secondary winding of the output transformer of the amplifier becomes active and out of phase with the original.

To work from a rotating transformer as a compared object, only the third harmonic is required. For other objects for which a friend (s) higher harmonic gives an unacceptably large amount of interference, it is necessary to expand the composition of the anti-interference elements. The compensating harmonic voltages are rectified by phase-sensitive rectifiers 13 and 14 and fed to the second and third, integrator inputs with the opposite sign with respect to interference.

The basic error of the circuit is obtained due to the inaccurate formation of the integration limits, which are determined by the inaccuracy of switching the keys of the detectors at the moments of zero crossing. This error is

GZ ICH-ACh-ChSK Ua

: o °,,

 IO °.

J sniM-av

where relative error; y is the angular form expressed inaccuracy of the formation of the limits of integration. With +0.5, for example

 0.005%. In practice, the implementation of the measurement method is accompanied by other errors, but their total impact can be reduced to 0.003%. Common

Claims (1)

Claim A device for comparing the output voltages of objects operating on alternating current, containing the compared objects, synchronous detectors, compensating channels, an integrator and installation units' of integration limits, distinguished by the fact that, in order to be able to directly compare the modules of unphased voltages, to increase noise immunity from quadrature and higher components, improved performance, inputs of comparison objects are connected in parallel, inputs of synchronous detectors, limit setting blocks integration channels and compensation channels are connected to the outputs of their respective comparison objects, the outputs of both synchronous detectors connected in series are connected to the first input of the integrator, the outputs of the compensation channels, each of which are connected in series * to a bandpass filter, phase shifter, amplifier and phase-sensitive rectifier, are connected to the second and third inputs of the integrator, and the output of the units for setting the integration limits are connected to the control inputs of the corresponding syn chronic detectors.