EP1390668B1 - Flame-monitoring device - Google Patents
Flame-monitoring device Download PDFInfo
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- EP1390668B1 EP1390668B1 EP02727938A EP02727938A EP1390668B1 EP 1390668 B1 EP1390668 B1 EP 1390668B1 EP 02727938 A EP02727938 A EP 02727938A EP 02727938 A EP02727938 A EP 02727938A EP 1390668 B1 EP1390668 B1 EP 1390668B1
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- European Patent Office
- Prior art keywords
- flame
- voltage
- monitoring device
- limiter
- diodes
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- 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.)
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- 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
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- 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
- F23N5/08—Systems for controlling combustion using devices responsive to thermal changes or to thermal expansion of a medium using light-sensitive elements
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23N—REGULATING OR CONTROLLING COMBUSTION
- F23N5/00—Systems for controlling combustion
- F23N5/26—Details
Definitions
- the present invention relates to a flame monitoring device according to the preamble of claim 1.
- a flame monitoring device in which an AC voltage is supplied to a transformer and subsequently to a peak voltage limiter.
- the peak voltage limiter prevents the transfer of voltage spikes from the mains to the working circuit.
- VDR Voltage-Dependent-Resistor
- a problem of such flame monitoring devices are non-flame rectifying effects on the burner, for example in the case of ionization electrodes due to chemical effects between the monitoring electrode and the reference ground.
- the document US-A-5,899,683 discloses a flame monitoring device in which an input AC voltage is limited by a voltage limiter to a balanced AC voltage, wherein the AC voltage applied to a flame sensor, which operates with the rectifying effect of a flame and flows through the existing flame, a current.
- the present invention has for its object to make flame monitoring devices of the type mentioned insensitive by appropriate measures against non-flame rectifier effects.
- the essence of the invention is thus that the voltage limiter generates an asymmetric limit voltage which acts on the sensor.
- Zener diodes If semiconductor components such as zener diodes are used to generate an asymmetrical voltage, component faults of the zener diode can also be controlled by the higher number of zener diodes in one direction. If a zener diode fails, enough diodes will still be available for safe operation of the voltage limiter. The more additional zener diodes are arranged to produce the asymmetry, the higher the errors can be compensated.
- the solution with Zener diodes shows in comparison to varistors (for small series resistances) no voltage dependence and it can also be temperature compensated by using Zener diodes with different temperature coefficients.
- the Zener diode solution enables AC stabilization with standard components available from several manufacturers.
- the realization of the AC voltage limitation by means of diodes, for example in the form of a diode path also has the advantage that a voltage switch, for example, it may be necessary that the limited AC voltage of an automatic burner must be switched within a switching sequence between two voltage values, in a simple manner by bridging can be done by some diodes of the diode path.
- the desired voltage swing is freely selectable via the selection of diodes.
- VDR voltage-dependent resistors
- Fig. 1 there is schematically illustrated a flame monitoring device which is e.g. is fed via the AC mains voltage 1 and via a transformer 2 with an input voltage U1.
- the behavior of the input voltage U1 is shown schematically in FIG. 4A.
- the input voltage U1 is limited to the limit voltage U2, see Fig. 4B.
- a flame 6 By a burner 5, a flame 6 can be generated.
- An ionization electrode 7 projects into the flame region of the flame 6.
- the alternating voltage U2 is applied to the burners 5 acting as electrodes and the ionization electrode 7.
- By the flame 6 and the applied AC voltage U2 results in a rectified ionisationsstrom.
- the AC voltage is filtered out and only the uniform portion which is used as a flame signal is forwarded to an amplifier 10, in which the flame signal is amplified and forwarded to a control device, not shown, for further processing.
- a UV sensor or any sensor which works on the rectification effect of the flame amplifier signal can also be used. These probes also exhibit unwanted rectifying effects, e.g. at mains voltages with DC offset or certain defects of the sensor.
- Such sensors, as well as the ionization electrode shown in FIG. 1, can be described by the equivalent circuits of FIGS. 2A and 2B to explain the behavior.
- FIG. 2A shows the burner with flame and ionization electrode illustrated in FIG. 1 between points A and B as an equivalent circuit for ideal behavior with a diode 21 and a resistor 20 in series.
- the diode produces the same rectifying effect as the flame.
- FIG. 2B shows the torch with flame and ionization electrode illustrated in FIG. 1 between points A and B as an equivalent circuit for the real behavior with a diode 21 and a resistor 20 in series, to which a resistor 22 is connected in parallel.
- current flows not only in the forward direction of the diode 21, but also in the reverse direction of the diode.
- FIG. 2C shows the burner with flame and ionization electrode illustrated in FIG. 1 between points A and B as an equivalent circuit for the contaminated electrode with a diode 21 and a resistor 20 in series, to which a resistor 22 is connected in parallel and a diode 23 and a resistor 24 is connected in series in parallel.
- FIG. 3 shows a voltage limiter according to the invention for generating an asymmetrical voltage consisting of diodes 31 which conduct from a certain voltage to also in the blocking direction, eg so-called zener diodes, additional zener diodes 32 being arranged in one direction such that the voltage in the forward direction of the diode 21 is increased relative to the voltage in the reverse direction. This means that a higher current flows when the flame is present.
- the installation direction of the voltage limiter results from the points C and D, which correspond to the points C and D in FIG.
- the number of Zener diodes used depends on the application and must be designed specifically for each case.
- the illustrated series resistors 33 are optional and serve to limit the surge current at transient overvoltages.
- the diode path should preferably be built up only via diodes of the same type and value, ie the same breakdown voltage, in order to simplify the error consideration in the event of a possible short circuit of one (or more) diode. It is also advantageous to use only diodes from the same manufacturer in order to further reduce the irregular error probability.
- a current i is measured. If the circuit for the ideal behavior according to FIG. 2A is incorporated into the circuit according to FIG. 1, the behavior according to FIG. 5A results for i, with a maximum current i5. This can be explained by the diode 21, by which the negative half-wave is cut off in the reverse direction.
- the behavior according to FIG. 5B results with a maximum current in the positive direction of i1 and in the negative direction of i2.
- i1 is greater than i5 (i1> i5), since in addition the resistor 22 is connected in parallel. Through this resistor 22, however, a current can now flow even at the negative half-wave, which has its maximum at i2, but is smaller in magnitude than i.
- FIG. 4C shows a symmetrical voltage U2 *, as known from the prior art, which is measured at the same measuring points C and D as the voltage U2. If the circuit for the real behavior according to FIG. 2B is installed in the circuit according to FIG. 1, as already explained above, the behavior according to FIG. 5C, with a maximum current, results in a symmetrical behavior of the voltage U2 * known from the prior art in the positive direction of i3 and in the negative direction of i4.
Abstract
Description
Die vorliegende Erfindung betrifft eine Flammenüberwachungsvorrichtung nach dem Oberbegriff von Anspruch 1.The present invention relates to a flame monitoring device according to the preamble of
Derartige Verfahren und Vorrichtungen sind für unterschiedliche Zwecke und Anwendungen bereits bekannt. So ist beispielsweise aus der
Ein Problem solcher Flammenüberwachungsvorrichtungen sind jedoch nichtflammenbedingte Gleichrichteffekte am Brenner, z.B. bei Ionisationselektroden durch chemische Einwirkungen zwischen Überwachungselektrode und der Bezugsmasse. Durch diese Gleichrichteffekte kann jedoch im Grenzfall bei nicht vorhandener Flamme ein Flammensignal nachgebildet werden. Dies kann zu Explosionen in der Brennanlage führen, weshalb man versucht die nichtflammenbedingten Gleichrichteffekte durch eine ausreichende Unempfindlichkeit der Flammensignalverstärker zu vermeiden.Such methods and devices are already known for different purposes and applications. For example, from the
However, a problem of such flame monitoring devices are non-flame rectifying effects on the burner, for example in the case of ionization electrodes due to chemical effects between the monitoring electrode and the reference ground. By means of these rectification effects, however, a flame signal can be emulated in the limit case when the flame is not present. This can lead to explosions in the firing system, which is why one tries to avoid the non-flame-induced rectification effects by a sufficient insensitivity of the flame signal amplifier.
Das Dokument
Der vorliegenden Erfindung liegt die Aufgabe zugrunde, Flammenüberwachungsvorrichtungen der eingangs genannten Art durch entsprechende Massnahmen gegen nichtflammenbedingte Gleichrichteffekte unempfindlich zu machen.The present invention has for its object to make flame monitoring devices of the type mentioned insensitive by appropriate measures against non-flame rectifier effects.
Die genannte Aufgabe wird erfindungsgemäss durch die in dem kennzeichnenden Teil des Anspruchs 1 angegebenen Merkmale gelöst.The above object is achieved according to the invention by the features stated in the characterizing part of
Kern der Erfindung ist es somit, dass der Spannungsbegrenzer eine asymmetrische Grenzspannung erzeugt, welche den Fühler beaufschlagt.The essence of the invention is thus that the voltage limiter generates an asymmetric limit voltage which acts on the sensor.
Durch die Erzeugung einer asymmetrischen Spannung können die negativen Auswirkungen von nicht flammenbedingter Gleichrichteffekte mit hohem Wechselstromanteil, wie sie z.B. durch Ablagerungen von Reinigungsmitteln oder Testsprays zwischen der Ionisationselektrode und der Bezugsmasse und z.B. Netzspannungen mit einem unerwünschten Gleichspannungsoffset entstehen können, besser unterdrückt werden. Dadurch können ungewollte Flammensignale bei nicht vorhandener Flamme vermieden werden.By generating an asymmetric voltage, the negative effects of high incidence non-flame ripple effects, as e.g. by deposits of detergents or test sprays between the ionization electrode and the reference mass and e.g. Mains voltages can arise with an undesirable DC offset, are better suppressed. As a result, unwanted flame signals can be avoided in the absence of flame.
Weitere vorteilhafte Ausgestaltungen der Erfindung ergeben sich aus den abhängigen Ansprüchen.Further advantageous embodiments of the invention will become apparent from the dependent claims.
Werden zur Erzeugung einer asymmetrischen Spannung Halbleiterbauelemente wie Zenerdioden verwendet, können durch die höhere Anzahl von Zenerdioden in eine Richtung auch Bauteilfehler der Zenerdiode beherrscht werden. Wenn eine Zenerdiode ausfällt, sind noch genügende Dioden für einen sicheren Betrieb des Spannungsbegrenzers vorhanden. Je mehr zusätzliche Zenerdioden zur Erzeugung der Asymmetrie angeordnet werden, desto höhere Fehler können ausgeglichen werden.
Die Lösung mit Zenerdioden zeigt im Vergleich zu Varistoren (bei kleinen Serienwiderständen) keine Spannungsabhängigkeit und es kann durch Einsatz von Zenerdioden mit unterschiedlichen Temperaturkoeffizienten auch temperaturkompensiert werden.If semiconductor components such as zener diodes are used to generate an asymmetrical voltage, component faults of the zener diode can also be controlled by the higher number of zener diodes in one direction. If a zener diode fails, enough diodes will still be available for safe operation of the voltage limiter. The more additional zener diodes are arranged to produce the asymmetry, the higher the errors can be compensated.
The solution with Zener diodes shows in comparison to varistors (for small series resistances) no voltage dependence and it can also be temperature compensated by using Zener diodes with different temperature coefficients.
Soll die (ungewollte) Eigenschaft der Spannungsabhängigkeit von Varistoren nachgebildet werden, kann dies durch hochohmigere Serienwiderstände in der Zenerdiodenreihe nachgebildet werden.If the (unwanted) property of the voltage dependence of varistors is to be simulated, this can be simulated by higher-resistance series resistances in the Zener diode series.
Die Lösung mit Zenerdioden ermöglicht die Wechselspannungsstabilisierung mit Standardbauelementen, welche über mehrere Hersteller beziehbar sind.
Die Realisierung der Wechselspannungsbegrenzung mittels von Dioden, z.B. in Form einer Diodenstrecke hat auch den Vorteil, dass eine Spannungsumschaltung, beispielsweise kann es erforderlich sein, dass die begrenzte Wechselspannung eines Feuerungsautomaten innerhalb einer Schaltfolge zwischen zwei Spannungswerten umgeschaltet werden muss, in einfacher Weise durch eine Überbrückung von einigen Dioden der Diodenstrecke erfolgen kann. Der gewünschte Spannungshub ist dabei über die Auswahl der Dioden frei wählbar.
Bei herkömmlichen spannungsabhängigen Widerständen (VDR) zur Spannungsbegrenzung wären zur Spannungsumschaltung beispielsweise zwei Varistoren und ein Schalter oder ein Varistor, eine Spannungsquelle und ein Schalter dafür erforderlich.The Zener diode solution enables AC stabilization with standard components available from several manufacturers.
The realization of the AC voltage limitation by means of diodes, for example in the form of a diode path also has the advantage that a voltage switch, for example, it may be necessary that the limited AC voltage of an automatic burner must be switched within a switching sequence between two voltage values, in a simple manner by bridging can be done by some diodes of the diode path. The desired voltage swing is freely selectable via the selection of diodes.
In conventional voltage-dependent resistors (VDR) for limiting the voltage, for example, two varistors and a switch or a varistor, a voltage source and a switch would be required for voltage switching.
Weitere Vorteile ergeben sich aus den bevorzugten Ausführungsbeispielen der erfindungsgemässen Vorrichtung bzw. des erfindungsgemässen Verfahrens, die anhand der nachfolgenden Zeichnungen näher erläutert werden.Further advantages will become apparent from the preferred embodiments of the inventive device and the inventive method, which are explained in more detail with reference to the following drawings.
Dabei zeigen:
- Fig. 1 zeigt schematisch eine Flammenüberwachungsvorrichtung;
- Fig. 2A zeigt eine Ersatzschaltung für eine ideale Flamme;
- Fig. 2B zeigt eine Ersatzschaltung für eine reale Flamme;
- Fig. 2C zeigt eine Ersatzschaltung für eine verunreinigte Elektrode;
- Fig. 3 zeigt einen asymmetrischen Wechselspannungsbegrenzer;
- Fig. 4A zeigt die Wechselspannung bei U1;
- Fig. 4B zeigt die asymmetrische Wechselspannung bei U2;
- Fig. 4C zeigt eine symmetrische Wechselspannung U2* aus dem Stand der Technik;
- Fig. 5A zeigt den Verlauf des Stroms i bei idealer Flamme;
- Fig. 5B zeigt den Verlauf des Stroms i bei einer verunreinigten Elektrode und asymmetrischer Wechselspannung;
- Fig. 5C zeigt den Verlauf des Stroms i bei einer verunreinigten Elektrode und symmetrischer Wechselspannung.
- Fig. 1 shows schematically a flame monitoring device;
- Fig. 2A shows an equivalent circuit for an ideal flame;
- Fig. 2B shows an equivalent circuit for a real flame;
- Fig. 2C shows an equivalent circuit for a contaminated electrode;
- Fig. 3 shows an asymmetrical AC limiter;
- Fig. 4A shows the AC voltage at U1;
- Fig. 4B shows the asymmetric AC voltage at U2;
- Fig. 4C shows a symmetrical AC voltage U2 * of the prior art;
- Fig. 5A shows the course of the current i at ideal flame;
- Fig. 5B shows the profile of the current i at a contaminated electrode and asymmetrical AC voltage;
- Fig. 5C shows the course of the current i at a contaminated electrode and symmetrical AC voltage.
In der Fig. 1 ist schematisch eine Flammenüberwachungsvorrichtung dargestellt, welche z.B. über die Netzwechselspannung 1 und über einen Transformator 2 mit einer Eingangsspannung U1 gespiesen wird. Das Verhalten der Eingangsspannung U1 ist in Fig. 4A schematisch dargestellt. Über einen Widerstand 3 und einen Spannungsbegrenzer 4 wird die Eingangsspannung U1 auf die Grenzspannung U2 begrenzt, siehe Fig. 4B.In Fig. 1 there is schematically illustrated a flame monitoring device which is e.g. is fed via the
Durch einen Brenner 5 ist eine Flamme 6 erzeugbar. In den Flammenbereich der Flamme 6 ragt eine Ionisationselektrode 7. Die Wechselspannung U2 wird auf die als Elektroden wirkenden Brenner 5 und die Ionisationselektrode 7 aufgebracht. Durch die Flamme 6 und die aufgebrachte Wechselspannung U2 entsteht ein gleichgerichteter lonisationsstrom.By a
Mittels eines Tiefpasses bestehend aus einem Widerstand 8 und einem Kondensator 9 wird die Wechselspannung ausgefiltert und nur der gleichförmige Anteil welcher als Flammensignal verwendet wird an einen Verstärker 10 weitergeleitet, in dem das Flammensignal verstärkt und an eine nicht dargestellte Regelvorrichtung zur Weiterverarbeitung weitergeleitet wird.By means of a low pass consisting of a
Anstatt der Ionisationselektrode kann auch ein UV-Sensor oder jeglicher Fühler der auf dem Gleichrichteffekt des Flammenverstärkersignals arbeitet, verwendet werden. Auch diese Fühler zeigen unter bestimmten Bedingungen unerwünschte Gleichrichteffekte, z.B. bei Netzspannungen mit Gleichspannungsoffset oder gewissen Defekten der Fühler. Solche Fühler, wie auch die in Fig. 1 dargestellte Ionisationselektrode, können durch die Ersatzschaltungen der Figuren 2A und 2B beschrieben werden um das Verhalten zu erklären.Instead of the ionization electrode, a UV sensor or any sensor which works on the rectification effect of the flame amplifier signal can also be used. These probes also exhibit unwanted rectifying effects, e.g. at mains voltages with DC offset or certain defects of the sensor. Such sensors, as well as the ionization electrode shown in FIG. 1, can be described by the equivalent circuits of FIGS. 2A and 2B to explain the behavior.
Figur 2A zeigt den in der Figur 1 zwischen den Punkten A und B dargestellten Brenner mit Flamme und Ionisationselektrode als Ersatzschaltung für ideales Verhalten mit einer Diode 21 und einem Widerstands 20 in Serie. Durch die Diode wird der gleiche Gleichrichteffekt wie durch die Flamme erzeugt.FIG. 2A shows the burner with flame and ionization electrode illustrated in FIG. 1 between points A and B as an equivalent circuit for ideal behavior with a
Figur 2B zeigt den in der Figur 1 zwischen den Punkten A und B dargestellten Brenner mit Flamme und Ionisationselektrode als Ersatzschaltung für das reale Verhalten mit einer Diode 21 und einem Widerstands 20 in Serie, denen ein Widerstand 22 parallel geschaltet ist. Dadurch fliesst Strom nicht nur in der Durchlassrichtung der Diode 21, sondern auch in der Sperrichtung der Diode.FIG. 2B shows the torch with flame and ionization electrode illustrated in FIG. 1 between points A and B as an equivalent circuit for the real behavior with a
Figur 2C zeigt den in der Figur 1 zwischen den Punkten A und B dargestellten Brenner mit Flamme und Ionisationselektrode als Ersatzschaltung für das reale Verhalten bei verunreinigter Elektrode mit einer Diode 21 und einem Widerstands 20 in Serie, denen ein Widerstand 22 parallel geschaltet und eine Diode 23 und ein Widerstand 24 in Serie parallel geschaltet ist.FIG. 2C shows the burner with flame and ionization electrode illustrated in FIG. 1 between points A and B as an equivalent circuit for the contaminated electrode with a
Figur 3 zeigt einen erfindungsgemässen Spannungsbegrenzer zur Erzeugung einer asymmetrischen Spannung bestehend aus Dioden 31, welche von einer gewissen Spannung an auch in Sperrichtung leiten, z.B. sogenannte Zenerdioden, wobei in eine Richtung zusätzliche Zenerdioden 32 so angeordnet sind, dass die Spannung in Durchlassrichtung der Diode 21 gegenüber der Spannung in Sperrichtung erhöht ist. Dies bedeutet, dass bei vorhandener Flamme ein höher Strom fliesst. Die Einbaurichtung des Spannungsbegrenzers ergibt sich aus den Punkten C und D, welche den Punkten C und D in der Fig. 1 entsprechen. Die Anzahl der verwendeten Zenerdioden ist jeweils vom Anwendungsfall abhängig und muss für jeden Fall spezifisch ausgelegt werden. Vorteilhaft ist jedoch, dass die Asymmetrie über zwei Dioden erfolgt, um auch bei einem anzunehmenden Zweitfehler keine Flammennachbildung zu erhalten.
Z.B. kann eine Diodenstrecke zur asymmetrischen Spannungsbegrenzung auf 342V mittels 15 gleicher Zenerdioden mit je 22V erfolgen (Uz = (15 * 22V) + (17 * 0.7V) = 341.9V) und in der anderen Halbwelle zur Spannungsbegrenzung auf 385V mittels 17 gleicher Zenerdioden mit je 22V erfolgen (Uz = (17 * 22V) + (15 * 0.7V) = 384.5V). Durch die Wahl von 32 Zenerdioden lässt sich die Asymmetrie auf nur 43 V begrenzen. Die dargestellten Serienwiderstände 33 sind optional und dienen zur Stossstrombegrenzung bei transienten Überspannungen.
Die Diodenstrecke sollte vorzugsweise nur über Dioden des gleichen Typs und des gleichen Wertes, d.h. der gleichen Durchbruchspannung, aufgebaut werden, um die Fehlerbetrachtung bei einem eventuellen Kurzschluss einer (oder mehrerer) Diode zu vereinfachen. Vorteilhaft ist es auch, nur Dioden des gleichen Herstellers zu verwenden, um die unregelmässige Fehlerwahrscheinlichkeit weiter zu verringern.FIG. 3 shows a voltage limiter according to the invention for generating an asymmetrical voltage consisting of
For example, a diode path for asymmetrical voltage limiting to 342V by means of 15 identical Zener diodes with 22V each done (Uz = (15 * 22V) + (17 * 0.7V) = 341.9V) and in the other half wave to limit the voltage to 385V by means of 17 identical Zener diodes each 22V (Uz = (17 * 22V) + (15 * 0.7V) = 384.5V). By choosing 32 Zener diodes, the asymmetry can be limited to only 43V. The illustrated
The diode path should preferably be built up only via diodes of the same type and value, ie the same breakdown voltage, in order to simplify the error consideration in the event of a possible short circuit of one (or more) diode. It is also advantageous to use only diodes from the same manufacturer in order to further reduce the irregular error probability.
Über dem Widerstand 8 in Fig. 1 wird ein Strom i gemessen. Wird in die Schaltung gemäss Fig. 1 die Schaltung für das ideale Verhalten gemäss Fig. 2A eingebaut, ergibt sich für i das Verhalten gemäss Figur 5A, mit einem maximalen Strom i5. Dies lässt sich durch die Diode 21 erklären, durch welche die negative Halbwelle in Sperrichtung abgeschnitten wird.Above the
Wird in die Schaltung gemäss Fig. 1 die Schaltung für das reale Verhalten gemäss Fig. 2B eingebaut, ergibt sich das Verhalten gemäss Figur 5B, mit einem maximalen Strom in positiver Richtung von i1 und in negativer Richtung von i2. Durch die Ersatzschaltung nach Fig. 2B folgt aber auch, dass i1 grösser ist als i5 (i1 > i5), da zusätzlich der Widerstand 22 parallelgeschaltet ist. Durch diesen Widerstand 22 kann nun jedoch auch bei der negativen Halbwelle ein Strom fliessen, der sein Maximum bei i2 hat, jedoch im Betrag kleiner ist als i.If the circuit for the real behavior according to FIG. 2B is incorporated into the circuit according to FIG. 1, the behavior according to FIG. 5B results with a maximum current in the positive direction of i1 and in the negative direction of i2. However, it also follows from the equivalent circuit according to FIG. 2B that i1 is greater than i5 (i1> i5), since in addition the
Durch den Spannungsbegrenzer 30 entsteht jedoch ein asymmetrisches Verhalten der Grenzspannung U2, wie dies aus Fig. 4B ersichtlich ist. In Figur 4C ist eine symmetrische Spannung U2* dargestellt, wie sie aus dem Stand der Technik bekannt ist und die an den gleichen Messpunkten C und D gemessen wird wie die Spannung U2. Wird wie oben schon dargelegt in die Schaltung gemäss Fig. 1 die Schaltung für das reale Verhalten gemäss Fig. 2B eingebaut, ergibt sich bei einem aus dem Stand der Technik bekannten symmetrischen Verhalten der Spannung U2* das Verhalten gemäss Figur 5C, mit einem maximalen Strom in positiver Richtung von i3 und in negativer Richtung von i4.By the
Entscheidend für die Erfindung ist nun jedoch, dass bei annähernd gleichen i2 und i4 (i2 = i4), i3 kleiner ist als i1 (i3 < i1), d.h. das Verhältnis von i1 zu i2 ist grösser als das Verhältnis von i3 zu i4 ([i1/i2) > [i3/i4]).
Dieses bessere Verhältnis für eine asymmetrische Spannung erlaubt nun die Verwendung empfindlicher Flammensignalverstärker, auch wenn nicht flammenbedingte Gleichrichteffekte unterdrückt werden müssen was eine bessere Auswertung des eigentlichen Flammensignals erlaubt.However, it is decisive for the invention that, with approximately the same i2 and i4 (i2 = i4), i3 is smaller than i1 (i3 <i1), ie the ratio of i1 to i2 is greater than the ratio of i3 to i4 ([ i1 / i2)> [i3 / i4]).
This better ratio for an asymmetrical voltage now allows the use of sensitive flame signal amplifier, even if not flame-related rectification effects must be suppressed which allows a better evaluation of the actual flame signal.
Selbstverständlich ist die Erfindung nicht auf die gezeigten und beschriebenen Ausführungsbeispiele beschränkt, sondern lediglich durch den beigefügten Ansprüche.Of course, the invention is not limited to the embodiments shown and described, but only by the appended claims.
Claims (5)
- Flame monitoring device, with which an input alternating voltage (U1) is limited to a critical voltage (U2) with a voltage limiter (4), with the critical voltage (U2) being applied to a flame probe (7), which operates with the rectifying effect of a flame, and through which a current (i) flows, particularly when a flame is present(6),
characterised in that
the voltage limiter (4) produces an asymmetrical critical voltage (U2), which is applied to the probe (7). - Flame monitoring device according to claim 1,
characterised in that
the voltage limiter (4) consists of several limiter elements (31, 32), which symmetrically limit the voltage and that in addition to producing the asymmetry, at least one more limiter element (32) is arranged so that a higher current (i1) can be achieved in the conducting direction of the flame probe (7), when a flame is present, than without asymmetry (i3). - Flame monitoring device according to claim 1 or 2,
characterised in that
the voltage limiter (4) consists of diodes (31, 32) connected in series, which also conduct in a reverse direction from a certain voltage, that the one half of an even number of diodes (31) is connected in each instance in the conducting direction and the other half in the reverse direction and that in addition to producing the asymmetry in one direction, at least one more diode (32) is arranged, so that a higher current (1) can be achieved in the conducting direction of the flame probe (7), when a flame is present, than without asymmetry (i3). - Flame monitoring device according to claim 3,
characterised in that
the diodes (31, 32) comprise the same type. - Flame monitoring device according to one of the preceding claims,
characterised in that
the probe (7) which operates on the rectifying effect of the flame is an ionisation electrode or a UV sensor.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE10125574A DE10125574A1 (en) | 2001-05-25 | 2001-05-25 | Flame monitoring device with which an asymmetrical voltage is applied across burner and ionization electrode to detect presence of flame |
| DE10125574 | 2001-05-25 | ||
| PCT/IB2002/001758 WO2002095295A1 (en) | 2001-05-25 | 2002-05-22 | Flame-monitoring device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP1390668A1 EP1390668A1 (en) | 2004-02-25 |
| EP1390668B1 true EP1390668B1 (en) | 2007-07-04 |
Family
ID=7686155
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP02727938A Expired - Lifetime EP1390668B1 (en) | 2001-05-25 | 2002-05-22 | Flame-monitoring device |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US7046154B2 (en) |
| EP (1) | EP1390668B1 (en) |
| AT (1) | ATE366395T1 (en) |
| DE (2) | DE10125574A1 (en) |
| WO (1) | WO2002095295A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102005024763B3 (en) * | 2005-05-31 | 2006-06-08 | Stiebel Eltron Gmbh & Co. Kg | Heating device, has combustion chamber with ionization electrode for detecting ionization signals and evaluation unit coupled with fuel valve for controlling of fuel valve in dependence of evaluated time process of alternating voltage |
| EP2154430B1 (en) * | 2008-08-15 | 2015-09-30 | Siemens Aktiengesellschaft | Control device for a gas burner, and use of the control device |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1075317A (en) * | 1964-05-22 | 1967-07-12 | Danfoss As | Ac-operated switching circuit |
| DE1230165B (en) | 1964-08-07 | 1966-12-08 | Danfoss As | AC-powered flame guard |
| US3551908A (en) | 1967-12-26 | 1970-12-29 | Combustion Eng | Flame detector |
| JPS59217417A (en) | 1983-05-25 | 1984-12-07 | Matsushita Electric Ind Co Ltd | Kerosene room heater |
| DE4122636C2 (en) * | 1991-07-09 | 1999-08-12 | Bosch Gmbh Robert | Device and method for monitoring a flame |
| DE19605803A1 (en) * | 1996-02-16 | 1997-08-21 | Daug Deutsche Automobilgesells | Circuit arrangement for ion current measurement |
| DK0806610T3 (en) * | 1996-05-09 | 2001-10-15 | Stiebel Eltron Gmbh & Co Kg | Procedure for operating a burner |
| DE19712373A1 (en) * | 1997-03-25 | 1998-10-01 | Bosch Gmbh Robert | Device for monitoring a burner |
| DE19712938C1 (en) * | 1997-03-27 | 1998-05-14 | Honeywell Bv | Burner flame monitor supply voltage circuit for power plant |
-
2001
- 2001-05-25 DE DE10125574A patent/DE10125574A1/en not_active Withdrawn
-
2002
- 2002-05-22 AT AT02727938T patent/ATE366395T1/en not_active IP Right Cessation
- 2002-05-22 WO PCT/IB2002/001758 patent/WO2002095295A1/en active IP Right Grant
- 2002-05-22 US US10/477,005 patent/US7046154B2/en not_active Expired - Lifetime
- 2002-05-22 DE DE50210419T patent/DE50210419D1/en not_active Expired - Lifetime
- 2002-05-22 EP EP02727938A patent/EP1390668B1/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| US7046154B2 (en) | 2006-05-16 |
| ATE366395T1 (en) | 2007-07-15 |
| EP1390668A1 (en) | 2004-02-25 |
| DE50210419D1 (en) | 2007-08-16 |
| US20040178915A1 (en) | 2004-09-16 |
| DE10125574A1 (en) | 2002-11-28 |
| WO2002095295A1 (en) | 2002-11-28 |
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