SU667904A1 - Method of measuring ac voltage mean value - Google Patents

Description

 ... i. . ., / The invention relates to the field of electrical measurements and can be used for; measuring the average value of the alternating voltage in the infra-low frequency range. The known methods for measuring the average value are based on integrating the measured voltage. During the iteration, the measurement time is significantly increased, since the constant value of the time of the integrating element, according to known ratios, must be equal to 10 ± 15 periods of the measured time. The best method is to measure the average value of alternating voltage by straightening and integrating 1. However, this method cannot measure the alternating voltage in the range of infra-low frequencies where the inertia of the moving part of the gauge is insufficient and the deflection angle of the gauge is proportional to the instantaneous value measured voltage. The use of an additional integrating link to eliminate oscillations of the measuring pointer of the body in this case significantly reduces the measurement performance, since the time constant of the integrating link must be equal to 10–15 periods of the measured stress. The measurement error is usually no better than ± 3% due to the riorpei of integration, and the increase in accuracy of cumera1? The aim of the invention is to increase the accuracy with increasing the speed of measurement of the average value of the input voltage. To achieve this goal, in the method of measuring the average value of the alternating straightening and integrating voltage, the amplitude value of the pulse is measured, which is extracted during each half-period of the measured stress from the pulsating voltage obtained by straightening and integrating, at the moment of time determined from expression. got married

5 L qinn f --- OA rnrv, .2nK e

A, Nos. 2 PM According to T Rshog (0 t «T)

where ri is 1, 3, 5.. ; "

- harmonic number of the measured voltage;

 St-t. - a parameter depending on the ratio of the time constant of the integrator to the period of the measured voltage; CH is the frequency of the first harmonic of the measured voltage. As a result of measuring the average voltage of 3Wa4eHKH by the present method. The output of the integrator will always be a pulsating voltage, the constant component of which is equal to the average value of the measured voltage. With a sufficiently large ratio of the time constant of the integrator to the period of the measured voltage (3-5) Schluchenna as a result of the integration curve

one

PC

(pc) 2

And (PU

(G4 t "T),

n 1, 3, 5.

; - harmonic number of the measured voltage; L ..

K 6 - the parameter depending on the ratio of a constant time; nor an integrating element to the period of the measured voltage;

2 ntinjr

the pulsating voltage will cross the line of the average value of the measured voltage at a certain point in time, in particular in the middle of the measured period of the measured voltage.

Claims (1)

1. Fremke A, B. Electrical measurements. Gosenergoizdat, ML., 1963, p., 111-119.