EP1922908B1 - Method for operation of a steam plasma burner and steam cutting device - Google Patents

Method for operation of a steam plasma burner and steam cutting device Download PDF

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Publication number
EP1922908B1
EP1922908B1 EP06774763A EP06774763A EP1922908B1 EP 1922908 B1 EP1922908 B1 EP 1922908B1 EP 06774763 A EP06774763 A EP 06774763A EP 06774763 A EP06774763 A EP 06774763A EP 1922908 B1 EP1922908 B1 EP 1922908B1
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EP
European Patent Office
Prior art keywords
cathode
anode
workpiece
current
steam
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German (de)
French (fr)
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EP1922908A2 (en
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Heribert Pauser
Alexander Speigner
Andreas Starzengruber
Max Stöger
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Fronius International GmbH
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Fronius International GmbH
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
    • H05H1/00—Generating plasma; Handling plasma
    • H05H1/24—Generating plasma
    • H05H1/26—Plasma torches
    • H05H1/32—Plasma torches using an arc
    • H05H1/34—Details, e.g. electrodes, nozzles
    • H05H1/36—Circuit arrangements

Definitions

  • the invention relates to a method for operating a steam plasma burner with a cathode and an anode formed as a nozzle for processing a workpiece, wherein during operation between the cathode and the anode and or or the workpiece via a current source, a current is impressed, wherein after the Igniting a pilot arc between the cathode and the anode as the water vapor plasma torch approaches the workpiece between the cathode and the workpiece forms a working arc and extinguishes the pilot arc by disconnecting the current source from the anode and increasing the current to a predetermined operating current; the working operation, the voltage between the cathode and the workpiece is monitored and to re-create the pilot arc, the power source is switched back to the anode when the voltage exceeds a threshold.
  • the invention relates to a steam cutting machine with a steam plasma burner with a cathode and an anode formed as a nozzle, a power source which is connected to the cathode on the one hand and the workpiece to be machined and the anode on the other hand, with a control device for controlling a switch in the Connection between the current source and the anode, and with means for measuring the voltage between the cathode and the workpiece.
  • the water or the liquid is conducted from a tank via a corresponding line to the burner and heated there by means of a heater to steam and passed through corresponding channels in the combustion chamber, where it generates a plasma as a plasma-forming medium.
  • the plasma jet emerges without current from the nozzle, where it can be used to melt workpieces due to the high energy density.
  • a connection of workpieces can also be carried out by means of a steam plasma burner.
  • the heating element of the steam plasma burner which vaporizes the liquid medium, is turned on so that the operating temperature is reached.
  • the steam plasma burner is in "standby" or idle mode.
  • a so-called pilot arc is ignited between the cathode and the anode.
  • the liquid medium evaporated by the heating element forms the plasma gas, which drives the arc to the outside through the outlet opening of the anode formed as a nozzle. In this state, the burner is in the so-called "non-transmitted mode".
  • a partial current begins to flow across the workpiece to the cathode, resulting in the formation of a working arc between the workpiece and the cathode when a certain current is exceeded.
  • the pilot arc is switched off by switching off the power source and the current is increased to the desired cutting current, so that the machining of the workpiece can be started. This mode is called the "transmitted mode”.
  • the water vapor plasma torch If the water vapor plasma torch is moved away from the workpiece, it may lead to the breaking of the working arc and to the interruption of the machining of the workpiece.
  • the pilot arc has to be ignited and the burner has to be brought into the untransmitted mode and finally into the transmitted mode.
  • the extinction of the arc is a problem, especially in the case of steam plasma burners, since the plasma medium which can still be pumped can lead to a cooling of the burner and thus to interruptions in the work process.
  • the control of switching between not transmitted and transmitted mode is therefore of great importance, in particular for water vapor plasma torches.
  • the US 5,828,030 A shows a plasma torch of the subject type, wherein the voltage between the electrode and the workpiece is measured and fed to a controller. An extinction of the arc is detected by exceeding a certain voltage level. In this case, the switch is closed and the pilot arc is restored, and re-ignition of the arc can be avoided.
  • WO 2004/022276 A1 shows a plasma torch in which various operating currents and voltages are monitored to optimize the switching from the pilot arc into an operating arc.
  • Object of the present invention is to provide an above-mentioned method for operating a steam plasma burner, through which an optimal switching of the operating conditions can be achieved.
  • a substantially uninterrupted machining of workpieces and thus an optimal machining result is to be achieved.
  • Another object of the present invention is to provide an above-mentioned steam cutting apparatus by which optimum operation of the steam plasma burner can be achieved.
  • the first object of the invention is achieved by an above called method in which the power source is disconnected from the anode when the current between the workpiece and cathode exceeds a threshold.
  • the essence of the method according to the invention lies in the rapid switching from the transmitted mode to the non-transmitted mode, as soon as the water vapor plasma torch is moved too far away from the workpiece and the work arc extinction is imminent, and when switching from non-transmitted mode to transmitted mode, as soon as measured current exceeds a defined threshold.
  • the removal of the water vapor plasma torch from the workpiece is determined by measuring the voltage between the cathode and the workpiece.
  • the partial flow between the cathode and the workpiece which begins to flow as the burner approaches the workpiece, is monitored.
  • the pilot arc is extinguished by switching off the current source from the anode, so that only the working arc burns. This represents switching from non-transmitted mode to transmitted mode.
  • the threshold value is adjustable, so that different working parameters and types of burners can be taken into account.
  • different threshold values are dependent on the steam plasma burner used in a memory deposited, and retrievable or adjustable.
  • the working current during operation is advantageously designed to be adjustable.
  • the strength of the working current is adapted to the workpiece to be machined.
  • the current source is switched off after a predetermined period of time from the anode, as soon as the current exceeds the threshold value. Setting this time ensures that the pilot arc will burn for a while before it is cleared. As a result, too high switching frequencies, which would burden the switch, and the occurrence of a vibration are prevented.
  • the time duration can be achieved by starting a timer at the time of detection of the exceeding of the threshold value.
  • the period of time over which the pilot arc must at least burn, before it is extinguished in the range between 1 and 1.4 ms.
  • the threshold value of the current between the workpiece and the cathode is likewise preferably adjustable.
  • the pilot arc can be ignited by applying a high-frequency voltage between the cathode and the anode.
  • the pilot arc is ignited by lifting an axially displaceable cathode of the anode.
  • the cathode at the anode In this state, therefore, there is a short circuit between the cathode and anode.
  • the cathode is preferably automatically lifted by the supplied liquid medium of the steam plasma burner from the anode, so that a pilot arc between the cathode and the anode can be ignited.
  • the voltage between the cathode and the anode is measured and compared with the voltage between the cathode and the workpiece and reduced in accordance with the working current. This ensures that when the cathode and anode meet, the working current is reduced, which leads to protection of the cathode and anode.
  • the voltage between the cathode and the anode can be measured and the detection of a short circuit prevents the current source from being disconnected from the anode.
  • it can be prevented that an arc is ignited when the anode and cathode are short-circuited between the burner and the workpiece. Only after ignition of a pilot arc between the nozzle and cathode, which is possible only when opening the short circuit between the anode and cathode, the switching off of the pilot arc and thus the achievement of the transmitted mode is possible.
  • connection and / or disconnection of the current source from the anode is carried out, for example, in steps or ramps according to a predetermined function, the components can be protected since the switching does not take place abruptly.
  • the flow rate of the water or the liquid of the steam plasma burner is adjustable.
  • the cooling of the burner can be improved by increasing the flow rate.
  • the object of the invention is also achieved by an above-mentioned steam cutting device with a device for measuring the current between the cathode and the workpiece, which is connected to the control device as well as the device for measuring the voltage between the cathode and the workpiece.
  • a device for measuring the current between the cathode and the workpiece By detecting the voltage between the cathode and the workpiece, it can be compared in the control device with a predetermined threshold value and controlled accordingly in the sequence of the switches in the connection between the current source and the anode.
  • the device for measuring the current between the cathode and the workpiece it is possible to switch from the non-transmitted mode to the transmitted mode in the event of a signal being exceeded certain threshold for the current between the cathode and the workpiece.
  • Another advantage is a device for measuring the current between the workpiece and the cathode, which measuring device is connected to the control device. Through this current measuring device the working current can be recorded during operation.
  • control device is formed by an analog circuit, the required or low switching times, in particular when switching from the transmitted mode to the non-transmitted mode, can be achieved. These can usually not be achieved by a software-based solution in a control device formed by a microcontroller.
  • the switch is preferably formed by a transistor, in particular an IGBT (insulated gate bipolar transistor).
  • IGBT insulated gate bipolar transistor
  • a memory for storing predetermined threshold values is provided, which is connected to the control device.
  • a steam cutting machine 1 having a base apparatus 1a for a water vapor cutting method.
  • the basic device 1a comprises a power source 2, a control device 3 and a blocking element 4 associated with the control device 3.
  • the blocking element 4 is connected to a container 5 and a steam plasma burner 6 comprising a burner handle 6a and a burner body 6b via a supply line 7, so that the Steam plasma burner 6 can be supplied with a arranged in the container 5 liquid 8.
  • the supply of the steam plasma burner 6 with electrical energy via lines 9, 10 from the power source. 2
  • a cooling circuit 11 For cooling the steam plasma burner 6 this is connected via a cooling circuit 11 at best with the interposition of a flow monitor 12 with a liquid container 13.
  • the cooling circuit 11 can be started by the control device 3 and thus a cooling of the burner 6 via the cooling circuit 11 can be achieved.
  • the burner 6 is connected via cooling lines 14, 15 with the liquid container 13.
  • the base unit 1a may have an input and / or display device 16, via which the most different parameters or operating modes of the steam cutting device 1 can be set and displayed.
  • the parameters set via the input and / or display device 16 are forwarded to the control device 3, which controls the individual components of the steam cutting device 1 accordingly.
  • the steam plasma burner 6 can have at least one operating element 17, in particular a pushbutton 18, via which the user can inform the controller 3 by activating and / or deactivating the button 18 of the burner 6 that a steam cutting process is started or carried out should.
  • presettings can be made, for example, at the input and / or display device 16, in particular that the material to be cut, the liquid used and, for example, characteristics of the current and the voltage are predefined.
  • further controls on the burner 6 may be arranged via the one or more operating parameters of the steam cutting device 1 are set by the burner 6 from. For this purpose, these controls can be connected directly via lines or via a bus system to the base unit 1a, in particular the control device 3.
  • the control device 3 activates after pressing the button 18, the individual components required for the steam cutting process. For example, first a pump (not shown), the blocking element 4 and the current source 2 are driven, whereby a supply of the burner 6 with the liquid 8 and with electrical energy is introduced. Subsequently, the control device 3 activates the cooling circuit 11, so that a cooling of the burner 6 is made possible. By supplying the burner 6 with the liquid 8 and with energy, in particular with current and voltage, the liquid 8 is now in the burner 6 in a gas 19, in particular in plasma, converted at high temperature, so that by the burner from the sixth outflowing gas 19, a cutting process on a workpiece 20 can be performed.
  • the Fig. 2 to 4 show schematic representations of a steam plasma burner 6 according to the invention in different operating conditions.
  • the steam plasma burner 6 has a housing 21, in which a cathode 22 is arranged, which is connected to the power source 2.
  • the anode 24 formed as a nozzle 23 is connected to the positive pole of the power source 2.
  • a pilot arc between the cathode 22 and the anode 24 For igniting a pilot arc between the cathode 22 and the anode 24, according to Fig. 3 the supply of the liquid medium, in particular water, turned on, whereby the axially displaceable cathode 22 lifts from the nozzle 23 and in the presence a corresponding current a pilot arc between the cathode 22 and the anode 24 is ignited.
  • the ignition of a pilot arc can also be done by connecting a high-frequency voltage.
  • the water evaporated in the heater is conducted into the combustion chamber where it serves as a medium for a plasma jet.
  • the plasma jet is forced out through the opening 25 in the anode 24 formed as a nozzle 23 and can be used for cutting but also joining workpieces 20 due to its high energy density.
  • the steam plasma burner 6 is in the so-called non-transferred mode.
  • a control device 25 which controls a switch 30 between the power source 2 and the anode 24 of the steam plasma burner 6, respectively.
  • the voltage U NUE between the cathode 22 and the anode 24 are detected by means of a voltage meter 26 and the current I UE from the positive pole of the current source 2 to the workpiece 20 by means of an ammeter 28.
  • the voltage U UE between the cathode 22 and the workpiece 20 can be determined with the aid of the voltmeter 27 and the current I CUT from the negative pole of the current source 2 to the cathode 22 of the steam plasma burner with the aid of an ammeter 29.
  • the detected data is supplied to the controller 25 which controls the switch for connecting the positive pole of the power source 2 to the anode 24.
  • it is detected via the voltage U NUE between the cathode 22 and the anode 24 of the steam plasma burner , which is detected by means of the voltage measuring device 26, when the short circuit between the cathode 22 and the anode or nozzle 24 has been canceled. Only then can the pilot arc between the cathode 22 and the anode 24 be ignited.
  • a small partial current I UE begins to flow over the transmitted current path. If the current I UE measured with the aid of the ammeter 28 exceeds a defined threshold value I UEs for the workpiece 20, the switch 30 is actuated by the control device 25 and thus the power source 2 is disconnected from the anode 24. As a result, the arc forcibly deflects from the cathode 22 to the workpiece 20 and the current of the current source 2 can be increased to a specific cutting current I CUT . In this case, the steam plasma burner 6 is in the so-called transferred mode.
  • the voltage between the cathode 22 and the workpiece increases as the current source 2 tends to maintain the adjusted cutting current I CUT .
  • the switch 30 is in turn closed and thus the anode 24 is again connected to the positive pole of the current source 2 in order to prevent the arc from tearing off.
  • the steam plasma burner 6 is again in the non-transferred mode according to Fig. 3 ,
  • the mode transmitted and not transmitted between the two operating states is changed as needed. It is important that the control of the switch 30 is very fast.
  • Analogously designed control devices 25 are more suitable for this purpose than implementations by microcontrollers.
  • This automatic control of the arc is of great importance when cutting certain workpieces, such as perforated sheets. In this case, it would come to an extinction of the arc by constantly changing the distance between the workpiece and the burner, which would require a re-ignition of the pilot arc.
  • pulsing the flow may be beneficial to some materials for cutting quality.
  • the inventive method the energy input is reduced.
  • control device 3 acts in the switching process.
  • a switching signal must be generated or deleted by the control device 3, wherein the control device 3 releases the switch 30 only when a threshold value for the switching signal is exceeded, ie, that only For example, if the switching signal exceeds 50V, switching from the non-transmitted mode to the transmitted mode is possible.
  • a threshold value for the switching signal ie, that only For example, if the switching signal exceeds 50V, switching from the non-transmitted mode to the transmitted mode is possible.
  • the analog control device 25 By the release of the control device 3, it is then possible for the analog control device 25 to open the switch 30 so that the arc can then be switched to the workpiece 20. This ensures that no arc can burn between the nozzle 23 and the workpiece 20 without the cathode 22 being lifted from the anode 24. For example, if the cathode 22 is not removed from the anode 24, it would not be possible during operation to switch between the transmitted mode and the non-transmitted mode. This also ensures that a safe heating of the burner 6 is achieved via the pilot arc, so that only water vapor exits the burner 6. By this intervention of the control device 3, this is prevented, since only an ignition between the nozzle 23 and cathode 24 must be made to clear this signal or to generate a corresponding signal, so that switching of the switch 30 is possible.
  • control device 3 can also take place in such a way that in the transmitted mode, ie where the arc between the workpiece 20 and cathode 22 burns when switching back to the non-transferred mode, ie the pilot arc, the control device 3 monitors the pilot arc. ie, that the pilot arc over a certain period of time, preferably 1.2msec, must burn between the nozzle 23 and the cathode 24, whereupon it is queried where the current now flows before the arc can be switched back to the workpiece 20 or the pilot arc is maintained. This ensures that a swing, so switch back and forth, can not occur because the switch used 30 high switching frequencies can not stand.
  • circuit design can be digital or analog, whereby the control means 25 is integrated in the control device 3 or realized by this in a digital structure.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Arc Welding In General (AREA)
  • Plasma Technology (AREA)

Abstract

The invention relates to a method for operation of a steam plasma burner (6), comprising a cathode (22) and an anode (24) in the form of a nozzle (23) for machining a workpiece (20), wherein during the operation a current is applied between the cathode (22) and the anode (24) and/or the workpiece (20) by means of a power supply (2). After starting a pilot arc between the cathode (22) and the anode (24) by approaching the steam plasma burner (6) to the workpiece (20), a working arc is formed between the cathode (22) and the workpiece (20) and the pilot arc is extinguished by switching off the power supply (2) to the anode (24) and the current increased to a given working current. In order to achieve an optimal operation of a steam plasma burner, the voltage (UUE) between the cathode (22) and the workpiece (20) is monitored during working operation and the power supply (2) reconnected to the anode (24) to reform the pilot arc when the voltage (UUE) exceeds a threshold (IUEs).

Description

Die Erfindung betrifft ein Verfahren zum Betreiben eines Wasserdampfplasmabrenners mit einer Kathode und einer als Düse ausgebildeten Anode zum Bearbeiten eines Werkstücks, wobei während des Betriebes zwischen der Kathode und der Anode und bzw. oder dem Werkstück über eine Stromquelle ein Strom eingeprägt wird, wobei nach dem Zünden eines Pilotlichtbogens zwischen der Kathode und der Anode bei Annäherung des Wasserdampfplasmabrenners an das Werkstück zwischen der Kathode und dem Werkstück ein Arbeitslichtbogen gebildet und der Pilotlichtbogen durch Wegschalten der Stromquelle von der Anode gelöscht wird und der Strom auf einen vorgegebenen Arbeitsstrom erhöht wird, und wobei während des Arbeitsbetriebs die Spannung zwischen der Kathode und dem Werkstück überwacht wird und zur Neubildung des Pilotlichtbogens die Stromquelle wieder an die Anode geschaltet wird, sobald die Spannung einen Schwellwert überschreitet.The invention relates to a method for operating a steam plasma burner with a cathode and an anode formed as a nozzle for processing a workpiece, wherein during operation between the cathode and the anode and or or the workpiece via a current source, a current is impressed, wherein after the Igniting a pilot arc between the cathode and the anode as the water vapor plasma torch approaches the workpiece between the cathode and the workpiece forms a working arc and extinguishes the pilot arc by disconnecting the current source from the anode and increasing the current to a predetermined operating current; the working operation, the voltage between the cathode and the workpiece is monitored and to re-create the pilot arc, the power source is switched back to the anode when the voltage exceeds a threshold.

Weiters betrifft die Erfindung ein Wasserdampf-Schneidgerät mit einem Wasserdampfplasmabrenner mit einer Kathode und einer als Düse ausgebildeten Anode, einer Stromquelle, welche mit der Kathode einerseits und dem zu bearbeitenden Werkstück und der Anode andererseits verbunden ist, mit einer Steuereinrichtung zur Steuerung eines Schalters in der Verbindung zwischen der Stromquelle und der Anode, und mit einer Einrichtung zur Messung der Spannung zwischen der Kathode und dem Werkstück.Furthermore, the invention relates to a steam cutting machine with a steam plasma burner with a cathode and an anode formed as a nozzle, a power source which is connected to the cathode on the one hand and the workpiece to be machined and the anode on the other hand, with a control device for controlling a switch in the Connection between the current source and the anode, and with means for measuring the voltage between the cathode and the workpiece.

Bei Wasserdampfplasmabrennern der gegenständlichen Art wird über eine Stromquelle ein Lichtbogen zwischen einer negativ gepolten Kathode und einer positiv gepolten Anode, welche als Düse an der Spitze des Brenners ausgebildet ist, gezündet. Das Wasser bzw. die Flüssigkeit wird von einem Tank über eine entsprechende Leitung zum Brenner geführt und dort mittels einer Heizeinrichtung zu Dampf erhitzt und über entsprechende Kanäle in die Brennkammer geleitet, wo es als plasmabildendes Medium ein Plasma erzeugt. Der Plasmastrahl tritt stromlos aus der Düse aus, wo er aufgrund der hohen Energiedichte zum Aufschmelzen von Werk-stücken verwendet werden kann. Neben dem Schneiden von Werkstücken kann mittels eines Wasserdampfplasmabrenners auch eine Verbindung von Werkstücken durchgeführt werden.In water vapor plasma torches of the subject type, an arc between a negatively poled cathode and a positively poled anode, which is formed as a nozzle at the tip of the burner, ignited via a power source. The water or the liquid is conducted from a tank via a corresponding line to the burner and heated there by means of a heater to steam and passed through corresponding channels in the combustion chamber, where it generates a plasma as a plasma-forming medium. The plasma jet emerges without current from the nozzle, where it can be used to melt workpieces due to the high energy density. In addition to the cutting of workpieces, a connection of workpieces can also be carried out by means of a steam plasma burner.

Die Verwendung von Wasser bzw. einer Flüssigkeit anstelle von Gas als plasmafähiges Medium hat den Vorteil, dass keine Gasflasche erforderlich ist. Wasser ist an den meisten Plätzen verfügbar bzw. kann einfach beschafft werden. Zur Bildung des plasmafähigen Gases muss allerdings das Wasser bzw. die Flüssigkeit verdampft werden.The use of water or a liquid instead of gas as a plasma-capable medium has the advantage that no gas cylinder is required. Water is available at most places or can easily be obtained. To form the plasma capable of plasma, however, the water or the liquid must be evaporated.

Nach dem Einschalten eines Wasserdampf-Schneidgeräts wird das Heizelement des Wasserdampfplasmabrenners, welches das flüssige Medium verdampft, eingeschaltet, so dass Betriebstemperatur erreicht wird. Ist die Betriebstemperatur erreicht, befindet sich der Wasserdampfplasmabrenner im "Standby-Modus" bzw. Ruhemodus. Um den Wasserdampfplasmabrenner in seinen Betriebszustand zu bringen, wird zwischen der Kathode und der Anode ein so genannter Pilotlichtbogen gezündet. Das durch das Heizelement verdampfte flüssige Medium bildet das Plasmagas, welches den Lichtbogen durch die Austrittsöffnung der als Düse ausgebildeten Anode nach außen treibt. In diesem Zustand befindet sich der Brenner im so genannten "nicht übertragenen Modus". Bei Annäherung des Brenners an das mit der Stromquelle verbundene Werkstück, beginnt ein Teilstrom über das Werkstück zur Kathode zu fließen, was bei Überschreitung eines bestimmten Stromes zur Bildung eines Arbeitslichtbogens zwischen Werkstück und Kathode führt. Sobald der Arbeitslichtbogen zwischen Kathode und Werkstück gebildet ist, wird der Pilotlichtbogen durch Wegschalten der Stromquelle ausgeschaltet und der Strom auf den gewünschten Schneidstrom erhöht, so dass mit der Bearbeitung des Werkstücks begonnen werden kann. Diesen Modus nennt man den so genannten "übertragenen Modus".After switching on a steam cutting device, the heating element of the steam plasma burner, which vaporizes the liquid medium, is turned on so that the operating temperature is reached. When the operating temperature has been reached, the steam plasma burner is in "standby" or idle mode. In order to bring the water vapor plasma burner into its operating state, a so-called pilot arc is ignited between the cathode and the anode. The liquid medium evaporated by the heating element forms the plasma gas, which drives the arc to the outside through the outlet opening of the anode formed as a nozzle. In this state, the burner is in the so-called "non-transmitted mode". As the torch approaches the workpiece connected to the power source, a partial current begins to flow across the workpiece to the cathode, resulting in the formation of a working arc between the workpiece and the cathode when a certain current is exceeded. Once the working arc is formed between the cathode and the workpiece, the pilot arc is switched off by switching off the power source and the current is increased to the desired cutting current, so that the machining of the workpiece can be started. This mode is called the "transmitted mode".

Wird der Wasserdampfplasmabrenner vom Werkstück wegbewegt, kann es zum Abreißen des Arbeitslichtbogens und zur Unterbrechung der Bearbeitung des Werkstücks kommen. Um mit der Bearbeitung fortzufahren, muss wiederum der Pilotlichtbogen gezündet und der Brenner in den nicht übertragenen Modus und schließlich in den übertragenen Modus gebracht werden. Gerade bei Wasserdampfplasmabrennern stellt das Erlöschen des Lichtbogens ein Problem dar, da das weiterhin geförderte plasmafähige Medium zu einer Auskühlung des Brenners und somit zu Unterbrechungen des Arbeitsvor-ganges führen kann. Die Steuerung der Umschaltung zwischen nicht übertragenem und übertragenem Modus ist daher insbesondere für Wasserdampfplasmabrenner von großer Bedeutung.If the water vapor plasma torch is moved away from the workpiece, it may lead to the breaking of the working arc and to the interruption of the machining of the workpiece. In order to proceed with the processing, again the pilot arc has to be ignited and the burner has to be brought into the untransmitted mode and finally into the transmitted mode. The extinction of the arc is a problem, especially in the case of steam plasma burners, since the plasma medium which can still be pumped can lead to a cooling of the burner and thus to interruptions in the work process. The control of switching between not transmitted and transmitted mode is therefore of great importance, in particular for water vapor plasma torches.

Im Stand der Technik existieren verschiedene Verfahren, welche die Umschaltung vom nicht übertragenen Modus in den übertragenen Modus in Abhängigkeit gemessener Ströme oder Spannungen steuern. Beispielsweise beschreibt die US 6 133 543 A eine Einrichtung und ein Verfahren zur Steuerung eines Plasmalichtbogens, wobei der Strom des Lichtbogens im übertragenen Modus erfasst wird und zur Steuerung der Zuschaltung der Stromquelle herangezogen wird. Dabei handelt es sich um einen herkömmlichen mit Gas betriebenen Brenner.In the prior art, various methods exist which control the switching from the non-transmitted mode to the transmitted mode in response to measured currents or voltages. For example, this describes US 6,133,543 A a device and a method for controlling a plasma arc, wherein the current of the arc is detected in the transmitted mode and is used to control the connection of the power source. This is a conventional gas-powered burner.

Die US 5 828 030 A zeigt einen Plasmabrenner der gegenständlichen Art, wobei die Spannung zwischen der Elektrode und dem Werkstück gemessen und einer Steuerung zugeführt wird. Ein Erlöschen des Lichtbogens wird durch Übersteigen eines bestimmten Spannungsniveaus erfasst. In diesem Fall wird der Schalter geschlossen und der Pilotlichtbogen wieder hergestellt, und eine Neuzündung des Lichtbogens kann dadurch vermieden werden.The US 5,828,030 A shows a plasma torch of the subject type, wherein the voltage between the electrode and the workpiece is measured and fed to a controller. An extinction of the arc is detected by exceeding a certain voltage level. In this case, the switch is closed and the pilot arc is restored, and re-ignition of the arc can be avoided.

Auch die WO 2004/022276 A1 zeigt einen Plasmabrenner, bei dem verschiedene Betriebsströme und Spannungen überwacht werden, um die Umschaltung vom Pilotlichtbogen in einen Betriebslichtbogen zu optimieren.Also the WO 2004/022276 A1 shows a plasma torch in which various operating currents and voltages are monitored to optimize the switching from the pilot arc into an operating arc.

Aufgabe der vorliegenden Erfindung ist es, ein oben genanntes verfahren zum Betreiben eines Wasserdampfplasmabrenners zu schaffen, durch welches eine optimale Umschaltung der Betriebszustände erzielt werden kann. Durch das erfindungsgemäße Verfahren soll eine im Wesentlichen unterbrechungsfreie Bearbeitung von Werkstücken und somit ein optimales Bearbeitungergebnis erzielt werden.Object of the present invention is to provide an above-mentioned method for operating a steam plasma burner, through which an optimal switching of the operating conditions can be achieved. By the method according to the invention a substantially uninterrupted machining of workpieces and thus an optimal machining result is to be achieved.

Eine weitere Aufgabe der vorliegenden Erfindung besteht in der Schaffung eines oben genannten Wasserdampf-Schneidgeräts, durch welches ein optimaler Betrieb des Wasserdampfplasmabrenners erzielt werden kann.Another object of the present invention is to provide an above-mentioned steam cutting apparatus by which optimum operation of the steam plasma burner can be achieved.

Gelöst wird die erste erfindungsgemäße Aufgabe durch ein oben genanntes Verfahren, bei dem die Stromquelle von der Anode weggeschaltet wird, wenn der Strom zwischen Werkstück und Kathode einen Schwellwert überschreitet. Der Kern des erfindungsgemäßen Verfahrens liegt in der raschen Umschaltung vom übertragenen Modus in den nicht übertragenen Modus, sobald der Wasserdampfplasmabrenner zu weit vom Werkstück wegbewegt wird und das Erlöschen des Arbeitslichtbogens bevorsteht und in der Umschaltung von nicht-übertragenen Modus in den übertragenen Modus, sobald der gemessene Strom einen definierten Schwellwert übersteigt. Die Entfernung des Wasserdampfplasmabrenners vom Werkstück wird durch Messung der Spannung zwischen Kathode und Werkstück ermittelt. Dadurch, dass bei Überschreitung eines voreingestellten Schwellwerts die Anode des Wasserdampfplasmabrenners wieder an die Stromquelle geschaltet wird und dadurch der Pilotlichtbogen zwischen Kathode und Anode erneut gezündet wird, bleibt der Brenner auch bei Erlöschen des Arbeitslichtbogens im nicht übertragenen Modus. Dadurch wird ein Auskühlen des Brenners durch das zugeführte plasmafähige Medium verhindert und ein unmittelbares Fortfahren des Arbeitsvorgangs bei Wiedererreichen des gewünschten Abstandes des Brenners vom Werkstück erzielt. Dabei muss die Zuschaltung der Stromquelle zur Anode möglichst rasch nach Überschreitung des Schwellwerts für die Spannung zwischen Kathode und Werkstück erfolgen, so dass sichergestellt werden kann, dass der Pilotlichtbogen vor Erlöschen des Arbeitslichtbogens gezündet wird. Durch die Überwachung des Stromes zwischen Werkstück und Kathode wird der Teilstrom zwischen Kathode und Werkstück, welcher bei Annäherung des Brenners an das Werkstück zu fließen beginnt, überwacht. Sobald der gemessene Strom einen definierten Schwellwert übersteigt, wird der Pilotlichtbogen durch Wegschalten der Stromquelle von der Anode gelöscht, so dass nur mehr der Arbeitslichtbogen brennt. Dies stellt die Umschaltung von nicht-übertragenen Modus in den übertragenen Modus dar.The first object of the invention is achieved by an above called method in which the power source is disconnected from the anode when the current between the workpiece and cathode exceeds a threshold. The essence of the method according to the invention lies in the rapid switching from the transmitted mode to the non-transmitted mode, as soon as the water vapor plasma torch is moved too far away from the workpiece and the work arc extinction is imminent, and when switching from non-transmitted mode to transmitted mode, as soon as measured current exceeds a defined threshold. The removal of the water vapor plasma torch from the workpiece is determined by measuring the voltage between the cathode and the workpiece. The fact that when exceeding a preset threshold value, the anode of the steam plasma burner is switched back to the power source and thereby the pilot arc between the cathode and anode is ignited again, the burner remains in the non-transferred mode even when the work arc. As a result, cooling of the burner is prevented by the supplied plasma-capable medium and achieved an immediate continuation of the operation in Wiedererreichen the desired distance of the burner from the workpiece. In this case, the connection of the power source to the anode must be made as soon as possible after exceeding the threshold value for the voltage between the cathode and the workpiece, so that it can be ensured that the pilot arc is ignited before the expiry of the working arc. By monitoring the flow between the workpiece and the cathode, the partial flow between the cathode and the workpiece, which begins to flow as the burner approaches the workpiece, is monitored. As soon as the measured current exceeds a defined threshold value, the pilot arc is extinguished by switching off the current source from the anode, so that only the working arc burns. This represents switching from non-transmitted mode to transmitted mode.

Vorteilhafterweise ist der Schwellwert einstellbar, so dass unterschiedliche Arbeitsparameter und Brennertypen berücksichtigt werden können.Advantageously, the threshold value is adjustable, so that different working parameters and types of burners can be taken into account.

Vorteilhafterweise sind verschiedene Schwellwerte in Abhängigkeit der verwendeten Wasserdampfplasmabrenner in einem Speicher hinterlegt, und abrufbar bzw. einstellbar.Advantageously, different threshold values are dependent on the steam plasma burner used in a memory deposited, and retrievable or adjustable.

Um die Wirkung des Brenners während des Arbeitsbetriebs justieren zu können, ist der Arbeitsstrom während des Arbeitsbetriebs vorteilhafterweise einstellbar ausgebildet. Die Stärke des Arbeitsstroms wird an das zu bearbeitende Werkstück angepasst.In order to be able to adjust the effect of the burner during the working operation, the working current during operation is advantageously designed to be adjustable. The strength of the working current is adapted to the workpiece to be machined.

Dabei ist es von Vorteil, wenn die Stromquelle nach einer vorgegebenen Zeitdauer von der Anode weggeschaltet wird, sobald der Strom den Schwellwert überschreitet. Durch die Einstellung dieser Zeitdauer wird sichergestellt, dass der Pilotlichtbogen eine gewisse Zeit brennt, bevor dieser wieder gelöscht wird. Dadurch werden zu hohe Schaltfrequenzen, welche den Schalter belasten würden, und das Entstehen einer Schwingung verhindert. Die Zeitdauer kann durch Starten eines Zeitgliedes zum Zeitpunkt der Erkennung der Überschreitung des Schwellwerts erfolgen.It is advantageous if the current source is switched off after a predetermined period of time from the anode, as soon as the current exceeds the threshold value. Setting this time ensures that the pilot arc will burn for a while before it is cleared. As a result, too high switching frequencies, which would burden the switch, and the occurrence of a vibration are prevented. The time duration can be achieved by starting a timer at the time of detection of the exceeding of the threshold value.

Vorteilhafterweise beträgt die Zeitdauer, über welche der Pilotlichtbogen mindestens brennen muss, bevor er wieder gelöscht wird, im Bereich zwischen 1 und 1,4 ms.Advantageously, the period of time over which the pilot arc must at least burn, before it is extinguished, in the range between 1 and 1.4 ms.

Der Schwellwert des Stroms zwischen dem Werkstück und der Kathode ist ebenfalls vorzugsweise einstellbar ausgebildet.The threshold value of the current between the workpiece and the cathode is likewise preferably adjustable.

Der Pilotlichtbogen kann durch Anlegen einer hochfrequenten Spannung zwischen Kathode und Anode gezündet werden.The pilot arc can be ignited by applying a high-frequency voltage between the cathode and the anode.

Ebenso ist es möglich, dass der Pilotlichtbogen durch Abheben einer axial verschiebbaren Kathode von der Anode gezündet wird. Bei einer derartigen Ausgestaltung befindet sich im ausgeschalteten Zustand des Wasserdampfplasmabrenners die Kathode an der Anode. In diesem Zustand besteht daher ein Kurzschluss zwischen Kathode und Anode. Erst im Betriebszustand wird die Kathode vorzugsweise automatisch durch das zugeführte flüssige Medium des Wasserdampfplasmabrenners von der Anode abgehoben, so dass ein Pilotlichtbogen zwischen der Kathode und der Anode gezündet werden kann.It is also possible that the pilot arc is ignited by lifting an axially displaceable cathode of the anode. In such a configuration is in the off state of the steam plasma burner, the cathode at the anode. In this state, therefore, there is a short circuit between the cathode and anode. Only in the operating state, the cathode is preferably automatically lifted by the supplied liquid medium of the steam plasma burner from the anode, so that a pilot arc between the cathode and the anode can be ignited.

Um den Kurzschluss zwischen der Anode und der Kathode zu überwachen, kann gemäß einem weiteren Merkmal der Erfindung während des Arbeitsbetriebs die Spannung zwischen Kathode und Anode gemessen und mit der Spannung zwischen Kathode und Werkstück verglichen werden und bei Übereinstimmung der Arbeitsstrom reduziert werden. Somit wird gewährleistet, dass bei Aufeinandertreffen von Kathode und Anode der Arbeitsstrom reduziert wird, was zu einer Schonung von Kathode und Anode führt.In order to monitor the short circuit between the anode and the cathode, according to a further feature of the invention during In operation, the voltage between the cathode and the anode is measured and compared with the voltage between the cathode and the workpiece and reduced in accordance with the working current. This ensures that when the cathode and anode meet, the working current is reduced, which leads to protection of the cathode and anode.

Weiters kann die Spannung zwischen Kathode und Anode gemessen werden und bei Detektion eines Kurzschlusses das Wegschalten der Stromquelle von der Anode verhindert werden. Durch diese Maßnahme kann unterbunden werden, dass bei kurzgeschlossener Anode und Kathode zwischen dem Brenner und dem Werkstück ein Lichtbogen gezündet wird. Erst nach Zündung eines Pilotlichtbogens zwischen Düse und Kathode, was erst bei Öffnung des Kurzschlusses zwischen Anode und Kathode möglich ist, wird auch das Wegschalten des Pilotlichtbogens und somit das Erreichen des übertragenen Modus möglich.Furthermore, the voltage between the cathode and the anode can be measured and the detection of a short circuit prevents the current source from being disconnected from the anode. By this measure, it can be prevented that an arc is ignited when the anode and cathode are short-circuited between the burner and the workpiece. Only after ignition of a pilot arc between the nozzle and cathode, which is possible only when opening the short circuit between the anode and cathode, the switching off of the pilot arc and thus the achievement of the transmitted mode is possible.

Wenn das Zu- und oder Wegschalten der Stromquelle von der Anode nach einer vorgegebenen Funktion beispielsweise stufen- oder rampenförmig durchgeführt wird, kann eine Schonung der Komponenten bewirkt werden, da die Umschaltung nicht abrupt erfolgt.If the connection and / or disconnection of the current source from the anode is carried out, for example, in steps or ramps according to a predetermined function, the components can be protected since the switching does not take place abruptly.

Vorteilhafterweise ist die Durchflussmenge des Wassers bzw. der Flüssigkeit des Wasserdampfplasmabrenners einstellbar. Dadurch kann beispielsweise auch die Kühlung des Brenners durch Erhöhung der Durchflussmenge verbessert werden.Advantageously, the flow rate of the water or the liquid of the steam plasma burner is adjustable. As a result, for example, the cooling of the burner can be improved by increasing the flow rate.

Gelöst wird die erfindungsgemäße Aufgabe auch durch ein oben genanntes Wasserdampf-Schneidgerät mit einer Einrichtung zur Messung des Stromes zwischen Kathode und Werkstück, welche so wie die Einrichtung zur Messung der Spannung zwischen Kathode und Werkstück mit der Steuereinrichtung verbunden ist. Durch die Erfassung der Spannung zwischen Kathode und Werkstück kann diese in der Steuereinrichtung mit einem vorgegebenen Schwellwert verglichen und in der Folge der Schalter in der Verbindung zwischen Stromquelle und Anode entsprechend gesteuert werden. Durch die Einrichtung zur Messung des Stromes zwischen Kathode und Werkstück kann eine gezielte Umschaltung vom nicht übertragenen Modus in den übertragenen Modus bei Überschreitung eines bestimmten Schwellwertes für den Strom zwischen Kathode und Werkstück erfolgen.The object of the invention is also achieved by an above-mentioned steam cutting device with a device for measuring the current between the cathode and the workpiece, which is connected to the control device as well as the device for measuring the voltage between the cathode and the workpiece. By detecting the voltage between the cathode and the workpiece, it can be compared in the control device with a predetermined threshold value and controlled accordingly in the sequence of the switches in the connection between the current source and the anode. By means of the device for measuring the current between the cathode and the workpiece, it is possible to switch from the non-transmitted mode to the transmitted mode in the event of a signal being exceeded certain threshold for the current between the cathode and the workpiece.

Von Vorteil ist auch eine Einrichtung zur Messung des Stromes zwischen Werkstück und Kathode, welche Messeinrichtung mit der Steuereinrichtung verbunden ist. Durch diese Strommesseinrichtung kann der Arbeitsstrom im Arbeitbetrieb erfasst werden.Another advantage is a device for measuring the current between the workpiece and the cathode, which measuring device is connected to the control device. Through this current measuring device the working current can be recorded during operation.

Zur Ermittlung eines Kurzschlusses zwischen dem Brenner und dem Werkstück kann auch eine Einrichtung zur Messung der Spannung zwischen Kathode und Werkstück vorgesehen sein, welche Messeinrichtung mit der Steuereinrichtung verbunden ist.In order to determine a short circuit between the burner and the workpiece, it is also possible to provide a device for measuring the voltage between the cathode and the workpiece, which measuring device is connected to the control device.

Wenn die Steuereinrichtung durch eine Analogschaltung gebildet ist, können die erforderlichen bzw. gewünschten niedrigen Umschaltzeiten, insbesondere bei der Umschaltung vom übertragenen Modus in den nicht übertragenen Modus erzielt werden. Diese können meist durch eine softwaremäßige Lösung in einer durch einen Mikrokontroller ausgebildeten Steuereinrichtung nicht erzielt werden.If the control device is formed by an analog circuit, the required or low switching times, in particular when switching from the transmitted mode to the non-transmitted mode, can be achieved. These can usually not be achieved by a software-based solution in a control device formed by a microcontroller.

Der Schalter ist vorzugsweise durch einen Transistor, insbesondere einem IGBT (insulated gate bipolar transistor) gebildet sein.The switch is preferably formed by a transistor, in particular an IGBT (insulated gate bipolar transistor).

Vorteilhafterweise ist ein Speicher zur Hinterlegung vorgegebener Schwellwerte vorgesehen, welcher mit der Steuereinrichtung verbunden ist.Advantageously, a memory for storing predetermined threshold values is provided, which is connected to the control device.

Die vorliegende Erfindung wird anhand der beigefügten Zeichnungen näher erläutert. Darin zeigen:

  • Fig. 1 eine schematische Darstellung eines Wasserdampf-Schneidgeräts;
  • Fig. 2 eine schematische Darstellung eines Wasserdampfplasmabrenners im Ruhezustand;
  • Fig. 3 eine schematische Darstellung eines Wasserdampfplasmabrenners im nicht übertragenen Modus; und
  • Fig. 4 eine schematische Darstellung eines Wasserdampfplasmabrenners im übertragenen Modus.
The present invention will be explained in more detail with reference to the accompanying drawings. Show:
  • Fig. 1 a schematic representation of a steam cutting device;
  • Fig. 2 a schematic representation of a steam plasma burner at rest;
  • Fig. 3 a schematic representation of a steam plasma burner in untransmitted mode; and
  • Fig. 4 a schematic representation of a steam plasma burner in the transferred mode.

In Fig. 1 ist ein Wasserdampf-Schneidgerät 1 mit einem Grundgerät 1a für ein Wasserdampf-Schneidverfahren gezeigt. Das Grundgerät 1a umfasst eine Stromquelle 2, eine Steuervorrichtung 3 und ein der Steuervorrichtung 3 zugeordnetes Sperrelement 4. Das Sperrelement 4 ist mit einem Behälter 5 und einem Wasserdampfplasmabrenner 6, der einen Brennergriff 6a und einen Brennerkörper 6b umfasst, über eine Versorgungsleitung 7 verbunden, so dass der Wasserdampfplasmabrenner 6 mit einer im Behälter 5 angeordneten Flüssigkeit 8 versorgt werden kann. Die Versorgung des Wasserdampfplasmabrenners 6 mit elektrischer Energie erfolgt über Leitungen 9, 10 von der Stromquelle 2.In Fig. 1 there is shown a steam cutting machine 1 having a base apparatus 1a for a water vapor cutting method. The basic device 1a comprises a power source 2, a control device 3 and a blocking element 4 associated with the control device 3. The blocking element 4 is connected to a container 5 and a steam plasma burner 6 comprising a burner handle 6a and a burner body 6b via a supply line 7, so that the Steam plasma burner 6 can be supplied with a arranged in the container 5 liquid 8. The supply of the steam plasma burner 6 with electrical energy via lines 9, 10 from the power source. 2

Zum Kühlen des Wasserdampfplasmabrenners 6 ist dieser über einen Kühlkreislauf 11 allenfalls unter Zwischenschaltung eines Strömungswächters 12 mit einem Flüssigkeitsbehälter 13 verbunden. Bei der Inbetriebnahme des Brenners 6 bzw. des Grundgerätes 1a kann der Kühlkreislauf 11 von der Steuervorrichtung 3 gestartet und somit eine Kühlung des Brenners 6 über den Kühlkreislauf 11 erreicht werden. Zur Bildung des Kühlkreislaufs 11 wird der Brenner 6 über Kühlleitungen 14, 15 mit dem Flüssigkeitsbehälter 13 verbunden.For cooling the steam plasma burner 6 this is connected via a cooling circuit 11 at best with the interposition of a flow monitor 12 with a liquid container 13. When the burner 6 or the basic unit 1a is put into operation, the cooling circuit 11 can be started by the control device 3 and thus a cooling of the burner 6 via the cooling circuit 11 can be achieved. To form the cooling circuit 11, the burner 6 is connected via cooling lines 14, 15 with the liquid container 13.

Weiters kann das Grundgerät 1a eine Eingabe- und/oder Anzeigevorrichtung 16 aufweisen, über welche die unterschiedlichsten Parameter bzw. Betriebsarten des Wasserdampf-Schneidgerätes 1 eingestellt und angezeigt werden können. Die über die Eingabe-und/oder Anzeigevorrichtung 16 eingestellten Parameter werden an die Steuervorrichtung 3 weitergeleitet, welche die einzelnen Komponenten des Wasserdampf-Schneidgerätes 1 entsprechend ansteuert.Furthermore, the base unit 1a may have an input and / or display device 16, via which the most different parameters or operating modes of the steam cutting device 1 can be set and displayed. The parameters set via the input and / or display device 16 are forwarded to the control device 3, which controls the individual components of the steam cutting device 1 accordingly.

Weiters kann der Wasserdampfplasmabrenner 6 zumindest ein Bedienungselement 17, insbesondere einen Taster 18, aufweisen, über welches der Benutzer durch Aktivieren und/oder Deaktivieren des Tasters 18 der Steuervorrichtung 3 vom Brenner 6 aus mitteilen kann, dass ein Wasserdampf-Schneidverfahren gestartet bzw. durchgeführt werden soll. Des Weiteren können an der Eingabe-und/oder Anzeigevorrichtung 16 beispielsweise Voreinstellungen getroffen werden, insbesondere, dass das zu schneidende Material, die verwendete Flüssigkeit und beispielsweise Kennlinien des Stromes und der Spannung vordefiniert werden. Selbstverständlich können weitere Bedienelemente am Brenner 6 angeordnet sein, über die ein oder mehrere Betriebsparameter des Wasserdampf-Schneidgerätes 1 vom Brenner 6 aus eingestellt werden. Hierzu können diese Bedienelemente direkt über Leitungen oder über ein Bussystem mit dem Grundgerät 1a, insbesondere der Steuervorrichtung 3, verbunden sein.Furthermore, the steam plasma burner 6 can have at least one operating element 17, in particular a pushbutton 18, via which the user can inform the controller 3 by activating and / or deactivating the button 18 of the burner 6 that a steam cutting process is started or carried out should. Furthermore, presettings can be made, for example, at the input and / or display device 16, in particular that the material to be cut, the liquid used and, for example, characteristics of the current and the voltage are predefined. Of course, further controls on the burner 6 may be arranged via the one or more operating parameters of the steam cutting device 1 are set by the burner 6 from. For this purpose, these controls can be connected directly via lines or via a bus system to the base unit 1a, in particular the control device 3.

Die Steuervorrichtung 3 aktiviert nach dem Betätigen des Tasters 18 die einzelnen für das Wasserdampf-Schneidverfahren benötigten Komponenten. Beispielsweise werden zuerst eine Pumpe (nicht dargestellt), das Sperrelement 4 sowie die Stromquelle 2 angesteuert, wodurch eine Versorgung des Brenners 6 mit der Flüssigkeit 8 sowie mit elektrischer Energie eingeleitet wird. Anschließend aktiviert die Steuervorrichtung 3 den Kühlkreislauf 11, so dass eine Kühlung des Brenners 6 ermöglicht wird. Durch die Versorgung des Brenners 6 mit der Flüssigkeit 8 und mit Energie, insbesondere mit Strom und Spannung, wird nunmehr im Brenner 6 die Flüssigkeit 8 in ein Gas 19, insbesondere in Plasma, mit hoher Temperatur umgewandelt, so dass durch das aus dem Brenner 6 ausströmende Gas 19 ein Schneidprozess an einem Werkstück 20 durchgeführt werden kann.The control device 3 activates after pressing the button 18, the individual components required for the steam cutting process. For example, first a pump (not shown), the blocking element 4 and the current source 2 are driven, whereby a supply of the burner 6 with the liquid 8 and with electrical energy is introduced. Subsequently, the control device 3 activates the cooling circuit 11, so that a cooling of the burner 6 is made possible. By supplying the burner 6 with the liquid 8 and with energy, in particular with current and voltage, the liquid 8 is now in the burner 6 in a gas 19, in particular in plasma, converted at high temperature, so that by the burner from the sixth outflowing gas 19, a cutting process on a workpiece 20 can be performed.

Die Fig. 2 bis 4 zeigen schematische Darstellungen eines erfindungsgemäßen Wasserdampfplasmabrenners 6 in verschiedenen Betriebszuständen. Der Wasserdampfplasmabrenner 6 weist ein Gehäuse 21 auf, in dem eine Kathode 22 angeordnet ist, die mit der Stromquelle 2 verbunden ist. Die als Düse 23 ausgebildete Anode 24 ist mit dem positiven Pol der Stromquelle 2 verbunden.The Fig. 2 to 4 show schematic representations of a steam plasma burner 6 according to the invention in different operating conditions. The steam plasma burner 6 has a housing 21, in which a cathode 22 is arranged, which is connected to the power source 2. The anode 24 formed as a nozzle 23 is connected to the positive pole of the power source 2.

Im Ruhezustand oder Standby-Modus gemäß Fig. 2 wird die axial verschiebbare Kathode 22 an die Düse 23 gepresst. In diesem Modus kann zwischen der Kathode 22 und der Anode 24 kein Lichtbogen gezündet werden, da ein Kurzschluss besteht. Die im Wasserdampfplasmabrenner 6 enthaltene Heizeinrichtung zum Verdampfen des Wassers kann bereits eingeschaltet werden, so dass das Arbeitsmedium bereits vorgeheizt wird.In idle or standby mode according to Fig. 2 the axially displaceable cathode 22 is pressed against the nozzle 23. In this mode, no arc can be ignited between the cathode 22 and the anode 24 because of a short circuit. The heater contained in the water vapor plasma burner 6 for evaporating the water can already be turned on, so that the working fluid is already preheated.

Zum Zünden eines Pilotlichtbogens zwischen der Kathode 22 und der Anode 24, wird gemäß Fig. 3 die Zufuhr des flüssigen Mediums, insbesondere Wasser, eingeschaltet, wodurch sich die axial verschiebbare Kathode 22 von der Düse 23 abhebt und bei Vorhandensein eines entsprechenden Stromes ein Pilotlichtbogen zwischen der Kathode 22 und der Anode 24 gezündet wird. Anstelle einer solchen Kontaktzündung kann die Zündung eines Pilotlichtbogens auch durch Zuschalten einer hochfrequenten Spannung erfolgen. Das in der Heizeinrichtung verdampfte Wasser wird in die Brennkammer geleitet, wo es als Medium für einen Plasmastrahl dient. Der Plasmastrahl wird durch die Öffnung 25 in der als Düse 23 ausgebildeten Anode 24 herausgepresst und kann aufgrund seiner hohen Energiedichte zum Schneiden aber auch Verbinden von Werkstücken 20 eingesetzt werden. Der Wasserdampfplasmabrenner 6 befindet sich im so genannten nicht übertragenen Modus.For igniting a pilot arc between the cathode 22 and the anode 24, according to Fig. 3 the supply of the liquid medium, in particular water, turned on, whereby the axially displaceable cathode 22 lifts from the nozzle 23 and in the presence a corresponding current a pilot arc between the cathode 22 and the anode 24 is ignited. Instead of such a contact ignition, the ignition of a pilot arc can also be done by connecting a high-frequency voltage. The water evaporated in the heater is conducted into the combustion chamber where it serves as a medium for a plasma jet. The plasma jet is forced out through the opening 25 in the anode 24 formed as a nozzle 23 and can be used for cutting but also joining workpieces 20 due to its high energy density. The steam plasma burner 6 is in the so-called non-transferred mode.

Um die Umschaltung vom Standby-Modus gemäß Fig. 2 in den nicht übertragenen Modus gemäß Fig. 3 zu optimieren, werden verschiedene Betriebsparameter gemessen und einer Steuerungseinrichtung 25, welche einen Schalter 30 zwischen der Stromquelle 2 und der Anode 24 des Wasserdampfplasmabrenners 6 steuert, zugeführt. Konkret werden die Spannung UNUE zwischen der Kathode 22 und der Anode 24 mit Hilfe eines Spannungmessgeräts 26 und der Strom IUE vom Pluspol der Stromquelle 2 zum Werkstück 20 mit Hilfe eines Strommessgeräts 28 erfasst. Darüber hinaus können die Spannung UUE zwischen der Kathode 22 und dem Werkstück 20 mit Hilfe des Spannungsmessgeräts 27 und der Strom ICUT vom negativen Pol der Stromquelle 2 zur Kathode 22 des Wasserdampfplasmabrenners mit Hilfe eines Strommessgeräts 29 ermittelt werden. Die erfassten Daten werden der Steuerungseinrichtung 25 zugeführt, welche den Schalter zur Verbindung des Pluspols der Stromquelle 2 mit der Anode 24 steuert. Dabei wird über die Spannung UNUE zwischen der Kathode 22 und der Anode 24 des Wasserdampfplasmabrenners, welche mit Hilfe des Spannungsmessgeräts 26 erfasst wird, erkannt, wann der Kurzschluss zwischen der Kathode 22 und der Anode bzw. Düse 24 aufgehoben wurde. Erst dann kann der Pilotlichtbogen zwischen der Kathode 22 und der Anode 24 gezündet werden.To switch from standby mode according to Fig. 2 in the non-transmitted mode according to Fig. 3 To optimize, various operating parameters are measured and a control device 25, which controls a switch 30 between the power source 2 and the anode 24 of the steam plasma burner 6, respectively. Specifically, the voltage U NUE between the cathode 22 and the anode 24 are detected by means of a voltage meter 26 and the current I UE from the positive pole of the current source 2 to the workpiece 20 by means of an ammeter 28. In addition, the voltage U UE between the cathode 22 and the workpiece 20 can be determined with the aid of the voltmeter 27 and the current I CUT from the negative pole of the current source 2 to the cathode 22 of the steam plasma burner with the aid of an ammeter 29. The detected data is supplied to the controller 25 which controls the switch for connecting the positive pole of the power source 2 to the anode 24. In this case, it is detected via the voltage U NUE between the cathode 22 and the anode 24 of the steam plasma burner , which is detected by means of the voltage measuring device 26, when the short circuit between the cathode 22 and the anode or nozzle 24 has been canceled. Only then can the pilot arc between the cathode 22 and the anode 24 be ignited.

Nähert sich der Wasserdampfplasmabrenner 6 nun dem mit dem positiven Pol der Stromquelle 2 verbundenen Werkstück 20, beginnt ein kleiner Teilstrom IUE über den übertragenen Strompfad zu fließen. Übersteigt der mit Hilfe des Strommessgeräts 28 gemessene Strom IUE zum Werkstück 20 einen definierten Schwellwert IUEs, wird der Schalter 30 von der Steuerungseinrichtung 25 betätigt und somit die Stromquelle 2 von der Anode 24 weggeschaltet. Dadurch schlägt der Lichtbogen gezwungenermaßen von der Kathode 22 zum Werkstück 20 über und der Strom der Stromquelle 2 kann auf einen bestimmten Schneidstrom ICUT erhöht werden. In diesem Fall befindet sich der Wasserdampfplasmabrenner 6 im so genannten übertragenen Modus. Wird der Wasserdampfplasmabrenner 6 vom Werkstück 20 weiter entfernt, steigt die Spannung zwischen der Kathode 22 und dem Werkstück an, da die Stromquelle 2 bestrebt ist, den eingestellten Schneidstrom ICUT aufrecht zu erhalten. Übersteigt die mit dem Spannungsmessgerät 27 erfasste Spannung UUE einen definierten Schwellwert UUES, wird der Schalter 30 wiederum geschlossen und somit die Anode 24 wieder mit dem positiven Pol der Stromquelle 2 verbunden, um ein Abreißen des Lichtbogens zu verhindern. In diesem Zustand befindet sich der Wasserdampfplasmabrenner 6 wieder im nicht übertragenen Modus gemäß Fig. 3. Somit wird zwischen den beiden Betriebszuständen übertragener und nichtübertragener Modus nach Bedarf gewechselt. Dabei ist es wichtig, dass die Steuerung des Schalters 30 sehr rasch erfolgt. Zu diesem Zweck eignen sich analog ausgeführte Steuerungseinrichtungen 25 mehr als Realisierungen durch Mikrokontroller. Diese automatische Steuerung des Lichtbogens ist beim Schneiden bestimmter Werkstücke, wie z.B. von Lochblechen, von großer Bedeutung. In diesem Fall würde es durch ständigen Wechsel des Abstandes zwischen Werkstück und Brenner zu einem Erlöschen des Lichtbogens kommen, was eine Neuzündung des Pilotlichtbogens erforderlich machen würde. Darüber hinaus kann das Pulsen des Stroms bei manchen Materialien für die Schneidqualität von Vorteil sein. Durch das erfindungsgemäße Verfahren wird die Energieeinbringung reduziert.When the water vapor plasma torch 6 now approaches the workpiece 20 connected to the positive pole of the current source 2, a small partial current I UE begins to flow over the transmitted current path. If the current I UE measured with the aid of the ammeter 28 exceeds a defined threshold value I UEs for the workpiece 20, the switch 30 is actuated by the control device 25 and thus the power source 2 is disconnected from the anode 24. As a result, the arc forcibly deflects from the cathode 22 to the workpiece 20 and the current of the current source 2 can be increased to a specific cutting current I CUT . In this case, the steam plasma burner 6 is in the so-called transferred mode. As the water vapor plasma torch 6 is further removed from the workpiece 20, the voltage between the cathode 22 and the workpiece increases as the current source 2 tends to maintain the adjusted cutting current I CUT . If the voltage U.sub.E detected by the voltmeter 27 exceeds a defined threshold U.sub.UES , the switch 30 is in turn closed and thus the anode 24 is again connected to the positive pole of the current source 2 in order to prevent the arc from tearing off. In this state, the steam plasma burner 6 is again in the non-transferred mode according to Fig. 3 , Thus, the mode transmitted and not transmitted between the two operating states is changed as needed. It is important that the control of the switch 30 is very fast. Analogously designed control devices 25 are more suitable for this purpose than implementations by microcontrollers. This automatic control of the arc is of great importance when cutting certain workpieces, such as perforated sheets. In this case, it would come to an extinction of the arc by constantly changing the distance between the workpiece and the burner, which would require a re-ignition of the pilot arc. In addition, pulsing the flow may be beneficial to some materials for cutting quality. The inventive method, the energy input is reduced.

Weiters ist es möglich, dass die Steuervorrichtung 3 in den Umschaltprozess einwirkt. Hierzu wird beispielsweise beim erstmaligen Zünden des Pilotlichtbogens, also bei der Aktivierung des Prozesses, von der Steuervorrichtung 3 ein Umschaltsignal erzeugt bzw. gelöscht werden muss, wobei die Steuervorrichtung 3 erst bei Überschreiten eines Schwellwertes für das Umschaltsignal den Schalter 30 freigibt, d.h., dass erst wenn das Umschaltsignal beispielsweise über 50V steigt eine Umschaltung vom nichtübertragenen Modus in den übertragenen Modus möglich ist. Damit ist sichergestellt, dass der Kurzschluss zwischen Kathode und Anode sicher aufgerissen ist, also die Kathode von der Anode abgehoben ist, und der Pilotlichtbogen zwischen der Kathode 22 und Anode 24 im inneren des Brenners 6 sicher brennt.Furthermore, it is possible that the control device 3 acts in the switching process. For this purpose, for example, when first activating the pilot arc, ie when activating the process, a switching signal must be generated or deleted by the control device 3, wherein the control device 3 releases the switch 30 only when a threshold value for the switching signal is exceeded, ie, that only For example, if the switching signal exceeds 50V, switching from the non-transmitted mode to the transmitted mode is possible. This ensures that the short circuit between the cathode and anode is safely torn, so the cathode is lifted from the anode, and the pilot arc between the cathode 22 and anode 24 inside the burner 6 burns safe.

Durch die Freigabe von der Steuervorrichtung 3 ist es der analog aufgebauten Steuerungseinrichtung 25 dann möglich, den Schalter 30 zu öffnen, damit der Lichtbogen dann auf das Werkstück 20 umgeschaltet werden kann. Damit wird nun sichergestellt, dass kein Lichtbogen zwischen der Düse 23 und dem Werkstück 20 brennen kann, ohne das die Kathode 22 von der Anode·24 abgehoben ist. Hebt nämlich die Kathode 22 beispielsweise nicht von der Anode 24 ab, so wäre es während dem Betrieb nicht möglich, dass zwischen den übertragenen Modus und den nichtübertragene Modus hin und her geschaltet werden kann. Auch wird damit sichergestellt, dass ein sicheres Aufheizen des Brenners 6 über den Pilotlichtbogen erreicht wird, sodass immer nur Wasserdampf aus dem Brenner 6 austritt. Durch diesen Eingriff der Steuervorrichtung 3 wird dies verhindert, da erst eine Zündung zwischen Düse 23 und Kathode 24 erfolgen muss, um dieses Signal zu löschen bzw. ein entsprechendes Signal zu erzeugen, damit ein Schalten des Schalters 30 möglich ist.By the release of the control device 3, it is then possible for the analog control device 25 to open the switch 30 so that the arc can then be switched to the workpiece 20. This ensures that no arc can burn between the nozzle 23 and the workpiece 20 without the cathode 22 being lifted from the anode 24. For example, if the cathode 22 is not removed from the anode 24, it would not be possible during operation to switch between the transmitted mode and the non-transmitted mode. This also ensures that a safe heating of the burner 6 is achieved via the pilot arc, so that only water vapor exits the burner 6. By this intervention of the control device 3, this is prevented, since only an ignition between the nozzle 23 and cathode 24 must be made to clear this signal or to generate a corresponding signal, so that switching of the switch 30 is possible.

Ein weiterer Eingriff der Steuervorrichtung 3 kann auch derart erfolgen, dass beim übertragnen Modus, wo also der Lichtbogen zwischen dem Werkstück 20 und Kathode 22 brennt, beim Zurückschalten in den nichtübertragnen Modus, also dem Pilotlichtbogen, von der Steuervorrichtung 3 ein Überwachung des Pilotlichtbogens erfolgt, d.h., dass der Pilotlichtbogen über eine gewisse Zeit, bevorzugt 1,2msec, zwischen der Düse 23 und der Kathode 24 brennen muss, worauf anschließend abgefragt wird, wo der Strom nun fließt, bevor der Lichtbogen wieder auf das Werkstück 20 geschaltet werden kann bzw. der Pilotlichtbogen aufrecht erhalten bleibt. Damit wird sicher gestellt, dass ein Schwingen, also hin und herschalten, nicht auftreten kann, da der eingesetzte Schalter 30 hohe Schaltfrequenzen nicht aushält.Another intervention of the control device 3 can also take place in such a way that in the transmitted mode, ie where the arc between the workpiece 20 and cathode 22 burns when switching back to the non-transferred mode, ie the pilot arc, the control device 3 monitors the pilot arc. ie, that the pilot arc over a certain period of time, preferably 1.2msec, must burn between the nozzle 23 and the cathode 24, whereupon it is queried where the current now flows before the arc can be switched back to the workpiece 20 or the pilot arc is maintained. This ensures that a swing, so switch back and forth, can not occur because the switch used 30 high switching frequencies can not stand.

Selbstverständlich ist es möglich, dass der Schaltungsaufbau digital oder analog erfolgen kann, wodurch bei einem digitalen Aufbau die Steuerungseinrichtungen 25 in der Steuervorrichtung 3 integriert bzw. durch diese verwirklicht wird.Of course, it is possible that the circuit design can be digital or analog, whereby the control means 25 is integrated in the control device 3 or realized by this in a digital structure.

Claims (19)

  1. A method for operating a steam plasma burner (6) including a cathode (22) and an anode (24) in the form of a nozzle (23) for processing a workpiece (20), wherein during operation a current is impressed between the cathode (22) and the anode (24) and/or the workpiece (20) by the aid of a power source (2), wherein, after the ignition of a pilot arc between the cathode (22) and the anode (24), a working arc is formed between the cathode (22) and the workpiece (20) by the steam plasma burner (6) approaching the workpiece (20), and the pilot arc is extinguished by the power source (2) being disconnected from the anode (24), and the current is increased to a predetermined operating current, and wherein the voltage (UUE) between the cathode (22) and the workpiece (20) is monitored during the working operation and the power source (2) is reconnected to the anode (24) to newly form the pilot arc when the voltage (UUE) exceeds a threshold value (UUEs), characterized in that the power source (2) is disconnected from the anode (24) when the current (IUE) between the workpiece (20) and the cathode (22) exceeds a threshold value (IUEs), so that only the working arc is still burning.
  2. The method according to claim 1, characterized in that the threshold value (UUEs) is adjustable.
  3. The method according to claim 1 or 2, characterized in that different threshold values (UUEs) are stored, and adjustable, as a function of the steam plasma burner (6) used.
  4. The method according to any one of claims 1 to 3, characterized in that the operating current (ICUT) is adjustable during the working operation.
  5. The method according to any one of claims 1 to 4, characterized in that the power source (2) is disconnected from the anode (24) after a pregiven time duration (Δt) as soon as the current (IUE) exceeds the threshold value (IUEs).
  6. The method according to claim 5, characterized in that said time duration (Δt) is 1 to 1.4 ms.
  7. The method according to any one of claims 1 to 6, characterized in that the threshold value (IUEs) of the current is adjustable.
  8. The method according to any one of claims 1 to 7, characterized in that the pilot arc is ignited by applying a high-frequency voltage between the cathode (22) and the anode (24).
  9. The method according to any one of claims 1 to 7, characterized in that the pilot arc is ignited by lifting an axially displaceable cathode (22) from the anode (24).
  10. The method according to claim 9, characterized in that, during working operation, the voltage (UNUE) between the cathode (22) and the anode (24) is measured and compared to the voltage (UNUE) between the cathode (22) and the workpiece (20), and the operating current is reduced in case of a match.
  11. The method according to claim 9 or 10, characterized in that the voltage (UNUE) between the cathode (22) and the anode (24) is measured and the disconnecting of the power source (2) from the anode (24) is prevented at the detection of a short-circuit.
  12. The method according to any one of claims 1 to 11, characterized in that the connecting and/or disconnecting of the power source (2) from the anode (24) is realized according to a pregiven function and, for instance, in a step- or ramp-like manner.
  13. The method according to any one of claims 1 to 12, characterized in that the flow rate of the water of the steam plasma burner (6) is adjusted.
  14. A steam cutting device (1) including a steam plasma burner (6) including a cathode (22) and an anode (24) in the form of a nozzle (23), a power source (2) connected to the cathode (22), on the one hand, and the workpiece (20) to be processed as well as the anode (24), on the other hand, a control device (25) for controlling a switch (30) arranged in the connection between the power source (2) and the anode (24), and a device (27) for measuring the voltage (UUE) between the cathode (22) and the workpiece (20), characterized in that a device (28) for measuring the current (IUE) between the cathode (22) and the workpiece (20) is provided, and that the measuring devices (27, 28) are connected to the control device (25), so the power source is disconnected from the anode when a certain threshold (IUEs) for the current (IUE) between cathode and workpiece is exceeded.
  15. The steam cutting device (1) according to claim 14, characterized in that a device (29) for measuring the current (ICUT) between the cathode (22) and the workpiece (20) is provided, which measuring device (29) is connected to the control device (25).
  16. The steam cutting device (1) according claim 14 or 15, characterized in that a device (26) for measuring the voltage between the cathode (22) and the anode (24) is provided, which measuring device (26) is connected to the control device (25).
  17. The steam cutting device (1) according to any one of claims 14 to 16, characterized in that the control device (25) is comprised of an analog circuit.
  18. The steam cutting device (1) according to any one of claims 14 to 17, characterized in that the switch (30) is comprised of a transistor, in particular an IGBT (insulated gate bipolar transistor).
  19. The steam cutting device (1) according to any one of claims 14 to 18, characterized in that a memory for storing predefined threshold values is provided, which memory is connected to the control device (25).
EP06774763A 2005-09-09 2006-09-06 Method for operation of a steam plasma burner and steam cutting device Not-in-force EP1922908B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AT0148205A AT502422B1 (en) 2005-09-09 2005-09-09 METHOD FOR OPERATING A WATER STEAM PLASMA CYLINDER AND WATER VAPOR CUTTING DEVICE
PCT/AT2006/000365 WO2007028182A2 (en) 2005-09-09 2006-09-06 Method for operation of a steam plasma burner and steam cutting device

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EP1922908A2 EP1922908A2 (en) 2008-05-21
EP1922908B1 true EP1922908B1 (en) 2012-04-11

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EP (1) EP1922908B1 (en)
JP (1) JP4907660B2 (en)
CN (1) CN101288347B (en)
AT (2) AT502422B1 (en)
WO (1) WO2007028182A2 (en)

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CN101288347B (en) 2012-12-26
EP1922908A2 (en) 2008-05-21
WO2007028182A3 (en) 2007-07-26
AT502422B1 (en) 2007-06-15
AT502422A1 (en) 2007-03-15
ATE553635T1 (en) 2012-04-15
US20090266799A1 (en) 2009-10-29
WO2007028182A2 (en) 2007-03-15
JP4907660B2 (en) 2012-04-04
CN101288347A (en) 2008-10-15
JP2009506892A (en) 2009-02-19

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