US1917921A - Frequency changer system - Google Patents

Description

Julyll, 1933. E. T. BURTON FREQUENCY CHANGER SYSTEM Filed Oct. 4, 1928 i 5 v C I BIAS OFC 5M; 0 5

Wl/ENTUR EVERETT Z' BURTON 5) ATTUENEY Patented July 11, 1933 UNITED. STATES PATENT OFFICE EVERETT '1. BURTON, OF HILLBURN, NEW JERSEY, ASSIGNOB T0 BELL TELEPHONE LABORATORIES; INCORPORATED, OF NEW YORK, N. 1., A CORPORATION OF NEW YORK FREQUENCY CHANGER SYSTEM Application filed October 4, 1928. Serial No. 310,238.

This invention relates to frequency changer systems where static frequency-transformers are employed for increasing the frequency of an alternating current.

An object of this invention is to increase the frequency of an alternating current without introducing certain types of distortion in the current wave of increased frequency. A feature of the invention resulting from the accomplishment of this object resides in the fact that the new frequency has substantially no current components of even orders of harmonics present therein.

Various types of frequency multipliers are known in the art, the most generally known types being rotary generators and the static or stationary frequency-(ransformers. Ptotary generators, particularly those which are designed to yield appreciable amounts of energy, entail considerable expense especially in systems employing high frequencies. The static frequency-transformers, to which the present invention relates, are particularly adaptable to use in signaling systems employing relatively high frequencies and in this field have been used to a large extent because of the economy effected and the efliciency with which the increase in frequency is obtained. Heretofore, in systems employing transformers for increasing the frequency, the chief concern was the production of harmonics which. when superimposed on the fundamental frequency, would result in the desired frequency. The current wave thus produced might be constituted of both the odd and even multiples of the new frequency and in order to eliminate the distortion introduced by the even multiples it was necessary to employ numerous complex networks which required frequent adjustments. Furthermore, in these systems the increase in frequency effected in a single step was relatively small. such as the doubling "or tripling of the fundamental, and if it were desired to obtain a much higher frequency the operation involved in the single step had to be repeated several times.

S'tatic frequency-transfru'mers employed in accordance with the present invention are capable of producing relatively high frequencies in a single step and when very high frequencies are desired they may be readily had by repeating the first step a less number of times than heretofore were needed with transformers.

A feature of the invention is the production of secondary impulses which may be so spaced that the new frequency may be an even or odd multiple of the fundamental as de sired. I

Another feature is the substantial elimination of all even multiples of the new frequency thereby avoiding the distortion due to such multiples.

Another feature resides in the fact that the lowest frequency voltage appearing in the secondary circuit is that of the desired multiple frequency.

The invention will he better understood by reference to the following detailed description taken in connection with the accompanying drawing in which:

Fig. 1 shows in schematic form the arrangement of a pair of static frequency-transformers for increasing the fundamental frequency twofold;

Fig. 2 graphically represents the input current of the fundamental frequency, the secondary voltage, and the output current of the double frequency in the arrangement shown in Fig. 1;

Fig. 3 shows a modification of Fig. 1 wherein the fundamental frequency is increased threefold;

Fig. at illustrates current and voltage waves of the arrangement shown in Fig. 3;

Fig. 5 shows a modification of Fig. 3 whereby the fundamental frequency is increased fivefold;

Fig. 6 represents the wave forms and the changes effected in increasing the frequency by the arrangement of Fig. 5; and,

Fig. 7 shows a combination of the arrangements shown in Figs. 1 and 5 whereby the fundamental frequency is increased ten times and then impressed on the grid circuit of a vacuum tube amplifier.

In the following detailed l'lescription like material, such as permalloy,

numbers represent like parts and theoretically ideal cases are discussed with the understanding that departures from ideal conditions always result from the limitations of apparatus, non-linearity of magnetization curves, etc.

Referring to Fig. 1 an alternating current of a certain frequency is received over con-- ductors 11 and 12 from a source f of frequency and passed through the primary windings 13 and 14 of a pair of high per-' meability transformers 15 and 16 which are of the type disclosed in applicants copending application corresponding to British Patent 312,338, accepted June 10, 1930. The cores of these transformers are oppositely biased by direct current of a value less than the maximum value of the alternating current, from source 17 through windings 13 and 14. Thus, while in one transformer the alternating and direct current components may be aiding, in the other they will be opposed and will neutralize each other twice during a half cycle when the alternating current passes through values equal to that of the direct current.

The transformer cores are of a magnetic which has a very high permeability at low magnetizin forces, and which consequently very soon ecomes saturated when those forces are increased, with the result that the permeability is again reduced to a very low value. Since the mutual inductance between the primary and secondary windings of a transformer is directly proportional to the permeability of the core it is evident that by using a biasing arrangement such as shown in Fig. 1 the mutual inductance of each transformer may be controlled to have two maxima during a half cycle of the alternating current, namely, at those values of this current at which the magnetizing force is zero.

Considering now the E. M. F. induced in the secondary windings, it is a well known fact that this E. M. F. is directly proportional to the rate of change of the primary current and to the mutual inductance. Therefore, when, as in the present arrangement, very reat variations of the permeability take p ace with correspondingly great variations in mutual inductance, the effect of the rate of change in current may be insignificant except at such times when the mutual inductance akes on values appreciably higher than those prevailing during saturation conditions. Even at such times an. increase in mutual inductance may more than offset a decrease in the rate of change of primary current. Thus at those instants when the alternating and direct currents in the transformer windings nearly neutralize each other the mutual inductance will be so high that an appreciable E. M. F. will be induced in one of the secondary windings. At any other times, whet-her when one current predominates over the other or when they aid each other, the core material will be saturated and the permeability and mutualinductance will Therefore, when the alternating current rises from zero in the opposite direction to the biasin current in one of the transformers 15 and 16. no secondary E. M. F. will be induced until its value approaches that of the biasing current. The mutual inductance then increases many fold and a voltage impulse is induced which lasts until the alternating current exceeds the biasing current by a small value. At this time the mutual inductance is again reduced and no secondary E. M. F. occurs until the decreasing alternating current again approaches the biasing current in value when another voltage impulse will occur. However, since the current now is decreasing this impulse will be of the opposite polarity of the first impulse. As the alternating current now continues to drop to its zero value and then rises through values of the opposite polarity, two impulses of voltage of opposite polarities are generated in the other of the secondary windings. Due to the reversed connections of windings 18 and 19, as shown in the drawing, the impulses produced in windin 19 are reversed so as to form with the impulses produced in winding 18 a series of impulses of alternate polarity, two impulses of opposite polarities being produced by each half cycle of alternating current in windings 13 and 14. By the insertion' of suitable networks such as constituted of condensers 20 and 21 and inductance coil 22 in the output circuit 27 of the transformer, a series of secondary current impulses may be produced in circuit 27 which are smoothed out to form a sinusoidal wave of a frequency double that of the alternating current in the input circuit comprising conductors 1]. and 1 In Fig. 2 curve A represents the input current wave of a particular frequency flowing through primary windings 13 and 14: curve B, the voltage variations produced in the secondary windings 18 and 19 by the primary current at intensities of primary current in dicated in curve A by broken lines m-m and m'm which are equal to the biasing currents in the primary windings 13 and 14; and curve C. the current wave in the output circuit; 27 after it has passed through a suitable nctwork and having a frequency twice that of the input circuit. It should be understood that the illustrated relation between curves B and C is not intended to show the phase relation between the impulses represented by these curves.

nemesis In Fig. 3 is shown a circuit arrangement wherein a current of a particular frequency is changed into a current of three times that frequency, This arrangement is similar to that shown in Fig. 1 except that an additional high permeability transformer, having no biasing current in its winding, is connected in series with the primary windings of the other transformers and the secondary wind= ings of the polarized transformers are so con nected to each other that the two secondary voltage impulses generated in one winding will follow those generated in the other winding in opposite order as to polarity. .l'n 3 an alternating; voltage of a particular frequency is received over conductors l1 and 12 and impressed upon the primary windings 13, 14 and 23. Transformers l5 and l6 are oppositely polarized by current from a source 17 as described above for Fig. 1, so that the mutual inductance between their primary and secondary windings is maintained at a negligible value except when the alternat ing current in the primary windings approximately neutralizes the polarizing current in either of the windings. The additional high permeability transformer is unbiased. The mutual inductance between its primary winding 23 and secondary winding 25 therefore rises to a high value for an instant times different from those of the windings l3 and 14, or every time the alternating current in primary winding 23 passes through amplitudes of about zero value. At such times a voltage impulse will be generated in the secondary winding, in the manner described above. The secondary Winding 25 is connected in series with the secondary windings 18 and 19 in such manner that the induced voltage impulses in winding 25 together with those in windings 18 and 19 will form a uniform series of impulses of regularly alternating' polarity, The voltage impulses produced in the secondary windings are short and are separated by somewhat long intervals oi" substantially zero voltages, but by inserting suitable network such as shown in Fig. 3 comprising condensers 20, 21 and 26 and inductance coil 22 in the output circuit 27, the series of short secondary voltage impulses may produce a substantially true sinusoidal current wave, and inasmuch as each half cycle of alternating current in the primary windings 13, 14 and 23 produces three voltage impulses of alternate polarities, the resultant current in the output circuit 2'? will he of a frequency three times that of the primary current.

Fig. 4 represents graphically the voltages and currents occurring in the circuit arrangement of Fig". 3. Curve It represents the input current wave of a certain frequency supplied from a suitable source and impressed upon the primary windings l3. l and 232 curve B, the short voltage impulses produced in secondary windings 25, i8 and ill, the impulse produced in winding; 25 being inverted with respect to the direction of variation of the primary current which produces it; and curve C represents the current produced by the voltage pulses shown by curve B after it has passed throu h the smoothing networks in the output circuit 27, the frequency of this secondary current the primary current shown in curve A.

In Fig. 5 is shown an arrangement wherein live high permeability transformers are employed for producing an alternating; current oi five times the frequency of the input current. Two of these transformers are polarized to a certain extent in opposite directions, two others are similarly polarized but to a different extent, and the remaining transformer is unpolarized. In this figure the polarized transformers have been shown with separate windings for effecting the polarization of each of the polarized trans formers but it should be understood that the polarizing current, if desired, may be applied to the primary windings as shown in Fig. 3. Assuming as hereinbefore that an alternating current of a certain frequency is received over conductors 11 and 12, the current in this arrangement is passed through the primary windings 13, 14, 35, 36 and 23 of transformers ll), 16, 37, 38 and 24; rcspcctivcly. 'llransforrners 15, 16, 3'? and 38 are polarized by separate windings connected as shown to a common source 17 of direct current, polarizing current for transformers 37 and 38 being made of a lower value than that for transformers 15 and 16 by resistance 29 in the polarizing circuit of the transformers 37 and 38. The secondary windings l8, 19, 30, 3i and 25 of transformers 15, 16, 37, 38 and 24 respectively are connected in series and form a part of the output circuit 2?. The windings 30 and 31 are connected to the other secondary windings 18, 19 and 25 in such manner that the induced voltages are inverted. By the insertion or suitable networks, such as oinprise condensers 20, 21, 32 and 26 and inductance coil 22, the series of voltage impulses induced in the secondary windings will produce in the output circuit a current or a substantially pure sinusoidal wave of a frequency five times that oil the primary current.

ln Fig. 6 curve A represents the input current wave supplied from a suitable means and impressed upon the primary windings 13, 14. 35, 36 and 23, shown in Fig. 5, a:m and a2-.v indicating the intensities at which the primary current overcomes the polarizing ilux in'translormcrs 15 and 16, and 1, 1 and y y indi'ntin the intensities at which the primary current overcomes the polarizine llun in transformers 37 and 38. Curve B represents the induced voltage impulses in the secondary windings, the first impulse shown being that produced in winding 25 being three times that of All) - when the rising primary current passes through its zero value; the second impulse being that produced in and inverted by winding 30 when the primary current reaches amplitude y-y; the third impulse being that produced in winding 18 when the primary current reaches intensity w:r; the fourth impulse is that produced in winding 19 when the decreasing primary current reaches intensity a: 00 after attaining the peak value; the fifth impulse is that produced in and inverted by winding 31 when the primary current passes intensity i g and so on similarly for the impulses produced by the other half cycle of the primary current, the impulses forming a uniform series of alternating potentials. Curve C represents the sinusoidal current wave effected by the suitable network inserted in the output circuit 27, having a frequency which is a fifth multiple of the frequency of the primary current.

In Fig. 7 is shown an arrangement wherein the frequency of an alternating current is increased ten times by combining the arrangements of Figs. 1 and 5. The alternating current of a particular frequency is received over conductors 11 and 12 and passed through primary windings 13 and 14 of transformers 15 and 16 in a wave form such as shown in curve A of Fig. 1. When transformers 15 and 16 are polarized in opposite directions by passing a direct current from source 17 through windings 13 and 14 or through separate windings as shown, the primary current produces in the secondary windings 18 and 19 a series of voltage impulses as shown in curve B of Fig. 2. These impulses after proper correction by suitable networks produce a sinusoidal current wave of a frequency double that of the input current in conductors 11 and 12.

The sinusoidal wave so produced is passed through primary windings to 44 of transformers 46 to respectively. Transformer pairs 46 and 47, and 48 and 49 are polarized to a different extent by direct current sources 51 and 52 respectively. By arranging the primary windings 40 to 44 and the secondary windings 53 to 57 in a manner similar to that shown for the windings in Fig. 5 the voltage impulses induced in the secondary windings by the current in the primary windings 40 to 44, form a wave having five impulses of alternate polarities to each half cycle or impulse of current in the primary windings 40 to 44. By, means of suitable networks a sinusoidal current wave is produced in the output circuit of a frequency five times that of the current in primary windings .40 to 44 and ten times-that of the current in the primary windings' 13 and 14.

It will be noted in curves A of Figs. 2, 4 and 6 that the input voltage shows a lag in the wave formed at points corresponding to the intensities at which the permeability of the transformer cores reaches its effective values. This is due to the self-induction of the primary windings which rises to a high value at intervals in which the permeability is eti'ected and therefore this self-induction momentarily serves as a high impedance during such intervals. The effects of this selfinduction is explained in more detail in applicants copending application corresponding to the British Patent 312,338 supra.

Likewise in the same figures of the drawing, the voltage impulses shown in curves B are of the same shape for both polarities, which impulses when smoothed out by suitable networks produce a symmetrical wave as shown in curves 0. The fact that the new waves are symmetrical for both polarities indicates the absence of the even multiples of the new frequency.

Various combinations of the arrangements shown may be made in order to increase the frequency any desired amount, it being understood that in cases Where a very high frequency is desired amplifying means such as a vacuum tube 60 shown in the output circuit of Fig. 7 may be employed for strengthening the impulses supplied either to the load or to devices for further increases in frequency. In such cases it may also be found desirable to insert the amplifying means between the secondary windings and the shaping network.

What is claimed is:

1. In a frequency multiplying device which comprises a winding upon a body of magnetic material, a direct current source connected to cause current to flow in at least a part of the winding, an alternating currentsource connected to cause alternating current to flow in at least a part of the winding, and a load circuit, the method of operation which comprises saturating in one direction the body by the direct current flow in said winding, causing a half cycle of said alternating current to unsaturate said body and further causin the same half cycle to saturate said b y in the opposite direction, and causing the same half cycle to successively unstaturate and saturate said body in the same direction as in the first operation, whereby a series of impulses equal in number to the number of said unsaturations appear in said output circuit.

2. The method of increasing a wave frequency which comprises maintaining a mass of highly permeable material normall magnetically saturated and superposing t ereon a periodically reversing magnetizlng force of continuous wave form having higher amplitudes than the force producing the normally saturated condition to momentarily unsaturate said material, utilizing successive momentary unsaturated conditions of said material to form a wave of a higher frequency consisting of electrical impulses of equal dulll Sill

force, a continuous wave of sed new:

ration and equal maximum amplitudes end of alternately opposite polarities and 1m pressing said wave of the higher Irequency on a load circuit wherein said lose mentioned Wave is smootlned-outv to form, utilizing the whole eneigy produced by the superposed quency wherein only the odd new frequency are present,

v 3. A method of increasing quency which comprises impre current of a predetermined directions on a plurality of serial coils respectively mounted on. cthe magnetic circuits in inal-ly maintained in a sotui" superimposing olternetin cuer value end oil defin te steady curient lo molly saturated magnetic ne whereby each-magnetic liei raced in one direction, is 5333c -i then nesaturated, but i ti-on, to pi oduce duri a negesive svveep o one so rent u plurality of voile vi note opposite pole nected coils sespec v imi'ty to the first mentioned mentioned coils losing connecs cull; in opposite relation vent alternate pairs of ad iecenc impressing said impulses on s with successive impulses 0' cos d, A method of inches quency which comprises j y ternating current quency on serially connected pm ELEM l mgs of a plurality of ti'nnsfo" mess core material of a hi h. pemne -li'ty low magnetizing forces e magnetic circuits of said transformers eing adapted to become saturated at intensities of alternating currentslightly above zero'value, superimposing on the alternatin current in said respective windings stea y currents of difiei'ent values to normally maintain said magnetic circuits in saturated condition, the maximum magnetizing force due to the alternating current minus the magnetizing force due to the direct current being suflicient to produce saturation of the cores, whereby 1n response to each positive and each negative sweep of sold el-= ternating current above the values of said steady currents a plurality of short, sharp voltage impulses of equal duration end eoucl maximum amplitudes are produced in serially connected secondary windings e1- ranged on said transfiormers, inverting certain of said voltage impulses wherehy the produced voltage wave is constituted of impulses of alternately opposite polarities, and impressing said volta e impulses through a smoothing-out networi to reduce in a load circuit a uniform sinusoi al curreni; wave &

5., In a frequency changer device, a circuit,-

a plurality of coils connected in series in said circuit and comorising cores designed to hecome saturate at intensities of current slightly above Zeno value, a plurality of other coils connected in series with each other and connected inductively with first mentioned coils, means for transmitting through the first mentioned coils a periodically alternating current of a particular (l ency s efiective to produce :1 short, sharp ge impulse either of the second inentioned coils every time said current thirough intensities near the points of Zion and unsetura'izion of said cores, sai a e impulses being equal dune-bio maximum amplitudes, 2. source normall biasing said first mentioned coils in o posits (il'lSClllOllS wher by range of amplicudcs v ch the voltage impulses produced is sted to include any a nsities off alcerneting cur? between :c 1d maximum values, and e circuit racing a smoothing-out ne iyvorlz which es the entire energy oi" the impulses produced in said shifted -mge es continuous poled qual dure'ti and equal oli'tudes.

V H. l l quency changer system, circuit comprising a plui'al ty of seriall conwhereby each magnetic circuit normally saturated in one direction is first neutmlized and then saturated in the oppositedirection to produce short, sharp voltage impulses of equal duration end equal maximum amplitudes in either of the second mentioned coils eveey time said alternating current passes through the intensities near the points of saturation and unsaturation and means for shaping the reproduced Waves to form sinusoidal Wave of increased frequency,

71 in a frequency changer system as set forth in claim 6, other coils respectively connected in series with said first and second mentioned coils, as magnetic circuit for the third mentioned coils arranged to be normally unsaturated, Whereh the periodically elternating current is e 'ective to produce a short, shar voltage impulse in the coil connected to 51s second mentioned coils every ice time the alternating current passes through the intensities slightly above or belowzero value to thereby increase the number of impulses produced by each half cycle of alternating current, and a load circuit including said second mentioned coils and one of said third mentioned coils wherein certain of said impulses are inverted to form in conjunction. with the other of said impulses a continuous uniform sine Wave of increased frequency 8. In a frequency changer device, a circuit, a plurality of transformers connected. in series with said circuit, and comprising cores designed to become saturated at an in tensity of current slightly above zero value means for transmitting through the trans former primary windings a periodically aiternating current of a particular frequency which is effective produce short, sharpvoltage impulse the transformer seco dary every time said our cnt passes througl "he intensities near the points oi? saturation and nnsatnnation a source 1f current i: biasing the "-r ,iiSiOEHlGES in posits (erections wiierebythe range of Eli:- 7 ch one vol impulses are inc. Ede any group of linainniinnv of -mpr ge Wave polarity I cniced Wave 0 form a sinnso creased ire money,

forth ing its primai y and s contrary Wi SPGCILlVGly connected in series W. mary and secondary or sai raliey of trans? iei's, she secondary it @llmOilGii: transform onda: l c

olC BEGUM, n

former arranged to be normally unsaturated whereby the periodically alternating current is effective to produce short, sharp voltage impulses of equal duration and equal maximum amplitudes in the secondary winding of the last mentioned transformer ever time said alternating current passes throug 1 intensities slightly above or below zero value to thereby increase the number of impulses of equal duration and equal maximum amplitilde produced by each half cycle of alternatcurrent, and. other means for shaping the impulses produced in the secondary Wind oi said last mentioned transformer to form in conjunction with the voltage imnoises produced in the secondary windings inrality of ransformers a continua sinusoidal wave of further ining input current, traversed by said said coil :1 polariz- 5 said core, the mag- O1 snppiiecl by and sources conneticaliy polarizcaiiy re lllt]

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