US2183316A - Current metering system - Google Patents

Description

Dec. 12, 1939. F. G. KEAR 2,183,315

CURRENT METERING SYSTEM Filed Feb. 26, 1957 z B FlGf.

TRANSMITTER amen 140v fieA/v/c Q/(EAR Gummy Patented Dec. 12, 1939 ington Institute of Technology, Inc., instcn.

Wash! D. 0., a corporation of Delaware Application February 20,1937, seriai'n l zaosw z (CL 171-229) This invention relates to electrical systems in;

e arev which two or more loads. such as energized from a common source of power and in which it is desired to establish a desiredf phase and magnitude relationship between the currents in the loads and to control the power.

supplied to the loads. V I It has been found, particularly"in adjusting antenna circuits to secure desired relationships f of the phase and magnitude of -the currents,

therein, that the current relationships, with re spect to either phase or magnitude, cannot be established by simple means. This is u el toj various conditions, aniongwhich-is' the factjthat,

usually employed in at the frequencies turns of the two windings. Further, the antennas themselves cannot be accurately tuned of slight differences in radiation characteristics,

between antennas in a given array. Heretofore a pre-determined current relationship has been secured, or approximated, in a given arrayby adjusting the tuningof one or more of the antennas or the circuits which supply the antennas by trial and error methods. This has'proved-to be an entirely unsatisfactory procedure because of the fact that the antenna currents involve two variable factors which are mutually interdependent, i. e. the phase and amplitude factors.

Thus, it has been found that in tuning one an-- tenna of an array'in order to produce a desired amplitude relationship, the phase relationship of e antenna currents is changed, while if an initial adjustment of phase relationship is made the amplitude relations of the currents are dis-.

turbed. The problems involved in tuning by trial and error methods are accentuated if more than two antennas or loads are to be adjusted to a desired current relationship, as it will be apparent that the possible variations of phase or amplitude of the antenna currents will in- 5 crease with the number of antennas in the array.

The present invention has for its principalobject the provision of a method of tuning any number of antennas which form" an array, by

which method either the phase or the amplitude of the current in an antenna or load may be varied without causing a similar or other variation in the other factor of the current.

The method according to this invention also has for an object to provide a means for securing any desired phase and magnitude relationship between the currents in interconnected circuit elements, such as antennas.

It is also an object of the invention to provide 7 apparatus which may be employed in carrying i0 out the method according to invention, I

radi broadcasting, the input transformers g the antennas do not act as simple transformers} due to leakage flux ordistributed capacity be'- tween the tums of one winding Qrbetween the this invention, and are as follows:

Referring to the drawing, wherein similar refcrence characters refer to like parts,

Fig. 1 is av diagram of a circuit which is particularly adapted for the energization of two loads. v 5

Fig. 2 is a diagram of a circuit which may be employed for energizing three loads; Fig.3 is a circuit diagram showing a practical embodiment of the circuit disclosed'in Fig. 2;

Fig. ("is a diagram showing a balahced-tol0 around circuit for energizing two loads, and I i? Fig. 5 is a diagram of a circuit which is similar :f'to that-disclosed in Fig. 2, but in which the 'jantenna currents are adjusted to difl'erent values.

According to the present invention, the am- 15 plitude and phase relationships of the currents in 'two or more antennas or other circuit elements may be adJusted by a procedure which involves the connection in series with one of the loads, of an impedance, which may be either 20 lp'ductiveor capacitative incharacter and which is of such magnitude as'to cause the impedances in the circuit, when arranged and considered ina pro-determined manner, to become equivalent to the desired current relationship. The 35 method may nnderstood by reference to an actual example.

In Fig. 1 there is disclosed a circuit which is designed for the encrs'ization of two antennas or loads which are represented by the impedgo ances Z1 and Z: andin which loads, respectively, are flowing the currents I! and I: in the directions shown by the arrows. The impedance Z1 is connected in parallel with, two series-connected voltage-dividing impedances Z: and Z4, 35 the outer terminals of which are; connected to the terminals of the secondary ofan input transformer T, which delivers alternating current at, voltage E, and in which impedances respectively,

are flowing the curl-eaten and n. One terminal to of the load'za is connected to the connection between impedances Z: and Z4, the other terminal of load Z: bcingso connected that load 2:

is in parallel-with either impedanceZa or. 24.. it being shown in Fig. 1- as being so'connected' 48 to impedance Z4. The'impedances Z3 and Zr may be either inductive or capacitative inchar- An examination of the circuit disclosed in Fig. 1 shows that certain relationships exist between. 50

the voltages, currents andimpedances of the elements thereon Certain of these relationships are of importance in the method according to.-

1 2 44; in which x is an impedancewhich may be con-l nected in series with load Z1, in a manner and.

for ap llose to be set forth hereinaiter. Inas- 00 much as the voltaae E divide: between impedand, inasmuch as the voltage across impedance Z4 is equal to that across impedance Z2, z,Ij=ZI4 and 14 and and since It will be seen that I have derived an expression for the relationship of the currents in two loads,

which is expressed entirely in terms of the impedances of the circuit in which the loads are when connected, and from which any pre-determined ratio of currents may be readily obtained by adjustment of the impedance; Z: and Z4.

The current ratio expression (1) as set i'orth above may be rewritten as follows:

will be a real number and the value of this ratio must first be ascertained in carrying out the method according to this invention.

If it be assumed that the loads Z1 and Z: are to be so adjusted that the current I1 will be three times the current I2, then For the purpose of determining the value of the ratio the single term Z: of the numerator o1 expression (1) may be disregarded, and the foregoing equation may berewritten as follows:

The impedances Z1 and Z: may be measured by any-known means and it will be assumed that, in the present case, these impedances are 75 ohms and 50 ohms respectively. I1 these values a e substituted in Equation 2 the value of the ratio may be round by solving the equation, in the following manner:

The known values may now be substituted back into Equation 1, giving bib If a value of -;i50 ohms is assumed for Z4, this impedance may actually be adjusted to that value although an inductive element may be employed. This will givefor Z: the value of 'l75 ohms and this impedance may actually be given that value. The relation (3) may now be rewritten as It will be seen again that a lack of equality exists between the two elements of this relation, such inequality being represented by the term -7'175. In order to bring the two terms of the relation into equality, a term must be added to the denominator o! the right hand term of the relation, which term may be denoted X, as follows:

The value of the term X must be so related to the value of the term Za as to maintain the predetermined relationship between the numerator and denominator of the right-hand item. In the present example the value of X must obviously be one-third the value of the term Z: in order to make the fraction equal to 3. In other words, the value of X in the present example is 58%.

The value of the term X measures the value of an added impedance X which is inserted into the circuit in series with the impedance Z1. It will be seen that the denominator of the right-hand term of the equation has been so changed that the term Z1 has become Z1+X and this change is given efiect in the circuit by inserting the added impedance in the described manner. The addition of the impedance X causes the desired current relationship P to be secured, with respect to both the phase and magnitude of the currents in the loads.

Current ratio According to the method described it will be seen that the desired phase and amplitude relationship between the currents in the two interconnected circuit elements is secured by increasing the impedance oi the circuit containing the load Z1 by an amount which may be easily calculated after the values oi the voltagedividing impedances have been determined. In practise this is effected by inserting the impedance X in the circuit containing load impedance Z1 and in series with the load impedance, this being diagrammatically illustrated in'Fig. 1. It the value oi the impedance X is properly chosen in the manner described, the desired phase and amplitude relation between the currents in the loads Z1 and Z: will be achieved without the necessity of resorting to trial and error methods. It will be apparent that impedance X may be either inductive or capacitative in character, but must be the same in character as Za.

I! the value of impedance Z: is much less than the line impedance, the ratio is-dependent upon the load to the extent that the voltages in the loads remain in phase. This may be illustrated as follows:

Across load Z: there exists the voltage E z z.+z I Z 2 E #7 I 3 2) *2: and

Ez,=z

It the value of the ratio Z Z is much less than one then the ratio oi these loads being such that the currents I1, 15'- and I5 flowing therein will have the relationship 2= s= 1 In order to achieve equality between the currents I: and Is, flowing in loads Z2 and Z5 respectively,

these two loads are connected in parallel and are both connected in parallel with one of the two voltage-dividing impedances Z3, Z4 which are connected in series and are both connected in parallel with the load Z1.

In this particular case the current relationship will obtain, inasmuch as the loads Z2 and Z5 are to be so adjusted that the currents flowing therein are equal. The total impedance of the circuit including loads Z2 and Z5 is measured and this value is taken as the value of the term Z2 oi the expression (1). If the current in load Z1 is to be twice that in either of loads Z2 and Z5, then it may be assumed that, when the impedances of these loads are measured the load Z1 is found to have an impedance of ohms, while the total impedance of the circuit containing loads Z2 and Z5 is 50 ohms. The values of the impedances Z5 and Z4 may be assumed as 50+50+(j25) 10o In order to bring this relation into equality, an additional term must be added to the denominator of the right-hand expression and this added term will, in the present example, be equal to Z3 in order to maintain the correct and pro-determined relation between the numerator and denominator. The equation now becomes 1, l00j25 n+1? 100+ or 7 I l00-j25 From this it will be seen that only the imaginary values of circuit elements will change with any change in Z1 and that good control will therefore be secured. The degree of control over phase and magnitude relations of the currents in the loads may be improved by choosing smaller values for Z5 and Z4. This particular discussion is of importance only in securing phase control.

The circuit disclosed inFlg. 2 is particularly designed for the energization of loads in which the current relationship n=n=nz is to be obtained. If an unequal relationship between the currents in all of the loads is to be secured the circuit disclosed in Fig. 5 may be employed. In this circuit arrangement one of the loads such as Z: is connected in parallel with one of the voltage-dividing impedances, such as Z4. Also connected in parallel with the impedance Z4 are two series-connected impedances Z11 and Z1. The load Z2 is connected in parallel with one of the voltage-dividingimpedances Z6, Z1, and is shown so connected with impedance Zv. The desired relationship between the phase and magnitude of the currents I1 and I5, flowing in loads Z1 and Z5, respectively, may now be secured by the method described. The ratio must first be determined and from this the value of Z: may be computed after assigning a chosen value to Z4. These values may now be substituted back into Equation 1 in order to determine the quantity which must be added to the de nominator in order to secure equality between the terms of the equation, this quantity measuring the value of the impedance X which is to be connected in series with load Z1 in order- .loads Z: and Z5 may now be secured by the.

method according to the invention, the impedance Xi being connected in series with load Z5 and having a value determined by the quantity added to the denominator of the right hand term of Equation 1 in order to make such equation a true equality. In this manner the desired relationship between the currents in loads Z2 and Z5 may be secured and inasmuch as the desired relationship between the currents in loads Z1 and Z5 had already been secured, it will be seen that the three loads have been adjusted in the predetermined manner.

In Fig. 3 or the drawing there is disclosed a circuit in which the invention is applied to the energization of three transmission lines, the connections being as actually made in practice. :The transmitter, which is disclosed in the drawing, supplies current at radio frequency to two leads A and B, across which are connected the two series-connected voltage-dividing impedances Z3 and Z4. Once! the output leads, such as A, is connected directly to a transmission line I, the same having an impedance Z1. Two transmission lines 5 and 6, having impedances Z5 and Z6 respectively, are connected in parallel and to the common connection between impedances Z3 and Z1. The method according to this invention is employed to determine the value of the impedance X which is connected in series with the load Z1 in order to secure the desired phase and magnitude relationship between the currents in the three loads. In the case illustrated in Fig. 3 the currents I5 and I5, flowing in loads Z5 and Z0 respectively, are intended to be equal. If such a relationship is not desired the means illustrated in Fig. 5 may be employed and a second added impedance, corresponding to impedance 2211 of Fig. 5, must be added to either of loads Z5 or Zc in order to secure the desired relationship between the currents in these loads.

In Fig. 4 oi. the drawing there is disclosed a circuit for so energizing two loads that they will be in phase with respect to each other and balanced with respect to ground. In this circuit the load 1 Z1 is connected across the terminals 01' the secondary or the input transformer.

having the values Z Z "2 Z4 and 3 respectively. The load Z51 is connected in parallel with the impedance Z4. method according to this invention is employed in order to determine the value of the added impedance which must be connected in series with the load Z1, in order to secure the desired phase and magnitude relation between the currents in the loads Z1 and Z2. In the present case, how--, ever, this added impedance is divided equally and two impedances X1 and X11, which are equal in value, are connected in series with the load Z1, one or these added impedances being connected in each branch of the circuit including load Z1, as clearly illustrated in Fig. 4.

I have provided, by the present invention a simple and easily practised method of adjusting the currents in two or more interconnected circuit elemets to a pre-determined relationship with respect to both phase and magnitude. 1 have disclosed, in this application, certain circuits illustrating the application of the invention and how the invention may be practised in certain specific cases. It is to be clearly understood, however, that the invention is not limited in any way by the description and drawing of this application, and that the scope 01' the invention must be sought in the appended claims.

I claim:

1. An electrical system comprising a source of power and a plurality of load devices connected to said source to be energized thereby, means for producing a pre-determined phase and magnitude relationship between the currents in said load devices, said means comprising a plurality 0i series-connected impedances connected across the output of said source, one of said load devices being connected in parallel with said impedances, another of said load devices being connected in parallel with one of said impedances, and a compensating impedance connected in series with said first-named load device and having the value Zs/r, in which Z3 is the impedance of that portion of the series-connected impedances which is not in parallel with saidsecond load device.

2. An electrical system for producing a predetermined phase and magnitude relationship P between currents in connected load devices which are energized by a common source oi. power and which have impedances Z1 and Z2 respectively, comprising series-connected impedances Z1 and Z4 connected across the output of said source and in parallel with one of said load devices Z1, said impedance Z4 being connected in parallel with the second of said load devices Z1, and a compensating impedance X connected in series to said load device Z1 and having the value

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