US2638566A - Synchronizing system for electronic tubes - Google Patents

Description

May 2, 1953 R. c. MIERENDORF 2,638,566

SYNCHRONIZING SYSTEM FOR ELECTRONIC TUBES Filed Feb. 16, 1951 IN V EN TOR. W? (7 ME/d/Ya rx Patented May 12,- 1953 SYNCHRONIZING SSTEM FOR ELECTRONIC TUBES Robert G. Mierendorf, Milwaukee, Wis, assignor to SquareD Company, Detroit; 'Mich.,a corporation of Michigan Application February 16, 1951, Serial Ida-211,358

8 Claims.

This invention relates to a circuit for effectin synchronous energization of an electronic tube.

More specifically, this invention relates to an electrical circuit for controlling the energization of an electronic tube in which conduction through the electronic tube is always initiated at the beginning of a positive half cycle of anode voltage. One object of the present invention is the provision of an improved synchronizing circuit' for an electronic tube whereby the electronic tube will conduct only full half cycles of current.

Another object of the present invention is the provision of an improved electronic tube initiating circuit operating duction-through the beginning of a half cycle of positive anode voltage regardless of the point on the voltage wave at which the initiating contact may be closed.

Another object of the present invention is the provision of an energizing circuit for an electronic tube in accordance with the preceding objects, in which voltages differing in time-phase are applied to the control and shield grids of the electronic tube to effect energization of the electronic tube at a particular point on the anode voltage wave.

Other objects and features of the invention will be readily apparent to those skilled in the art from the specification and appended drawing illustrating certain preferred embodiments in which the drawing is a diagrammatic representation of an electronic welder circuit in which the present invention is incorporated.

In the drawing there is shown a pair of main supply lines 5 and 2, which are connected to asource of energy, not shown. Disposed across these supply lines is a transformer 3 having a secondary 4 which supplies a pair of conductors 5- and 6 which electrical energy. Connected across these conductors 5 and 6 is a transformer 1 having a secondary winding 8 which is of opposite polarity to the primary of transformer I.

The secondary winding 8 is connected between the conductor 6 and a conductor- 9. In series with each other, and connected between the conductors 6 and 9', are a resistor H and initiating contact l2. To a point between the resistor H and the contact l2 there is connected one terminal of a capacitor I3, the other terminal being connected through a resistor 14 to the control grid 15 of an electronic tube 16, which has an anode ll, a cathode l8, and a shield grid l9. The shield grid 19 is connected to a junction between the elements of a series cirto effect initiation of con- 1 electronic tube only at the cuit' which comprises a resistor 2 l and a capacitor 22, this series circuit being disposed between the conductors 6 and 9. Also connected to the conductor 9' is a resistor 2.3 which is electrically connected to the control grid 15 of the. electronic tube "5' through the resistor hi. Also connected to the control grid I5 is one terminal of a capacitor 24 the other terminal thereof being electrically connected to cathode l8 of tube It.

' Across the conductors 5 and 6 there is disposed a transformer 25 having a secondary 26 which serves to supply heat to the cathode l8 of the tube ('6.

The anode H of the tube [6 is connected to the conductor 5 through a circuit which comprises a weld-no weld switch 21, which is in series with a parallel circuit, one leg of which includes an inductor 28' and a capacitor 29; the other leg includes a relay coil 3| of an electromagnet. Energization of the relay coil 31 effects movement of a movable contact 32 into position to bridge contacts 33 in the igniter circuits of a pair of inversely paralleled ignitrons 34 and 35, which are conventionally disposed between the main supply lines i and 2. These ignitrons serve to energize a welding transformer 36 in series with theignitrons across the supply lines, transformer 36 having a secondary winding 31 across which a pair of welding electrodes 38 are dis posed.

U on connection of the main line conductors l and 2 to a source of electrical energy, the transformer 3' will be energized, the transformer 3 secondary winding serving to energize transformers I and 25, secondary 26 of the latter transformer supplying energy to heat cathode [8. With the switch 21' closed, anode voltage will be supplied to the main electrodes H and I8 01: thetube It. With the initiating contact 12 in the position indicated in the drawing, during those half cycles in which the anode H of the tube l 6 is driven negative with respect to the cathode t8, current will pass through resistor H, capacitor ('3, and thepath between the control grid [-5 and the cathode it of tube IE to charge capacitor l3. This current flow through the control grid when the anode is negative is due, of course, to the" fact that secondary 8 is of a polarity opposite to that of the secondary 4. This chargeon capacitor l3 establishes a D. C. voltage in the control grid circuit of the tube [6 which provides a voltage between the control grid l5" and the cathode l8 of tube It which is negative at all times, except for short periods during which anode I1 issubstantially negative with respect 3 to the cathode I8, so that tube It will not conduct. During these aforementioned short periods, the charge upon capacitor I3 is reestab lished by control grid conduction of tube I5.

To the shield grid I9 of the tube I6, there is applied the voltage across capacitor 22 which slightly lags the voltage of the secondary winding 8. The shield grid I9 conducts current during the positive half cycles of voltage applied thereto, and by virtue of the phase displacement between the shield grid voltage and the voltage of secondary winding 8, the shield grid will remain positive for a short period during which the anode I1 goes positive, the shield grid I9 going substantially negative after this short period and remaining so until after the anode II goes negative.

When the initiating contact I2 is closed, further recharging of the capacitor I3 is prevented, the capacitor I 3 thereby discharging through resistors 9| and 23, the voltage at the control grid I5 of tube I 6 during this discharging period being comprised of the decaying voltage of the capacitor I3, upon which is superimposed a small A. C. voltage due to current flow through resistors 23 and I 4 and capacitor 24. This A. C. voltage component lags the voltage of the secondary winding 8 and, therefore, tends to maintain the control grid i5 positive at the beginning of a positive half cycle of anode |'I voltage. As the voltage upon capacitor 3 is dissipated, tube I6, therefore, will begin to fire only during those periods in which the shield grid and the anode are both positive, these moments occurring only at the beginning of a positive half cycle of anode voltage. If conduction of tube I5 is not initiated at the beginning of one positive half cycle, the shield grid voltage, which is substantially negative during the remainder ofthat half cycle, will prevent firing of the tube until the beginning of the succeeding positive half cycle of anode voltage, regardless of the fact that the capacitor l3 voltage may be dissipated, and the control grid lose its negative bias, during said one positive half cycle. Assuming that the switch 21 is closed, tube l6 will then begin to conduct current. This current will effect the energization of the coil 3| which will, after a predetermined period, effect closure of the movable contactor 32 upon the fixed contacts 33. One relay of this type which is designed to provide substantially transient free weld current initiation by effecting closure of the contacts at approximately the normal current zero for the associated welder is shown and described in the copendin application of Robert C. Mierendorf and Ernest G. Anger, entitled Electro-Magnetic Relay, Serial No. 152,594, filed March 29, 1950. This relay will close the contacts about 240 after the initiation of current flow through the-energizing coil. It should be noted that this closure therefore occurs during the half cyclewhich follows the first conducting half cycle of tube I6.

Upon closure of the contacts 33, current will flow from the main power lines to effect ignition of the ignitron having positive anode voltage,

current then flowing from the positive power line through the ignitron to energize welding transformer 35, the secondary 31 thereof effecting current flow through the welding electrodes 38 and the work associated therewith. Ignitrons 34 and 35 will continue to conduct successive half cycles of current until such time as the movable contactor 32 is no longer bridging the fixed contacts 33.

The circuit paralleling the relay vcoil 3| is so '4 designed as to maintain the coil 3| energized during those half cycles of non-conduction of tube It which follow conducting half cycles. Upon opening of the initiating switch 22, a charge will be reestablished on capacitor I3 and operation of the tube IE will be interrupted. During the first half cycle of non-conduction of tube I 6, capacitor 29 will, in the conventional manner, be discharged through relay coil 3| to maintain its energization. Upon the second half cycle of non conduction, the inductor 28, which is chosen to have a value such that the combination of the inductor 28 and the capacitor 29 are in resonance, will cause a rapid reversal of current flow through the relay coil 3| and consequent rapid deenergizati'on thereof. The contacts 33 will therefore always be opened during the second half cycle which follows a conducting half cycle of tube I G. This resonated circuit is described and claimed in the copending application of Ernest G. Anger entitled Electric Control Circuit, Serial No. 148,190, filed March 7, 1950.

' It will readily appear that tube I6 may begin to conduct only upon the beginning of a positive half cycle of anode voltage and therefore only full half cycles of current wil1 pass through the tube. Current flow through relay coil 3| will therefore occur only in full half cycles. Furthermore, as contacts 33 are always closed during the first half cycle following a conducting half cycle of tube is, and as contacts 33 are always opened during the second half cycle following such conduction, weld current fiow will therefore always be initiated in half cycles of the same polarity and will be interrupted during half cycles of opposite polarity. Furthermore, it is obvious that while the feature of the present invention which provides for synchronous start of current flow through tube I6 has been described in conjunction with the operation of a Welder circuit, it is equally adapted to use with any circuit in which it is desirable to obtain only full half cycles of current flow through the controlling electronic tube.

While certain preferred embodiments of the invention have been specifically disclosed, it is understood that the invention is not limited thereto, as many variations will be readily apparent to those skilled in the art and the invention is to be given its broadest possible interpretation within the terms of the following claims.

What is claimed is:

1. In a control circuit, an electronic tube having an anode, a cathode, and at least a pair of auixilary electrodes, means for-applying a first alternating voltage between said anode and cathode, means for applying a second alternating voltage displaced in phase from said first voltage between one of said auxiliary electrodes and said cathode such that said one auxiliary electrode is positive when said anode begins to go positive but negative shortly thereafter,

initiating means, voltage establishing means between said cathode and other auxiliary electrode for preventing conduction of said tube until after the operation of said initiating means, means for dissipating the effect of said last mentioned means after the operation of said initiating means whereby said tube will begin conducting only during the period in which both said anode and said one auxiliary electrode are positive, and control means responsive to current flow through said tube.

2. In a control circuit, an electronic tube having an anode, a cathode, and at least a pair of auxiliary electrodes, means for openin a:

alternatingvoltage between said anode an oath ode, means forapplyinga second alternatin voltage displaced in phase from said first voltage between one of said auxiliary electro'desand said cathode which tends to makesaid tube become conductive during a redetermined illlltihififibltibfl or a positive half. cycle or anodevoltage and which prevents conduction or said tubeduring the remainder of the positive half cycle, voltage" after the operation of and initiating means whereby said tube will begin conducting only during said predetermined portion of a positive half cycle of anode voltage and control means responsive to current flow through said tube.

3. In a control circuit, an electronic tube havin an anode, a cathode, and at least a pair of auxiliary electrodes, means for applying a first alternating voltage between said anode and cathode, means for applying a second alternating voltage displaced in phase from said first voltage between one of said auxiliary electrodes and said cathode such that said one auxiliary electrode is positive when said anode begins to go positive but negative shortly thereafter, means for establishing a direct voltage between said other auxiliary electrode and said cathode whereby said other electrode is normally negative to said cathode during those periods in which said anode is positive, an initiating switch, means for dissipating said direct voltage after operation of said initiating switch whereby said tube will begin to conduct only during the period in which said one auxiliary electrode and said anode are both positive, and control means responsive to current flow through said tube.

4. In a control circuit, an electronic tube having an anode, a cathode, and control and shield grids, means for applying a first alternating voltage between said anode and cathode, means for applying a. second alternating voltage displaced in phase from said first voltage between said cathode and shield grid such that said shield grid is positive when said anode begins to go positive but negative after said anode has been positive for a short interval, initiating means, means for establishing a direct voltage between. said cathode and control grid for preventing conduction of said tube until after operation of said initiating means, means for eliminating the effect of said last mentioned means after the operation of said initiating means whereby said tube will begin to conduct only during the interval when both said anode and shield grid are positive, and control means responsive to current flow through said tube. i

5. In a control circuit, an electronic tube having an anode, a cathode, and control and shield grids, means for applying a first alternating voltage between said anode and cathode, means for applying a second alternating voltage displaced in phase from said first voltage between saidcathode and shield grid such that said shield'grid is positive when said anode begins to go positive but negative after said anode has been positive for a short interval, a capacitor, means connecting said capacitor to said control grid, means for charging said capacitor with a polarity such that said control grid is negative with respect to said cathode when said anode is positive, an initiating switch, means for dissipating the charge upon 6, said capacitor after "the operationv "or said .lnitiat-' ing" switch whereby said-tube will begin to co both" said duct oniy'during the i ter'val when anode and shield grid are positive, and contror means responsive to current flow through said tube.

inga'n anode, a cathode, and control andshield grids, meansiar applying a first alternating volt-- age between saidanodeand cathode, plying a second alternating voltage displaced degrees from said first voltage, a first series circuit' including a first resistor and a first capac'-: itor'connect'e-d across said second voltage, means connecting-saidcathode to the terminal-of said: first capacitor spaced from said first resistor, means connecting said shield grid between said-- first resistor and said first capacitor, whereby said shield grid voltage is displaced in phase from said first and second voltages an amount such that said shield grid is positive when said anode begins to go positive but negative after said anode has been positive for a short interval, a second series circuit including a second resistor, a second capacitor, the control grid and the cathode connected across said second voltage, whereby said second capacitor is charged during positive half cycles of said second voltage, the charge upon said second capacitor making the control grid negative at all times when the anode is positive, an initiating switch in parallel with that part of said second series circuit which includes said second capacitor, the control grid and the oathode whereby recharging of saidsecond capacitor is prevented after operation of the initiating switch, means for dissipating the charge upon said second capacitor after operation of the initiating switch whereby the tube will begin to conduct only during the interval when both the anode and shield grid are positive, and control means responsive to current flow through the tube.

'7. In a control circuit comprising an electronic tube and means responsive to the conduction thereof; an electronic tube having an anode, a cathode, and at least a pair of control electrodes; means for applying a first alternating voltage between said anode and cathode, initiating means, means for applying a direct voltage between one of said control electrodes and said cathode which prevents conduction of said tube, means for dissipating the effect of said last mentioned means upon operation of said initiating means, and means for applying a voltage between said other control electrode and said cathode which makes said other control electrode positive with respect to said cathode as said anode becomes positive and which makes said other control electrode negative with respect to said cathode a small fraction of a half cycle after said anode has become positive, whereby said tube can begin to conduct only during the initial portion of a half cycle.

8. In a, control circuit comprising an electronic tube and means responsive to the conduction thereof, an electronic tube having an anode, a cathode, and at least a pair of control electrodes, means for applying a first alternating voltage between said anode and cathode, means supplying a second alternating voltage displaced substantially 180 degrees from said first voltage, a first series circuit connected across said second voltage including a first resistor and the first capacitor, means connecting said cathode to the terminal of said first capacitor spaced from said Gain a control circuit, an electronic tube havmeans SUD first resistor, means connecting one of said control electrodes between said first resistor and said first capacitor whereby the voltage between said one control electrode and said cathode is displaced in phase from said first and second alternating voltages an amount such that said one of said control electrodes is positive when the anode begins to go positive but negative after said anode has been positive for a vsmall portion of' a half cycle; a second series circuit connected across said second alternating voltage including a second resistor, -a second capacitor, the other of said control electrodes and said cathode; said second capacitor being charged during positive half cycles of said second alternating voltage, said other control electrode being made negative when said anode is positive by said charge on said second capacitor; an initiating switch in parallel with that part of second series circuit which includes said second capacitor, the other of said control electrodes and said cathode, whereby recharging of said second capacitor is prevented after operation of said initiating switch; and means for discharging the charge upon said secondcapacitor after operation of said initiating means whereby the tube will begin to conduct only during the interval when both the anode and said one control electrode are positive.

7 ROBERT C. MIERENDORF.

References Cited in the file Of this patent UNITED STATES PATENTS Number Name Date 2,359,080 Bivens Sept. 26, 1944 2,463,318 Schneider Mar. 1, 1949

Images