US2449077A - Power converter - Google Patents

Description

Sept. 14, 1948- N. E. LINDx-:NBLAD 2,449,077

Ponza CONVERTER T' 1 l a Filed Jan. 27. 194:5

/000lr L 7,445

M14/verrou 05cm LA ron ATTORNEY v Patented Sept. 14, 1948 POWER CONVERTER Nils E. Lindenblad, Port Jefferson,

N. Y., assigner to Radio Corporation of America, a corporation of Delaware Application January 27, 1943, Serial No. 473,677

n The present invention relates to apparatus for converting direct current power to periodically recurring high voltage pulses, suitable for use (by way of example) in exciting an electron discharge device.

The present invention finds particular application in connection with pulse transmission systems wherein it is desired to periodically excite an electr-on discharge device oscillator with pulses of high voltage momentarily applied to the oscillator, as a result of which it is possible to btain a higher output from the oscillator than during a normal or continuous steady state. It is in conjunction with such a pulse transmission system that the present invention will herein after be described, although it should be understood that this particular application of the invention is given for reasons o1' exposition, and not by way of limitation.

Briefly stated, the converter of the present invention comprises a trickle source of relatively low voltage direct current (such as 1000 volts by way of example), a storage condenser adapted to be continuously charged by this direct current source, a load such as the primary oi.' a transformer across which it is desired to obtain high voltage pulses of, let us say, 2000 or 4000 volts, and a condenser of relatively small capacity compared to the storage condenser adapted to be connected in series between the large storage condenser and the transformer but whose connections are continuously reversed relative to both the storage condenser and the load. Features of the invention reside in the different forms of apparatus employed for reversing the connections of the small condenser relative to its charging source and itsioad.

A more detailed description of the invention follows in conjunction with a drawing, wherein:

Figs. 1 to 4 illustrate four different embodiments of the present invention, and

Fig. 1a graphically shows the form of the pulse obta.1.able from the system of the invention.

A11 four embodiments of the invention diagrammatically illustrate the power system for supplying a magnetron oscillator I with high voltage pulses of microsecond duration. Such a magnetron oscillator may be used in a radio loeating system for producing pulses of ultra short waves below one meter in length. It is desired that the pulses be short compared to the interval oi' time between them. The power supply system constituting the invention is designed to convert direct current power of relatively low voltage supplied through lead I0 to power pulses of rela- 2 v tively high voltage and to supply these high voitage pulses to an electrode of the oscillator I, such as the cathode, in order to cause the oscillator to produce oscillations solely during the interval in which the pulses of .high voltage appear. Because the oscillator I functions momentarily under these conditions, it is possible to obtain a higher output from it than` during a normal or continuous steady state. To these ends, the invention contemplates applying to the oscillator a much higher voltage than normally applied to a magnetron electrode but for a very short period of time, thus enabling "high output power at short waves to be derived from the oscillator.

Referring to Fig. 1 in more detail, a direct current charging source of, let us say, 1000 volts, is Y applied to lead IIJ for charging the large condenser II through a choke coil I2. This direct current charging source may be a rectier, a direct current generator, or a battery. The choke coil is provided for smoothing purposes. The upper electrode of condenser II is connected to the upper terminal of the primary winding of a step-up transformer I3 through a small condenser I4 whose connections between the condenser and the transformer are adapted to be continuously reversed. Condenser II is designed to be much larger in capacity than condenser I4, for example ten to fifteen times larger, in order that the voltage at the condenser II should not drop appreciably whenl furnishing charge to the condenser I4. The armatures of the condenser I4 are connected to electrodes I5 and I6 which are shown contacting electrodes I1 and I8, re-

spectively. The reversal of the connections of condenser I4 can be obtained by rotating the condenser in the direction of the arrows, such that at one time the electrodes assume the posi#- tion in the drawing, while at another predetermined time the electrodes I5 and I6 are reversed to contact the electrodes I8 and I'I., respectively.

By thus continuously rotating the condenser I4, or its connections, I am able to obtain pulses at regular intervals through the primary winding of transformer I3 which have an initial voltage of 2000 volts across the primary, or twice the voltage value of the direct current charging source. The reasons for this will now be given: Let us assume that we first connect the circuit in the manner indicated inthe drawing of Fig. 1. Ilhere will then be produced a pulse through the primary winding of transformer I3 having an initial voltage of the direct current charging source supplied to lead I IJ. Thus, if the direct current charging source is 1000 volts, there will 3 be a pulse or kick through the primary winding of transformer I3 of 1000 volts between its ter- Now, if the connections of condenser I4' are reversed by rotating the condenser and its w electrode so that electrode I6 touches electrode I1, and electrode i touches electrode I8, there is produced in eiect a series circuit of condensers II and i4 with the polarities of the .condensers in additive relation. There will then be obtained across the primary winding of transformer I3 a pulse having an initial voltage of 2000 volts. This initial voltage of the pulse will, o course, diminish according tothe time constants of the associated circuit. With continuous rotation of the condenser I4 or its connections, I am able to obtain periodically appearing pulses through the primary winding of the transformer i3, each of which has an initial 2000 volts. It should thus be noted that only the first .pulse through the primary winding of the transformer has an initial voltage equal tothe voltage of the direct current charging source, whereas all subsequent pulses have a voltage which is double the voltage of the charging source. The phenomenon may bemore readily understood by referring to Fig.

1a, which shows the wave form of the double voltage pulses acioss the primary Winding of transformer I3. It should be noted that the pulse has an initial voltage of 2000 volts which gradually diminishes. Point X on the curve of Fig. la may represent, by way of example, the point at which the condenser I4 is completely discharged through the transformer i3 and begins to recharge in the opposite direction. It will thus be seen that the whole complete pulse through the transformer includes both the discharge and the charging of the condenser I4 as one continuous Y or uninterrupted phenomenon. The particular position in time of the point X on the slope of the pulse of Fig. 1a. is dependent upon the values of the circuit elements, such as inductance, capacity and load resistance. The entire'duration of the pulse of Fig.` la may be one microsecond or so.

By designing the transformer I3 as a step-up transformer having a voltage ratio of one to ten,

it is thus possible to obtain across the secondary lwinding a voltage pulse of 20,000 volts for momentary application to an electrode of the magnetron oscillator. If the connections :from the condenser I4 are continuously and repeatedly reversed at a rate of 240 per second, it is possible to derive pulses of one microsecond duration from the oscillator I which are separated from one another by much longer intervals of time, say of the order of thousands of microseconds.

Fig. 2 shows an alternative form for accompushing the same results described above in connection with Fig. 1. In Fig. 2, the small condenser I4 is stationary and the connections from the condenser I4 to the condenser II and the primary winding of step-up transformer I3 arev ing surface connected to a plurality of brushes or contacts 32 and 33 while the lower charging surface o condenser I4 is connected to a plurality of contacts 34 and 35. The relatively low voltage source applied to lead Il! is connected to a plurality of contacts 33 and 31, whilethe upper terminal of the primary winding of transformer I3 is connected to a plurality oi contacts 3l and 39. In one position of the dis-charger, one segment 3l will bridge contacts 31 and 32, while at the same time another segment 3| will bridge contacts 39 and 35, thus producing a complete circuit from the direct current charging source through the condenser I4 and the primary winding of transformer I3. In this position, there is no direct connection between contacts 3i and 34, or between contacts 33 and 33. In another position of the discharger, a segment 3i will bridge contacts 36 and 34, while simultaneously another segment 3l will bridge contacts 38 and 33. At this particular time, there will be no direct current connection between contacts 31 and 32, or between 33 and 35, by virtue of the fact that the segments which previouslly bridged them have now passed beyond these contacts in their path of travel. In this last position, the circuit will again be complete rom` the direct current charging source through the condenser I4 and through the primary winding of the transformer I3, but, it should be noted, that the connections of the condenser I4 have now been reversed relative to the rst position. As the discharger revol-ves, this cycle of operations will bevrepeated, thus producing repeated voltage pulses through the primary winding of the transformer I3 in the same direction but of double the value of the direct current charging source.

Fig. 3 shows a modification of Fig. 2, by means `of which it is possible to obtain a pulse acrom the primary winding of transformer I3 of four times the voltage of the direct currentharging source. This is done by supplying another condenser I I of relatively large value in series with the primary Winding of thetransformer I3 and by connecting another direct current charging source to the junction between the condenser II' and the primary winding, as shown. The two direct current charging sources supply the same values of direct current voltage to the system. It should be noted that the polarlties of the two direct current charging sources which are connected to condensers Il and II' are diiferent. The system thus employs two direct current charging sources, one a positive direct current source and the other a. negative direct current source, across opposite terminals of the condenser I4. It is now possible to charge the condenser I4 to twice the voltage of either direct current charge; and by reversingthe connections to condenser I4, the system is able to derive a pulse of voltage which has an initial value of four times the voltage of either direct current charging source or twice the voltage across the condenser In Fig. 3, condensers II and II' must' be of large capacity relative to condenser I4 (let us say, ten to Iteen times as large), although the A two condenser-s II' and II' may or may not be equal in value.

Fig. 4 illustrates still another embodiment of the inventionand differs from Fig. 3 solely in the Varrangement for reversing the connections between condenser I4 and the condenser II and the primary winding of step-up transformer I3. In Fig. 4, there is employed a rotating brush arrangement having a pair of metallic brushes 2l and 2I mounted on an insulating disc 22. This insulating disc is adapted to be rotated at a. speed of 3600 revolutions per minute by means of driveshaft23,intuxnlinkedtoasmallmotor (not shown). The brushes 20, 2| are adapted to contact four stationary segments 25, 26, 21 and 2l mounted in the four quadrants of a circle, as the disc 22 revolves. Thus, in the position shown in the drawing, the brush will bridge stationary segments 25 and 2l and provide a path from the direct current charging source and the condenser Il through the segments 25 and 28 to one plate of the condenser I4. At the same time, the segment 2l will bridge the stationaryl segments 26 and 21, completing a path from the other plate of the condenser Il through the primary winding of the transformer I3. At another position during the rotation of the disc 22 in the direction of the arrow, the brush 20 will bridge the stationary segments 25 and 26, while the brush 2| will bridge the stationary segments 21 and 2l, thus reversing the connections of the condenser Il in an obvious manner. Except for the arrangement for reversing the connections of the condenser I4, the system is substantially the same as thatof Fig. 3. It should be understood, of course, that the rotating brush and stationary segment arrangement of Fig. 4 can be used in a similar capacity for the equivalent elements in Figs. 1 and 2.

For want of a better name for the connecting device of condenser Il, I have used the time honored name dischargen It is evident that the device may be called either a commutator or a rotary spark gap. It is a commutator in the sense that the stationary and the moving contacts are actually brought into contact with one another. On the other hand, the device isa rotary gap because the microsecond pulse is all completed. before actual contact is made. Due to the relatively low voltage of 1000 to 2000 volts.

it is diiicultto maintain the required small elec-l trode spacing in any other way than to eventually let it reach zero.

What is claimed is:

1. Apparatus for converting direct current power to periodically repeated spaced pulses of short duration, comprising a condenser having in electrical parallel relation thereto the series circuit of another condenser and an inductance coil, one of said condensers having a capacity which is at least several times larger than the other, a source of direct current charging voltage connected across said condenser of larger capacity. and means for periodically reversing the connections of the smaller of the two condensers relative to the larger condenser and the inductance coil, and a load coupled to said inductance coil.

2. Apparatus for converting direct current power to periodically repeated spaced pulses of Cil voltage, a storage condenser, a connection from one terminal of said storage condenser to said source, a connection from the other terminal of said storage condenser to ground. a connection from said source to a contact, another contact and a connection from it to one terminal of an inductance coil whose other terminal is connected to ground, a load coupled to said inductance coil, a condenser which is relatively small compared to said storage condenser, and means for connecting said small condenser` between said contacts and for periodically reversing the connections from said small condenser to said contacts, whereby recurring pulses of the same p0- larity but of initial values of voltage higher than the voltage of said source are passed through said load. f

4. Apparatus for converting direct current power to periodically repeated spaced pulses of short duration, comprising a source of direct current charging voltage, a storage condenser connected across said source, a commutator arrangement having a plurality of spaced bars, four pairs of brushes aligned in such manner that short duration, comprising a source of direct current charging voltage, a storage condenser of relatively large value coupled to and arranged to be charged by said source, a load, a condenser of relatively small value connected in series relation between said storage condenser and said load, and means for periodically reversing` the connections of said small condenser relative to the larger condenser and the inductance coil, whereby the charges on both condensers additively combine each time said connections are reversed to produce a pulse through said load with an initial value of voltage greater than the voltage of said direct current source, and said small condenser recharges in the opposite direc-y tion from the chargestored on said storage condenser.

3. In combination, a source of direct current the rst pair of brushes is connected together at the same time that the third pair is connected together, at which time the brushes of the other pairs are not connected together, and the second pair is conneced together at another time when the fourth pair is also connected together, a connection from a brush of the rst pair and a correspondingly located brush of the fourth pair, a connection from a brush of the second pair and a correspondingly located brush of the third pair, a condenser connected between said last two connections, said last condenser having a relatively small capacity compared to sai-d storage condenser, a connection between the other brush of said first pair and the other brush of said second pair, and a lead from said last connection to one terminal of said source, a connection between the remaining -brushes of said third and fourth pairs, an inductance coil. a lead from one terminal of said coil t0 said last connection, and a connection from' the other terminal of said coil to the other terminal of said source.

5. Apparatus in accordance with claim 4,. in-

cluding a condenser which is relatively large compared to said small condenser serially connected in said last connection, and another source of direct current charging voltage connected across said last condenser, said last direct current charging source supplying a voltage whose polarity is opposite to that ofsaid tlrst source.

6. Apparatus for converting direct current power to periodically repeated spaced pulses of short duration, comprising a sourceof direct current charging voltage, a storage condenser coupled to said source, four equal length stationary metallic segments arranged end to end on a circle and having gaps between adjacent ends, a pair of rotating brushes adapted to bridge opposite gaps, simultaneously, a condenser of relatively small capacity compared to the storage condenser connected between the rst and third segments, a connection between one terminal of said source and the second segment, a load, a connection from one end of said load to the fourth segment, and a connection from the other end of said load to the other terminal of said source.

7. Apparatus for converting direct current power to periodically repeated spaced pulses of short duration, comprising a source of direct curasador? rent charging voltage, a storage condenser coupled to said source, four equal length stationary segments arranged end to end on a circle and separated from one another, electrically, a pair of rotating brushes one of which is adapted to bridge the adjacent ends of two of said segments while the other brush is adapted to bridge the adjacent ends of the other two segments, a condenser of relatively small capacity compared to the storage condenser connected between the first and third segments, a connection between one terminal of said source and the second segment, a load, a connection from one end of said load to the fourth segment, a connection from the other end of said load to the other terminal of said source, and a condenser which israt least comparable to said storage condenser serially arranged in said last connection. and another source of direct current charging voltageconnected across said last condenser, said two direct current sources supplying voltages of different polarities to said apparatus.

8. Apparatus for converting direct current power to periodically repeated spaced pulses of short duration, comprising a source of direct current `charging voltage, a. storage condenser coupled to said source, four equal length stationary metallic segments equally spaced from one another and arranged in the four quadrants of a circle, a pair of rotating brushes opposltely disposed on a diameter of said circle and adapted to bridge the ends of adjacent segments as they rotate, a condenser of relatively small capacity compared to said storage condenser connected to two oppositely located segments on said circle, an inductance load, and connections from the other two oppositely located segments on said circle to' said source and load, respectively.

9. Apparatus for converting direct current i power to periodically repeated spaced pulses of short duration', comprising a source of direct current charging voltage, a storage condenser f coupled to said source, four equal length sta- Vtionary segments arranged end to end on a circle and separated from one another electrically. a pair of rotating brushes one of which is adapted to bridge the adjacent ends of two Yof said segments while the other brush is adapted to bridge the adjacent ends of the other two segments, a condenser of relatively small capacity compared to the storage condenser connected between the ilrst and third segments, a connection between oneterminal of said source and the second segment, a load, a connection from one end of said load to the fourth segment, a connection from the other end of said load to the other terminal of said source.

10. Apparatus for converting direct current power to periodically repeated spaced pulses of short duration, comprising a condenser having in shunt thereto the series circuit of another condenser and an inductance coil, one of said condensers having a capacity which is at least several times larger than the other, a source of direct current charging voltage coupled across said condenser of larger capacity, means including a commutator and brush arrangement for periodically reversing theconnections of the smaller of the two condensers relative to the larger condenser 'and said coil, and a load coupled tosaid coil.

11. Apparatus for converting direct current power to periodically repeated spaced pulses of in shunt thereto the series circuit of another condenser and an inductance coil, one of said condensers having a capacity which is at least several times larger than the other, a source of direct current charging voltage coupled across said condenser of larger capacity, means including a rotating brush and a plurality of stationary segments for periodically reversing the connections of the smaller of the two condensers relative to the larger condenser and the coil, and a. load coupled to said coil.

12. Apparatus for converting the output of a direct current voltage source to periodically repeated spaced pulses of short duration and of greater voltage, comprising a source of direct current voltage, a condenser coupled to and arranged to be charged by said source, a load through which said condenser discharges, and a rotating discharger having a plurality of spaced stationary brushes and a plurality of spaced conducting segments mounted on a rotating support for periodically reversing the connections between said condenser and said load.

13. Apparatus for converting 'direct current power to periodically repeated spaced pulses of short duration, comprising a source of direct -current charging voltage, a commutator arrange- 'a connection from a brush of the second pair and a correspondingly located brush of the third pair, a condenser connected between said last two connections, a connection between thev other brush of said rst pair and the other brush of vsaid second pair, a lead from said last connection to one terminal of said source, a connection between the remaining brushes of said third and fourth pairs. a load, a lead from one terminal o said load to said last connection, and a-lead from the other terminal of said load to the other terminal of said source.

REFERENCES CITED The following references are of record inthe ile of this patent;

Y UNITED STATES PATENTS Number Name Date 1,273,812 Berlin July 30, 1918 1,859,940 Spaeth May 24, 1932 1,956,416 Elder Apr. 24, 1934 1,992,908 Cockeroft et al. Feb. 20, 1935 2,038,960 Schattenik' Apr. 28, 1936 2,070,435 Katzman Feb. 9, 1937 2,086,323 Garstang July 6, 1937 2,107,742 Ruben Feb. 8, 1938 2,184,315 Peters et al. Dec. 26, 1939 2,239,786 Jones Apr. 29, 1941 2,267,233' Elstom Dec, 23, 1941 FOREIGN PATENTS Number Country Date 562,203 France Aug. 29, 1923

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