US1924303A - Phase shifting reactor - Google Patents

Description

C. A. BODDI E PHASE sHIF'rING REAcToR Aug. 29, 1933.

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' nested Aug. 29, 1933 UNITED STATES PHASE SHIFTING REACTOR A Clarence A. Boddie, Wilkinsburg, Pa assignor to' .Westinghouse Electric & Manufacturing Company, a Corporation of Pennsylvania Application December 7, 1923. serial No. 324,568 3 claims. (c1. 117-352) My invention relates to signaling systems, and

it has particular relation to systems of the type wherein signaling is accomplished through the medium of high-frequency oscillatory currents 5 guided from a transmitting station to a receiving station over metallic conductors.

Inasmuch as Imany places, between which it is desired to maintain communication, are interconnected' by power-lines of various types, signaling between such -places is very often carried on over the power lines instead of over lines especially installed for signaling purposes. In applying high-frequency energy to power-line network, for either communication or control purenced by yreason of the presence oi parallel conducting paths, having diifering lengths and differing electrical characteristics, between the transmitting and receiving stations. The energy arriving at the receiving station over one of lthe paths may be completely, or partially, neutralized by energy arriving over a parallel path, depending, of course, upon the phase positions and magnitudes of the several waves.

Under certain conditions it may be desirable to limitthe signaling energy to one only of a plurality of parallel paths, in the manner fully explained in my copending application, Serial Number 296,294, while under other circumstances it may be preferable, in order to obviate interruptionto communication, to utilize all of the parallel paths simultaneously. A

Interference between signaling energy arriving at a receiving station has, in the past been minimized to some extent by the careful selection of frequencies which would not be likely to arrive at their destination in phase opposition. By this procedure, however, the number of available frequency-channels is greatly reduced, and series limitations are imposed on the universal applica-v tion of high-frequency telephone systems.

For example, if we assume that a high-frequency transmitter and a receiver are inter-connectedv through two parallel wave-conveying channels, one having a length of nity miles and the other a length of fifty two miles, high frequency currents at 46.5 kilocycles originating at the transmitter will arrive at the receiver exactly in phase opposition, and with very nearly equal' magnitudes. At a frequency of 93 kilocycles the currents will arrive in phase, thus making available for communication purposes, in the system under discussion, only those frequencies not in the neighborhood of 46.5 kilocycles, and odd multiples thereof.

poses, however, certain diftlculties are experi-v It is', accordingly, an object of my invention to make it possible to use, in a high frequency communication system, those frequencies that are normally notpermissible.

Another object of my'invention is to provide 60 means whereby signals, at a given high frequency, may be eiiciently transmitted over aplurality of wave-conveying channels having s uch physical charactersitics as to normally preclude the eicient transmission of, signals at the frequency chosen.

n practicing my invention I interpose a tuned phase-shifting reactor, or a plurality of tuned reactors, in certain of the branches of a powerline network which, considered from the standpoint of wave-conductivity, have characteristics that normally differ from those of the remaining branches in which the reactors are not interposed.

The reactor that I prefer to employ comprises an inductor, capable of carrying the normal power current, and a condenser conected in shunt thereto. I so choose the values of inductance and capacity of the reactor that it is resonant to afrequency either above or below that employed forv communication purposes, depending on whether a capacitative or an inductive reactance is necessary in the branch of the network in which the reactor is interposed.

The purpose of the reactor is to cause the signal potential in the section of the power-conductor, beyond it to either lag or lead-thepotential at the side of the reactor nearest the transmitting station, whereby the receiving apparatus, which is influenced by signals over all parallel branches of the power-line network,l shall be subjected to potentials in additive phase relation.

i. e., such relation as shall produce a resultant greater than if the said signals were to arrive in exact phase opposition.

The novel features that I consider characteristics of my invention are set forth with particularity in the appended claims. The invention, in its generic aspect, however, both as tothe organization and. its method of operation, together'4 with additional objects and advantages thereof, will best be understood from the following description of a specinc embodiment, when read in connection with the accompanying drawing.

The single figure of the drawing is a diagrammatic view of a'. portion of a power-line network 105 comprising a preferred embodiment of my inventir i, no attempt having been made to illustrate the various generators, transformers, etc., except in a highly conventionalized manner.

The system shown in the drawing comprises a 11o V would act merely as high impedance.

main generating station 1 which is connected to a substation 2 by means of a plurality of power lines 3 and 4.

As is commonly the case in power-line networks, the main generating station is connected to the substation 2 by additional transmission lines 5 and 6, thelatter lines serving to supply power to territory not reached by the lines 3 and 4 rst mentioned. A substationv 7 may be interposed between the power lines 5 andy 6 and the main generating station, and an additional substation 8 may be connected to the lines at an intermediate point.

In order that communication may be carried on between the substation 2 and the main generating station 1, each of the said stations is provided with combined high-frequency transmitting-receiving equipment l0, which equipment is coupled to both transmission lines 3 and 4 in order that an all-m'etallic circuit shall be provided for /the signaling currents. The transmitting-receiving apparatus may, of course, be utilized for accomplishing remote-control of the apparatus at the substation, but, since the purpose for which the signaling currents are intended forms no part of my invention, the drawing has not been complicated by the inclusion therein of the additional circuits and apparatus required.

It is obvious, from an inspection of the drawing, that high-frequency currents originating at either of the transmitting-receiving stations are offered two paths in parallel leading to the other station, one path over the main power-lines 3 and 4, and the other path through the substation 7 and the branch lines 5 and 6.

If the physical lengths of the two parallel waveconducting channels thus dened between the main generating station and the substation 2 differ by one-half of a wave-length of the communication frequency, or by an odd multiple thereof, or if the electrical length of one 'of the paths, irrespective of its physical length, differs from the electrical length of the other path, the signals arriving at the receiving apparatus over the two paths will be non-additive in phase. The phase difference may be such as to result .in an entire obliteration of the signal frequencies at the receiver, or it may be sufficient to merely reduce the amplitude of the signals.

In order, therefore, that the currents traversing the channel having the shortest length shall arrive at the receiver in phase, or nearly in phase, with those traversing the longer channels, I interpose as many tuned reactors, each comprising an inductor 11 and a condenser 12, serially inthe conductors constituting one or more of the channels as are required to insure the requisite phase-shift.

It is important that thereactors shall not be tuned to resonance with the carrier-current frequencies being used since, in such event, they If it is desired that the potential shall lag in the shorter line, the reactors interposed therein must be so proportioned and tuned as to offer inductive reactance to the signaling currents; if the same result is to be gained by modifying a longer channel, the reactors introduced therein should offer a.

- to a frequency capacitative reactance to currents at the signaling frequencies.

Beneficial results can sometimes be secured by interposing reactors in both the longer and shorter channels since, in this manner, the phase angles between the several potentials may be more perfectly controlled.

Among the principal advantages attending the practice of my invention may be mentioned the fact that, in choosing the transmitting frequency for any given power-line network, the physical character of the line is no longer the controlling factor. If the desired frequency is one that the line will not efficiently transmit, the interposition, in the line, of one or more tuned reactors will usually so balance the parallel channels that communication can be carried on satisfactorily.

The multi-channel transmission of signal, or control, energy is, in effect, an increase in the factor of safety of the communication system, a feature of great value when certain of the powerlines are liable to be temporarily out of service.

In addition, I have established, by careful ceiver if a plurality of parallel channels are utilized than if the signals are sent over a single.

Inasmuch as numerous modications of my improved .transmission system will be apparentto those skilled in the art to which it pertains, my invention is not to be restricted to'thevspecic embodiment thereof selected for purposes of illustration, but it is to be limited onlyby the prior art and by the spirit of the appended claims.

I claim as my invention:

1. In a high-frequency transmission system, a transmitter and a receiver of electrical energy so inter-connected through a plurality of waveconveyingchannels constituted by metallic power-lines that potentials arriving at said receiver from said transmitter are in out of phase relationship to one another, and reactive means interposed in at least one of said power lines for altering said phase relationship to substantially an in-phase relationship.

2. In a high-frequency transmission system comprising a power-line network, a transmitter of electrical energy, a receiverI of electrical energy, a plurality of wave-conveying channels constituted by a portion of said power line network inter-connecting said transmitter and receiver, and tuned means capable of carrying the power current interposed in at least one of said channels, whereby potentials appearing at said receiver from said transmitter may be maintained in additive phase-relation.

3. In a high-frequency transmission system, a transmitter and a receiver of electrical energy inter-connected through a plurality of waveconveying channels constituted by metallic power-lines, and tuned means interposed in at least one of said lines, whereby potentials appearing at said receiver from said transmitter are in additive phase-relation, said means being tuned different from the high frequency it is desired to transmit.

CLARENCE A. BODDIE.

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