US3740574A - Ionic flame monitor - Google Patents

Ionic flame monitor Download PDF

Info

Publication number
US3740574A
US3740574A US00214129A US3740574DA US3740574A US 3740574 A US3740574 A US 3740574A US 00214129 A US00214129 A US 00214129A US 3740574D A US3740574D A US 3740574DA US 3740574 A US3740574 A US 3740574A
Authority
US
United States
Prior art keywords
flame
voltage
signal
input
output
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US00214129A
Other languages
English (en)
Inventor
J Taylor
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Combustion Engineering Inc
Original Assignee
Combustion Engineering Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Combustion Engineering Inc filed Critical Combustion Engineering Inc
Application granted granted Critical
Publication of US3740574A publication Critical patent/US3740574A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23N—REGULATING OR CONTROLLING COMBUSTION
    • F23N5/00—Systems for controlling combustion
    • F23N5/02—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium
    • F23N5/12—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using ionisation-sensitive elements, i.e. flame rods
    • F23N5/123—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using ionisation-sensitive elements, i.e. flame rods using electronic means

Definitions

  • Non-flame AC signals having voltages above or below the certain frequency, but above the certain voltage are prevented from indicating flame presence if their voltage is above a second certain level which is above that of most flame signal voltagesv
  • a voltage level detection circuit clamps the monitor output circuitry to a no-flame condition whenever the AC signal voltage is above the second certain level.
  • the invention relates to flame monitors and more particularly to flame monitors of a type which use the principle of flame ionization for determining the presence or absence of a flame.
  • flame combustion of fuels is used as a source of heat. It is essential in most such applications, in the interests of safety and economy, that there be at no time a sizable accumulation of unburned fuel in the combustion zone (such as might occur upon flame failure or initial failure of the fuel to ignite). Such unburned fuels may be ignited due to spurious causes and precipitate an explosion.
  • flame monitors or detectors for indicating flame failure and preventing the resulting buildup of the potentially hazardous condition. These flame monitors may be light sensitive devices or they may respond to differential pressures within a combustion chamber or they may rely upon the electrical properties of the flame to provide an indication of flame presence or absence.
  • flame monitors have been developed which exploit the fact that an ionizing process occurs within the flame due to the fuel combustion. In the combustion process, excess energy is liberated by the combining of two or more elements to form a com-- pound with a lower potential energy level. Ions, taking the form of electrons and positive atom nuclei, are formed by the heat of the combustion process. High speed photography has shown that most flames do not burn in a continuous uniform manner, but rather as many tiny discreet packets, the sum total of which form the flame seen by the eye. In each of these burning packets is a collection of ions having positive and negative potentials.
  • an electrical potential preferably a DC potential
  • the AC current so generated may be used to develop a flame signal which is subsequently used to indicate the presence or absence of flame.
  • ionic flame monitors have been developed which exploit the fact that the AC voltage fluctuations generated by the flame are rich in frequencies within a particular range. Signal analysis has revealed that the flame generated AC signal is particularly rich in frequencies within the range from 200 Hz to 2,000 Hz. This characteristic of the flame generated AC signal has permitted the development of flame monitors which attempt to recognize only a particular range of flame signal frequencies as being indicative of flame presence, andthereby preclude the possibility of a false external signal at a different frequency, for instance 60 Hz line voltage, being sensed as an indication of flame presence.
  • This type of ionic flame detector typically uses some form of frequency discriminator connected intermediate the flame electrodes and the flame switch in the output circuitry of the monitor to pass, to the switch, flame signal energy within the range of frequencies most common in a flame and to reject or strongly attenuate other signal frequencies, such as stray 60 Hz currents.
  • frequency discriminators are often effective for this purpose only within a limited range of input voltages and may pass sufficient signal energy to indicate flame presence when the strength of the signal applied to the discriminator is of extremely high magnitude, even though the frequency of the applied signal may be within the normal rejection or attenuation range.
  • This problem may arise with flame monitors op erating in a region where 60 Hz line voltage and second harmonic components thereof are present.
  • instances may occur in which AC voltages appear at the input to the frequency discriminator and have frequency characteristics similar to those generated by a flame but are of a larger amplitude than the flame signal generated by a flame.
  • an object of the present invention to provide an ionicflame monitor which will accurately indicate and/or respond only to an AC signal of the frequency and magnitude actually generated by a flame and will indicate flame absence at all other times including those in which high voltage signals from sources other than a flame are passed by the frequency discriminator.
  • a flame monitor for determining the presence or absence of a flame within a flame zone through detection of a flame generated AC voltage.
  • a pair of electrodes or flame rods are spaced apart from oneanother and disposed within the flame zone such that they are in contact with the flame when it is present.
  • a source of DC potential is impressed across the flame electrodes for increasing the rate of ion migration to the oppositely poled electrodes, thus resulting in a flame generated signal of significant strength.
  • Flame signal processing means are operatively connected across the electrodes to sense any AC signals appearing thereacross and have circuit characteristics which process the signals in a manner which normally provides an output response indicative of flame presence whenever the AC signal sensed is substantially any voltage within a particular frequency range characteristic of a flame generated signal or is above some particular AC voltage level in a frequency range other than that characteristic of a flame.
  • means are provided to effect an output response indicative of flame absence whenever the AC voltage across the electrodes exceeds a predetermined peak value.
  • This peak value is selected such that it is slightly greater than the highest AC peak voltages normally generated in the actual flame signal, thus permitting that output response commensurate with flame presence only when the AC signal across the electrodes is within both the frequency and voltage ranges characteristic of a flame generated signal.
  • the signal processing mean preferably include a flame switch and signal coupling means, said flame switch being responsive to signal energy passed from the electrodes by said coupling means for controlling the output response indicative of the flame presence or absence.
  • the coupling means preferably are frequency discriminating and may include a filter which has highpass characteristics. A clamp is applies to the flame switch circuit to effect the flame absent response whenever the AC voltage across the electrodes exceeds the above mentioned predetermined particular peak value.
  • a discharge device having a break-down potential at said particular value of peak voltage is connected across said electrodes.
  • the discharge device conducts, providing a voltage drop across an impedance means in series therewith.
  • this voltage drop is utilized to actuate a switch and close a low impedance circuit between the flame switch input'circuit and ground.
  • This low impedance circuit to ground clamps the flame switch input and prevents it from responding to signal energy in the manner required to indicate flame presence.
  • the flame switch having its input circuit clamped to ground potential, effects an output response indicative of flame absence, thus insuring that only an AC signal as generated by a flame, will be able to effect the flame present re sponse of the flame switch.
  • FIG. 1 there is shown a functional block diagram of the ionic flame monitor of the invention.
  • a flame issues from some type of burner, for instance ignitor 12.
  • An electrode such as flame rod 14 is spaced from ignitor l2 and positioned such that it is contacted by the flame 10 in a zone occupied by the As earlier described, the ion packets within a flame 10 create potential variations between electrodes 12 and 14 giving rise to an AC current therebetween. The amplitude of this current is enhanced by the DC potential impressed across the flame 10 between electrodes 12 and 14 and a flame signal may be derived from the AC voltage fluctuations appearing across resistor 22 due to the flame generated AC current in the circuit including resistor 22 and the electrodes.
  • the AC flame signal developed across resistor 22 is connected to flame signal processing means 24 through conductor 26.
  • Conductor 26 is connected at one end to conductor 20 intermediate resistor 22 and flame rod 14 and is connected at its other end to the input of signal processing means 24.
  • the signal energy appearing at conductor 26 will comprise, when flame 10 is present, an AC signal as generated by the flame, superimposed on a DC potential provided by supply 16.
  • Signal processing means 24 include coupling means 28 and flame switch means 30.
  • the input circuit of signal processing means 24 is also the input to coupling means 28.
  • Coupling means 28 typically serves to separate the flame when a normal flame condition exists. Ignitor l2 AC component of the signal from the DC component and to pass to the output thereof signal energy having a magnitude determined by the AC frequency of the signal applied at the input thereto. This signal energy appearing at the output of coupling means 28 is connected to the input circuit of flame switch means 30 by conductor means 32.
  • Flame switch means 30 comprise circuit means responsive to the magnitude of the signal energy connected thereto by conductor means 32 to provide a first output response when the signal energy magnitude is equal to or greater than a certain value and to provide a second output response when the signal energy magnitude is below said certain value.
  • the response of flame switch means 30 may be electrical or electromagnetic in nature and typically serves to place utilization means 34 in one of two states.
  • Utilization means 34 typically includes a two state load device 36 such as a lamp, a fuel control valve or the like, a power supply 38 and connecting circuit means including switch contacts 40.
  • the circuit means serve to apply power to said load device 36 when switch contacts 40 are closed and the power is interrupted when contacts 40 are open.
  • the output response of flame switch 30 and accordingly of signal processor 24 is here represented by broken line 42 in FIG. 1 and may be indicative of an electromagnetic field created by flame switch means 30 and operative to open or close contacts 40 associated with load device 36. It is desirable to recognize only certain AC signal frequencies as being indicative of the existance or presence of flame 10. Therefore, the coupling means 28 have frequency discriminating characteristics which strongly attenuate signals having frequencies below those characteristically present in a flame signal and passing, with only slight attenuation, signals having frequencies in the range characteristic to a flame generated AC voltage. Thus, the signal energy magnitude at the output of coupling means 28, for an input signal of the same magnitude, will be greater when the input signal is in the flame frequency range than when it is below this frequency range.
  • the larger output signal magnitude from coupling means 28 is utilized to effect said first output response from flame switch means 30 and, when the magnitude of the output signal is below a certain value, then said second output response from switch means 30 is effected.
  • said first output response from flame switch means 30 and accordingly flame signal processor 24 is commensurate with flame presence and said second output response is commensurate with flame absence.
  • an AC signal of fairly uniform magnitude will appear at the input to coupling means 28 resulting in an output signal therefrom of fairly uniform magnitude.
  • the sensitivity of the input circuit to flame switch means 30 may be initially adjusted to effect that output response indicative of flame presence for input signals of this magnitude and greater and to effect that output response indicative of flame absence when the input signal magnitude is below this value.
  • the nature of coupling means 28 are often such that when the voltage amplitude of the input signal thereto is increased the magnitude of the signal output therefrom is also increased regardless of frequencies.
  • an AC signal appearing on conductor 26 and having a voltage significantly above that of a normal flame signal may provide a signal of large enough magnitude at the output of coupling means 28 to effect the flame present response from switch means 30 even though it is at a lower frequency thanan actual flame signal.
  • This con dition might arise through a short of the AC line supply across electrodes 12 and 14 or it may also occur as the result of high voltage arcing or discharges occurring in close proximity to the electrodes and associated circuitry. If a flame 10 is not present when these signals occur, an output response from switch means 30 commensurate with flame presence could have dangerous consequences particularly if load device 36 is a fuel control valve.
  • circuit means are provided to prevent the flame present" response whenever the AC voltage appearing across electrodes 12 and 14 exceeds a particular value.
  • the particular value chosen is such that it is slightly greater than substantially any AC voltage which would be generated by flame 10.
  • clamping means 44 are operatively connected across electrodes 12 and 14 to sense the amplitude of AC voltage appearing thereacross and responds in a manner which clamps the input circuit to flame switch 30 whenever the AC voltage appearing across electrodes 12 and 14 exceeds the particular value.
  • the input circuit to flame switch 30 is clamped. by connecting it through a low impedance circuit to ground potential thus preventing the output response commensurate with flames presence and rather providing that response commensurate with flame absence.
  • Clamping means 44 include voltage level detection means 46 and a clamping switch 48.
  • Clamping switch 48 includes means for responding to a switching voltage to open or to close a circuit between ground potential and the input circuit'to flame switch 30.
  • Voltage level detection means 46 are connected across electrodes l2 and 14 to sense the AC voltage appearing thereacross and to provide said switching voltage to close clamp switch 48 when the AC voltage sensed is greater than said particular value referred to above.
  • ignitor 12 is electrically connected to ground and is the source for a flame 10.
  • Flame rod 14 is spaced from ignitor 12 and is positioned to be in contact with flame 10 under normal flame conditions.
  • a transformer 50 having its primary connected to a source of 60 Hz 120V line current is used to provide the necessary power to the flame monitor.
  • a secondary coil 52 is center tapped to ground and diodes 54 and 56 connected to opposite ends thereof in parallel provide a full wave rectified DC voltage at the junction 58.
  • Resistor 60 and capacitor 62 are connected in series between junction 58 and ground and serve to limit and filter the voltage appearing at junction 58.
  • a second resistor 64 is connected in parallel with capacitor 62 to ground and acts as a bleeder to discharge the capacitor when AC power to the circuit is removed.
  • a resistor 22 is connected at one end to the junction between resistor 60 and capacitor 62 to receive a filtered DC voltage of several hundred volts, in this instance 500V DC.
  • resistor 22 is connected to conductor 20 which is in turn connected to flame rod 14, thus impressing a DC potential of some 500V across electrodes l2 and 14.
  • Resistor 22 typically has a value of K ohms and is utilized to develop the flame signal.
  • This current through resistor 22 provides a voltage drop thereacross which results in an AC flame signal voltage appearing at conductor 20 between resistor 22 and flame rod 14.
  • This AC flame signal is connected to the input of flame processing means 24 by conductor means 26.
  • coupling means 28 is comprised of a transformer 66 and capacitors 68 and 70 connected to form a combination double tuned circuit and impedance matcher.
  • the input circuit of coupling means 28 includes the primary of transformer 66 connected in series with capacitor 68 and connected across electrodes 12 and 14 through conductor 26.
  • the output circuit of coupling means 28 includes the secondary of transformer 66 in series with capacitor 70.
  • One side of both the primary and secondary of transformer 66 is connected to ground.
  • the turns ratio of transformer 66 primary to secondary is typically ten to one.
  • Capacitor 68 is connected to conductor 26 to receive the AC signals appearing across the electrodes.
  • transformer 66 is a TA-47 manufactured by Stancor and capacitors 68 and 70 respectively have values of 0.01 pf and 0.33 [.Lf.
  • the tuned impedance matching circuit of coupling means 28 serves to couple the high impedance flame rod circuit to the low impedance input of the circuitry coupled thereafter with maximum signal development and also strongly attenuates signals below about 200 Hz to eliminate 60 and Hz AC pickup. Because of the high input and low output impedance characteristics of coupling means 28, the circuit across flame electrodes 12 and 14 is not heavily loaded, thus permitting the development of a strong flame signal at the input, and subsequently at the output, of the coupling means. The signal energy at the input to coupling means 28 appears as a high voltage, low current whereas the energy at the output is of higher current and lower voltage.
  • the filtering or energy transfer characteristics of coupling means 28 are seen graphically in FIG. 3 wherein the ratio of energy-out to energy-in, measured along the vertical axis, is plotted against frequency measured along the horizontal axis. It will be noted that the output signal energy from coupling means 28 relative to the signal input energy thereto is only slightly attenuated for signal frequencies above 200 Hz, but that for frequencies below 200 Hz and particularly below 150 Hz the attenuation is great. It must, however, be noted that at a particular frequency the output energy is a particular function of the input energy as determined bythe filter characteristics, and an increased input signal will result in an increased output signal even though at that frequency the output signal may be greatly attenuated relative to the input.
  • the AC signal generated by flame 10 is rich in frequencies of 200 Hz and above and coupling means 28 have been tuned to pass this frequency range and attenuate lower frequency signals.
  • an AC signal-voltage of some 60V will be developed across the input to coupling means 28 and will result in an output voltage of about 1V.
  • a non-flame generated high voltage AC signal appears across the electrodes, it may also be coupled to the output circuitry through coupling means 28. This will be particularly true if its frequency is in the filter pass range, but a signal of substantial magnitude may also appear at the output of the coupling means for input signals having frequencies in the 60 to 120 Hz range if the input voltage is sufficiently large.
  • flame switch means 30 are connected to a low voltage (26V) source of AC voltage provided by secondary 70 of transformer 50.
  • Flame switch means 30 include a load relay coil 72 in series with gate means, such as silicon control-rectifier (SCR) 74, across the AC voltage of transformer secondary 70.
  • SCR silicon control-rectifier
  • Relay 72 operates to electromagnetically actuate the contacts 40 in utilization circuit 34 described above. Contacts 40 are open when relay 72 is not energized and are electromagnetically closed when the relay is energized.
  • Relay 72 is energized by current conduction therethrough when SCR 74 is in its triggered conductive state.
  • SCR 74 includes a cathode 73 connected to ground
  • a trigger circuit comprising the SCR trigger electrode 76 and cathode 73, is
  • a signal in this instance a triggering voltage, applied thereto to initiate conduction by the SCR only when the signal is above a certain magnitude.
  • SCR 74 will cease to conduct after each cycle unless the enabling trigger signal is maintained at trigger electrode 76.
  • a capacitor 78, connected in parallel with relay coil 72, and a resistor 80, connected in series with said coil 72 and SCR 74 serve to delay the initial energization of the relay coil 72 by 0.25 second following triggering of the SCR. Further, capacitor 78 maintains the relay coil 72 energized for a short period, 1.5 2 seconds, following termination of conduction by and through SCR 74.
  • the trigger signal applied to trigger electrode 76 is a function of the signal output from coupling means 28.
  • This trigger signal is developed across a resistor, such as potentiometer 82, connected in the trigger circuit between trigger electrode 76 and ground.
  • a resistor such as potentiometer 82
  • the magnitude of the signal energy appearing at the output of coupling means 28 may be sufficient to use as the trigger signal applied to potentiometer 82 to provide the trigger signal.
  • an amplifier 84 be interposed between the output coupling means 28 and the Y the output circuit of coupling means 28, or part of the input circuit to flame switch 30, or more generally, as merely a signal conductor between the two.
  • a DC power source for amplifier 84 is provided by means of rectifying diode 86 and fllter capacitor 88 operatively connected across the secondary of transformer 50.
  • a 40V DC potential appears at the junction 90 between capacitor 88 and the cathode of diode 86.
  • This DC potential is connected to amplifier 84.
  • the output of amplifier 84 is an AC voltage, the magnitude of which is proportional to the magnitude of the input signal thereto.
  • This amplifier output signal is applied to the wiper arm of potentiometer 82.
  • the AC signal energy passed by coupling means 28 is scaled such that it will provide a triggering voltage to the trigger electrode of SCR 74 when it is above a certain selected magnitude and will be below the triggering potential when it is below the certain magnitude.
  • the threshold magnitude at and above which the signal output from coupling means 28 is intended to trigger SCR 74 into conduction is established as that which occurs for a normal flame signal voltage of about 45-60 peak volts AC across electrodes 12 and 14 and being predominantly above about Hz in frequency. If it is desired that a flame signal of lesser magnitude be capable of triggering SCR 74, the sensitivity may be readily adjusted by varying the setting of potentiometer 82. Potentiometer 82 typically has a resistance value of 0-1 K ohm.
  • coupling means 28 does not attenuate all input signals to the same energy levels for a particular frequency, but rather attenuates them by some amount relative to input amplitude.
  • input signals from sources other than a flame and having AC voltages greater than 60-80V, whether in the normal flame frequency range or below it, may be passed by the coupling means at a sufficient magnitude to effect triggering of SCR 74, which energizes relay 72 causing a response commensurate with flame presence when in fact a flame may not be present.
  • clamping means 44 are provided.
  • the term high voltage is meant to refer to AC voltages greater than those occurring in a normal AC flame signal.
  • Clamping means 44 include a switch 48, responsive to a signal provided by AC voltage level detection means 46, to close a low-impedance circuit to ground across the input or trigger circuit of SCR 74 and accordingly, flame switch means 30. This low impedance circuit itconducts.
  • Voltage level detection means 46 comprise a circuit connected across electrodes 12 and 14 including, in series, DC isolation means such as capacitor 90, voltage threshold break-down means such as neon lamp 92 and Zener diode 94, and impedance means, such as resistor 98, across which a switching voltage may be developed.
  • DC isolation means such as capacitor 90
  • voltage threshold break-down means such as neon lamp 92 and Zener diode 94
  • impedance means such as resistor 98
  • One terminal of capacitor 90 is connected to conductor 20 and the other is connected to the voltage threshold break-down means.
  • Resistor 98 is connected between the voltage threshold break-down means and ground.
  • Capacitor 90 will be charged to the DC potential applied across the electrodes 12 and 14 and thus serves to isolate or prevent that DC potential from appearing across the voltage threshold break-down means. With the DC potential thus isolated, the only potential appearing across Zener diode 94 and neon lamp 92 is the AC voltage appearing between electrodes 12 and 14; This AC potential is passed" by capacitor 90.
  • the voltage threshold break-down means are selected to break down and conduct when a potential difference greater than about 70 or 80 volts is impressed across them. This potential is slightly above the 45-60 peak AC voltageappearing between electrodes 12 and l4of the aforedescribed flame monitor due to the pres ence of flame
  • neon lamp 92' hasfa break-down potential of about 60V
  • Zener diode 94 has a break-down voltage of about V.
  • Zener diode 94 might be replaced with a Diac.
  • the Zener diode 94 is poled to conduct freely when electrode l4 is negative relative to ground and to break down and conduct at and above about 15V when the electrode is positive relative to ground. The fact that Zener 94 conducts at a much lower voltage'than 15V for'the former (or negative) polarity does not interfere withproper operation of the clamping switch 48, as will become evident hereinafter.
  • the combination of neon lamp 92 and Zener diode 94 might be replaced with a single Zener diode 95, as seen in FIG.'4, having a break-down voltage of 70 to 80V.
  • the neon lamp 92 serves to visually indicate the presence of the excessive AC voltage across the electrodes when lamp may signal this condition to an When the Zener diode and neon-lamp conduct, the current through resistor 98 creates a voltage drop thereacross'. This voltage will be that instantaneous voltage appearing across electrodes 12 and 14 minus :the voltage drop of about 70V across the Zener diode and neon lamp.
  • Resistor 98 has a resistance of 47 K ohml I
  • the voltage developedacross resistor 98 is utilized as a switching voltage for the clamping switch 48.
  • the clamping, switch includes a transistor 99 having its emitter 100 connected to ground and its collector 102 connected to the input circuit of flame switch means 30. More particularly, collector 102 is electrically connected by conductor 104 to the trigger electrode 76 of SCR 74. Transistor 99 will be switched on,'or conduct, when the voltage at base 106 is a positive 0.6V.
  • the switching voltage developed across resistor 98 is connected to the base 106 of transistor 99 through diode 108 and current limiting resistor 110. The.
  • anode of diode 108 is connected to the junction of resistor 98 and the voltage threshold break-down means, with its prevents discharging of capacitor 112 by the opposite (or negative) polarity of the AC voltage across electrodes l2 and 14, and further, applies to base 106 only that polarity of voltage capable of biasing the transistor 99 into conduction.
  • Zener diode 94 of FIG. 2 or Zener diode 95 of FIG. 4 poled as described above and diode 108 connected as described hereinbefore Zener 94 or Zener 95 will be connected to permit a positive voltage on the anode of diode 108 only when the AC potential applied to the opposite electrodes of the Zener exceeds its break-down voltage. Though the Zener may conduct in the opposite direction at much lower voltages, diode 108 will then be reverse biased and will not conduct.
  • transistor 99 In operation, if an AC signal having a voltage greater than about 70 peak volts appear across electrodes 12 and 14, it will cause breakdown and conduction by the voltage level detection means 44 and will switch transistor 99 into conduction. When transistor 99 conducts, it serves to provide a low impedance path from SCR trigger electrode 76, through conductor 104, collector 102, and emitter 100 to ground. This low impedance circuit clamps the trigger electrode 76 to ground and prevents any signal passed by coupling means 28, regardless of magnitude, from triggering SCR 75 and providing a possibly false indication of flame presence.
  • the flame switch means 30 are thus prevented from indicating flame presence so long as the high AC voltage is present across electrodes 12 and 14. When the over-voltage condition ceases or is corrected, the flame switch means will resume operation in its normal manner.
  • An SCR might be substituted for transistor 99 if it is desired to permanently clamp the input circuit to flame switch means 30 when an excessive AC voltage is first detected, and would not release the clamp until some operator action was taken.
  • a pair of electrode means spaced from oneanother and disposed within said flame zone to be in contact with said flamewhen present; circuit means operatively-connected tosaid electrode means for applying a direct current potential between said'electrode means to develop a flame generated AC signal additionally appearing between'said electrode means when a flame is present; coupling means having an input and an output and adapted for passing to said output thereof AC signal energy characteristic of AC signal energy applied to said input thereof; means electrically connecting said electrode means with said coupling means input for applying AC signal energy thereto; flame switch circuit means having an input circuit operatively connected to the output of said coupling means and responsive to signal energy appearing thereat for providing an output response commensurate with flame presence when the magnitude of said signal energy is at least as great as a certain value and providing an output response commensurate with flame absence when the magnitude of said energy is less than said certain value; and clamping means op er
  • clamping means include AC voltage level detection means connected across said electrode means for developing a switching voltage when AC voltage exceeding said predetermined level appears across said electrode means; and switch means responsive to the presence of said switching voltage for clamping the input circuit of said flame switch'circuit means to a maximum electrical energy level less than that required to provide said response commensurate with flame presence, whereby the output response of said flame switch circuit means is commensurate with flame absence.
  • said flame generated AC signal applied to the input of said coupling means comprises AC electrical energy above a certain frequency and having an AC voltage substantially en tirely within a range less than said predetermined level and said coupling means include filter means operatively connected between the input and output of said coupling means for attenuating the input signal of said coupling means to an output magnitude less than that required to provide said response commensurate with flame presence when said coupling means input signal is less than said certain frequency and said predetermined level of AC voltage and for passing the input signal of said coupling means to the output thereof at a magnitude at least as great as said certain value required to provide said response commensurate with flame presence when said AC flame signal is present and the AC voltage at said input is below said predetermined level and when said AC voltage present at said means for conducting only when a potential thereacross exceeds said predetermined level of AC voltage; means for isolating said threshold discharge means from said DC potential established between said pair of electrode means; and impedance means for developing thereacross said switching voltage when said threshold discharge means conduct
  • said switch means for clamping said input circuit of said flame switch circuit means comprise an electronic switch having first, second, and third electrodes, said first electrode being operatively connected to said impedance means across which is developed said switching voltage and acting to close a circuit between said second and third electrodes when said switching voltage is applied thereto and said second and third electrodes respectively being connected to ground potential and to the input circuit of said flame switch circuit means.
  • said flame switch circuit means include a load relay for providing a response commensurate with flame presence when energized and triggerable gating means for gating energizing power to said load relay when triggered by a trigger signal
  • said gating means comprise a silicon controlled relay having an anode, cathode, and a trigger electrode and wherein energizing power is passed by circuit means from a power source to said relay by a current path through said anode and cathode in a triggered conductive state, said trigger signal being provided by that signal energy connected to the input circuit of said flame switch circuit means and being above said predetermined level.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Control Of Combustion (AREA)
  • Regulation And Control Of Combustion (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
US00214129A 1971-12-30 1971-12-30 Ionic flame monitor Expired - Lifetime US3740574A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US21412971A 1971-12-30 1971-12-30

Publications (1)

Publication Number Publication Date
US3740574A true US3740574A (en) 1973-06-19

Family

ID=22797899

Family Applications (1)

Application Number Title Priority Date Filing Date
US00214129A Expired - Lifetime US3740574A (en) 1971-12-30 1971-12-30 Ionic flame monitor

Country Status (6)

Country Link
US (1) US3740574A (forum.php)
JP (1) JPS5411537B2 (forum.php)
AU (1) AU468481B2 (forum.php)
CA (1) CA984931A (forum.php)
GB (1) GB1418042A (forum.php)
YU (2) YU34935B (forum.php)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3836857A (en) * 1972-05-12 1974-09-17 Hitachi Ltd Flame detector
US4039844A (en) * 1975-03-20 1977-08-02 Electronics Corporation Of America Flame monitoring system
US4177033A (en) * 1976-11-25 1979-12-04 Plessey Handel Und Investments Ag Flame detection arrangements and the like
FR2463361A1 (fr) * 1979-08-13 1981-02-20 Cem Comp Electro Mec Procede et dispositif de controle de la presence d'un arc dans un bruleur
US4404616A (en) * 1980-04-16 1983-09-13 Hitachi, Ltd. Igniting and flame detecting device
US6356199B1 (en) * 2000-10-31 2002-03-12 Abb Inc. Diagnostic ionic flame monitor
US20060199122A1 (en) * 2005-02-24 2006-09-07 Alstom Technology Ltd Self diagonostic flame ignitor
US20110070550A1 (en) * 2010-09-16 2011-03-24 Arensmeier Jeffrey N Control for monitoring flame integrity in a heating appliance
US20160116170A1 (en) * 2014-10-22 2016-04-28 Grand Mate Co., Ltd. Ignition controlling device of gas appliance
CN112648646A (zh) * 2020-12-10 2021-04-13 广州市红日燃具有限公司 集成灶离子感应式防火墙预警装置及预警方法

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2141854A (en) * 1983-05-31 1985-01-03 Shigeru Fukumoto Gas accident prevention
CA1335829C (en) * 1985-09-02 1995-06-06 Kenneth Garry Kemlo Flame detection
AU633015B2 (en) * 1989-09-13 1993-01-21 Onesteel Manufacturing Pty Limited Improved flame detection

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2766440A (en) * 1951-12-10 1956-10-09 Phillips Petroleum Co Flame detector
US3437884A (en) * 1966-11-21 1969-04-08 Protection Controls Inc Flame monitoring circuit

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2766440A (en) * 1951-12-10 1956-10-09 Phillips Petroleum Co Flame detector
US3437884A (en) * 1966-11-21 1969-04-08 Protection Controls Inc Flame monitoring circuit

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3836857A (en) * 1972-05-12 1974-09-17 Hitachi Ltd Flame detector
US4039844A (en) * 1975-03-20 1977-08-02 Electronics Corporation Of America Flame monitoring system
US4177033A (en) * 1976-11-25 1979-12-04 Plessey Handel Und Investments Ag Flame detection arrangements and the like
FR2463361A1 (fr) * 1979-08-13 1981-02-20 Cem Comp Electro Mec Procede et dispositif de controle de la presence d'un arc dans un bruleur
US4404616A (en) * 1980-04-16 1983-09-13 Hitachi, Ltd. Igniting and flame detecting device
US6356199B1 (en) * 2000-10-31 2002-03-12 Abb Inc. Diagnostic ionic flame monitor
US20060199122A1 (en) * 2005-02-24 2006-09-07 Alstom Technology Ltd Self diagonostic flame ignitor
US7492269B2 (en) * 2005-02-24 2009-02-17 Alstom Technology Ltd Self diagonostic flame ignitor
US20110070550A1 (en) * 2010-09-16 2011-03-24 Arensmeier Jeffrey N Control for monitoring flame integrity in a heating appliance
US9366433B2 (en) 2010-09-16 2016-06-14 Emerson Electric Co. Control for monitoring flame integrity in a heating appliance
US20160116170A1 (en) * 2014-10-22 2016-04-28 Grand Mate Co., Ltd. Ignition controlling device of gas appliance
US10151492B2 (en) * 2014-10-22 2018-12-11 Grand Mate Co., Ltd. Ignition controlling device of gas appliance
CN112648646A (zh) * 2020-12-10 2021-04-13 广州市红日燃具有限公司 集成灶离子感应式防火墙预警装置及预警方法

Also Published As

Publication number Publication date
JPS4873829A (forum.php) 1973-10-05
GB1418042A (en) 1975-12-17
YU34935B (en) 1980-04-30
AU468481B2 (en) 1974-07-04
YU236372A (en) 1979-10-31
JPS5411537B2 (forum.php) 1979-05-16
CA984931A (en) 1976-03-02
AU5051972A (en) 1974-07-04

Similar Documents

Publication Publication Date Title
US3740574A (en) Ionic flame monitor
US3995200A (en) Ground monitor and circuit breaker actuating device
US3728706A (en) System for indicating aerosols in the atmosphere
GB1284427A (en) Ignition and flame detection apparatus
US3377125A (en) Electrical ignition system for gaseous fuel burners and the like
US2798213A (en) Checking technique and system
US3348104A (en) Bias-controlled a. c.-operable voltage threshold circuit, and systems employing same
US4404616A (en) Igniting and flame detecting device
US4020479A (en) Fire detector
JPH0338530B2 (forum.php)
US4023073A (en) Open circuit detector
US2721276A (en) Condition sensing apparatus
US5179490A (en) Ground-safety controller
CA1156326A (en) Fuel supply and ignition control system employing flame sensing via spark electrodes
US2852702A (en) Condition responsive apparatus
US3947218A (en) Safety circuit for monitoring a flickering flame
US3445172A (en) Fail-safe system
US2579884A (en) Flame failure safeguard
US2207577A (en) Electric protective system
US4427363A (en) Flame rectification detectors
US2825012A (en) Flame detector
US2799781A (en) Explosion detection and suppression
EP0050953B1 (en) Flame detection circuit
US3755799A (en) Ultraviolet flame detector
US3671815A (en) Flame detection apparatus