US 3628089 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
United States Patent 3,191,093 6/1965 Morrison etal.
lnventor David C. Baker Sidney, N.Y. Appl. No. 861,119 Filed Sept. 25, 1969 Patented Dec. 14, 1971 Assignee The Bendix Corporation PULSE-GENERATING APPARATUS 10 Claims, 1 Drawing Fig.
11.8. C1 315/227, 315/239 Int. Cl H051) 37/00 Field of Search 315/227, 205, 206, 209, 238, 239; 307/1 10; 321/15 References Cited UNITED STATES PATENTS 3,450,942 6/1969 Segalletal 3,450,972 6/1969 Linkroum Primary Examiner- Roy Lake Assistant Examiner- Lawrence .1. Dahl Attorneys Raymond J. Eifler and Flame, Hartz, Smith &
Thompson ABSTRACT: A condenser discharge-type electrical pulsegenerating circuit, such as for a combustion engine ignition circuit, wherein two storage condensers are charged in parallel to discharge across a relatively low voltage trigger gap which connects the condensers in series to discharge across a higher voltage control gap and through the primary winding of a transformer, the secondary winding of which is connected in series with a still higher voltage ignition gap, the ignition gap being connected in series with the control gap and one of the condensers, whereby long trigger gap life and high output power are attained.
PULSE-GENERATING APPARATUS This invention relates to electrical apparatus and more particularly to means for controlling the operation of electrical pulseor spark-generating apparatus having an intermittently discharged storage condenser.
An object of the present invention is to provide novel control means for an electrical pulseor spark-generating apparatus of the type indicated.
,Another object is to provide novel control means for an electrical pulseor spark-generating apparatus incorporating a storage condenser which is intermittently discharged through a control gap.
A further object is to provide means for controlling breakdown of the control gap, such means being subjected to only a small part of the energy which is discharged through the control gap.
A still further object of the invention is to provide a control means for electrical pulse-generating apparatus which is simple, rugged, and long lived and which provides maximum power output for a given input voltage.
The above and further objects and novel features of the invention will more fully appear from the following description when the same is read in connection with the accompanying drawing. 1t is to be expressly understood, however, that the drawing is for the purpose of illustration only, and is not intended as a definition of the limits of the invention.
The single FIGURE of the drawing is a wiring diagram of one embodiment of an electrical pulseor spark-generating circuit in accordance with the invention.
The circuit shown in the drawing is adapted for use as an untimed ignition circuit for jet and gas turbine-type engines. The invention is not, however, limited to such uses or systems.
The ignition circuit shown is of the condenser discharge type which is energized by a suitable source 13 of alternating electrical current or a source of interrupted direct current connected to input terminals A and B of the ignition circuit. The current source is connected to the primary winding of a power input transformer 11 having a secondary winding 12. The circuit includes a radiofrequency-filtering means 14 which is preferably, although not necessarily, employed, the means 14 being interposed between the power source and the transformer 11 to attenuate high-frequency noise generated within the ignition circuit and thus preventing interference from being transmitted to other circuits connected to the current source.
A voltage-doubling type of energy storage means is con nected across the secondary winding 12 of transformer 11. Such storage means is incrementally charged by the energy source through transformer 11; the energy storage means is periodically discharged to a pulse-absorbing load, which in this instance is an ignition spark gap 29. The storage means comprises a small condenser 15 which is connected across the secondary winding 12 through a diode or half-wave rectifier 16, a second small condenser 17 connected across winding 12 through a reversely polarized diode or half-wave rectifier 19, and a main relatively large tank condenser connected across condensers l5 and 17 in series. It will be apparent that with the diodes 16 and 19 connected as shown, when the condensers are being charged the lower terminals of condensers 15, 17, and 20 are negative whereas the lower terminal of a condenser 31, to be described, is positive. The diodes l6 and 19 may be protected against damage, the operating life thereof may be enhanced, and the required rating thereof may be minimized by providing current-limiting resistors 21 and 22 in the circuit, as shown. One side of the above-described energy storage means is shown as being connected to a common ground 23, and the high-potential side thereof is connected through a control gap to the ungrounded electrode of an ignition spark gap 29. It will be understood that, if desired, all of the points in the circuit designated 23 may be connected by a common ungrounded conductor.
The input electrode 24 of control gap 25 is connected to the high-potential side of the ignition circuit beyond the main tank condenser 20. The output electrode 26 of the control gap 25 is connected to one terminal of the secondary winding 27 of a step-up transformer 28, the other terminal of the secondary winding 27 being connected to the ungrounded electrode of the ignition spark gap 29.
Connected across the electrodes 24, 26 of the control gap 25 is a circuit having a large resistance 30, a small condenser 31 and, if desired, a choke coil 32 in series. Connected to the high-potential side of the ignition circuit between the point of connection of the choke coil 32 (if used) and the input terminal of the secondary winding 27 of transformer 28 is one terminal of a small resistance 33, the other terminal of which is connected to ground. One terminal of the primary winding 35 of the step-up transformer 28 is connected between the resistance 30 and the condenser 31, the other terminal of the primary winding 35 being connected to the input electrode 34 of a trigger gap 36, the other electrode 37 of which is connected to ground. The ionizing or breakdown voltage of the trigger gap 36 is substantially less than that of the control gap 25 and much less than that of igniter gap 29.
in one successful embodiment the power transformer 11 steps up the supply voltage, which in this instance may be assumed to be 400 cycle, 1 15 volt, to a level in excess of 1,400 volts peak. Each half-cycle of this voltage is rectified by one of the diodes 16, 19 to charge one of the doubler condensers 15, 17. The voltage across condensers 15, 17 is additive and therefore the voltage charging the main storage condenser 20 and trigger condenser 31 is in excess of 2,500 volts peak.
While the storage condenser 20 is being charged, condenser 31, which is then connected in parallel therewith, is charged through resistance 30, the charging circuit for condenser 31 being completed to ground through choke coil 32 and resistance 33. As above explained, with the diodes 16, 19 disposed as shown, the input electrode 24 of the control gap 25 is positive with respect to the output electrode 26 thereof. When the trigger gap 36 breaks down, the positive end of condenser 31, that is, that connected to electrode 34 of the trigger gap 36 through the primary winding 35, is momentarily grounded, causing the condensers 20, .31 momentarily to be connected in series through the trigger gap and the voltages of condensers 20 and 31 to be additive. Such added voltages exceed the 3,500-volt ionizing potential of the main discharge or control gap 25 to thereby render said gap conductive to the charge of the main storage condenser 20. The subsequent discharge of condensers 20 and 31 in series through the primary winding 35 of the transformer 28 and trigger gap 36 to ground results in a stepped-up voltage across the secondary 27 of transformer 28. This high voltage, on the order of 15-20 kilovolts, is also impressed across the output cable and the igniter plug 29. Once the initial arc has been formed across the igniter plug 29 by this voltage, the energy contained in the storage condenser 20 is channeled through the control gap 25, the secondary winding 27 of transformer 28 and through the preformed arc of the igniter gap 29 to ground. This energy is termed the follow-through. After the voltage across the two condensers 20, 31 decreases to low values, their associated gaps 25, 36 deionize and the cycle repeats itself.
It should be noted that with this type of circuit the trigger gap 36 controls the ionization of the main discharge or control gap 25. The normal ionization voltage of the control gap 25 is much higher than the level at which gap 36, and hence, gap 25 are thus triggered. The trigger gap 36 in the disclosed circuit is subjected to only 5 percent of the energy being discharged through the control gap 25. As a result, the life of the trigger gap 36 is greatly increased.
Discharging the two condensers 20, 31 in series across the primary of transformer 28 makes it possible to obtain a desired high voltage across the secondary winding with a minimum number of turns. This results in increased current flow and hence a maximum power output.
Typical values of components pans which make up the above-described system are as follows:
Conde nsc rs l and [7 0.06 f.
3.5-3.6 f. 3! O.()5U.O65 pf. Resistances Ohms 21 and 22 2,000
30 50,000 33 L250 Transformers Primary/Secondary Turns Ratio l l 450/6000 28 4/17 Coil I Number of Turns 32 6 No. 18 wire Control Gaps Ionizing Potential 3,500 volts 36 2.500 vullS Although only a single embodiment of the invention has been illustrated and described in the foregoing specification, it is to be expressly understood that the invention is not limited thereto but may be embodied in specifically different circuits. For example. the main tank or storage condenser 29 may be incrementally charged by means other than the voltagedoubling system shown. For example, such condenser may be charged directly from the secondary winding of a step-up transformer powered by an alternating current source. Such transformer may also be powered by' an interrupted direct current source. Various other changes may also be made, such as in the electrical values suggested herein by way of example, and in the types of rectifiers illustrated without departing from the spirit and scope of the invention, as will now be apparent to those skilled in the art.
What is claimed is:
1. Electrical apparatus having a source of electrical energy, a multisection storage condenser means connected to said source so as to be incrementally charged thereby with the sections of the condenser connected in parallel, a step-up transformer having primary and secondary windings, a load circuit including said secondary winding and a high-voltage discharge gap connected to be energized by the discharge of the storage condenser means, a first control gap interposed between one section of the storage condenser means and the load circuit having a breakdown potential less than that of said discharge gap, a second control gap having a breakdown potential less than that of the first control gap and less than the voltage attainable by the parallel-connected sections of the storage condenser means as charged by said source, first circuit means connecting the second gap to the storage condenser means so that the second gap is ionized when the charge on the parallelconnected sections of the storage condenser means reaches the breakdown potential of said second gap, and second cir cuit means for thereupon connecting said sections of the storage condenser means in series and subjecting the first gap to the full voltage of the series-connected sections of the storage condenser means so as to ionize the first gap and discharge the storage condenser means to said primary winding to thereby induce a voltage across said secondary winding to ionize said discharge gap and discharge said one section across the latter.
2. Electrical apparatus according to claim 1 wherein said one section of the storage condenser has a capacity substantially greater than that of the other of said condenser sections.
3. Electrical apparatus according to claim 1 wherein the first circuit means includes the primary winding of the transformer and the second gap connected in series.
4. Electrical apparatus according to claim 3 wherein the primary winding of the transformer and the second gap are connected in series between the junction of said condenser sections and ground.
5. Electrical pulse-generating apparatus comprising a source of electrical energy, first and second storage condensers connected in parallel across said source to be simultaneously charged thereby, a voltage step-up transformer having primary and secondary windings, a control gap having a predetermined breakdown potential, a triggering gap having a breakdown potential less than that of said control gap, a control circuit comprising said condensers, said gaps and said primary winding connected in series, a triggering circuit comprising said second condenser, said triggering gap and said primary winding in series, whereby the triggering gap is rendered conductive when the charge on said second condenser attains the breakdown voltage of said triggering gap to thereby connect said condensers in series, voltage-adding relation across said control gap to render it conductive to the discharge of said condensers in series through the primary winding in the control circuit, a discharge gap having a sparkover voltage greater than the breakdown voltage of said control gap, means connecting said discharge gap across said secondary winding to be ionized by the voltage induced across the latter in response to the discharge of said condensers in said control circuit, and a load circuit connected across said first condenser comprising said control gap, said secondary winding and said discharge gap in series.
6. Apparatus as defined in claim 5 comprising an inductance connected in series with said second condenser in the charging circuit therefor and in said triggering circuit.
7. Apparatus as defined in claim 6 comprising a resistor in said charging circuit.
8. Apparatus as defined in claim 7 comprising a second resistor common to said charging and triggering circuits.
9. Electrical pulse-generating apparatus comprising a source of electrical energy, first and second storage condensers connected in parallel across said source to be simultaneously charged thereby, a voltage step-up transformer having primary and secondary windings, a control gap having a predetermined breakdown potential less than the sum of the voltages to which said condensers are charged in parallel by said source, a triggering gap having a breakdown potential less than that of the control gap, a triggering circuit comprising said second condenser and said primary winding connected in series across said triggering gap, a control circuit comprising said first condenser, said second condenser, said triggering gap and said primary winding connected in series relation across said control gap, whereby said triggering gap is rendered conductive when said second condenser is charged to the breakdown potential of the triggering gap and the sum of the voltages of the charges on said series-connected condensers in the control circuit is applied across said control gap to render the same conductive to the discharge of said condensers in series through the primary winding, a discharge gap having a sparkover voltage greater than the breakdown potential of said control gap, means connecting said discharge gap across said secondary winding to be ionized by the voltage induced across the latter in response to the discharge of said condensers through the primary winding in said control circuit, and a load circuit connected across said first condenser comprising said control gap, said secondary winding and said discharge gap in series.
10. Apparatus as defined in claim 9 wherein said control gap comprises spaced electrodes, one of which is operatively connected to the positive terminal of one of said condensers, and the other of which is operatively connected to the negative terminal of the other of said condensers as charged in parallel by said source.