US1934227A - Frequency changing system - Google Patents

Description

NW. 7, 1933. C EHRENSPERGER I 1,934,227

FREQUENCY CHANGING SYSTEM Filed Sept. 20, 1952 s Sheets-Sheet 1 Nav. 7,,1933.. c EHRENSPERGER 1,934,227

FREQUENCY CHANGING SYSTEM Filed Sept. 20, 1932 s Sheets-She et 2 1933. EHRENSPERGER 1,934,227

FREQUENCY CHANGING. SYSTEM Filed Sept. 20, 1932 3 Sheets-Sheet I lllllll ag I13 Patented-Nov. 7 1933 PATENT OFFICE ofswlhcdanl signer w (lieqmsmajoint stockcompany Applicafimseptembanm SerblNo. 634,058, and Septembu' 25, 1931 inGelmny llflaims.

This invention relates to improvements in alternating current frequency converting systems utilizing electron discharge devices. and more particularly to systems in which a variable amount of in-phase current or of reactive current to be exchanged in either direction be-- tween lines which are not always rigidly maintained 'in an invariable frequency relation; and issimilarinsome ofitsaspectstothefrequency converting system disclosed in the joint application of S. Widmer and C. Serial No. 634,055, filed September 20, 1932.

It is well known to connect two alternating current lines or two portions of a. single alternating current line by a frequency converter comprising an input transformer an electron discharge device and an output transformer, which current supplied from one line to the input transformer is rectified and then crmverted into alternating current by the electron discharge device, and supplied to the second line through the output transformer. In general, a system of the above character permits connection only of lines rigidly maintained in an invariable frequency relation, and does not permit a regulation of the flow of current in either direction. By energizing the control of the electron discharge device in on the frequencies of both the input and the output circuits, the system may be made operable for such an energy transfer in either direction between two lines even when the frequency relation bet-ween such lines in The controllingmeans may also be provided with means for. adjustment which permit separate regulation of the direction and of the intensity of the flow of iii-phase current and of reactive current between the lines.

It is, therefore, one of the objects of the present invention to provide a frequency converting system utilizing an electron discharge device operable' for permitting flow of energy in either direction between two alternating cunmt lines which are not rigidly maintained in an invariable frequency relation.

Another object of the present invention is to provide a frequency converting system utilizing an electron discharge device in which the direction of the flow of energy between two alternating current lines which are notrigidlymaintained in an invariable frequency relation may be determined by automatically or manually operated control means.

Another object of the present in is to provide a frequency converting systan uflhzim an electron discharge device in which the intensity of flow oi in-phase current between two' alternating current lines which are not rigidly maintained in an'invariable frequency relation, may be detennined by automatically or manually operated control means.

Another object of the present invention is to provide a. frequency converting system utilizing an electron discharge device in which the intensity of flow of reactive current between two alternating current lines which are not rigidly maintained in an invariable frequency relation, may be determined by automatically or manually operated control means.

Another object of the present invention is to provide a frequency converting system utilizing an electron discharge device in which the voltage induced in the primary windings of the output transformer may be adjusted in phase and in magnitude with respect to the voltage of the output line by automatically or manually operated control means. V V

Objects and advantages other than those above set forth will be apparent from the following dscrlptions when read in connection with the accomm y drawings in which:

Fig. 1 'tically illustrates one embodiment of the present invention for converting alternating currents at one frequency into single phase alternating currents at the same or at another frequency, and in which the flow of in-phase current and of reactive current may be separately regulated both in direction and in magnitude;

Fig. 2 atically illustrates a modified t of the present invention for converting polyphase alternating current into single phase alternating current and dilfering from. the embodiment shown in Fig. 1 in that the flow of in-phase current and of reactive current may be automatically regulated both in direction and in magnitude; and

Fig. 3 tically illustrates another modified embodiment of the present invention dilfering from the embodiment illustrated in Pig. 2 in that the control means are simplified for autanatically regulating the flow of .only inphase current both in direction and in magnitude.

Referring more particularly to the drawings by characters of reference, the reference num-. eral 6" designates a polyphase alternating current line which is shown as a 3-phase line as being the type of line most frequently met in practice. Line 6 may be energized at any commercial frequency, but such frequency need not be maintained at a constant value and may present regular or irregular variations in time. It is assumed that it is desired to transmit energy between line 6 and a single phase alternating current line 7. Line '7 may be energized at any desired frequency and such frequency may be without relation to the frequency of the voltages in Line 6. The frequencies of lines 6 and 1 may be substantially equal as would be the case when such lines are part of electrical systems operated at the same normal frequency. The frequency converting system will be described assuming that it is desired to obtain a flow of energy from line 6 towards line '7, and the system elements will be designated accordingly. Line 6 supplies current to winding 8 of an input transformer having two secondary windings l1 and 12 and line '7 is connected with the secondary winding 16 of an output transformer having a primary winding 14. windings 11, 12 comprise star connected portions such as 11a and 12a etc. severally connected with anodes such as 21a and 22a etc. of an electron discharge device 17 operable as an electric current rectifier and provided with a cathode 18 connected with the neutral point of winding 14. The two portions 14a and 14b of winding 14 are severally connected with the neutral points of windings 11 and 12. Rectifler 17 is provided with control electrodes such as 31a and 320 etc. associated severally with the anodes and usually energized at a negative potential with respect to cathode 18 from a battery 24 through banks of resistances 26 and 27. The control electrodes may also be energized at a positive potential with respect to cathode 18 from a second battery 28 through the segments of a distributor 36 and of two distributors 41 and 42. Distributors 41 and 42 are provided with brushes mounted on the shaft of a synchronous motor 29 energized from line 6 and 'have their segments spatially adjustable by means of a lever 34. Distributors 41 and 42 are each provided with six segments, the segments of distributor 41 being connected with control electrodes 31a, 31b, etc, and its brush being connected with segment 36a of distributor 36. Distributor 42 is similarly connected with the remaining control electrodes of rectifier 1'7 and has the brush thereof connected with segment 36b of distributor 36. Distributor 36 is provided with a brush energized from battery 28 rotated by a synchronous motor 3'! energized from line 7. The segments of distributor 36 are in contact with the brush thereof during one-half of each revolution of the brush and are spatially adjustable by means of a lever 38.

In operation, assuming that lines 6 and '1 are energized at their respective operating frequencies, winding 16 of the output transformer will be periodically energized at a positive potential from line 7. During each period of positive energization of winding 16, winding. 140 must also be energized at a positive potential to permit transfer of energy from line 6 to line 7. During such period, the brush of distributor 36 is in contact with segment 36a. thereof thereby energizing the brush of distributor 41 at a positive potential from battery 28. Distributor 42 then has its brush disconnected and is thus inoperative, so that the control electrodes associated therewith are energized at a negative potential from battery 24 and prevent flow of current through winding 12. The brush of distributor 41. being rotated in synchronous motor 29, perthe generator windings.

mits sequential energization of control electrodes 31a, 311), etc. from battery 28 through segment 36a. Such control electrodes are positively energized in the sequence in which the associated anodes 21a,-21b, etc. are energized at positive potentials from winding 11. Winding portions 11a, 11b, etc. therefore sequentially carry current as is well known in the electric current rectifier art, such currents flowing to the cathode 18 of rectifier 1'7 and combining to form a single current wave flowing through winding 1411 back to the neutral point of winding 11. Such current will flow during the entire period during which winding 16 is energized at positive potential, during which time the brush of distributor 36 will remain in contact with segment 3611. During the following half cycle of the voltage of line '7, winding 16 will be energized at a negative potential. Winding 14b then receives current from winding 12, by a process similar to that described above for winding 14a, the flow of such current being controlled by distributor 42. During the period of negative energization of winding 16, the brush of distributor 36 is in contact with segment 36b to permit connection of battery 28 to the brush cf distributor 42. The above cycle of successive energization of the portions of winding 14 is repeated during each cycle of the voltage in line 7 to permit continuous flow of current from line 6 to line 7. It will be understood that current supplied to winding 8 from line 6 is rectified for a period of time in winding 11 and during another.period in winding 12, such cycle of rectification being repeated during each cycle of the voltagev inline 7. Windings 11 and 12 thus intermittently transmit direct current to winding portions 14a and 14b, thereby inducing alternating currents in winding 16.

.As is well known, when two alternating current generators or converters are supplying current to a common outputline, both generators may be considered as supplying current to the current consuming devices connected with the output circuit and also as producing the flow of circulating currents within their own windings and the line. When the voltages of the generators are diil'erent in magnitude, a reactive current will circulate through the windings, such magnitude being determined by the difference in the generator voltages and by the reactances of When the voltages of the two generators are out of phase, a circulating current will again be present, such current then being in phase with the line voltage and of a magnitude determined by the phase dinerences of the generator voltages and by the generator winding reactances. Similarly, in frequency converting systems such as described above, the flow of reactive current between the two lines will be determined by the difference between the induced voltage in the primary windings of the output transformer of the system and the line voltage. The magnitude of such induced voltage may be controlled by adjustment of the segments of distributors 41 and 42 by means of lever 34. As is well known, ad- Justment of such distributors will cause a change in the rectified output voltage of rectifier 1'7, which output voltage is applied sequentially to winding portions 14a and 14b and is substantial- 1y equal to the induced voltage in such windings. Similarly, adjustment of distributor 36. by mean: of lever 38 will'vary the time of the alternating current cycle of line 7 at which the output voltre: Iv

portion is energized at each brush new of reactive current in a system of the character described, it is necessary that each control electrode of the rectifier be energized twice at intervals of about 180 electrical degrees'during each cycle of the voltage in line 6. In the present embodiment, such tained by conductively connecting each segment of distributor 41 with a segment of distributor- 42 energized one-half cycle later during each cycle of the voltage in line 6.

When it is desired to reverse the transfer of current between the two lines, it being impossible to reverse the direction of current flow through rectifier 1'7, it becomes necessary to produce the transfer of current when the voltages in lines 6 and 7 are negative instead of positive, such reversal of the voltages determining the reversal of the flow of energy. Such reversal is obtained by shifting the segments of distributors 41 and 42 by 180 degrees, thereby shifting the 'energization of the control electrodes associated. therewith by 180 electrical degrees relative to the voltage in line 6. The segments of distributor 36 are then also displaced by 180 degrees, thereby shifting the energization of the brushes of distributors 41 and 42 by 180 electrical degrees relative to the voltage of line '7. The process of current transfer from line '7 to line 6 then becomes similar to the process described above for the transfer of current from line 6 to line '7. Such current transfer occurs through winding portion 14 when such windin a negative potential and also through winding portions such as 11a, 11b, etc. of winding 11, when such portions are also at a negative potential less than the negative potential of winding portion 14a, so that the anodes 21a, 21b, etc. of rectifier 1'7 are again at a positive potential with respect to cathode 18 to permit flow of current therethrough.

In the embodiment shown in Fig. 2 it is again assumed that current is to be transferred from a three phase line 6 to a single phase alternating current line '7 energized at a frequency which may or may not be the sameas the frequency of line 6. In the present embodiment, energie zation of the control electrodes is obtained through a drum type distributor driven by synchronous motors, the distributor consisting of drums of insulating material with conductive strips of which the development of one drum 52 is shown in thedrawings. The distributor drum 52 carries, on the surface thereof, two current conducting strips 54 and 55 which are conductively connected with a slip ring 58 whereby they may be energized at a positive potential from battery 28. Current is transmitted from st ps 54 and 55 to a plurality of brushes 59, being a strip of current conductive material wound as a helix on a second distributor drum of insulating material 61. Each brush or helix 59 is conductively connected with one of a plurality of slip rings 62 whereby the voltage of battery 28 may be applied to control electrodes such as 31:: through resistances 2'7. Helixes '59 are equal in number to the number of portions of winding 11 and may make one .or several revolutions on drum 61.

.speed depending dual energiaation is ob- Drum 52 is also in contact'with a second set of electrical brushes 63 mounted on a distributor drum 64 and connected with slip rings 68 for energizing control electrodes such as 32a associated with the several portions of winding 12.- Drums 61 and 64 are mechanically connected for synchronous rotation thereof and are driven by a synchronous motor 69. Motor 69 may have the armature thereof energized from line 6 and the field thereof energized from line '7, thereby, permitting rotation of drums 61 and 64 at a upon the relative frequencies of lines 6 and '7. When lines 6 and '7 are energized at exactly their normal frequencies, the armature of motor 69 will remain stationary. Drum 52 may be connected with its motor 37 through a mechanical coupling to permit adjustment of the the distributor and the motor during simultaneous rotation thereof; such coupling is adjustable by movement of a lever '70 which may be controlled manually or which may be actuated by a solenoid 72 energized in response to the current in line '7 through a current transformer 73. Similarly, drums 61 and 64 may be connected with motor 69 through another coupling '74 to permit the adjustmentof the angular relation thereof, such coupling being adjusted by movement of a lever '75 which may be actuated by a solenoid '76 energized in response to the voltage of line '7.

In operation, thecontrol electrodes of recti- .flerl'7 are generally maintained at a negative potential relative to the potential of cathode 18 by means of battery 24. Assuming that it is desired to transfer energy from line 6 to line '7, and assuming that the voltage in line '7 at the instant considered is such that winding 11 is to be brought to a positive potential, rotation of synchronous motor 3'7 brings strip 54 of distributor 52 into sequential contact, with the different electrical brushes 59 assembled on drum 61. The control electrodes associated with the portions of winding 11 are thus sequentially brought to a positive potential and permit sequential operation of the associated anodes. Winding 11 therefore carries alternating currents at the frequency of the voltage of line 6, such currents combining at cathode 18 to form a single current impulse through windingportion 14a back winding 11. After on -half cycle of the voltage of line '7, strip 54 of distributor 52 will have rotated by one-half of a revolution and will come into sequential contact with brushes 63 mounted on drum 64. that described above, winding 12 thereupon produces a wave of rectified current circulating throughwinding portion 147). Such changing energization of winding portions 14a. and 1471 are repeated at in line '7, thereby inducing, in winding 16, an alternating current at the frequency of line '7.

During each half cy-le of the voltage in line relative angular position of I .to the neutral point of By a. process similar to the frequency of the voltage I approximate the sinusoidal shape. In the present embodiment also, it is necessary that the control electrodes of the rectifier be energized at a positive potential twice during each cycle or the single phase line voltage. To obtain such result, drum 52 is provided with a second conductive strip 55 which contacts with each of helical brushes 59 and 63 about 180 electrical degrees after strip 54 makes such contact. As in the embodiment illustrated in Fig. 1, the intensity'of' flow of reactive current is determined by the time of energization of the control electrodes of the rectifier relative to the voltage cycle of the S-phase'line. Such. time of energization may be adjusted by adjustment of coupling 74, such adjustment being attained manually or, if desired, automatically in response to the variations of any electrical quantlty such as the voltage in line 7 by means of solenoid 76. When the relation between the frequencies of the voltages of lines 6 and 7 is at its rated value, motor 69 is at a standstill and a constant value of the reactive current exchanged between lines 6 and 7 is obtained automatically. When the frequencies of the voltages in lines 6 and 7 vary from their rated relation, motor 69 rotates drums 61 and 64 to reestablish the proper sequence of energization of the control electrodes of the rectifier to permit continuation of the flow of current at its original value.

As in the embodiment illustrated in Fig. 1, the flow of in-phase current is determined by the time of energization of the control electrodes controlling each winding 11 and 12 relative to the voltage wave of the output line 7. Such energization may be adjusted by varying the position of coupling 71 by means of lever 70, such adJustment being also obtained, if so desired, by means of solenoid 72 energized from current transformer 73. It is also possible to reverse the direction of the flow of energy between the two lines, the flow of reactive energy being reversed by adjustment of coupling 74 to permit displacement of the energization of the control electrodes by an angle of 180 electrical degrees with respect to the voltage of line 6 and the flow of in-phase energy being adjusted by means of coupling 71, thereby displacing the energization of the control electrodes by 180 electrical degrees with respect to the voltage wave of line 7.

In the embodiment illustrated in Fig. 3, the control of rectifier 17 is shown as simplified to permit flow of only, in-phase current between lines 6 and 7. In the present embodiment, the control electrodes are connected into two groups, severally associated with windings 11 and 12, the two groups being connected with the terminals of a single phase generator 77 driven by synchronous motor 37 energized from line 7. Gen: erator 77 is connected with motor 37 through coupling 71 as in the embodiment shown in Fig. 2. Coupling 71 may be adjusted by hand or may be adjusted according to any predeter-- mined schedule applied through means herein represented as a timing mechanism 81.

In operation, assuming that winding 11 is to receive a positive current impulse to be transmitted to line 7, coupling 79 is so adjusted that the control electrodes 31a, 311), etc. associated with winding 11 are all energized at a positive potential with respect. to the cathode from generator 77. The anodes 21a, 211), etc. severally connected. with the portions of winding 11 are,

therefore, all operable for carrying current, and winding 11 will produce rectified currents which combine at cathode 18 into a single current impulse transmitted over winding portion 14a back to the neutral point of winding 11. During the next half cycle of the voltage of line 7, generator 77 maintains the control electrodes associated with winding 11 at a negative potential, thereby making winding 11 inoperative. The control electrodes 32a, 32b, etc. associated with winding 12 are then energized at a positive potential so that, by a process similar to that described above, a current impulse is sent through winding portion 14b. Current impulses are thus sent through winding portions 14a and 14b during each cycle of the voltage in line 7, thereby inducing in winding 16 an alternating current transmitted to line 7. As in the embodiments previously described, the intensity and the direction of flow of in-phase current circulating be tween the two lines is determined by the time of energization of the control electrodes relative to the voltage wave of line 7. In the present embodiment, such time may be varied by adjustment of coupling 71, thereby shifting the output voltage of generator 77 with respect to the voltage of line 7. This adjustment may be obtained by hand or in response to the variation of electrical or mechanical quantities and may be obtained, as shown in Fig. 3, by means of a timing mechanism 81.

Although but a few embodiments of the present invention have been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. In a system for transmitting energy between alternating current lines, an alternating current line of one frequency, a transformer connected with said line, an electron discharge device having anodes with associated control electrodes and a cathode, the anodes and the cathode of said device being connected with said transformer,. an alternating currentline of a frequency other than that of the first said line, a trans- .former connecting the cathode of said device with the second said line, said transformers being interconnected, a source of potential arranged for connection with the control electrodes of said device, and means cooperatively controlled in response to the frequencies of said lines for controlling the connection of said source with .the control electrodes to vary the energy flow between said lines.

2. In a system for transmitting energy between alternating current lines, an alternating current line of one frequency, a transformer connected with said line, an electron discharge device having anodes with associated control electrodes and a cathode. the anodes and the cathode of "said device being connected with said transformer, an alternating current line at a frequency other than that of the first said line, a transformer connecting the cathode of said device with the second said line, said transformers being interconnected, a source of podevice having anodes with associated control electrodes of said device, and means for controlling the connection of said source with the control electrodes to control the direction of the energy flow between said lines.

3. In a system for transmitting energy between alternating current lines, an alternating current line at one frequency, a transformer connected with said line. an electron discharge device having anodes with associated control electrodes and a cathode, the anodes and the cathode of said device being connected with said transformer, an alternating current line at a frequency other than that of the first said line, a transformer connecting the cathode of said device with the second said line, said transformers being interconnected, a source of potential arranged for connection with the control electrodes of said device, and means for controlling theconnection of said source with the control electrodes to control the intensity of the energy fiow between said lines. 7

4.. In a system for transmitting energy between alternating current lines, an alternating current line at one frequency, a transformer connected with said line, an electron discharge device having anodes with associated control electrodes and a cathode, the anodes and the cathode of said device being connected with said transformer, an alternating current line at a frequency other than that of the first said line, a transformer connecting the cathode of said device with the second said line, said transformers being interconnected, a source of potential arranged for connection with the control electrodes of said device, and means for controlling the connection of said source with the control electrodes to control both the intensity and the direction of the energy fiow between said lines.

5. In a system for transmitting energy between alternating current lines; an alternating current line at one frequency, a transformer connected with said line, an electron discharge device having anodes with associated control electrodes and a cathode, the anodes and the oathode of said device being connected with said transformer, an alternating current line at a frequency other than that of the first said line.

vice having anodes witlrassociated control electrodes and a cathode, the anodes and the oathode of said device being connected with said transformer, an alternating current lineat afrequency other than that of the first said line, a transformer connecting the cathode of said device with the second said line, said transformers being interconnected, a source of potential arranged for connection with the control electrodes of said device, means responsive to the frequency of the first said lineto control the sequential positive energization of the control electrodes thereby controlling the fiow of energy between said lines, and means responsive to the frequency of the second said line to control the connection of the positive terminal of said source with the first said means.

7. In a system for transmitting energy bethe control electrodes to control the sequential tween alternating current lines, an alternating current line at one frequency, a transformer connected with said line, an electron discharge device having anodes divided into groups with severally associated control electrodes and a cathode, the anodes and the cathode of said device being connected with said transformer, an alternating current line at a frequency other than that of the first said line, a transformer connecting the cathode of said device with the second said line, said transformers being interconnected, a source of potential arranged for connection with the control electrodes of said device, a plurality of distributors connected with positive energization thereof, means for operating said distributors in response to the frequency of the first said line, a distributor controlling the connection of said source with the first said distributors, 'and' means responsive to the frequency of the second said line for operating the last said distributor. I

8. In a system for transmitting energy between alternating current lines, an alternating currentline at one frequency, a transformer connected with said line, an electron discharge device having anodes divided into groups with severally associated control electrodes and a cathode, the anodes and the cathode of said device being connected with said transformer, 5

an alternating current line at a frequency other than that of the first said line, a transformer connecting the cathode of said device with the second said line, said transformers being interconnected, a source of potential arranged for connection with the control electrodes-of said device, a plurality of distributors connected with the control electrodes tocontrol the sequential positive energization thereof, means for operating said distributors in response to the frequency of the first said line, a distributor controlling the connection of said source with the first said distributors, means responsive to the frequency of the second said line for operating the last said distributor, and means for varying the operation of said distributors by variation of the relations in space thereof.

9. In a system for transmitting energy between alternating current lines, an alternating current line at one frequency, a transformer connected with said, line. an electron discharge device having anodes with associated control electrodes and a cathode, the anodes and the cathode of said device being connected with said transformer, an alternating current line at a frequency other than that of the first said line, a transformer connecting the cathode of said device with the second said line, said transformers being niterconnected, a source of potential arranged for connection with the control electrodes of 135 said device. a distributor having a plurality of movable portions for controlling the connection of the control electrodes with said source, means responsive to the frequency of one of said lines vtribiitor, and means responsive to the relative said transformer, an alternating current line at a frequency other than that of the first said line, a transformer connecting the cathode of said device with the second said line, said transformers being interconnected, a source of potential arranged for connection with the control electrodes of said device, a distributor having a plurality of movable drums for controlling the sequential connection of the control electrodes with said source, a motor for driving one of the drums responsive to the frequency of I one of said lines, and a motor for driving the other drums of said distributor in response to the frequency diiferences between said lines.

11. In a system for transmitting energy between alternating current lines, an alternating current line at one frequency, a transformer connected with said line, an electron discharge device having anodes with associated control electrodes and a cathode, the anodes and the cathode of said device being connected with said transformer, an alternating current line at a frequency other than that of the first said line, a transformer connecting the cathode of said device with the second said line, said transformers being interconnected, a source of potential arranged for connection with the control electrodes of said device, a distributor having a plurality of movable drums for controlling the connection of the control electrodes with said source, a motor for driving one of the drums responsive to the frequency of one of said lines, a motor for driving the other drums of said distributor in response to the frequency differences between said lines, and means for varying the relative angular position of said distributor drums and said motors.

12. In a system for transmitting energy between alternating current lines, an alternating current line at one frequency, a transformer connected with said line, an electron discharge device having anodes with associated control electrodes and a cathode, the anodes and the cathode of said device being connected with said transformer, an alternating current line at a frequency other than that of the first said line, a transformer connecting the cathode of said device with the second said line, said transformers being interconnected, a source of potential arranged for connection with the control electrodes of said device, a distributor having a. plurality of movable drums for controlling the connection of the control electrodes with said source,-a motor for driving one of the drums of said distributor responsive to the frequency of one of saidlines, a motor for driving the other drums of said distributor in response to the frequency diiferences between said lines, and means for varying the relative positions of the drums of said distributor to vary the time of energization of the control electrodes relative to the cycle of the voltages of said lines.

13. In a system for transmitting energy between alternating current lines, an alternating current line at one frequency, a transformer connected with said line, an electron discharge device having anodes with associated control electrodes and a cathode, the anodes and the cathode of said device being connected with said transformer, an alternating current line at a frequency other than that of the first said line, a transformer connecting the cathode of said device with the second said line, said transformers being interconnected, a source of potential arranged for connection with the control electrodes of said device; a distributor having a plurality of movable drums for controlling the connection of the control electrodes with said source, a motor for driving one of the drums responsive to the frequency of one of said lines, a motor for driving the other drums of said distributor in response to the frequency differences between said lines, and means for automatically varying the relative angular positions of said distributor and said motors, said means being responsive to predetermined conditions affecting operation of the system.

14. In a system for transmitting energy between alternating current lines, an alternating current line at one frequency, a transformer connected with said line, an electron discharge device having anodes with associated control electrodes and a cathode, the anodes and the cathode of said device being connected with said transformer, an alternating current line at a frequency other than that of the first said line, a transformer connecting the cathode of said device with the second said line, said transformers being interconnected, a source of'potential arranged for connection with the control electrodes of said device, a distributor having a plurality of movable drums for controlling the connection of the control electrodes with said source, a motor for driving one of the drums responsive to the frequency of one of said lines, a motor for driving the other drums of said distributor in response to the frequency differences between said lines, adjustable couplings connecting said distributor with said motors for varying the angular relations therebetween, and means for actuating said couplings automatically in response to predetermined conditions affecting operation of the system.

CHARLES EHRENSPERGER.

een'rlricareor connection.

@atent No. 1,934,227. i I November 7, 193;.

names eeaensrenoen.

it is hcreby certified that error appears in the printed specification of the tfoove numbered patent requiring correction as follows: Page 4, line 146, claim 2, strike out the words "device having anodes with associated" and insert instead the syllable and words tential arranged for connection with the; page 5, line 134, ciaim 9, for "niterconnected" read interconnected; and that the aid Letters Patent nhouid be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and seated this 12th day of December. A. D. 1933.

F. M. Hopkins {Sean I I v Acting Commissioner of l nen.

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