US2395389A

US2395389A - Magnetic frequency multiplier

Info

Publication number: US2395389A
Application number: US535480A
Authority: US
Inventors: Huge Henry Martin
Original assignee: CLOSMAN P STOCKER; E M HEAVENS
Current assignee: CLOSMAN P STOCKER; E M HEAVENS
Priority date: 1944-05-13
Filing date: 1944-05-13
Publication date: 1946-02-26
Anticipated expiration: 1963-02-26

Description

Feb. 26, 1946.

H. M. HUGE MAGNETIC FREQUENCY MULTIPLIER 3 Sheets-Sheet 2 Filed May 13, 1944 WZORUWEEOu WWW WNW WZORUMEEOQ XQTSQQQ INVENTOR. HEN/ P) M HUGE BY M AT RNEYS.

Feb. 26, 1946. H. M. HUGE MAGNETIC FREQUENCY MULTIPLIER Filed May 13, 1944 3 Sheets-Sheet 3 WEOR UMEEOU waotuwzzou QQ QQ Patented Feb. 26, 1946 MAGNETIC FREQUENCY MULTIPLIER Henry Martin Huge, Lorain, Ohio, assignor of one-half to E. M. Heavens and one-half to Ciosman P. Stocker Application May 13, 1944, Serial No. 535,480

24 Claims.

frequency of a polyphase alternating current source by the use of biased saturable magneti cores.

It is another object of my invention to provide a symmetrical output wave shape by balancing out even harmonics of the output frequency.

A further object of this invention is to control the.biasing current in response to variations of load.

A still further object of this invention is to stabilize the output voltage of my frequency changer by the use of saturating inductances.

Still another object of my invention is to use a rectifier to supply biasing current to my frequency multiplier and to vary the biasing current in response to load variations.v

Another object of my invention is to utilize a current transformer 'to supply the biasing rectifler and to produce variations in the magnetic permeability of the current transformer core for further controlling the biasing current.

A further object of my invention'is to obtain part of the biasing power from a current transformer'and another part from a potential transformer. I

Another object of my invention is to control the biasing current by combining the biasing voltages from two potential transformers, at least one of which has variable potentials.

Another object of my invention is to balance the alternating current out of the source of biasing current.

An additional object is to drive a polyphase induction motor from a frequency doubler.

Other objects and a fuller understanding of my invention may be had by referring to the following speciflcations and claims, in connection with the accompanying drawings: I Figure 1 shows a three-legged reactor having a center-tapped primary winding as utilized in my invention,

Figure 2 shows a second type of reactor with an untapped primary winding, and

Figure 3 is a schematic diagram showing how the reactors of Figures 1 and 2 may be interconnected in one embodiment of my invention.

Figure 4 shows a different type of reactor which Figure 5 shows still another combination with which the reactors of Figures 1 and 2 may be replaced.

Figure 6 shows an alternate method of connecting the secondary windings of Figure 3.

Figure 7 is a schematic diagram of a preferred embodiment of my invention, having biasing current supplied by three-phase rectifiers fed from current transformers in the supply line, and also showing saturable stabilizing inductances in parallel with the output, and

Figure 8 shows another method of supplying controlled biasing current from a single-phase current transformer in addition to a single-phase voltage obtained from the alternating current source.

In general, this invention utilizes a combination of biased saturating reactors. combined to multiply the frequency of the alternating current source and to balance the source frequency out of the secondary circuit. In addition, the even harmonics of the output frequency are cancelled by combining the outputs of two or more frequency multipliers whose primary circuits are supplied from voltages displaced in phase from each other. In the case of the frequency doublers shown in the drawings, a pair of frequency doublers is used in which the primary phase displacement is so that the double frequency voltages are out of phase with each other, while the voltages of even harmonics of the double frequency are in phase with each other. Thus when the secondary windings are phased to add the double frequency voltages in the output, the even harmonics of the double frequency are cancelled.

Another feature of my invention is the controlled biasing current'provided by the rectifier energized from a current transformer in series with the input to the frequency doubler, so that increased load on the doubler brings about the increase in biasing current needed under the heavier load.

Referring more particularly to Figure 1, there is shown a three-legged magnetic core structure l6, having a primary winding H on the central core member, and secondary windings l4 and IS with direct current windings l2 and IS on the two outer core members. The primary winding II is provided with a center tap IT. The secondary windings i4 and I5 are phased noninductively with respect to the primary winding ii. The D. C. windings i2 and I3 are phased in the same polarity as the secondary windings.

may also be used in the practice of my invention. 55 With this arrangement, a flow of direct current through windings i2 and I3 produces a unidirectional flux in the two outer members of the core Hi.

When alternating current is applied to primary winding H, the two outer core members react unequally to primary magnetization, since a pulsation of primary flux which adds to the unidirectional fiux through coils i3 and i5 opposes the unidirectional flux through coils i2 and II. Thi produces a difference in saturation of the two outer core members and causes the primary flux to divide unequally between them The unequal division of flux reverses with the reversal of the primary magnetizing current, so that, for example, the positive pealcs of primary flux may be driven through coils l3 and '15, and the negative peaks through coils i2 and 14. Because of the phasing of the secondary winding these pulsations of flux induce voltage of twice the primary frequency in the secondary.

The double frequency voltage which is induced imposed on it, particularly when the double frequency flux density is high.

The structure of Figure 2 is similar to the structure shown in Figure 1 and comprises a three-legged magnetic core 26, having primary winding 2| on its central member, and secondary windings 24 and together with direct

current windings

22 and 23 on its outer members. It differs from Figure 1 in that the center tap ll shown in Figure 1 is omitted in Figure 2.

Figure 3 shows an embodiment of my invention which makes use of three reactors of the type shown in Figure 1 and three reactors of the type shown in Figure 2. The first three reactors are designated A, B and C, and may be considered as a first poiyphase frequency doubler while the sec ond three are designated D, E and F and may be .described as a second polyphase frequency doubler.

This pair of three-phase frequency doublers is connected to the three-phase source' Ill and the two doublers are arranged to have 90 phase displacement between their energizing voltages.

Interconnections of the windings are shown diagrammatically in Figure 3 with the primary connections shown on the left side of the diagram, the direct current connections in the central part of the diagram, and the secondary connections on the right hand side of the diagram. The positioning of the primary coils in the diagram of Figure 3 indicates the phases of the primary voltages. The primary windings of the reactors A, B and C are delta-connected directly to the three-phase source i0 and the primary windings of the reactors D, E and F are supplied with voltages displacedin phase from the sourcevoltages The displacement in phase is obtained through the use of the center taps HA, i118 and NC on the primary windings of reactors A, B and C. Thus, for example, primary winding 2IF is connected on the one end to the junction between primary winding HA and HB, and on the other end to the center ,tap HC of winding IIC. Thus I have two groups of three reactors each, the first group being delta-connected to the three-phase source, and each of the reactors of the second group having its primary winding connected to a primary center tap of the first group and to the junction between the other two primary windings of the first group.

The primary windings 2ID, 21E and HF are preferably made with fewer turns than the primary windings HA, HB and HG since the applied voltage on the windings 2ID, 2IE and 2|P is less than on the windings HA, HB and HC, and I prefer to keep substantially the same number of turns per volt in all the primary windings. This makes it possible to make the units according to Figure l with substantially the same dimensions as the units according to Figure 2. and

'- to operate the cores I6 and 25 at substantially the same flux density.

The direct current windings IZA, IBA, 12B, I33, I20, and 13C of the reactors A, B and C are connected in series and connected to the source of the direct current 28. Similarly the direct

current windings

22D, 23D, 22E, 23E, 22F and 23F are connected in series and connected to the source of direct current 28. The positioning of these coils in Figure 3 corresponds to the positioning of the corresponding primary coils. The voltages in these series circuits approximately cancel each other so that very ittle alternating current is impressed on the dir. i, current source 28.

The secondary connections shown in Figure 3 provide for the series connection of the secondary circuits of two reactors whose primary circuits are energized out of phase with each other. The windings are polarized so that the double frequency voltages appearing in the windings add together. This is possible since a 90 displacement at the fundamental frequency results in displacement at the second harmonic frequency. Thus the pair of secondaries C and 15C with 24F and 251 supply one phase of the polyphase output. Similarly, HA and I 5A in series with 24D and 25D supply the second phase and B and ISB in series with 24E and 25E supply the third output phase. Figure 3 shows these output phases connected in delta, although a star connection could be used. The

capacitors

29, 30 and 3! are connected one across each of the three output phases and are energized by the three-phase voltage of twice the source frequency.

As previously mentioned, the 90 phase displacement between primary voltages produces a 180 displacement between secondary voltages of twice the source frequency. The phase displacement at four times the source frequency is 360 or 0, and at other even multiples of twice the source frequency, there is likewise no phase displacement. Therefore, when the secondary windings are polarized to add the voltages of twice the source frequency, all even multiples of twice the source frequency are cancelled in the output voltage although odd multiples of twice the source frequency may remain. This means that the voltage which is supplied to the capacitors 29, II and SI and therefore to the load, is substantially free of even harmonics, and is, in fact, substantially free of all' harmonics. The delta-connection of the secondary windings and of the'direct current windings suppresses the third harmonics in the load voltage so that the lowest harmonic having a tendency to appear is the fifth, but the reactance of the three capacitors 2!, 30 and II at the fifth harmonic of the output frequency is low so that the fifth and higher harmonics are also suppressed and it is possible to obtain a substantially sinusoidal wave shape from my frequency converter.

The frequency doubling process explained in connectionwith Figure l is also involved in the operation of the circuit of Figure 8; however,

because of 'the fact that the harmonic voltages which are generated as explained in connection with Figure l are not supplied to the capacitors 29, 89 and II, which are highly instrumental in aiding in the excitation of the output voltage. there is no tendency for these capacitors to excite harmonics of the output frequency. Therefore,

I is allowed to circulate between the par-,-

all the energy which would normally be wasted in \used in, F re 1, it would be necessary to split the primary windings 94 and 99 in Figure 4. The direct current winding 32, and the secondary winding 99 in Figure 4 are on the center member of the core i9 and the primary windings l4 and I! are arranged on the two outer core members and areconnected non-inductively with respect to the secondary winding 99. As in Figure l, the

unidirectional flux produced by direct current through the biasing winding causes unequal reactions to the primary magnetizing current in the with respect to the primary windings so as to be non-inductively arranged with respect to the primary. As in the arrangement of Figures 1, 2 and 4, the unequal reaction to primary magnetization produced by the unidirectional flux in the magnetic flux paths produces an induced voltage of twice the primary frequency in the secondary circuit.

The specific types of frequency doubling reactors shown in Figures 1, 2, 4 and 5 are shown as examples of the types of reactors which can be'utilized in the practice of my invention. Other biased saturable reactor arrangements or common-core combinations of the arrangements may also be applied without departing from the true scope of my invention, which utia biasing fluxto cause unequal reactions to primary magnetization in a plurality of mag- I neticflux paths to cause a double frequency voltage to be induced in a secondary circuit.

In Figure 6, alternate secondary connections are shown for the circuit of Figure 3. In Figure 6, the secondary windings are connected in parallel instead of in series as in Figure 3. In this case the currents of the output frequency are added together instead of their voltages, and the current oi. even harmonics of the output ireallel windings. As in Figure 3, the voltages supplied to the capacitors 29, 99 and ii are substantially free of harmonics. Furthermore, the parallel arrangement shown in Figure 8 need not be restricted to delta-connection secondaries; as in Figure 3, a star connection may be used.

Figure '7 shows a controlled bias applied to the circuit of Figure 3 and also shows saturable reactors l0 and BI connected in parallel with the condensers 29, I9 and Ii. The circuit arrangement shown in Figure 'I is particularly advantageous whenit is required to drive a polyphase induction motor load. I have found that when starting an induction 'motor from a frequency changer of the type shown in Figure 3, it is desirable to increase the biasing current during the starting interval and it is also advantageous to provide greater capacity in parallel with the motor. Both of these requirements are met with the arrangement of Figure 7, which shows the direct current source 29 of Figure 3 replaced by a set of three-phase rectiflers 49,

which are energized from the

secondaries

49, 49 and 41 of current transformers whose

primary windings

42, 49 and 44 are connected in series with the input to the frequency multiplier.

The current transformers may be wound on a common three-phase core and I prefer to connect the

secondary windings

49, 49 and 41 in delta, as shown in order to allow the third harmonic component of the input current to circulate freely between the secondary windings and thus to keep down the peak voltage on the rectiiler 49.

The action of the three saturating inductances 49, Ill and ii in parallel with the three

capacitors

29, 39 and-9i is to reduce the enective value of these capacitors when the output voltage ex- 40 ceeds a fixed value. When the output voltage is suiliciently great to saturate the inductances 49, 80 and ii, the exciting current passed by these inductances, being out o phase with the current oi the capacitors 29, 99 and 3|, reduces the net value of capacitive current in the output network. A stabilizing action is thus obtained because the reduction of capacitive current tends to reduce the output voltage. When the output voltage is dropped below its normal value as might happen when starting an induction motor load, the voltage across the saturable stabilizing inductances 49, 59 and BI is insuilicient to saturate them and the total value of the capacitors 29, I9 and 9| is eiIective in supplying exciting current for the motor and for the frequency changer. At the same time, the increased .load on the frequency changer causes. an increase in current through the

current transformer primaries

42, 49 and 44, thereby increasing the biasing current supplied by the rectifiers 49, causing the frequency multiplier to supply increased power during the starting interval.

' As a means of controlling the amount of variation in the biasing current which is provided by these current transformers, I prefer to operate the magnetic cores oi the current transformers at a relatively high flux density so that the magnetic permeability of their cores decreases with increasing excitation within the normal range of operating flux densities. In this manner I am able to control the amount of variation in the biasing current supplied by the rectifiers 49 over a somewhat dlflerent range than the actual current variation through the current transformer primaries, making it possible to maintain optimum biasing current under wide variations of load. The combined effects of the saturable stabilizing inductances together with the controlled biasing arrangement makes it possible to supply large amounts of powerwhen needed to supply overloads on the frequency changer and to maintain high operating efficiency under nor-' mal loads.

ing 53 in series with the one input lead to thepair of frequency doublers and having its secondary winding 54 connected to a single-phase rectifier bridge 55. Figure 8 also shows another method of maintaining the required biasing current under wide variations of load. For this purpose secondary winding 52 is coupled to primary winding 2 iE and connected in series with the current transformer secondary 5. I prefer to choose for this purpose a primary winding having a voltage approximately in phase with the voltage de veloped across winding 5 so that the fixed voltage appearing across winding 52 may be added in phase with the variable voltage appearing across winding 54, and the sum of these two voltages supplied to the rectifier bridge 55. However, depending upon the type of load being supplied and the circuit constants involved, the required effect may be obtained by coupling winding 52 to a primary whose voltage is displaced in phase from the voltage induced in winding 54. With the arrangement shown in Figure 8, it may be advantageous to provide an air-gap in the magnetic core 56 of the current transformer so that when the current through primary winding 54 of this transformer falls below the value required to supply the optimum biasing current, the voltage supplied by winding 52 may become more effective in supplying the required biasing current. The circuits of Figure 8 is in other respects similar to the circuit of Figure 'l and with the exception of the method controlling the biasing current just outlined, the operation of the circuit of Figure 8 is substantially the same as that of Figure 7. The use of three-phase rectifiers as cuit of Figure 8 by providing a three-phase current transformer and three potential transformer secondary windings supplied with voltage from the alternating current source as winding 52 is supplied in Figure 8.

It will be noted that the description is confined to the multiplier circuits working as frequency doublers. However, by re-arranging the secondary connections with the second harmonic voltages cancelling it is possible to obtain a fourth harmonic output voltage. It will beapparent to those skilled in the art that a continuation of the above principles would permit balancing out even harmonics of the output frequency when it is four times the input frequency.

Other circuits embodying the features of my invention may also be used. For example, it is possible to obtain a controlled biasing current from a current transformer connected in series with the load instead of in series with the input to the frequency doublers as has been shown. The necessary increase in biasing current with energized from the input potential and the other rectifier being energized from the output potential. If the outputs of the two rectifiers oppose each other and the output of the rectifier supplied from the input potential is the greater, then a drop in output voltage as might occur with the application of an induction motor load would increase the biasing current and produce the desired result. The circuits shown simply represent the preferred embodiments of my invention for the applications described. I prefer to obtain the biasing power from the input circuit where an abundance of power is ordinarily available. In addition, I have found that a high degree of stability is obtainable with the arrangements shown in Figures 7 and 8.

Other combinations may also be used in the arrangement of the output circuit including the capacitors and stabilizing inductances; These elements need not be connected in delta as has been shown in the drawings, they may be starconnected where desired, and in fact, they may be connected in series with the load in some cases. The stabilizing inductances may be omitted when the load variations are not too great, or, when series capacitors are used, the stabilizing inductances may either be shunted across the load or across the capacitors.

The method of obtaining the phase displacements between the two frequency multipliers represents the most economical method when using 40 the reactor as shown in Figures 1 and 2, but it may be desirable in some cases to supply separate phase-splitting transformers to provide this phase displacement.

Although the description has been limited to the methods of applying my invention to a threephase frequency doubler, it may also be applied to other numbers of phases and also to frequency multiplication by other even integers. In general, the circuits become more complicated as the order of multiplication increases, but the essen tial principles remain unchanged.

Although I have described my invention with a certain degree of particularity, it is understood that the present disclosure has' been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

What I claim is:

1. A three-phase frequency doubler comprising first and second sets of biased frequency doubling reactors adapted to'be energized from a threeconnected with respect to the output frequency for supplying the sum of the outputs of the first second sets of reactors to a load and for cancelling even harmonics of the output frequency out of the H assassa load, and a plurality of capacitors energized with said output frequency.

I 2. In combination with a biased-core magnetic frequency multiplier, controlled biasing means ondary being connected to the rectifier.

3. In combination with a biased-core magnetic frequency multiplier, controlled biasing means comprising a current transformer and a rectifier, said rectifier being adapted to supply biasing current to the frequency multiplier, the primary of the current transformer being energized with the input current to the frequency multiplier, the secondary being connected to the rectifier, said current transformer having a magnetic core which decreases in permeability with increasing fiux' density within the normal range ofoperating flux densities.

4. A three-phase frequency multiplier comprising six three-legged saturable reactors, each of said reactors having a primar winding on its center ieg,.and having secondary windings and biasing windings on the two outer legs, the secondary windings being connected in series opposition with respect to the primary winding, the biasing windings being connected in series in the same polarity as the secondary windings, a first group of three of the six reactors having center-tapped primar windings delta-connected and adapted to be energized from a three-phase alternating current source, the second group comprising the three remaining reactors each having it primary winding connected to a primary center tap of the first group and to the junction between the other two primary windings of the first group, the biasing windings of the first group being connected in series to a source of direct current, the biasing windings of the second group being connected in serie and connected to the same source of direct current, each of the secondaries of the first group being connectedin series with a secondary of the second groupin which the voltage of twice the sourc frequency is substantially of the same phase, and a three-phase output network energized from said secondaries and includin three capacitors energized with the three-pha'sevoltage of twice the source frequency and shunted by three saturable stabilizing inductances.

5. A three-phase frequency multiplier comprising six three-legged saturable reactors, each of said reactors having a primary winding on its center leg, and having secondary windings and biasing windings on the two outer legs, the secondary windings being connected in series opposition with respect to the primary winding, the biasing windings being connected in series in the same polarity as the secondary windings, a first group of three of the six reactors having center-tapped primary windings delta-connected and adapted to be energized from a three-phase alternating current source, the second group comprising the three remaining reactors each having its primary winding connected to a primary center tap of the first group and to the Junction between the other two primary windings of the first group, the biasing windings of the first group being connected in series to a source of direct current, the biasing windings of the second group being connected in series and connected to the same source of direct current, each of the secondaries oi the first group being connected in series with a secondary of the second group in which the voltage of twice the source frequency is substantially of the same phase, and a three-phase-output network energized from saidsecondaries and including three a capacitors energized with the three-phase voltage of twice the source frequency.

6. A polyphase frequency multiplier adapted to be energized by a polyphase A. C. source and to supply a polyphase output, comprising in combination, saturable magnetic core means, biasing means for producing unidirectional. flux in said core means, primary and secondary circuit means comprising windings on the core means and polyphase capacitive means connected to the secondary circuit means, said primary and secondary circuit means being non-inductively arranged on the core means, secondary voltage of twice the source frequency being produced by the effect of the unidirectional flux on the saturable core ary voltages of even harmonics of the output fre-,

quency inopposing phases to substantially balance even harmonics out of the output voltage and out of the voltage supplied to said polyphase capacitive means.

7. A three-phase frequency doubler comprising six saturable reactors each having two magnetic flux paths with primar and secondary windings thereon, the primary windings being adapted to be energized from a polyphase A. C. source'and to magnetize both magnetic flux paths of each reactor, the secondary windings being non-inductively wound on the two flux paths of each reactor with respect to the primary windings, biasing means adapted to produce unidirectional flux through the flux paths causing them to react unequally to primary magnetization and thereby to induce in thesecondary windings voltage of twice the source frequency, the secondary of each reactor being connected in series with the secondary of another reactor, with substantially ninety degrees phase displacement between the primary voltages of the two reactors.

8. A polyphase frequency multiplier comprising biasing means in combination with a pair of three-phase doublers adapted to operate with substantially ninet degrees phase displacement between their energizing voltages to provide inphase outputs at twice the energizing frequency and cancelling outputs at even harmonics of twice the energizing frequency, said three-phase doublers comprising saturating magnetic core means, said biasing means comprising a rectifier connected to the secondary of a transformer whose primary is connected in series with the input to said pair of three-phase doublers.

9. A polyphase frequency multiplier comprising biasing means in combination with a pair of three-phase doublers adapted to operate with substantially ninety degrees phase displacement between their energizing voltages to provide inphase outputs at twice the energizing frequency and cancelling outputs at even harmonics of twice the energizing frequency, said three-phase doublers comprising saturating magnetic core means, said biasing means comprising rectify- 76 ing means energized partly from the input curmeans with voltage of the source frequency being voltage to the multiplier.

16. A polyphase frequency multiplier comprising biasing means in combination with 'a pair of three-phase doublers adapted to operate with substantially ninety degrees phase displacement between their energizing voltages to provide inphase outputs at twice the energizing frequency and cancelling outputs at even harmonics of twice the energizing frequency, said three-phase doublers comprising saturating magnetic core means, said biasing means comprising rectifying means supplied with an input voltage varying in response to the variations of load on the output of said. multiplier.

A polyphase irequency multiplier comprising a pair of three-phase frequency doublers adapted to operate with substantially ninety degrees phase displacement between their energizing voltages, to provide in-phase outputs at twice the energizing frequency and cancelling outputs at even harmonics of twice the energizing frequency, said three-phase doublers comprising biased saturating magnetic core means, said multiplier further comprising polyphase capacitive means and saturable inductive stabilizing means, said polyphase capacitive means being connected across the combined outputs of the pair of frequency doublers and being shunted by the saturabie inductive stabilizing means.

12. A polyphase frequency multiplier adapted to be energized by a polyphase AC source and to supply a polyphase load, said multiplier comprising a pair of polyphase frequency doublers adapted to operate with substantially ninety degrees phase displacement between their ener izing voltages. to provide in-phase outputs at twice the energizing frequency and cancelling outputs at even harmonics of twice the energizing frequency, said polyphase doublers comprising saturating mag etic core means, said multiplier further comprisug biasing means for producingunidirectional flux in said magnetic core means, polyphase capacitive means, and saturable inductive stabilizing means, said biasing means comprising rectifying means adapted to be energized with voltage varying in response to variations of said polyphase load, said polyphase capacitive means and saturable inductive stabilizing means being connected in parallel across the combined outputs of the pair of frequency doub ers.

13.1n combination, a plurality of frequency multiplying elements, polyphase capacitive means, saturable inductive stabilizing means, and biasing means, each of said frequency multiplying elements comprising a plurality of saturable magnetic flux paths having winding means thereon. said winding means comprising primary and secondary circuit means, the biasing means being coupled to the secondary circuitmeans to produce unidirectional flux in the flux paths causing them to react unequally to primary magnetization, said plurality of frequency multiplying elements being adapted to be energized from a polyphase source of alternating current, said biasing means comprising rectifying means energized from a current transformer connected between the source and the frequency multiplying elements, the polyphase capacitive means and saturable inductive stabilizing means being connected in parallel to the secondary circuits of said plurality of elements.

14. A threephase frequency. doubler comprising six saturable reactors each having two magnetic flux paths with primary windings thereon. the windings being adapted to be energised-[frame W Ac source to magnetize fiux paths of each reactor. the secondary windings being noninductively wound on the two flux paths of each reactor with respect to the. primary windings. biasing means'adapted to produce unidirectional flux through the flux paths causing them to react unequally to primary magnetization and thereby to induce in the secondary winding voltage of twice the source frequency, the secondary of each reactor being connected in series with the secondary of anotherreactor, with substantially ninety degrees phase displacement between the primary voltages of the two reactors, the combined secondaries of the six reactors being deltaconnected in an output circuit including three capacitors connected to the said secondaries and energized with voltage of twice the source frequency.

15. A polyphase frequency multiplier comprising first and second three-phase frequency doublers comprising biased saturating magnetic core means adapted to operate with substantially ninety degrees displacement between their energizing voltages and having secondary circuits for supplying output voltages of twice the energizing frequency, each secondary of the first doubler being connected in series with a secondary of the second doubler having output voltage of substantially the same phase. the combined secondaries of the first and second doublers being deltaconnected, said multiplier further comprising polyphase capacitive means connected in parallel with saturable inductive stabilizing means and connected across the combined secondaries of the doublers.

- 16. In combination, first and second threephase frequency doublers adapted to operate with substantially ninety degrees phase displacement between their energizing voltages and comprising saturating magnetic core means with serially connected biasing winding means thereon, a rectifier adapted to supply direct current to the biasing winding means, a current transformer adapted to be magnetized with the energizing current to said doublers and having secondary connections to the rectifier, said frequency doublets having secondary circuits for supplying three-phase output of twice the energizing frequency, the secondary circuits of the two doublers being connected together, with voltages of twice the energizing frequency added substantially in phase, the secondary circuits being delta-connected, and a plurality of capacitors energized from the secondary circuits and aiding in the excitation of secondary voltage.

17. In combination, first and second threephase frequency doublets adapted to operate with substantially ninety degrees phase displacement between their energizing voltages and comprising saturating magnetic core means with serially connected biasing winding moans thereon. a rectifier having direct current terminals connected to the biasing winding means. the induced voltages in the serially connected biasing winding means substantially cancelling each other, a current transformer adapted to be magnetized with the energizing current to said doublers and having secondary connections to the rectifier, said frequency doublers having secondary circuits for supplying three-phase output of twice the energizing frequency, the secondary circuits of the two doublets being connected together with voltages of twice nected biasing winding means thereon, a rectifier adapted to' supply direct current to the biasing winding means, a current transformer adapted to be magnetized with the energizing current to said doublers and having secondary connections to the rectifier, said frequency doublers having secondary circuit for supplying three-phase output of twice the energizing frequency, the secondary circuits of the two doublers being connected together, with voltages of twice the energizingfrequency added substantiall in phase. the secondary circuits being delta-connected, a plurality of capacitors energized from the secondary circuits and aiding in the excitation of secondary voltage, and saturable inductive stabilizing means connected substantially in parallel with said ca-- pacitors.

19. A polyphase frequency multiplier comprising biasing means in combination with a pair of three-phase doublers adapted to operate with substantially ninety degrees phase displacement between their, energizing voltages, to provide inphase outputs at twice the energizing frequency and cancelling outputs at even harmonics of twice the energizing frequency, said three-phase doublers comprising saturating magnetic core means,

said biasing means comprising rectifying means energized partly from the input voltage to the multiplier and partly from the output voltage of the multiplier.

20. In combination, a plurality of frequency,

multipliers adapted to be energized from alternating input voltages displaced in phase from each other and to supply output voltages in substantially the same phase and of a frequency which is an even harmonic of the frequency of the energizing voltage, each of said plurality of frequency multipliers comprising a plurality of saturable magnetic flux paths, primary and secondary circuit means'inductively related to said flux paths and biasing means for producing in said flux paths a unidirectional fiux to cause the paths to react unequally to primary magnetization and to induce harmonic voltages in the secondary circuit means.

21. A three-phase frequency multiplier comprising six three-legged saturable reactors, each of said reactors having a primary winding on its center leg, and having secondary windings and biasing windings on the two outer legs, the secondary windings being connected in series opposition with respect to the primary winding, the biasing windings being connected in series in the same polarity as the secondary windings, a first group of three of the six reactors having centertapped primary windings delta-connected and adapted to be energized from a three-phase alternating current source, the second group comprising the three remaining reactors each having its primary winding connected to a primary center tap of the first group and to the junction between the other two primary windings of the first group, the biasing windings of the first and second groups being connected in series and connected to a source of direct current, each of the sec-r ondaries of the first group being connected in series with a secondary of the second group in which the voltage of twice the source frequency is substantially of the same phase, and a threephase output network energized from said secondaries and including three capacitors energized with the three-phase voltage of twice the source frequency and shunted by three saturable stabilizing inductances.

22. In combination, a plurality of frequency multipliers adapted to be energized from alternating input voltages displaced in phase from each other and to supply output voltages in substantially the same phase and of a frequency which is an even harmonic of the frequency of the energizing voltage and to supply cancelling output voltages of even harmonics of the output frequency, each of said plurality of-frequency multipliers comprising a plurality of saturable magnetic flux paths, primary and secondary circuit means inductively related to said flux paths and biasingmeans for producing in said flux paths a unidirectional fiux to cause the paths to react ,unequally to primary magnetization and to induce harmonic voltages in the secondary circuit means.-

23. In a biased core magnetic frequency multiplier having winding means, a biasing arrangement comprising, in combination, first and second rectifiers and first and second energizing circuit means, the first and second rectifiers being connected to said winding means and being polarized to produce opposing biasing currents therein, the first energizing circuit means being connected to supply the first rectifier with input voltage of the frequency multiplier, and the second energizing circuit means being connected to supply the second rectifier with output voltage of the frequency multiplier.

24. In a biased core magnetic frequency multiplier, a controlled biasing arrangement comprising, in combination, a plurality of transformer means, and rectifying means connected with said transformer means, one of said transformer means being energized from the input voltage to the frequency multiplier, another of said transformer means being energized from the input current to the frequency multiplier, said rectifying means supplying a biasing current to the frequency multiplier and varying said biasing current in response to variations in the potentials supplied by the plurality of transformer means. HENRY MARTIN HUGE.