US1279009A - Polyphase-generator with tuned spark-gap. - Google Patents

Description

L. ROUZET.

POLYPHASE GENERATOR WITH TUNED SPARK GAP.

APPLICATION FILED IAN-8.19M.

1 ,279,009. PsitentedSept. 17 1918.

LUCIEN ROUZET, 0F PARIS, FRANCE.

I'OLYPI-IASE-GENERATDR WITH TUNED SPARK-GAP.

Specification of Letter Patent. Patented Sept, 17, 1918,

Application filed January 8, 1915. Serial No. 1,204.

To all whom it may concern:

Be it known that I, LUCIEN Ronzn'r, en-

gineer, a subject of the Republic otFrance, and resident of 26 Rue du Printemps, Paris, Seine, France, have invented a Polyphase- Generator with Tuned SparloGap, of which the following is a specification;

In devices for producinghigh frequency by means of condenser discharges, one seeks very often, for example in transmitters for wireless telegraphy, the possibility of a rapid succession of discharges, in order to obtain a musical sound sufficiently high for eflicient reception.

When using alternating monophase current, the'frequency has had to be raised si multaneously with the height of the musical sound as, if a too great number of discharges per period is produced, said discharges are not equivalent to one another and the sound produced can no longer be regulated. For a perfect regularity the limit is of two sparks per period and for an acceptable regularity it is not possible to go beyond six sparks per period. Six sparks per period correspond to the superposition of two sounds of which the fundamental sound corresponds to two acoustic oscillations per period, which oscillations are due to two oscillations stronger than the four others, and the third harmonic sound corresponding to six oscillations per period.

If one increases the frequency for the purpose of raisingthe number of d ischargcs per second, 6., the height. of the tone pro duced, one meets with great difficulties such I as that of the construction of generators with verp high frequency, etc. Specially two of t iese inconveniences are very 1mportant, viz:

1. To regulate the chargin circuit it is necessary to diminish the coe cient of self induction of the circuit in proportion as one raises the frequency so that one soon meets with great difiiculties for obtaining sufficiently low self-induction circuits.

2. In proportion as one raises the fro qucncy,one diminishes the duration of the charge, while the duration of the discharge and therefore of the short-circuit of the condenser and of the=transformer through the spark gapis not diminished, so that in the systems working with low frequency the duration of the short-circuit is short in comparison with the duration of the load while, on the contrary, in devices with higher fre= quency, the duration of the short circuit becomes of the same order as that of the charge and thus the eiiiciency is lowered most considerably. Further, as, with high frequency, the natural period of the circuit of charge has to be very low, the intensity produced during the short circuit tends to rise and the losses of energy owing to the short circuit still further increase.

The present invention has for its object to increase the number of discharges per second (height of the sound) while maintaining lower frequencies. As will be seen in the following, the new devices with polyphase currents allow of avoidingthe inconveniences of the circuits of charge with. high frequencies. The self induction coefficients of tuning keep within their value of low-frequency and each condenser has a very great duration of charging in comparison with the duration of its short circuit.

This invention enables one not only to avoid great difficulties but it has furthermore the advantage of a much more steady Working of the apparatus, for example of the alternator whose output is much more steady when 'iolyphase currents are used.

The accompauying drawing illustrates as an example dili'ci'cnt ways of carrying out the invention: in said drawings:

Figure 1 shows a three phase star connected system according to the present ill". vention,

Figs. 2 and 3 show curves oi the intensities given out from a single phase system with spark gap tuned for two sparks per period. I

Fig. it shows the curves of the intensities in the three phases of a three phase system as well as in the neutral wire. In Fig. 1, which shows schematically a polyphase' device constructed according to the present in.vention, thc number of phases is three; (i is the star-connected three-phase source of current which can be, for example, the winding of analternator, or the secondary winding of a transforn'ier.

Each phase of the three phase current feeds a condenser. The number of con denscrs in the example Fig. 1 will therefore be three, C C and These latter are star-connected; their neutral point 9 is connected to the neutral wire and the points d, e, are connected to the phase conductors. lhe tuning of each of the phase-circuits will be effected btions L L and 3 respectively.

The spark gap shown in Fig. 1 consists of three groups oi fixed electrodes 0-a, 06 and 0-c and of one group of movable electrodes 0 1n,- the points a, b, 0, are connected to the three condensers in cl, 0, f, and point 0 is connected to point g through the exciting circuit S of the circuit antenna-earth, R' Supposin 0m turns for example around point 0, Ebur sparks in series will be produced when 0- m coincides with 0b,' the same happens when 0m coincides with 0-c and with 0u. Therefore three discharges, 6. c. the successive discharges of the condensers C C C will take place per revolution. If om rotates for example at a rate of two revolutions per period, two discharges per period will be produced on each phase, 2'. e. a totality of six discharges will take place during the time of one period. In order to obtain exactly the same period on each discharge circuit, small additional self-inductions 1,, 1,, X can be provided on the phase conductors of each of the discharge' circuits.

As will be seen, durin the rotation of o-m, the condensers C 6,, (1,, will be discharged successively on the device for exciting the antenna. Each condenser will act as in a monophase device with the frequency of the alternator, while the number of discharges will be that corresponding to a three times higher monophase frequency. Each circuit of charge, 1'. each phase will be tuned according to the frequency of the alternator and the cocfiicient of self induction for the tuning of these circuits will keep within easily realizable limits; finally, for each condenser, the duration of charge will remain great with respect to the duration of the short circuit,

The synchronous spark gap, the most appropriate for use in connection with the present device, is the spark gap with electrodes in series of the type described in my U. S. Patent No. 1,176,320, dated March 21, 1916, filed September 11th, 1911, which by making it possible in choose the number of sparks in series, enables one to regulate the duration of the short-circuit for the discharge and to avoid any trouble occurring from. too long a short circuit, so that the discharge can be provoked at the moment when the charging current passes through zero, the charging circuit being tuned, to this effect, according to the chosen number of discharges per period.

If, for exam do, the operation of the device shown in i ig. 1 is considered, it is obvious that the total system works as a superposition of three single-phase systems. As

meansot the selt-induc-- the condenser C, discharges for example twice per period, the phase to which it is connected will work as a single-phase tern with two discharges per period, and the current passing through its phase-conductors 'ill vary according to curve 2', Fi 2. 'lhis-curve Z is the curve .of a single-p iase system with two discharges per period such as produced by the transmitting apparatus disclosed in my aforesaid specification and its conformation is shown in the magazine Llndustrie Electrigue, No. 493 and 494 of 1912. Nevertheless, it may be remarked that as the dis-char e must be produced close to the maximum 0% the tension curve of alternator E, the charge will begin under the influence of tension of one sign While it will end under the influence of tension of the 0pposite sign. The zero of curve E therefore lies between the times at which two consecutive discharges are produced. The intensity starting from zero, the charge is be ginning) increases in one direction and, as the tension decreases, reaches its maximum rather quickly; the intensity will then pass again through zero and increase in the other direction, whereby it reaches a maximum higher than the first one and, at the end of the charge, that is, at the moment of the dis charge it will finally fall to zero again. As already explained, the intensity will only fall to zero if the charging current circuit, is accurately tuned, also if the discharges are produced exactly at the most favorable moment and if the beginning of the charge is not disturbed by boostin voltages caused by ruptures of the are. This result is obtained by means of the single-phase device disclosed in my above cited specification.

Should the intensity not pass throu h zero the operation of the device would ie detective as shown by the irregular intensity curves indicated in Fig. 3. As the first. discharge takes place at t there is a great arc rupture efiect which will, for example, pro duce an excess voltage resulting in a quicker commencement of the charge so that curve 2 differs from curve 1 and ends for example beyond zero at t. The rupture of the are at t will not have the. same effect as at, t and therefore curve 3 will still be different from the two first ones, and so on.

W ith a poly-phase system it is necessary to bear in mind that the rupture of the are will promote boosting voltages which may possibly be also carried on to the other phases. It therefore still more important,

when working with a poly-phase system, in

order to insure an accurate working and to obtain a curve such as 2', Fig. 2, to avoid these boosting voltages or at any rate to reduce same to a negligible value as in the single-phase system.

In a generator the more regular the shape of the curve of intensity, the more regularly spark gap does not necessitate rin the generator works, and. in a poly-phase generator the total output of all the phases must be'taken into consideration. In an installation for power and light, it is necessary to balance the phases as much as possible and Considering the neutral wire of a ...tar-,connected three-phase system the phases are balanced when no current passes through said neutral wire that is, when the sum of the intensities of the phases passing through said wireis zero.

If-we now consider a polyphase generator for producing high frequency currents, the sum ot the currents passing through the neutral wire will be obtained. by thesuperposition of curves similar to that indicated in Fig. 2, but displaced with respect to one another according to the number of phases.

Fig; 4: shows the superposition of the curves 11,, i, and 1', of the phases of a three phase star-connected system. The sum of the currents passing through the neutral wire is represented therefore by the curve L. In such a three phase syste this curve is of regular shape and the cur ent varies with a frequency equal to the threefold frequency of the phase voltage.

L A series of types of apparatus can be designed according to the above principle.

Several systems of connections constitute nevertheless particular cases and present special advantages, such as, for example, the polyphase three phase system with star connection shown in Fig. 1. In such apparatus, owing to the star connection, the exciting circuit for the antenna is connected between two fixed points and the rotating partof ths brush connecting means. The self 1nductions for tuning can, either be provided on the conductors for the three phases, or on the neutral wire, or on the neutral wire and the phase conductors simultaneously. One could for example provide the "regulating self-induction L. on the neutral wire of the distributed on each phase according to a three-phase system shown in Fig. 1. A self induction on the neutral wire can'work a lhough the tensions per phase at the alternator are all equal as are also the capacities (3,, (1,, C in fact, with, for example, two discharges per period for each of the condensers, the intensities given out on each phase are those shown in Fig. '2, which is the curve of the intensities with a monophase system with a k gap tuned for two sparks per period, and the intensity in the neutral wire, will be equal to' the sum of the intensities given out on each phase as already above explained. The sum of the curves of intensities shown in Fi 2 is not zero at each moment; the neutral wire can therefore not be dispensed with in this case.

The'polyphase spark gap can, of course, be designed in many various ways. The groups of fixed and movable electrodes can termined on each the discharge circuits corresponding to the difi'erent phases of the polyphase system. I claim:

1. A polyphase generator for high frequency currents comprising, in combination, a source of. polyphase current, a condenser battery the elements of which are uniformly distributed on each phase according to a star-connected system, circuits of charge equal in number to the number of phases but provided with a common neutral wire connecting the In -..tral point of the source of current to the ncsfi-al point of the condenser battery, disclmrge circuits equal in number to the number of phases but also provided with acommon neutral wire connecting the neutral point of the condenser battery to the spark-gap, a S1Jaikgap mechanism and means for driving the spark gap synchronously with the source of current, said mechanismcomprising a movable and a fixed member each carrying a number of sparkpoints which are adapted to register for the production of sparks in series, and regulata-ble self-induction coils for adjusting the period of each of the chargingcircuits in accordance with the movement of the spark-gap mechanism in such a way that the discharges of each condenser on each phase are produced at the moment when the intensity of the charging current passes throu h zero.

2. 1i 'polyphase generator for high frequency currents comprising, in combination, a source of polyphase current, a condenser battery the elements of which are uniformly star-connected system, circuits of charge equal in number to the number of phases but provided with'a common neutral wire connecting the neutral point of the source of current to the neutral point of the condenser battery, discharge circuits equal in number to the number of phases but also provided with a common neutral .wire connecting the neutral point of the condenser battery to the spark-gap, a' spark-gap mechanism and' means for driving the spark gap synchro nously with the source of current,sa1d mechanism comprising a movable and a fixed support each carrying a number of spark-p0ints which are adapted to register for the production of sparks in series, and regulatable self-induction coils for adjusting the period of each of the charging circuits inaccordance with the movement of the spark-gap.

mechanism, the number of phases being regular variations or a current which is alehosen in such a way that, during the workmost zero or even zero.

ing of the spark-gap, the sum of the currents of charge of each phase, 71. e. the cur: LUCI EN ROUZET' 5 rent passing through the neutral Wire eon- W itnesses;

neeting the condenser battery to the source ROBERT GENTIZON,

of eurrent, is an alternating current with G. JUVENELLE.

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