EP0589603B1 - Circuits d'excitation et méthodes comprenant des mesures protectrices pour des commutateurs à l'état solide - Google Patents

Circuits d'excitation et méthodes comprenant des mesures protectrices pour des commutateurs à l'état solide Download PDF

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Publication number
EP0589603B1
EP0589603B1 EP19930307213 EP93307213A EP0589603B1 EP 0589603 B1 EP0589603 B1 EP 0589603B1 EP 19930307213 EP19930307213 EP 19930307213 EP 93307213 A EP93307213 A EP 93307213A EP 0589603 B1 EP0589603 B1 EP 0589603B1
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European Patent Office
Prior art keywords
capacitor
current
plug
circuit
charging
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EP19930307213
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German (de)
English (en)
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EP0589603A2 (fr
EP0589603A3 (fr
Inventor
Howard Vincent Bonavia
Dale Frank Geislinger
Michael John Terzo
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Unison Industries LLC
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Unison Industries LLC
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P7/00—Arrangements of distributors, circuit-makers or -breakers, e.g. of distributor and circuit-breaker combinations or pick-up devices
    • F02P7/02—Arrangements of distributors, circuit-makers or -breakers, e.g. of distributor and circuit-breaker combinations or pick-up devices of distributors
    • F02P7/03—Arrangements of distributors, circuit-makers or -breakers, e.g. of distributor and circuit-breaker combinations or pick-up devices of distributors with electrical means
    • F02P7/035—Arrangements of distributors, circuit-makers or -breakers, e.g. of distributor and circuit-breaker combinations or pick-up devices of distributors with electrical means without mechanical switching means
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P11/00—Safety means for electric spark ignition, not otherwise provided for
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P15/00—Electric spark ignition having characteristics not provided for in, or of interest apart from, groups F02P1/00 - F02P13/00 and combined with layout of ignition circuits
    • F02P15/001—Ignition installations adapted to specific engine types
    • F02P15/003—Layout of ignition circuits for gas turbine plants
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P3/00—Other installations
    • F02P3/06—Other installations having capacitive energy storage
    • F02P3/08—Layout of circuits
    • F02P3/0807—Closing the discharge circuit of the storage capacitor with electronic switching means
    • F02P3/0838—Closing the discharge circuit of the storage capacitor with electronic switching means with semiconductor devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P3/00—Other installations
    • F02P3/06—Other installations having capacitive energy storage
    • F02P3/08—Layout of circuits
    • F02P3/0876—Layout of circuits the storage capacitor being charged by means of an energy converter (DC-DC converter) or of an intermediate storage inductance
    • F02P3/0884—Closing the discharge circuit of the storage capacitor with semiconductor devices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P9/00—Electric spark ignition control, not otherwise provided for
    • F02P9/002—Control of spark intensity, intensifying, lengthening, suppression

Definitions

  • the invention relates to an exciter for an igniter, comprising a charging circuit, a storage capacitor connected to be charged by the charging circuit, a discharge circuit connected to discharge the storage capacitor and connectable to a plug to cause the plug to produce sparks in response to discharge of the capacitor, the charging circuit being connectable to an AC power source for continuously delivering power to the charging circuit to produce charging current for charging the storage capacitor, the discharge circuit including a solid state switching device connected to the storage capacitor and for connecting the storage capacitor to the plug, and a trigger circuit for triggering the switching device.
  • the invention also relates to a method for producing sparks from an igniter plug, comprising the steps of repeatedly producing a half-wave rectified charging current from an AC power source with the AC power source continuously delivering power to produce the charging current, repeatedly charging a storage capacitor with the charging current from a power source, repeatedly triggering a switching device in a discharge circuit to discharge the storage capacitor through the plug to produce the sparks, and turning the switching device off during a non-charging half-cycle of the charging current after the storage capacitor discharges.
  • Such exciters and methods are known, for example, from GB-A-1 108 636.
  • the charging current is highly dependent on the character of the AC source; that is, as the voltage of the source changes, the charging current changes in a generally dependent manner. This may not be satisfactory in certain applications, such as where precise operation is required.
  • the discharge circuit is triggered by an independently operating timing circuit.
  • Such an exciter is relatively complex and its correct operation and spark rate timing may be affected by factors affecting the timing circuit which triggers the discharge circuit. The invention aims to deal with these problems.
  • the known exciter as first set forth above is therefore characterised, in accordance with the invention, in that the charging circuit includes a regulating circuit to regulate the charging current to charge the storage capacitor at a generally constant rate between sparks, and in that the trigger circuit triggers the switching device in response to the charge on the storage capacitor, the charging circuit and the trigger circuit operating to maintain a generally constant spark rate.
  • the known method as first set forth above is characterised, in accordance with the invention, in that the igniter plug is an igniter plug in an engine, and by the step of regulating the charging current such that the charging current charges the storage capacitor at a generally constant rate between sparks, in that the triggering step comprises the steps of detecting the charge on the storage capacitor and triggering the switching device in response to the detected charge, and in that the charging step and the triggering step operate to maintain a generally constant spark rate.
  • US-A-5 032 969 shows an exciter having a DC power source which is interrupted when the storage capacitor becomes fully charged.
  • an exciter in accordance with the present invention is generally designated by the numeral 10.
  • Such an exciter is particularly well suited for use in an ignition system for a gas turbine engine, such as, for example, in aircraft engines.
  • exciters in accordance with the invention can also be used other than in the aircraft applications.
  • One of the basic functions of the exciter 10 is to produce high energy sparks at the igniter plug gap, which is shown in a simplified schematic manner in Fig. 1 and designated with the numeral 12.
  • An important requirement imposed by engine manufacturers is that the spark rate should be generally constant over a wide operating temperature and input voltage range of the exciter.
  • the plug 12 of course, is physically positioned in the combustion chamber of the engine (not shown).
  • the exciter 10 is connected to the plug by a high tension lead wire 14 and a return 16.
  • the exciter 10 includes an uninterrupted charging circuit 20 and a discharge circuit 22.
  • the charging circuit 20 is connectable by leads 24,26 to an AC power supply 28, such as, for example, a 115 VAC 400Hz supply from the engine power plant.
  • an AC power supply 28 such as, for example, a 115 VAC 400Hz supply from the engine power plant.
  • the AC power supply 28 energizes the charging circuit 20 to operate in a continuous manner.
  • the AC power supply 28 connects in parallel with a capacitor 30 which may be provided for power factor correction, as is well known to those skilled in the art.
  • a pair of current regulating inductors 32a and 32b are connected in series between the power supply 28 and a primary winding 34 of a power transformer T1.
  • the inductors 32a,b operate to maintain a generally constant current through the primary winding of the transformer T1, and this current is generally independent of variations of input voltage as long as the ratio of input voltage to input frequency remains generally constant.
  • a pair of capacitors 33 are provided for low pass filtering.
  • the discharge circuit 22 further and preferably includes a cascaded set of switching devices 46a, 46b, 46c and 46d.
  • the devices 46a-d are SCR thyristor devices or GTO devices. Although four devices are shown in Fig. 1, the actual number of such devices used will depend on the particular requirements of the ignition system, primarily the type of switching device used, the type of plug used, and the operating voltages, currents and temperatures. For example, a standard SCR can only withstand or block 1000-1500 VDC, therefore, if the capacitor 38 needs to be charged to 3000 VDC or more then several SCR devices need to be used. It will be appreciated that the series string of switching devices 46 can also be thought of as a single switching device connected between the main capacitor 38 and the plug 12. Those skilled in the art will readily appreciate that the voltage imposed on the capacitor 38 will depend on the type of plug being used, as well as the type of output conditioning circuit employed with the discharge circuit, as will be more fully explained herein.
  • the switching devices 46a-d are triggered on in response to a current pulse applied to their respective gate terminals 48a-d. These trigger pulses are applied to the gates 48a-d by a set of corresponding pulse transformers 50a-d.
  • a trigger circuit 52 monitors the charge on the main storage capacitor 38.
  • the trigger circuit 52 includes a comparator device 54, such as, for example, part no. ICM 7555 manufactured by Maxim.
  • a series pair of resistors 56,58 provide a resistor divider circuit connected in parallel with the main capacitor 38.
  • the resistor divider junction node 60 is connected to input pins 2 and 6 of the comparator device 54.
  • the device 54 latches a low going signal at an output pin 3 and at pin 7.
  • the low signal at pin 7 pulls the node 60 towards a second lower threshold detected at pin 2, in essence resetting the comparator so that the output at pin 3 goes back high after a predetermined time, thus creating a pulse at pin 3.
  • This pulse may be, for example, 30 ⁇ seconds in duration.
  • the pulse duration can be set by selection of a discharge resistor 59 value.
  • the output pulse from the comparator 54 pulses on an FET switch 62 which in turn pulses on a PNP switch 64.
  • the pulsed PNP switch conducts current through the primary of the pulse transformers 50a-d thereby triggering the switching devices 46a-d on.
  • Power for the trigger circuit 52 can be conveniently provided using a tertiary winding 66 of the power transformer T1.
  • the tertiary current is rectified and filtered by a diode 68 and capacitor 70 to provide a DC voltage supply for the comparator device 54.
  • This DC supply may also be used to establish the bias voltages for the FET and PNP switches 62,64.
  • the switching devices 46a-d are connected in series between the main capacitor 38 and an output conditioning circuit 72.
  • the output circuit 72 may include a current limiting saturating core inductor 74 that momentarily limits the initial current surge through the switches 46a-d when these devices are initially switched on. This may be important when conventional SCRs are used for the switching devices because the extremely high current surges could otherwise damage or degrade the SCR devices.
  • the current and voltage waveforms can be divided into three rather distinct time periods.
  • the storage capacitor 38 is charged to about 3000 volts, and when the switching device is closed, the high impedance gap of the plug 12 sees a voltage above the gap breakover voltage (of course, in a high tension circuit, the capacitor 38 voltage is stepped-up such as with a step-up transformer in the output circuit so as to increase the voltage across the plug gap sufficient to create the arc).
  • the next time period of interest occurs as the capacitor 38 energy is transferred to the saturable inductor 74 as the capacitor discharges to zero volts and the inductor 74 current, in essence the loop current through the plug 12, increases to about 2000 A (amps).
  • energy is now transferred from the high voltage source of the capacitor 38 to the high current source of the inductor 74 to supply energy to the low impedance spark gap.
  • the energy stored in the inductor 74 which may be nearly 95% of the energy initially stored on the capacitor 38, is transferred to the arc of the plug 12.
  • the inductor 74 circulates current around the loop consisting of the inductor 74, the plug 12, and the clamp rectifier 71. The current then decays from a peak of about 2000 A (amps) to zero during this time.
  • a current multiplier is used in the output circuit 72 to circumvent this current limitation.
  • the output circuit 72 includes a current multiplier 76 connectable in series with the igniter plug 12.
  • the current multiplier 76 may be realized conveniently in the form of an autotransformer T2 having windings 78 and 80 on a common core, with a rectifier 79 being series connected between winding 80 and the return line 16.
  • the primary winding of T2 consists of both windings 78,80 in series after the arc is established; and the secondary is winding 80 which means that winding 80 is shared by the primary and secondary.
  • the windings 78 and 80 may have the same number of turns.
  • the rectifier 79 blocks magnetizing current through the common winding 80, which prevents the autotransformer 76 from initially operating which would otherwise limit open circuit voltage to the plug 12; and the inductance of inductor 74 and the winding 78 impedes the arc inception current to the plug 12 thus protecting the switching devices.
  • the autotransformer begins operating such that current now flows through windings 78, 80 and the plug 12.
  • Fig. 2 illustrates typical current characteristics for current through the switching devices 46a-d (REF 1) and current through the plug 12 (REF 2) using a current multiplier 76.
  • the current multiplier 76 can be used to provide the plug 12 with discharge current peaks and transition rates similar to those provided by a spark gap and at the same time reduce current peaks and transition rates conducted by the solid state switch to levels consistent with their capability.
  • inductor 74 need not be of the saturable type.
  • AC power applied to transformer T1 continuously energizes the charging circuit 20 which charges the main capacitor 38 at a generally constant average rate. However, during each negative half-cycle of the AC supply, no charging current is applied to the capacitor 38 due to operation of the half wave doubler circuit connected between the charging circuit 20 and the storage capacitor 38.
  • the comparator 54 When the capacitor is sufficiently charged to a voltage level adequate to produce a spark at the plug 12, the comparator 54 generates a trigger pulse that gates the switching devices 46a-d on. The capacitor 38 is thus shorted across the plug 12 and transformer T2.
  • the main capacitor 38 discharges through the current multiplier 76 and a high energy spark is created.
  • the switching devices 46 are able to turn off because the current through the devices falls below the sustaining level needed to keep the devices on when the succeeding half cycle of charging current is blocked.
  • the circuit is self-commutated without the need for a controlled switch or a controlled reactance to interrupt the supply of charging current or the need for a forced commutation circuit to by-pass charging current around the switching devices.
  • the switching devices 46a-d turn off, the capacitor 38 immediately begins charging again at the same generally constant average rate between sparks and the process repeats continuously as long as AC power is provided to the charging circuit 20.
  • the capacitor 38 In a typical exciter, the capacitor 38 is charged to about 3000 VDC. The capacitor discharges in 100 ⁇ seconds or less and can produce discharge currents as high as 2000 amps. Because the AC supply is preferably operating at 400 Hz, there is at least a 1.25 millisecond commutation period during which no charging current is applied to the capacitor 38. This is more than adequate time to insure that the switching devices 46a-d turn off within one cycle of the discharge time.
  • An important aspect of this invention is that an exciter is provided that operates in a continuous and uninterrupted charging mode without the need for timing circuits to achieve a constant spark rate.
  • the AC charging circuit 20 By designing the AC charging circuit 20 to continuously charge the capacitor 38 at a generally constant average rate between sparks, the AC charging power need not be interrupted and can be continuously applied to the capacitor 38. Because the comparator 54 always trips at the same reference level, a constant spark rate can be maintained without using any timer circuits. This is particularly useful with GTO devices used for the switches 46a-d. A GTO thyristor exhibits very low leakage currents even at high operating temperatures. Thus, a continuous mode exciter according to the invention will provide a constant spark rate over a wide range of temperatures.
  • GTO devices have high sustaining currents compared to conventional SCR devices. Therefore, GTO devices can be used with the continuous mode charging circuitry of the present invention without the need for the half wave rectifier. This is because the higher sustaining currents of the GTO allow the device to turn off as the capacitor 38 discharges, without the need for the half-wave commutation period needed by SCR devices.
  • the continuous mode technique is a significant improvement over the pulse width modulated exciter designs that rely on timer circuits to maintain a constant spark rate.
  • conventional SCRs exhibit high leakage currents at elevated operating temperatures. These leakage currents can affect the spark rate timing due to their load on the charging of the main capacitor 38. Leakage may cause, for example, charging power loss of 1 to 2 watts with conventional SCRs. However, in some applications the total power delivered by the charging circuit far exceeds the total power loss due to leaky SCRs even at elevated temperatures. In such circumstances, the continuous mode exciter as described herein can be used to achieve a spark rate that is sufficiently constant for engine specifications. The use of the half-wave doubler circuit permits the self-commutation to occur thus obviating the need to interrupt power to the discharge circuit.
  • the efficiency of the exciter 10 can be further improved by physically placing the current multiplier 76 at the plug 12. This substantially lowers the currents through the discharge circuit 22 and the high tension lead 14.
  • the current multiplier concept can be applied to any exciter, including those of the spark gap switching device type, to realize this improvement in output efficiency.
  • the current multiplier is particularly advantageous with solid-state switches such as SCRs and GTOs because the exciter can achieve the same peak output power characteristics of a spark gap exciter while reducing the di/dt and peak currents in the switching devices to safe operating values.
  • Use of the current multiplier also reduces the peak currents discharged from the main storage capacitor 38, which can be expected to improve the operating life of the main capacitor.
  • Fig. 1 may generally be referred to as a unidirectional discharge.
  • Fig. 4 illustrates in simplified form the basic elements of a capacitive discharge circuit.
  • Those elements are the energy storage capacitor, C, a switching device such as a spark gap or alternatively a solid state switching means, S, a freewheeling diode Dx, an arc current inductor, L, and the plug, P.
  • the capacitor is charged to a suitable voltage at which time the switch is closed, allowing the capacitor voltage to instantaneously appear across the plug to strike an arc.
  • the diode Dx is initially reverse biased by the voltage on the capacitor so that all current flows through the capacitor, inductor and the plug, as indicated by the current loop I 1 .
  • the circuit of Fig. 4 is idealized because it neglects stray inductance.
  • a significant problem that can occur with capacitive discharge circuits is the presence of stray inductance (primarily lead length inductance of internal wiring and inductance associated with the storage capacitor's electrode winding).
  • the discharge circuit actually includes a third or inner current loop (designated by I 3 ) consisting of the capacitor, the switching device and the free wheeling diode, back to the return line.
  • I 3 third or inner current loop
  • stray inductance exists in both loops I 2 and I 3 , it is only shown in the inner loop I 3 because the energy transfer inductor, L, dominates any effects that might be caused by stray inductance in the outer loop, I 2 .
  • the stray inductance may be on the order of 1 micro Henry, while the energy transfer inductor may have a value such as 5 to 20 micro Henry.
  • this oscillatory current flows through the diode in the reverse direction, although the total current through the diode, I Dx , always flows in the forward direction. It should further be noted that the current in the outer loop I 2 is unaffected by this oscillatory current. Thus, the freewheeling diode, although it appears in effect in parallel with the storage capacitor, is actually ineffective to prevent these reverse voltages and currents.
  • the presence of the oscillatory current in the inner current loop I 3 can be explained as follows. As the current in loop I 1 begins its sine wave ascent (it is sinusoidal due to the effective LC network present in loop I 1 prior to time t 1 ), it is commutated at time t 1 when the capacitor is discharged and most, but not all the capacitor energy, has been transferred to the inductor L. Some of the energy, albeit small, is trapped in the stray inductance L S in loop I 3 . At the time t 1 , there is a single energy source L in loop I 2 and a single energy source L S in loop I 3 . Because loop I 3 contains the capacitor C, there is a resonant circuit consisting of capacitor C and the stray inductance L S .
  • the value L S is small so that the inner loop current oscillates at a high frequency defined approximately by 1/ ⁇ (L S C). This oscillatory current decays exponentially by time t 2 due to circuit impedance in the inner loop I 3 such as the diode Dx resistance.
  • a clamp diode across the storage capacitor with a polarity that allows normal charging of the capacitor but which by-passes the capacitor in the opposite direction so that the capacitor cannot resonate with the stray inductance L S in the inner loop.
  • This clamp diode effectively eliminates the reverse oscillatory voltages and currents that would otherwise damage the switching devices and the storage capacitor, as well as eliminates the reverse currents through the freewheeling diode Dx.
  • the reverse parallel diodes are removed and a clamp diode rectifier 150 such as part no. BYM56E available from Philips is placed directly in parallel with the main storage capacitor 38. This effectively shunts the capacitor 38 to prevent reverse currents or voltages appearing due to the stray inductance.
  • a clamp diode rectifier 150 such as part no. BYM56E available from Philips is placed directly in parallel with the main storage capacitor 38.
  • the free wheeling diode 71 which is also in the outer current loop of the discharge circuit (consisting of the inductor 74, the current multiplier 76, the plug 12 and the diode 71), is ineffective against the stray inductances of the inner loop because that diode 71 is effectively in parallel with the capacitor 38 and the stray inductance L S .
  • the clamping diode 150 is in series with the switching devices 46 which are in parallel with the free wheeling diode 71, the clamping diode 150 should be chosen to have a higher internal resistance so as not to divert arc current from diode 71 through the switches 46 when energy is transferred from the inductor 74 to the plug 12. This higher impedance does not adversely affect circuit efficiency because the clamp diode 150 only conducts a small fraction of the current conducted by the free wheeling diode 71.
  • diode strings will be used for both the free wheeling diode 71 and the clamp diode 150 in order to meet system voltage requirements.
  • the relative impedance of the clamp diode 150 can be increased, for example, by also using a series non-inductive resistor, selecting the clamp diode to have a smaller die size, or using more diodes in the diode string, to name just a few options available to the designer.
  • the rectifier 150 thus prevents reverse voltages and charging currents from occurring due to the inner loop stray inductances, thus protecting the switching devices 46.
  • the invention as explained however, also achieves benefits with spark gap circuits because the clamp diode limits oscillatory currents through the main storage capacitor and the free wheeling diode used for unidirectional discharge circuits.
  • a dual charger exciter circuit 500 is shown with a spark gap switching device 502, this is merely for convenience and should not be construed in a limiting sense.
  • a solid state switching device could also be used with the provision for a trigger circuit, such as shown in Fig. 1 herein.
  • the dual charger is realized in a conventional manner and includes, in this example, an AC charging circuit 504, and a DC invertor charging circuit 506.
  • the dual circuit 500 is typically used, for example, for ignition circuits in which a high energy spark is required for starting an engine, and then a lower energy spark is used for maintaining engine operation.
  • the exciter 500 includes two storage capacitors 508 and 510.
  • the DC invertor receives a DC system input voltage 512 and charges both capacitors 508, 510. This provides high energy storage for the parallel capacitors such that when the spark gap triggers a high energy spark is created.
  • the DC invertor is turned off by disconnection of the DC input, and system AC power 514 is applied to the AC charger 504.
  • the AC charger charges only the smaller capacitor 508 due to the presence of the blocking diode 520.
  • Most of the circuit of Fig 7. is conventional spark gap technology and well known to those skilled in the art.
  • the dual charging circuit is fully described in US Patent No. 3,629,652 issued to Maycock et al. In that patent, two AC charging circuits are used rather than an AC charger and a DC charger, but the present invention can be used with either embodiment as well as others.
  • the blocking diode 520 as used in the Maycock et al. patent for example, is subject to reverse and damaging oscillatory currents and voltages due to the presence of the stray inductance L S which we have previously described herein.
  • the unidirectional or free wheeling diode 522 is ineffective to prevent these reverse phenomena.
  • clamping diodes 530 and 532 are provided directly in parallel with the storage capacitors 508, 510 respectively to prevent these reverse currents and voltages by shunting the capacitors in the reverse charging direction thus eliminating the resonant circuit that would otherwise be present if the parallel clamping diodes were not used.
  • the devices may have different transition times for turning on when the gate terminals are triggered. This can result in excessive voltages across the anode/cathode junction of the slower devices. For example, in Fig. 1, if devices 46a and 46b begin to conduct current at an appreciably faster rate than device 46c, excessive anode/cathode voltages may appear across the slower device 46c. To reduce this effect, we have provided snubber circuits 200 for each switching device 46. Each snubber circuit 200 operates in substantially the same manner, therefore, only one will be described.
  • Each snubber circuit 200 includes a capacitor 202, a diode 204, and a gate return resistor 206. A series string of static balancing resistors 208 are also provided.
  • the snubber capacitor 202 is connected between the diode 204 and the corresponding gate terminal 48 of the switching device 46. For purposes of explaining operation of the snubber circuits 200, assume that switching device 46a and 46b begin to turn on before device 46c. Without the snubber circuits, voltage would rapidly build across the anode/cathode junction of the slower device.
  • the static balancing resistor 208 in each snubber circuit serves at least two purposes. First, these resistors operate in a conventional manner to provide static balance across the switching devices so that no single device 46 sees an excessive anode/cathode potential while the main capacitor 38 is charging. The balancing resistors 208 also serve to discharge the snubber capacitors after each spark discharge period of the exciter 10.
  • the snubber circuit 200 is particularly useful when the switching device is a GTO type thyristor. This is because these devices are particularly susceptible to excess anode/cathode voltages due to slower and less predictable turn on time delays from the time that the gate current is applied to the time that the device operates in the thyristor region.
  • the devices exhibit fairly consistent and predictable turn on delays that are short enough that additional drive to the gate terminals is not needed. Therefore, a snubber circuit for conventional SCR devices can be used that has the snubber capacitor connected between the snubber diode and the cathode of the SCR. This snubber design simply shunts any charge build up due to devices 46 turning on at different rates around the slower devices.
  • each snubber circuit 200 includes a diode 210 connected between the gate terminal 48 and the corresponding pulse transformer 50. This diode is provided to block current from the snubber capacitor 202 from being shunted away from the gate terminal 48 due to the low impedance of the pulse transformer secondary winding. This diode is not needed in an SCR snubber circuit because the latter returns the snubber capacitor current to the SCR cathode, not the gate terminal.
  • a high tension discharge circuit In some engine designs, the plug 12 requires a high voltage level to generate the spark across the plug electrodes. This voltage may be on the order of 15 kV or higher. Because solid-state switches cannot withstand such high voltages, a voltage step-up transformer is used in the output circuit 72. The use of voltage step-up transformers for high tension exciters has been well known since the 1960s.
  • a typical design includes a transformer T3 having a primary winding connected in series with the main capacitor 38 (not shown in Fig. 3A) and an excitation capacitor 90. The transformer T3 secondary 92 is connected in series with the plug 12.
  • the switching devices 46a-d When the switching devices 46a-d are triggered on, discharge current from the capacitor 38 initially flows through the primary of T3 until the capacitor 90 charges. During this time a high voltage spike is induced in the secondary 92 that appears across the plug 12 to create a spark. After the capacitor 90 charges, the primary of T3 no longer conducts current, and the capacitor 38 completes discharge through the secondary 92 and the current multiplier.
  • the step-up transformer T3 can be used in parallel with the current multiplier 76 of the present invention to first provide high voltage at low current to the plug 12 in order to initiate the spark and then provide low voltage and high current to the plug 12.
  • Fig. 3B shows yet another variation in which the current multiplier 76 and voltage step-up transformer can be realized using a single transformer T4.
  • discharge current from the capacitor 38 initially flows through the primary 94 and excitation capacitor 96. This creates a high voltage spike in the center tapped secondary winding 98 and a high current spike in the other secondary winding 100. After the capacitor 96 charges, the main capacitor 38 completes its discharge through the secondaries 98,100.
  • Fig. 1 can be easily modified with respect to polarities of the charging current, capacitor 38 and the switching devices 46.
  • the switching devices could be reversed and the capacitor 38 negatively charged by the charging circuit 20.
  • the switching circuit generally outlined by the box 300, could also be interchanged positionally with the main capacitor 38.
  • the particular topology of the circuit shown and described with respect to Fig. 1 is not critical to realize the advantages of the invention, and can be easily changed to suit the needs of the specific application.

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  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Ignition Installations For Internal Combustion Engines (AREA)

Claims (19)

  1. Excitateur pour un circuit d'allumage, comprenant un circuit de charge (20), un condensateur accumulateur (38) connecté en vue d'être chargé par le circuit de charge (20), un circuit de décharge (22) connecté en vue de décharger le condensateur accumulateur (38) et connectable à une bougie (12) pour faire en sorte que la bougie (12) produise des étincelles en réponse à la décharge du condensateur (38), le circuit de charge (20) étant connectable à une source d'énergie en courant alternatif (28) pour fournir continuellement de l'énergie au circuit de charge (20) en vue de produire un courant de charge pour charger le condensateur accumulateur (38), le circuit de décharge (22) comportant un dispositif de commutation à l'état solide (46) connecté au condensateur accumulateur (38) et pour connecter le condensateur accumulateur (38) à la bougie (12), et un circuit de déclenchement (52) pour déclencher le dispositif de commutation (46), caractérisé en ce que le circuit de charge comporte un circuit de régulation (32a, 32b) en vue de réguler le courant de charge en vue de charger le condensateur accumulateur (38) à une vitesse généralement constante entre les étincelles, et en ce que le circuit de déclenchement (52) déclenche le dispositif de commutation (46) en réponse à la charge sur le condensateur accumulateur (38), le circuit de charge (20) et le circuit de déclenchement (52) fonctionnant pour maintenir une fréquence d'étincelles généralement constante.
  2. Excitateur selon la revendication 1, caractérisé par un redresseur à une alternance (42, 44) connecté entre le circuit de charge (20) et le condensateur accumulateur (38) de telle sorte que les alternances du courant de charge soient bloquées fournissant ainsi une période de commutation pour le dispositif de commutation (46) après la décharge.
  3. Excitateur selon la revendication 1, caractérisé en ce que le dispositif de commutation (46) est un thyristor, blocable par la gâchette ou redresseur commandé au silicium.
  4. Excitateur selon l'une quelconque des revendications précédentes, caractérisé par un multiplicateur de courant (76) connecté au dispositif de commutation (46) et pour la connexion à la bougie (12) en vue d'augmenter substantiellement le courant à travers la bougie (12) quand le condensateur accumulateur (38) se décharge.
  5. Excitateur selon la revendication 4, caractérisé en ce que le multiplicateur de courant (76) est structurellement placé près de la bougie (12) en vue de réduire la perte d'énergie durant la décharge dudit condensateur (38).
  6. Excitateur selon la revendication 4 ou 5, caractérisé en ce que ledit multiplicateur de courant (76) comprend un autotransformateur (T2) ayant un premier enroulement en série entre ledit dispositif de commutation (46) et la bougie (12), et un deuxième enroulement connecté à la bougie (12) de telle sorte que le courant appliqué à la bougie (12) durant la décharge soit substantiellement supérieur au courant déchargé par ledit condensateur (38).
  7. Excitateur selon la revendication 6, caractérisé en ce que ledit multiplicateur de courant (76) est connecté à un circuit élévateur de tension (T3, 90).
  8. Excitateur selon la revendication 7, caractérisé en ce que ledit multiplicateur de courant (76) et le circuit élévateur de tension comprennent un transformateur à noyau unique ayant un premier enroulement connecté en série auxdits dispositif de commutation (46) et condensateur (38), un deuxième enroulement (92) connecté aux bornes de ladite bougie (12) en vue d'augmenter substantiellement la tension aux bornes de la bougie avant qu'un arc ne soit amorcé, et un troisième enroulement connecté à la bougie en vue d'augmenter substantiellement le courant allant à la bougie après qu'un arc est amorcé.
  9. Excitateur selon la revendication 8, caractérisé par une diode en série entre ledit secondaire et la bougie.
  10. Excitateur selon l'une quelconque des revendications précédentes, caractérisé en ce que ledit circuit de déclenchement (52) comprend un comparateur (54) pour comparer ladite tension de condensateur à une tension de référence, ledit comparateur produisant un signal de déclenchement en réponse à une relation prédéterminée entre ladite tension de condensateur et ladite référence.
  11. Excitateur selon l'une quelconque des revendications précédentes, caractérisé en ce que le circuit de régulation (32a, 32b) comprend un moyen inductif.
  12. Excitateur selon la revendication 11, caractérisé en ce que le circuit de charge (20) comprend un transformateur (T1) ayant un enroulement primaire (34) connecté en vue d'être excité par la source d'énergie (28) à travers le moyen inductif (32a, 32b), et un enroulement secondaire (36) connecté au condensateur accumulateur (38).
  13. Excitateur selon l'une quelconque des revendications précédentes, caractérisé en ce que le dispositif de commutation comprend une pluralité de commutateurs à l'état solide connectés en série (46), et par un circuit d'amortissement (200) connecté à chacun de ces commutateurs (46), chaque circuit d'amortissement (200) comprenant un condensateur (202) connecté entre une gâchette et une anode, par l'intermédiaire d'une diode (204), du commutateur respectif (46).
  14. Excitateur selon l'une quelconque des revendications précédentes, caractérisé par un moyen de redressement (150) en parallèle avec le condensateur de stockage (38) en vue d'empêcher les courants et tensions inverses.
  15. Excitateur selon la revendication 14, caractérisé par un deuxième circuit de charge (506), un deuxième condensateur (510) connecté en vue d'être chargé par le deuxième circuit de charge (506), et un deuxième moyen de redressement (532) connecté en parallèle avec le deuxième condensateur (510) pour empêcher les courants et tensions inverses aux bornes du deuxième condensateur (510).
  16. Excitateur selon la revendication 14 ou 15, caractérisé en ce que le moyen de redressement (150, 532) empêche les courants inverses en empêchant la résonance entre le condensateur de stockage ou le condensateur respectif (38, 510) et l'inductance parasite associée à celui-ci, l'inductance parasite résultant essentiellement de l'inductance de longueur de conducteur interne et/ou de l'inductance dans le condensateur (38, 510).
  17. Méthode de production d'étincelles à partir d'une bougie d'allumage (12), comprenant les étapes de production répétée d'un courant de charge redressé sur une alternance à partir d'une source d'énergie de courant alternatif (28), la source d'énergie de courant alternatif (28) fournissant de manière continue de l'énergie en vue de produire le courant de charge, chargeant de manière répétée un condensateur accumulateur (38) avec le courant de charge provenant d'une source d'énergie (28), déclenchant de manière répétée un dispositif de commutation (46) dans un circuit de décharge (22) en vue de décharger le condensateur accumulateur (38) à travers la bougie (12) en vue de produire les étincelles, et bloquant le dispositif de commutation (46) durant une alternance à absence de charge du courant de charge après que le condensateur accumulateur (38) se décharge, caractérisée en ce que la bougie d'allumage (12) est une bougie d'allumage (12) dans un moteur, et par l'étape de régulation du courant de charge de telle sorte que le courant de charge charge le condensateur accumulateur (38) à une vitesse généralement constante entre les étincelles, en ce que l'étape de déclenchement comprend les étapes de détection de la charge sur le condensateur accumulateur (38) et de déclenchement du dispositif de commutation (46) en réponse à la charge détectée, et en ce que l'étape de charge et l'étape de déclenchement fonctionnent pour maintenir une fréquence d'étincelles généralement constante.
  18. Méthode selon la revendication 17, caractérisée par l'étape d'augmentation substantielle du courant fourni à la bougie d'allumage (12) durant la décharge du condensateur (38) en utilisant un multiplicateur de courant (76).
  19. Méthode selon la revendication 18, caractérisée en ce que l'étape d'augmentation substantielle du courant fourni par la bougie d'allumage (12) suit une étape d'augmentation substantielle de la tension appliquée à la bougie (12) durant la décharge du condensateur (38).
EP19930307213 1992-09-22 1993-09-14 Circuits d'excitation et méthodes comprenant des mesures protectrices pour des commutateurs à l'état solide Expired - Lifetime EP0589603B1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
US94931992A 1992-09-22 1992-09-22
US949319 1992-09-22
US99486592A 1992-12-22 1992-12-22
US994865 1992-12-22

Publications (3)

Publication Number Publication Date
EP0589603A2 EP0589603A2 (fr) 1994-03-30
EP0589603A3 EP0589603A3 (fr) 1995-02-15
EP0589603B1 true EP0589603B1 (fr) 1999-05-19

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Application Number Title Priority Date Filing Date
EP19930307213 Expired - Lifetime EP0589603B1 (fr) 1992-09-22 1993-09-14 Circuits d'excitation et méthodes comprenant des mesures protectrices pour des commutateurs à l'état solide

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Country Link
EP (1) EP0589603B1 (fr)
DE (1) DE69324981D1 (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5488536A (en) * 1993-04-01 1996-01-30 Simmonds Precision Engine Systems, Inc. Exciter circuit using gated switches
EP0679804B1 (fr) * 1994-04-25 1999-03-10 Unison Industries Limited Partnership Circuit d'excitation avec des commutateurs à commande
US6603216B2 (en) * 2001-10-10 2003-08-05 Champion Aerospace Inc. Exciter circuit with ferro-resonant transformer network for an ignition system of a turbine engine
CN108590914B (zh) * 2018-03-13 2020-11-06 上海交通大学 时空可控高能点火装置

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1108636A (en) * 1965-04-10 1968-04-03 Gas Council High tension spark ignition apparatus for burner installations
JPS58214670A (ja) * 1982-06-05 1983-12-13 Sigma Electron Planning:Kk 内燃機関点火装置
US5030883A (en) * 1987-09-25 1991-07-09 Simmonds Precision Products, Inc. Constant spark rate system and method
US5032969A (en) * 1990-02-15 1991-07-16 Cooper Industries, Inc. Turbine engine igniter exciter circuit
US5049786A (en) * 1990-08-09 1991-09-17 Coen Company, Inc. High energy ignitor power circuit
EP0481609A3 (en) * 1990-10-19 1992-09-02 Lucas Industries Public Limited Company Ht exciter for turbine ignition system

Also Published As

Publication number Publication date
DE69324981D1 (de) 1999-06-24
EP0589603A2 (fr) 1994-03-30
EP0589603A3 (fr) 1995-02-15

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