US3902099A

US3902099A - Energizing circuit for magnetron using parallel transformers

Info

Publication number: US3902099A
Application number: US400352A
Authority: US
Inventors: Albert E Feinberg
Original assignee: Advance Transformer Co
Current assignee: Advance Transformer Co
Priority date: 1973-09-24
Filing date: 1973-09-24
Publication date: 1975-08-26
Anticipated expiration: 1992-08-26

Abstract

A magnetron energizing circuit uses two transformers of the high leakage reactance type having isolated secondaries with an end terminal of each secondary connected to a common point. The secondaries are connected to series condensers respectively to provide leading current flowing in the secondary circuits at all times to produce saturation in the respective cores of the transformers under the secondaries whereby to achieve substantially constant current and good regulation for variations in the primary voltage. The combined secondaries and condensers are connected through a rectifier or rectifiers to a magnetron used for heating purposes, the magnetron participating in the overall operation of the circuit and being of the continuous wave type so as to achieve heating as for example in cooking ovens.

Description

United States Patent 11 1 Feinberg 1451 Aug. 26, 1975 1 1 ENERGIZING CIRCUIT FOR MAGNETRON USING PARALLEL TRANSFORMERS Albert E. Feinberg, Chicago, 111.

[73] Assignee: Advance Transformer Company,

Chicago, Ill.

[22] Filed: Sept. 24, 1973 [21] Appl. No.: 400,352

[75] Inventor:

[52] US. Cl. 315/105; 315/277; 315/282;

321/15; 321/24; 321/27; 323/61; 328/267 [51] Int. Cl. l-l02j 3/24 [58] Field of Search 315/94, 101, 105, 200 R,

[56] References Cited UNITED STATES PATENTS 3,584,288 6/1971 Bochm 328/262 X Primary Examiner-Paul L. Genslcr Armrncy, Agenl, or FirmSilverman 8L Cass, Ltd.

] 57 ABSTRACT A magnetron energizing circuit uses two transformers of the high leakage reactance type having isolated secondaries with an end terminal of each secondary connected to a common point. The secondaries are connected to series condensers respectively to provide leading current flowing in the secondary circuits at all times to produce saturation in the respective cores of the transformers under the secondaries whereby to achieve substantially constant current and good regulation for variations in the primary voltage. The combined secondaries and condensers are connected through a rectifier or rectifiers to a magnetron used for heating purposes, the magnetron participating in the overall operation of the circuit and being of the continuous wave type so as to achieve heating as for example in cooking ovens.

11 Claims, 3 Drawing Figures A.C. LINE ENERGIZING CIRCUIT FOR MAGNETRON USING PARALLEL TRANSFORMERS BACKGROUND OF THE INVENTION The invention herein relates to magnetron energizing circuits for providing pulsed dc power to a magnetron from a relatively low frequency low voltage ac. power source.

The principles of operation of the circuits herein are based upon the disclosures of US. Pat. No. 3,396,342 and reference may be had to said patent for the details thereof. Suffice it to say that the power supply circuit which includes the magnetron is a highly simplified one utilizing a transformer having a primary winding connected to an ac. source and a secondary winding in step-up relationship therewith but physically isolated therefrom and loosely coupled so as to provide a high leakage reactance during the operation of the transformer. A series condenser provides a continuous leading current in the secondary circuit and hence its capacitive reactance is chosen to be greater than the total effective inductive reactance in series therewith, the latter inductive reactance comprising the leakage reactance and the inductive reactance introduced by the secondary winding itself. The components described are connected through rectifier means to a continuous wave magnetron, the rectifier means being either a single rectifier element acting in conjunction with the condenser to provide a half-wave voltage doubler type of circuit; or a pair of rectifier elements connected with two condensers effectively to produce a fullwave voltage doubler type of arrangement. Another modification uses a full-wave rectifier in a straight rectified pulsed voltage circuit. In all cases the magnetron anode is grounded and the cathode is at high potential, the cathode being energized either by an independent transformer or by means of a filament winding closely coupled to the primary.

All three circuits are in commercial use as of the present time, primarily in domestic heating ovens using magnetrons of relatively low power.

It is possible to use similar magnetrons which do not have higher anode voltages but which are nevertheless capable of achieving approximately twice the power output. In order to do so using the basic circuit, it would be necessary to design transformers which are capable of handling larger currents and/or higher voltages. This would be expensive. The invention herein teaches circuits which utilize the same transformers that are utilized in low power circuits but with unique parallel connections to achieve generally the same power. In each of the circuits, the only components which are doubled in quantity are the transformers and the condensers.

SUMMARY OF THE INVENTION The invention comprises a circuit in which there are two transformers, capacitive means, and a rectifier all connected to provide the pulsed dc. to a magnetron with good regulation. The primaries of the transformers are connected to an ac line of relatively low frequency and low voltage in parallel. The secondaries are physically isolated from the respective primaries and coupled in a manner to provide a high leakage reactance in the secondaries during the operation thereof. One terminal of each secondary is connected to a common point with the same instantaneous polarity and the other terminal of each secondary is connected through respective first and second capacitive reactance means such as, for example, a series condenser, the respective capacitor reactance means having such capacitance as to provide a leading current in the respective secondary winding during the operation of the circuit. Both capacitive reactance means are connected to a continuous wave magnetron whose anode is grounded and whose cathode is at high potential, there being rectifier means between the magnetron and the capacitive reactance means so that a rectification takes place. In this way the alternating current produced by the combination of the capacitive reactance means and the secondary of the transformer is rectified to pulsed do which energizes the magnetron. The connections of capacitive reactance and rectifying means are such that there is either straight rectification, half-wave voltage doubling, or full-wave voltage doubling. Three different circuits for providing this type of performance are disclosed.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a circuit diagram of a magnetron energizing apparatus constructed in accordance with the invention in the configuration of a half-wave voltage doubler circuit;

FIG. 2 is a circuit diagram of a magnetron energizing apparatus constructed in accordance with the invention in the configuration of a full-wave voltage doubler circuit; and

FIG. 3 is a circuit diagram of a magnetron energizing apparatus constructed in accordance with the invention in the configuration of a full-wave rectifier circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. I, the circuit is designated generally by the reference numeral 10 and comprises basi cally two transformers T1 and T2, capacitive reactance means in the form of two condensers C1 and C2, a rectifier which in this case comprises a single diode D1, a magnetron of the continuous wave type which is designated M, and a filament transformer T3 for the magnetron filament.

The transformers TI and T2 include respectively primary windings P1 and P2 each of which is connected in parallel across the line represented by the

terminals

12 and 14. This line could be, for example, volts 60 Hertz as provided by ordinary mains. Each transformer has an iron core of laminated electrical steel or other ferromagnetic design which is symbolized by the parallel lines at 16 and 18 respectively and each transformer has an isolated secondary winding designated respectively S1 and S2. The relationship between the turns of the respective windings of the transformers is such that a substantially high voltage will be developed in the secondary windings, usually of the order of kilovolts for a commercial magnetron. The secondaries, S1 and S2, are loosely coupled with respect to the primaries P1 and P2 and there may be shunts arranged in the core as indicated at 20 and 22 so that it is understood that during the operation of the transformers TI and T2 a high leakage reactance will be developed in the secondary windings. One terminal of each secondary winding is connected at a common point 24 which, in this case, is grounded. The opposite terminals of the secondary windings are connected to the condensers CI and C2 respectively, these condensers thereby comprising series connected capacitive reactance means. The black dots shown at the terminals of the secondaries opposite point 24 signify that the instantaneous voltage polarity for the parallel connected secondaries S1 and S2 is the same so that the secondaries are intended to be energized and function simultaneously. The condensers Cl and C2 have a common terminal at 26 which connects to the lead line 28 that is maintained at high voltage. The rectifier D1 is connected from the line 28 to ground. The line 28 is also connected to the cathode 30 of the magnetron M, the anode 32 of the magnetron being connected to ground by way of the lead 34.

The pick-up probe 36 feeds the waveguide 38 with high frequency energy produced by the magnetron M and the wave guide leads to a horn 40 which is located in a magnetron oven (not shown). The circuit 10 of FIG. 1 is the most simplified of the circuits since it utilizes only one condenser in addition to the added transformer. The operation of the circuit is no different than that of the circuit shown in FIG. of said US. Pat. No. 3,396,342, except that the power is substantially doubled for the same circuit parameters.

The transformer T3 is connected to the line by means of the

leads

42 and 44 and is illustrated as a completely separate transformer. Its primary P3 and secondary S3 are closely coupled as in the case of ordinary power transformers, the secondary winding being connected across the filament 46.

Transformers of the construction of T1 and T2 as disclosed in said US. Pat. No. 3,396,342, may have filament windings wound directly onto the primary windings in which case those filament windings will be connected in parallel and directly to the filament 46 instead of utilizing an additional transformer T3, or may be supplied on one of the two transformers TI and T2.

One additional advantage of the circuit of FIG. I is that the secondary windings S1 and S2 may be grounded as shown at 24 thereby decreasing the need for high voltage insulation as the case would be in other circuits which will be described hereafter.

As mentioned, the circuit 10 functions as a half-wave voltage doubler type of circuit. The diode D1 in this case serves as a return path for current through the capacitive reactance means CI and C2 on alternate half cycles of the voltage output.

The apparatus 10' illustrated in FIG. 2 differs from the apparatus 10 of FIG. I in that it is a full wave voltage doubler configuration of the circuit. The rectifying means in this case comprise the two diodes D1 and D2 which operate on alternate half cycles in conjunction with the capacitive reactance means. Thus, on one half cycle the capacitive reactance means C1 and C3 operate in conjunction with the diode D2 and on the other half cycle the capacitive reactance means C2 and C4 act in conjunction with the diode D1 during discharge thru the magnetron.

Again, the transformers T1 and T2 have their prima ries P1 and P2 in parallel connected to the line 12, I4 and their secondaries S1 and S2 connected much the same as the case in FIG. I. The common terminal in this circuit is 241 but it cannot be grounded because of the particular type of configuration and hence the insulation requirements of the transformers T1 and T2 are somewhat more stringent than in the case of the configuration of FIG. 1. By simple analysis it can readily be shown that the circuit of FIG. 2 is in effect two halfwave voltage doubler circuits back to back but utilizing only the two transformers T1 and T2 as taught by FIG. 1

FIG. 3 illustrates a third apparatus 10 which is a full wave rectifier configuration of the circuit of the invention. The circuit is a modification of that illustrated in FIG. 2 of said US. Pat. No. 3,396,342. Again, the transformers T1 and T2 have their primaries P1 and P2 connected in parallel across the

ac line

12, 14. The secondary windings SI and S2 are high leakage reactance secondary windings with a common terminal at 24 that in this case is also not grounded and their opposite terminals connected through series condtnsers Cl and C2 to the rectifier means which in this case comprise a bridge rectifier formed of the diodes D1, D2, D3, and D4. The line 28 in this circuit is connected to the terminal 50 of the bridge rectifier S2 and the opposite terminal 54 of the rectifier is connected through the line 56 to the terminal 24. The left-hand terminal 53 of the rectifier 52 is grounded and the right-hand terminal 60 of the rectifier is connected through the line 62 to the cathode 30 of the magnetron M. The remaining details of the circuit 10" are obvious and the operation is not materially different from the operation of the apparatus shown in FIG. 2 of said US. Pat. No. 3,396,342.

The transformers T1 and T2 in every case may be no different from those which are available commercially for lower power circuits and an example is described in detail in said US. Pat. No. 3,396,342.

It is most convenient to tie the transformer secondaries S1 and S2 together at the common point 24, but the circuits lltl and 10" will not be affected in any Way if the condenser and secondary winding in each series combination is interchanged. Thus, for example, in FIG. 1, Cl and S1 could be interchanged without effect.

The use of two condensers in circuits l0 and 10" instead of a single common condenser provides stability. Even if transformers TI and T2 were made on the identical production line, it is practically impossible to have identical characteristics in the secondaries. One secondary winding will start to develop a slightly higher voltage and will commence to upset the balance, resulting in a wasteful circulating current in the loop including the secondaries. The condensers inside the loop develop voltages which offset this tendency. It is feasible to use an economical condenser having a common foil and independent individual foils instead of two physically separate condensers.

What it is claimed and desired to secure by Letters Patent of the United States is:

I. An operating circuit for energizing a magnetron from an ac. line of relatively low voltage and low frequency which comprises a. a magnetron having an anode and a cathode;

b. a generally constant current transformer and condenser means combination which comprises i. two step-up transformers each having a primary winding connected to said ac. line;

ii. each transformer having a secondary winding isolated from its primary winding but coupled in high leakage reactance operating relation to its respective primary winding, the secondary windings each having a first terminal at the same instantaneous polarity connected to a common juncture; and

iii. paired condenser means with one terminal of each pair connected in series with one of the respective secondary windings, and with a common midpoint,

c. the anode and cathode of the magnetron being connected to the combination to be subjected to the output voltage thereof; and

d. rectifier means connected to the common midpoint of said paired capacitor means providing inphase return paths for current through the condenser means on alternate half-cycles of the voltage output, said current from each secondary winding being additive in total pulse magnitude the ca pacitive reactance of the condenser means being sized with respect to the inductive reactance in said transformer and condenser means combination so as to provide a leading current in the secondary circuit including both secondary windings to provide good regulation notwithstanding normal variations of the line voltage.

2. An operating circuit as claimed in claim 1 in which said common juncture and magnetron anode are at ground potential, the rectifier means comprise a rectifier having its cathode connected to ground and its anode connected to the cathode of the magnetron, and said condenser means comprising two condensers, each being connected in series with a respective one of said secondary windings to form individual secondary-series-condenser combinations, said last-mentioned combinations being connected from said first common juncture to the anode of the rectifier and forming therewith said common midpoint, the resulting configuration acting as a half-wave voltage doubler circuit during operation.

3. An operating circuit as claimed in claim 1 in which said rectifier means comprise two rectifiers with the cathode of the first rectifier and the anode of the second rectifier connected to said common juncture, the anode of the first rectifier being connected. to the cathode of the magnetron and the cathode of the second rectifier being connected to the anode of the magnetron, the condenser means comprising two pairs of condensers, each pair being connected across the magnetron and the second terminal of each secondary winding being respectively connected to the junctions between the respective pairs of condensers, the resulting configuration acting as a full-wave voltage doubler circuit during operation.

4. An operating circuit as claimed in claim 1 in which the rectifier means comprise a four terminal bridge rectifier having its positive terminal connected to the magnetron anode and its negative terminal connected to the magnetron cathode, the common juncture being connected to the third terminal of the bridge rectifier, each secondary winding has a respective condenser of said condenser means connected in series therewith whereby to form individual secondaryscries-condenser combinations, the combinations being connected between said common juncture and the fourth terminal of said bridge rectifier.

5. An operating circuit as claimed in claim I in which each secondary winding has a respective condenser of said condenser means individually connected in a series arrangement for one half cycle operation and each secondary and series condenser combination is connected to said common midpoint.

6. The operating circuit as claimed in claim 5 in which the first terminals of the secondaries are connected together to form the common juncture, the second terminals of the secondaries are respectively connected to one terminal of said respective condensers and the second terminals of said condensers are connected together to form the common midpoint.

7. An operating circuit as claimed in claim 5 in which each secondary winding has an additional respective condenser of said condenser means individually connected in a series arrangement for the alternate half cycle operation.

8. In a magnetron energizing circuit for providing pulsed do. to said magnetron and comprising a high leakage reactance, substantially constant current output, iron-core, power transformer and condenser means combination, the transformer having a primary winding adapted to be energized from a low voltage ac. line and a secondary winding in voltage step-up relationship, the magnetron having anode and cathode connected respectively to the terminals of the secondary winding with the condenser means comprising a portion of series loop circuitry including the magnetron and secondary winding, and rectifier means connected across the magnetron providing a return path through the condenser means at least on alternate half cycles of current, the secondary winding and condenser means forming a first series combination; means for increasing the power output of the energizing circuit without materially altering any of the components thereof and comprising:

a second transformer substantially the same as said first-mentioned transformer and having a secondary winding equivalent to the first-mentioned secondary winding, second condenser means connected with the second-mentioned secondary winding to form therewith a second series combination, the combinations being connected in parallel with the secondaries polarized to have common instantaneous voltage polarity during operation to operate in concert, and the primary winding of the second transformer being adapted to be connected for energizing from a line in parallel with the firstmentioned primary winding, and the condenser means in each case having a capacitance of such value relative to the total inductance of the secondary winding with which it is combined during operation such as to produce at that time a leading current in each secondary winding and the circuit has a half-wave voltage doubler configuration, with the rectifier means comprising a rectifier having its anode connected to the magnetron cathode, its cathode connected to the magnetron anode, and both combinations connected across the rectifier.

9. The invention as claimed in claim 8 in which both secondary windings are arranged at one end of their respective combinations and connected together at that end, said end being grounded and the magnetron anode being grounded.

10. In a magnetron energizing circuit for providing pulsed dc to said magnetron and comprising a high leakage reactanee, substantially constant current output, iron-core, power transformer and condenser means combination, the transformer having a primary winding adapted to be energized from a low voltage a.c.

line and a secondary winding in voltage step-up relationship, the magnetron having anode and cathode connected respectively to the terminals of the secondary winding with the condenser means comprising a portion of series loop circuitry including the magnetron and secondary winding, and rectifier means connected across the magnetron providing a return path through the condenser means at least on alternate half cycles of current, the secondary winding and condenser means forming a first series combination; means for increasing the power output of the energizing circuit without materially altering any of the components thereof and comprising:

a second transformer substantially the same as said first-mentioned transformer and having a secondary winding equivalent to the first-mentioned secondary winding, second condenser means connected with the second-mentioned secondary winding to form therewith a second series combination, the combinations being connected in parallel with the secondaries polarized to have common instantaneous voltage polarity during operation to operate in concert, and the primary winding of the second transformer being adapted to be connected for energizing from a line in parallel with the firstmentioned primary winding and the condenser means in each case having a capacitance of such value relative to the total inductance of the secondary winding with which it is combined during operation such as to produce at that time a leading current in each secondary winding and the circuit has a full-wave voltage doubler configuration, with the rectifier means comprising a pair of series connected rectifiers having a common juncture and the anode of one connected to the magnetron cathode while the cathode of the other is connected to the magnetron anode, the series combinations each having a pair of condensers arranged in series with its secondary winding connected respectively between condensers at their one terminals and to the common juncture at their second terminals, the condenser pairs being connected across the two rectifiers, the operation of the circuit being such that each secondary is in series with alternate condensers of its pair on alternate half cycles.

11. In a magnetron energizing circuit for providing pulsed dc. to said magnetron and comprising a high leakage reactance, substantially constant current output, iron-core, power transformer and condenser means combination, the transformer having a primary winding adapted to be energized from a low voltage a.c. line and a secondary winding in voltage step-up relationship, the magnetron having anode and cathode connected respectively to the terminals of the secondary winding with the condenser means comprising a portion of series loop circuitry including the magnetron and secondary winding, and rectifier means connected across the magnetron providing a return path through the condenser means at least on alternate half cycles of current, the secondary winding and condenser means forming a first series combination; means for increasing the power output of the energizing circuit without materially altering any of the components thereof and comprising:

a second transformer substantially the same as said first-mentioned transformer and having a secondary winding equivalent to the first-mentioned secondary winding, second condenser means connected with the second-mentioned secondary winding to form therewith a second series combination, the combinations being connected in parallel with the secondaries polarized to have common instantaneous voltage polarity during operation to operate in concert, and the primary winding of the second transformer being adapted to be connected for energizing from a line in parallel with the firstmentioned primary winding and the condenser means in each case having a capacitance of such value relative to the total inductance of the secondary winding with which it is combined during operation such as to produce at that time a leading current in each secondary winding and the circuit has a full-wave rectifier configuration, with the rectifier means comprising a bridge rectifier having one pair of opposite terminals connected across the magnetron and the other pair connected across the both combinations.

Claims

1. An operating circuit for energizing a magnetron from an a.c. line of relatively low voltage and low frequency which comprises a. a magnetron having an anode and a cathode; b. a generally constant current transformer and condenser means combination which comprises i. two step-up transformers each having a primary winding connected to said a.c. line; ii. each transformer having a secondary winding isolated from its primary winding but coupled in high leakage reactance operating relation to its respective primary winding, the secondary windings each having a first terminal at the same instantaneous polarity connected to a common juncture; and iii. paired condenser means with one terminal of each pair connected in series with one of the respective secondary windings, and with a common midpoint, c. the anode and cathode of the magnetron being connected to the combination to be subjected to the output voltage thereof; and d. rectifier means connected to the common midpoint of said paired capacitor means providing in-phase return paths for current through the condenser means on alternate half-cycles of the voltage output, said current from each secondary winding being additive in total pulse magnitude the capacitive reactance of the condenser means being sized with respect to the inductive reactance in said transformer and condenser means combination so as to provide a leading current in the secondary circuit including both secondary windings to provide good regulation notwithstanding normal variations of the line voltage.

3. An operating circuit as claimed in claim 1 in which said rectifier means comprise two rectifiers with the cathode of the first rectifier and the anode of the second rectifier connected to said common juncture, the anode of the first rectifier being connected to the cathode of the magnetron and the cathode of the second rectifier being connected to the anode of the magnetron, the condenser means comprising two pairs of condensers, each pair being connected across the magnetron and the second terminal of each secondary winding being respectively connected to the junctions between the respective pairs of condensers, the resulting configuration acting as a full-wave voltage doubler circuit during operation.

4. An operating circuit as claimed in claim 1 in which the rectifier means comprise a four terminal bridge rectifier having its positive terminal connected to the magnetron anode and its negative terminal connected to the magnetron cathode, the common juncture being connected to the third terminal of the bridge rectifier, each secondary winding has a respective condenser of said condenser means connected in series therewith whereby to form individual secondary-series-condenser combinations, the combinations being connected between said common juncture and the fourth terminal of said bridge rectifier.

5. An operating circuit as claimed in claim 1 in which each secondary winding has a respective condenser of said condenser means individually connected in a series arrangement for one half cycle operation and each secondary and series condenser combination is connected to said common midpoint.

8. In a magnetron energizing circuit for providing pulsed d.c. to said magnetron and comprising a high leakage reactance, substantially constant current output, iron-core, power transformer and condenser means combination, the transformer having a primary winding adapted to be energized from a low voltage a.c. line and a secondary winding in voltage step-up relationship, the magnetron having anode and cathode connected respectively to the terminals of the secondary winding with the condenser means comprising a portion of series loop circuitry including the magnetron and secondary winding, and rectifier means connected across the magnetron providing a return path through the condenser means at least on alternate half cycles of current, the secondary winding and condenser means forming a first series combination; means for increasing the power output of the energizing circuit without materially altering any of the components thereof and comprising: a second transformer substantially the same as said first-mentioned transformer and having a secondary winding equivalent to the first-mentioned secondary winding, second condenser means connected with the second-mentioned secondary winding to form therewith a second series combination, the combinations beinG connected in parallel with the secondaries polarized to have common instantaneous voltage polarity during operation to operate in concert, and the primary winding of the second transformer being adapted to be connected for energizing from a line in parallel with the first-mentioned primary winding, and the condenser means in each case having a capacitance of such value relative to the total inductance of the secondary winding with which it is combined during operation such as to produce at that time a leading current in each secondary winding and the circuit has a half-wave voltage doubler configuration, with the rectifier means comprising a rectifier having its anode connected to the magnetron cathode, its cathode connected to the magnetron anode, and both combinations connected across the rectifier.

10. In a magnetron energizing circuit for providing pulsed d.c. to said magnetron and comprising a high leakage reactance, substantially constant current output, iron-core, power transformer and condenser means combination, the transformer having a primary winding adapted to be energized from a low voltage a.c. line and a secondary winding in voltage step-up relationship, the magnetron having anode and cathode connected respectively to the terminals of the secondary winding with the condenser means comprising a portion of series loop circuitry including the magnetron and secondary winding, and rectifier means connected across the magnetron providing a return path through the condenser means at least on alternate half cycles of current, the secondary winding and condenser means forming a first series combination; means for increasing the power output of the energizing circuit without materially altering any of the components thereof and comprising: a second transformer substantially the same as said first-mentioned transformer and having a secondary winding equivalent to the first-mentioned secondary winding, second condenser means connected with the second-mentioned secondary winding to form therewith a second series combination, the combinations being connected in parallel with the secondaries polarized to have common instantaneous voltage polarity during operation to operate in concert, and the primary winding of the second transformer being adapted to be connected for energizing from a line in parallel with the first-mentioned primary winding and the condenser means in each case having a capacitance of such value relative to the total inductance of the secondary winding with which it is combined during operation such as to produce at that time a leading current in each secondary winding and the circuit has a full-wave voltage doubler configuration, with the rectifier means comprising a pair of series connected rectifiers having a common juncture and the anode of one connected to the magnetron cathode while the cathode of the other is connected to the magnetron anode, the series combinations each having a pair of condensers arranged in series with its secondary winding connected respectively between condensers at their one terminals and to the common juncture at their second terminals, the condenser pairs being connected across the two rectifiers, the operation of the circuit being such that each secondary is in series with alternate condensers of its pair on alternate half cycles.

11. In a magnetron energizing circuit for providing pulsed d.c. to said magnetron and comprising a high leakage reactance, substantially constant current output, iron-core, power transformer and condenser means combination, the transformer having a primary winding adapted to be energized from a low voltage a.c. line and a secondary winding in voltage step-up relationship, the magnetron having anode and cathode connected respectively tO the terminals of the secondary winding with the condenser means comprising a portion of series loop circuitry including the magnetron and secondary winding, and rectifier means connected across the magnetron providing a return path through the condenser means at least on alternate half cycles of current, the secondary winding and condenser means forming a first series combination; means for increasing the power output of the energizing circuit without materially altering any of the components thereof and comprising: a second transformer substantially the same as said first-mentioned transformer and having a secondary winding equivalent to the first-mentioned secondary winding, second condenser means connected with the second-mentioned secondary winding to form therewith a second series combination, the combinations being connected in parallel with the secondaries polarized to have common instantaneous voltage polarity during operation to operate in concert, and the primary winding of the second transformer being adapted to be connected for energizing from a line in parallel with the first-mentioned primary winding and the condenser means in each case having a capacitance of such value relative to the total inductance of the secondary winding with which it is combined during operation such as to produce at that time a leading current in each secondary winding and the circuit has a full-wave rectifier configuration, with the rectifier means comprising a bridge rectifier having one pair of opposite terminals connected across the magnetron and the other pair connected across the both combinations.