i.e., the minimum permissible angle for a photocompensated fluxmeter is

20.10 -6 (19) 10-8 tad; K -- - - = 1 0 0 0 A/rad.

aamin = 2 ' max 2-10 -8

On the basis of the above calculations a photocompensated microvoltamperewebermeter type F18 was produced by the "Vibrator" plant [9]. The actual value of the instrument's transfer constant was K = 50 A/tad.

Conclusions. The above relationships determine for a given galvanometer design and an operation under lab- oratory conditions the possible transfer constant for a given PI voltage sensitivity and a given resistance of the measur- ing circuit.

It is also possible to determine a photocompensated fluxmeter's maximum permissible transfer constant for a given drift constant and a given frequency characteristic of the output instrument.

1o 2. 3. 4.

5,

6. 7. 8. 9.

L I T E R A T U R E C I T E D G. P. Kul'bush, Tochnaya industriya, 1931, No. 11. M. Czerny, Annalen der Physik, 1932, Bd. 12. L. Merz, VDE Fachberichte, 1939, No. 11. V. N. Mil'shtein, Power Relations in Electrical Measuring Instrument [in Russian], Gosen~rgoizdat, Moscow (1960).

B. A. Seliber and S. G. Rabinovich, Avtomatika i telemekhanika, 1956, ,No. 8. G. Ising, Annalen der Physik, 1931, Bd. 8. H. Pohl, Zschr. angew. Phys., 1958, 10, No. 3. S. G. Rabinovich and A. N. Tkachenko, Izmeri te l 'naya tekhnika, 1959, No. 5. S. G. Rabinovich and A. N. Tkachenko, Pribory i tekhnika ~ksperimenta, 1961, No. 4.

T E S T I N G H I G H - P R E C I S I O N T H R E E - P H A S E E L E C T R I C I T Y METERS

A . M . I l y u k o v i c h

Translated from Izmeri te l 'naya Tekhnika, No. 70 pp. 28-31, July, 1962

Single-phase reference electricity meters are tested by means of reference high-precision devices such as "de and ac work balances," oscillating counters, comparators, etc. [1], which are rather cumbersome and complicated. Hence, the testiflg of high-precision three-phase electricity meters (with an error of the order of 0.t - 0.3%) by means of two or three such devices becomes impossible in practice.

This difficulty is overcome in the main in two ways: by the use of one single-phase reference instrument in conjunction with devices which maintain complete symmetry in the three-phase testing circuit; by testing the three-phase electricity meters by means of several single-phase reference meters each of which has previously been checked by a single-phase reference instrument.

In the first instance it is necessary to provide extremely high stability for the three-phase test circuit supplies. An exception to this rule is provided by the firm Siemens-Schuckert with its special device, called by the firm "Three -phase current work balance," which controls and maintains an "integral" symmetry of the three-phase test circuit [1]. The drawback of this method consists of its complexity. Moreover, the additional devices for providing sym- metry lower the accuracy in testing three-phase meters as compared with the accuracy attained for testing single- phase meters. The same defects, and perhaps to an even greater extent, affect the method in which several s ingle- phase reference electricity meters are used for testing a three-phase meter.

568

The most rat ional solution of this problem seems to con ;st in checking high-precis ion three-phase e lec t r ic i ty

meters directly, by means of s ingle-phase reference installatior:: . This method has been developed and approved by

the VNIIK (Al l -Union Scientif ic Research Institute of the Commi t t ee of Standards, Measures and Measuring Instru-

ments) for three-phase , two-e l emen t and t h r ee - e l e me n t reference meters type OS [2].

f

L 'L t .... _ _ . . J

I Z -~- ....... f - - - - - n

I , I

Fig. i .

�9 U~j

U,o / It3

Fig. 2.

The c i rcui t for testing a two-e l emen t meter OS-2 is shown in Fig. 1 and a vector d iagram i l lustrat ing the phase relat ions of the currents and voltages in the winding of tested meter 1 and reference meter 2 are shown in Fig. 2. Current Izs is made to flow through the current windings of the three-phase meter connected in series op- posing, and through the current winding of the reference meter . Voltages Ul0 and Us0 are appl ied to the two vol tage windings of the tested three-phase meter . The vo l t sge winding of the reference mete r is connected to the l ine vol tage Ulz ,

which equals the vector d i f ference of vol tages U10and Us0. In this instance the power Pr measured by the reference instru- men t ts equal to the scalar product (1)

and the power Pt measured by the tested two-e l emen t meter is equal to the sum of two scalar products

Pt = ( U l o / ' l s ) - t - [U~0 ( - - 1 1 ~ ) ] ~ (2)

Since 010 - s = IJzs we find that Pr = Pt, i . e . , t he reference instrument for any cos ~o measures the same power as the tested meter without the necessity of mainta in ing an accura te equal i ty of voltages U10 and Us0.

It wil l be seen from Fig. 2 that the current in the first e l ement of the tested meter ' s current winding lags with respect to the vol tage in its vol tage winding by 30* + ~0, and the current in the second e l emen t leads its vol tage by 30 ~ - cp. Thus the same condit ions are preserved as those for a normal Aron Circui t connect ion of a two-e l emen t

me te r to a three-phase three-conductor network (Fig. 3).

�84 2 /

~r , , - -

/ / r z

Fig. 8.

/ ,

Y -.. . .

The difference between the circuits shown in Figs.

1 and 3 consists in the fact that the current and vol tage of the first e l ement wil l have different phase shifts with

respect to those of the second e lement in Fig. 1 as c o m - pared with Fig. 8. As a result of this the torques due to

the in teract ion between e lements will have different values in the circuits of Figs. 1 and 8, thus leading to a var ia t ion in the meter readings when passing from one c i r cu i t t o the other. Thus, in Fig. 1 the currents in the

series c ircui ts of e lements I and II (I I = Ils and I i i - I13 ) are reversed in phase, whereas in Fig. 8 they are at 120 ~

to each other (I I = I I and I i i = I s ). Hence, if the m a g - net ic fluxes produced by currents I I and IIi in terac t with

each other and produce a torque Mn, then any change in the phase difference between the currents wil l alter the value of Mzz , since it depends not only on the magni tude of the currents, but also on the phase difference between them. When passing from the c i rcui t of Fig. 1 to that in Fig. 3 s imi lar changes may be produced in torques MUU

569

and MUI, due to the interact ion of the vol tage circuits of different e lements (MUU) and the interaction of the cur-

rent and vol tage circuits of different e lements (MuI).

The existence of interact ion between different e lements is obviously the main reason why the method of check- ing commerc ia l three-phase e lec t r ic i ty meters by means of a single reference s ingle-phase meter , although known

for a long t ime , has not been used in p rac t ice [3, 4]. The indirect de terminat ion and correction of errors which arise in changing from an "a r t i f i c ia l " to an "ac tua l" three-phase meter connection, and which are due to the interact ion between various elements , has not been tr ied, since in checking c o m m e r c i a l e lec t r ic i ty meters i t is important to re- duce the testing t ime to the minimum.

In testing high*precision th tce-phase e lec t r ic i ty meters, when accuracy is of greater importance, it becomes expedient to check by means of the ar t i f ic ia l c i rcui t and introduce corrections obtained indirect ly for the interact ion between elements . Moreover, it is important to bear in mind that the in teract ion between elements in high~prcci* sion meters cannot be large, since i t would otherwise be impossible to provide satisfactory behaviour of the meters with a changed order of phases, asymmetr ica l loading, asymmetr ica l voltages, etc.

Let us examine a technique of introducing corrections for changed interactions between elements when chang- ing from an ar t i f ic ia l to an actual connect ion of meter OS-2 to the network. The only interact ion which should be accounted for in this meter consists of torque MUI arising between the vol tage circui t of the first e l ement and the current c i rcui t of the second e lement . This is due to the fact that these circuits are p laced re la t ive ly close to each other. It is obvious that for other designs of the measuring mechanism of a three-phase e lec t r ic i ty meter one of the three torques due to interact ion wil l be considerably larger than the other two, and since the largest of them must be

smal l , as has been pointed out above, the other two in the major i ty of cases can be neglec ted . Torque MUI was de- te rmined in the following manner. The first e l ement was provided with the nominal current and vol tage with a cos ~p = 1, whereas the second e lement was on lyconnec tcd to the circui t which produces the interact ion, namely, the

current c i rcui t . Moreover, the current through that c ircui t was set at its maximum value determined by the heat ing

conditions and equal to 400% of the nominal~ The operat ion of the second e lement ' s current circuit produces two torques, namely , that of se l f -braking and a torque due to interact ion with the vol tage c i rcui t of the first e lement .

The first torque does not depend on the phase of the current in the second c lement , but the second torque does de- pend on it. Hence, by changing the phase of the current in the second c lement we shall obtain variations in the ro- tat ing speed of the moving part due to changes in the interact ion between elements . By varying the phase of the

current between 0 and 360"C we can obta in a relat ion between the speed of rotat ion n of the second e l e m e n t s moving part and the phase ~, of its current. By referring the deviat ions in speed for each phase of the current to the mean

speed n o in the second e lement , i t is possible to find the relat ion between the error due to interact ion in a given operat ing condit ion and the phase of the current in the second e lement . This relat ionship is sinusoidal, since the in- teract ion torque, just l ike any other induced torque, has a sinusoidal re lat ion to the phase difference between the

magne t ic fluxes which produce it.

In prac t ice the most expedient method of determining the re la t ion of the above error to the phase of the current in the second e lement consists of the following. After the c i rcui t has been switched on and the current in the second e l emen t has acquired a cer ta in phase a meter reading is taken, and then the phase of the current in the second e l e -

ment is reversed and another reading taken. It is desirable to repeat these readings several t imes.

Half the difference in the readings of the meter for a forward and reversed direction of current in the second e l emen t referred to the mean reading is ~he required error for the given phase of the current in the second element . Interact ion errors for other phases of the current in the second e lement are found in a similar manner. This method of de termining the interact ion error provides sufficiently high accuracy of testing, since variations in the readings of the meter due to changes in the conditions of the exper iment , and in par t icular , due to the heating of the meter ,

do not affect the results thus obtained.

The adjustment of the above error for an operating condit ion of the meter provides no difficulty. For this pur- pose i t should be divided by 4 ~ because readings were taken at four t imes the nominal current in the second c l e - ment , and because under normal operat ing conditions both e lements are connected instead of only the one used for testing purposes, thus making the operat ing torque larger than the testing torque by a factor of ~ whereas the in- teract ion torque remains the same under both conditions. Thus, we obtain the relat ion between the interact ion error AUI and the phase of the current in the second e lement . This relationship is shown in Fig. 4 for e lec t r ic i ty meter OS-2. Angle y is measured between the vol tage in the para l le l c i rcui t of the first e l ement and the current in the

series c i rcui t of the second e lement .

570

~#tT* *0,08

0

-0.04 ~ - - -

/ \

i t -aoo L ,eo " ran e~o ~a~ ~o ~ f

L.

l (7

1 / - -

Fig. 4. Fig. 5.

2

I

i �9

By means of the above relationship it becomes possible to ca lcula te the actual variation in the interaction

error of the meter when passing from one method of connect ing m another. Thus, in the connection of Fig. 1 the

phase difference between the voltage in the first e lement U I = U10 and the current in the second e lement Iii =-I13 for cos r = 1 amounts to 210" (Fig. 2). The interaction error will then, according to Fig. 4, be equal to zero.

For a connect ion of Fig. 3 the phase difference between the voltage in the first e lement U I = U12 and the current

in the second e lement Iii --- I s is equal to 270 ~ , and the error due to the interact ion torque is equal to + 0.06 %,

Hence, in passing from the connection of Fig. I to that of Fig. 3 the meter acquires for cos q = I an additional

error equal to + 0.06 90. In a similar manner it is possible to find the difference in the meter readings when con-

nected according to Fig. 1 and Fig. 3 for cos g = 0.5. It amounts to -0.01%. These errors can be corrected for

when the meter is calibrated in a connect ion of Fig. 1, so that when it is connected according to Fig. 3 it will pro- vide correct readings. It should be noted that the accuracy in determining the corrections by the above method

is sufficiently high, since they are obtained under test conditions when they are larger than under operating condi-

tions by a factor of 4 r Moreover, as has already been pointed out, in determining the interaction effect the variation in the moving part rotating speed with a reversal of the current (180 ~) in the second e lement was measured, and

not the actual speed itself, which also raises the accuracy in determining the error.

Tests of the interact ion between elements on several models of the O8 electricity meters have shown that they

were the same for all of them, i .e . , they are only determined by the design of the meter, and it is not necessary to find corrections for each tested meter.

In checking the three-phase th ree-e lement high-precision electr ici ty meters an artificial circuit for testing

by means of a single reference single-phase device can also be used (Fig. 5). All the elements of tested meter 1 are connected to the same phase voltage and current as reference instrument 2. In this connection the tested meter

measures the same power as the reference instrument and the phase relat ion between the voltage and current of each

e lement corresponds to that normally obtained with the meter connected to a four-wire network, when each e lement

is connected to the voltage and current of the corresponding phase [5]. In a manner similar to the previously ex-

amined instance of checking a two-e lement meter the difference in the artificial and actual connections consists in the changing of the current and voltage phases between different elements, Hence, in this instance it is also

necessary to apply corrections for changes in the interact ion torques between elements when transferring from one

connect ion to another. For this purpose the technique described above can be used.

A three-phase th ree-e lement reference electr ici ty meter OS-3 [2] has been tested by means of the circuit

shown in Fig. 5. In this case, however, it was possible to avoid applying corrections when changing from an art if i-

cial to an actual connection. The fact of the matter is that in a three-phase threere lement meter it is possible to

change the direction of one of the three interact ion moments by changing the direction of both the current and

voltage of one of the elements. The two elements will then be in opposition to each other, and will compensate

each other for any value of cos r The polarity of one of the meter OS-3 elements was reset in such a manner, thus avoiding the necessity of corrections when changing from one connect ion to another, since the measured inter-

action moments between the first and the second elements and between the second and third elements proved to be the same.

571

Conclusions. The method of testing high-precision three-phase electricity meters in artificial connections by means of a single reference instrument is satisfactory. This method can also be used for testing multiphase wattmeters.

L I T E R A T U R E C I T E D 1. N.G. Vostroknutov and A. M. Ilyukovieh, Electricity Meter Testing [in Russian]. Gos~nergoizdat, Moscow(1961). 2. A.M. Ilyukovich, "Reference ac electricity meters type OS." In collection: New Measuring Instruments and

Methods for Testing Them [in Russian]. Standartgiz., No, 6, Moscow (1961). 3. W. Beetz, ETZ, 1929, No. 5, S. 1835-1837. 4. Pieri, ETZ., 1988, No. 18, S. 472. 5. P .N. Goryunov,S. M. Pigin, and N. N. Shumilovskii, Electricity Meters [in Russian], Gosgnergoizdat, Moscow

(1951).

E L E C T R O N I C PHASE METER

S. M. K a m y n i n

Translated from Izmeritel 'naya Tekhnika, No. 7, pp. 81-82, July, 1962

An electronic two-channel phase meter whose schematic is shown in Fig. 1 has been developed at the Elee-

trotechnical Institute of the Ukr. SSR Academy of Sciences.

~q50

T, Ts:

mA

V

Fig. 1.

Voltage U t is fed along the first channel through the phase-shifting bridge, which serves to set the phase- meter zero, to trigger T~ at whose output square-wave voltage pulses are produced. These pulses are converted into triangular pulses by integrating network R1CI, and after amplification in a two-stage amplifier are fed to the

screen grid of tube T 4.

Voltage U~ is fed along the second channel to trigger T s whose outPUt rectangular voltage pulses are trans- formed into peaked voltage pulses by differentiating network ~C2. The peaked voltage pulses are then fed to the

control grid of tube T 4.

The converting stage consists of tube T 4 and transforms the phase difference into the amplitude of peaked

voltage pulses.

572