WO2009023003A1 - Method for automatically controlling a plasmotron operation mode and a plant for carrying out said method - Google Patents

Abstract

The invention can be used in electrical engineering, plasma metallurgy and plasma chemistry for automatically controlling a plasmotron operation mode. The method is based on a control complex combining control systems, the multipurpose compatibility thereof, the adjustment of the plasmotron operation mode and the energy characteristics thereof. The inventive plant for automatically controlling a plasmotron operation mode comprise a current arc adjuster (1), an arc generating unit (2), a gas-water panel (3) and a plant control panel (4). When the operational parameters of the plasmotron correspond to the specified values, a control unit (43) emits a signal for closing a locking relay (47) and authorises the plasmotron operation. When arcing is unstable, the maximum permissible switching frequency of a transistor key (8) is set, and once the transition processes have been ended and the arc voltage has achieved the specified value, the frequency is reduced to a minimum permissible value.

Description

 A method for automatically controlling the plasma torch operating mode and installation for its implementation An interrelated group of inventions relates to electrical engineering, in particular, to converting electric energy into thermal energy using a plasma torch, its control method and device for its implementation, which can be used in plasma metallurgy and plasma chemistry.

A known method of power supply of direct current plasmatrons with porous injection of plasma-forming gas using thyristor rectifiers operating in current stabilization mode. The plasmatron power supply is a stabilizer with increased requirements for dynamic characteristics. The plasma torch was powered from two controlled rectifiers connected to a 6.3 kW network, through an ATMNU-10000/14 autotransformer and a TMPU-16000/10 isolation transformer. On the DC side, the rectifiers were connected in series. The control of both rectifiers was common.

This method is not effective, since DC control has a narrow dynamic range, especially when changing the flow rates of plasma-forming gases through the plasma torch. Due to the incomplete controllability and discreteness of the thyristor converter, as well as the non-linearity and inertia of the electric arc with increasing gas flow to 1.5 kg / s and the current-voltage ratio over 2.5, self-oscillations of the current occur in the system on lower subharmonics with a frequency of 15-120 Hz and amplitude up to 30-50% of the rated current (Low-temperature plasma generators. Abstracts of the Xl All-Union Conference on low-temperature plasma generators (Novosibirsk June 20-23, 1983) part 1. - A. A. Durasov, O.D. Zaraisky, A. S.Krasovsky et al. Siste MA of power supply of high-power direct current plasmatrons, pp. 16-17).

The closest in technical essence and the achieved result (prototype) adopted a method of stabilization and regulation of power supply of plasmatrons, in which the current of each plasmatron individually set using pulse-width modulators. A regulating element is sequentially included in the current circuit - a key, with which a constant voltage source is periodically connected to the load. The average value of the voltage in the circuit and the current in the load is regulated by changing the duty cycle of the pulses, i.e. time on state with a constant period. To avoid the cessation of current in the load when the key is off, a choke and a diode are included in the circuit. In the key conduction interval, the inductor stores energy, which during a pause is transmitted to the load through the diode. As a result, a direct current with ripples flows in the load, the value of which depends on the inductance of the inductor and the load resistance. An isolation filter may be required to isolate individual power supplies. Current feedback allows you to get steeply falling external characteristics with high stability of a given current.

Among the shortcomings it should be noted the generation of various kinds of interference associated with the pulsed nature of the work, and the difficulties of implementation at high powers due to the lack of powerful high-frequency semiconductor devices (Multi-arc systems. Novikov O.Ya., Tamkivi P.I., Timoshevsky A.N. and et al., Novosibirsk: Nauka, Sib. Department, 1988. - pp. 90-92).

A device for controlling the operation mode of an electric arc installation, comprising an indirect-action plasma torch, a rectifier connected to the cathode and anode of the plasma torch, a plasma-forming gas source, a trigger control and arc discharge control unit, the input of which is connected to a common rectifier circuit, characterized in that the control unit the starting mode and the excitation of the arc discharge is equipped with coils of circuit breakers with delay lines, which are connected via control contacts to the circuit Excitation of the arc discharge of the plasma torch through thermal relays, the rectifier is made in the form of a semi-controlled three-phase diode-thyristor rectifier, in each phase of which an additional diode is introduced, and a resistor is connected in parallel with the thyristor (Patent of Ukraine Ш21208, class 6 H 05 В 7/18, application. 11.05 .1994, publ. 16.10.2000, bull. N ° 5).

However, the proposed installation does not provide stable operation of the plasma torch and the regulation of operating modes for the following reasons:

- during operation, due to high ripple current, breakdown of thyristors occurs; - the excitation key does not provide a reliable and stable start of the plasma torch;

- the reliability of the electric strength of the interelectrode gaps of the plasma torch is not controlled, which leads to their premature burnout; - temperature and overheating of the electrodes are not controlled plasmatron.

The closest in technical essence and the achieved result (prototype) adopted device for controlling an electric arc installation containing a plasma torch, a source of plasma-forming gas, a control unit for starting mode and excitation of an arc discharge, including a high-frequency step-up transformer, a semi-controlled three-phase diode-thyristor rectifier connected to the cathode and the plasma torch anode, in each phase of which an additional diode, a resistor, a current circuit breaker connected in parallel to the thyristor, is inserted, According to the invention, in a semi-controlled three-phase diode-thyristor rectifier, a resistor is connected in series with the thyristor, on the anode side, and a high-frequency transformer is made on several separate closed magnetic circuits, the primary windings of which are connected in series, and the secondary winding covers all the magnetic circuits and is connected in series to the cathode circuit, and control units for the start-up mode and excitation of the arc discharge introduced devices for monitoring the temperature of cooling water in the plasma electrodes otron, for example thermocouples, with comparison units, a device for monitoring the electric strength of the interelectrode gaps of the plasma torch, each of which includes a high-frequency transformer, the primary winding of which is connected to the electrodes through a capacitor, and the secondary is connected to the comparison units, an electrode wear monitoring device, in the form of a tubular electrode, installed in the cavity of the cathode of the plasma torch with the possibility of longitudinal movement, isolated relative to the end swirl of the cathode and connected with additional An additional adjustable source of voltage of negative or positive polarity associated with the comparison unit, and also through the flow regulator is connected to a plasma gas source, while the control circuit of the current circuit breaker is powered through series-connected contacts of the comparison units (Patent of Ukraine N ° 74047, cl. 7 H 05 B 7/18, declared 08/26/2003, publ. bull. MlO, 2005). However, this device does not allow you to quickly respond to changes in arc current. The frequency at which the semi-controllable thyristor regulator operates determines the conditions under which the inductance of the inductor must be sufficiently large. The operation of an additional resistor connected in series with the thyristor leads to large power losses and reduces the overall efficiency of the device. The basis of the first of the group of inventions is the task of improving the method for automatically controlling the plasma torch operating mode by reducing the amplitude of current and voltage ripple, expanding the range of regulation of the plasma torch operating mode, which will allow changing the energy characteristics of the plasma torch, ensuring its reliable and economical operation.

The second of the group of inventions is based on the task of improving the installation of automatic control of the plasma torch operation mode, in which, by introducing new elements and assemblies into the control circuit, to create an easy-to-maintain and reliable system that optimizes and extends the control capabilities of the plasma torch and expands the scope installation application.

The first task is solved in that in a method for automatically controlling the plasma torch operating mode, in which a constant voltage source is periodically connected to the plasmatron using a transistor switch, the average voltage and current in the plasmatron being controlled by changing the duty cycle of the pulses, and continuous current is maintained in the plasmatron due to the installation of a choke in the circuit, which stores energy in the interval of the key conductivity, and during pause transfers energy through the diode to the plasma he, according to the invention, set the upper and lower limits of the operating current of the plasma torch, arc voltage and voltage of each neutrode from the control panel of the installation and additionally set the upper and lower limits of the values of flow, pressure and temperature of gases and water for each channel of the gas-water console, while if the sensor signals are within the specified limits, the control unit gives a signal to close the blocking relay and allows the plasma torch to work, if the signals on any channel go beyond the specified limits, then the remote control The setup signal is used to turn off the plasma torch, and the current is stabilized by the program method in the control unit, by comparing the values of the specified operating current with the signal of the analog current sensor, and during startup, at rapidly changing values of the arc current from zero to the set value, the maximum allowable frequency is used , and after the end of transient processes, when the specified value of the arc current is reached, the frequency decreases to the minimum possible value, while expanding the zone of arc binding by period changing the flow rate of plasma-forming gas in one of the gas supply channels using a pneumatic gas modulator control panel, while the signal from the analog current sensor to the control unit is continuously analyzed in automatic mode and, when an unstable arc burning occurs, the maximum allowable switching frequency of the transistor switch is set, and after the end of transient processes, when the arc current reaches the set value, the frequency reduced to the lowest possible value.

A way to automatically control the plasma torch operating mode is a control complex, which provides a combination of control systems, their universal compatibility, which allows optimizing and expanding control capabilities.

The second task is solved in that the installation of automatic control of the plasma torch, containing a three-phase rectifier, an arc excitation unit with a high-voltage transformer connected to the cathode and anode of the plasma torch, according to the invention, the installation further comprises an arc current regulator, a gas-water console and a control panel of the installation, the output terminals of the arc current regulator are connected to the output terminals of the arc excitation unit, the output terminals of the excitation unit are connected to the corresponding m to the electrodes of the plasma torch, and the control panel of the installation is connected by information buses to the current regulator, the arc excitation unit and the gas-water console, the high-voltage transformer of the arc excitation unit connected to a high voltage unit, the control input of which is connected to the output of the arc excitation control unit, in the positive bus of which is installed arc current sensor, the output of which is connected to the input of the control unit, and the output of the control unit is connected to the coil of the contactor connected through a resistor to the capacitor and the output the bottom terminal of the plasma torch neutron, and additional capacitors are connected to the negative polarity bus via a charging resistor and a series resistor and a diode, and the output of the control unit is connected to the control winding of the blocking relay, while the arc current regulator consists of an input protection block with terminals for connecting the power supply network, three-phase rectifier, capacitor, transistor switch, the output of which is connected to a diode and inductor, in series with which the limit sensor is connected a current sensor and analog, and the current sensor output is connected to the control current regulator, wherein the control input of the transistor switch connected to the generator output two-input, one of whose inputs is connected to the output of the control unit, and the second connected to the output of the sensor current limit. The gas-water remote control includes a plasma-forming gas supply system, which consists of an inlet manifold to which a pressure sensor and flow controllers are connected, each of which contains an electric control valve, a flow sensor, a pressure sensor, a temperature sensor, and a computing device, moreover, in one of the supply valves gas, a pneumatic modulator is installed, and the coolant supply and exhaust system consists of a pressure manifold to which a temperature sensor, a pressure sensor and a drain are connected the first collector to which water flow meters, temperature sensors are connected, the gas-water console is equipped with an information system consisting of a control unit with computing devices for each gas flow controller, water flow meters, water temperature sensors and pressure sensors, while the control unit contains a communication interface , display and keyboard, and the output of the control unit is connected to the control winding of the interlock relay. Safe start-up of the plasma torch and constant monitoring of its operation after start-up are provided by the arc excitation unit. The control unit as part of the arc excitation unit monitors the presence of voltage on the negative bus. The appearance of voltage from the power source serves as a command for the control unit to start the start. In addition, data on the current state of the plasma torch and on the voltages at the cathode and neutrode are constantly transmitted through the communication line to the control panel.

During start-up, when the cathode-neutrode gap breaks down, the resistance of this gap decreases sharply and the charged capacitor bank discharges, and as the capacitor bank discharges, the voltage on the negative bus decreases, which leads to the appearance of current through the power source and the inductor at its output. The capacity of the capacitor bank is selected so that the maximum energy is sufficient to maintain the arc while the current in the inductor reaches a sufficient value. The resistance of the discharge resistor is chosen so that the discharge current does not exceed the permissible limits. The gas-water remote control is intended for supplying plasma-forming gases to the plasma torch with preset values of mass flow rate for each channel, as well as for supplying / discharging cooling water to the heat-loaded parts of the plasma torch. The control unit on the communication line receives from the control panel the set values of the mass flow rate of the plasma-forming gas. The control unit transmits the received tasks to the flow control unit, which provides adjustment and maintaining set flow rates when changing the gas inlet pressure, backpressure in the channel, gas temperature, and other destabilizing factors. A pneumatic modulator is installed in one of the gas supply channels, which is necessary to reduce wear of the cathode surface, expanding the arc attachment zone by periodically changing the gas flow (modulation) along one of the channels. In this case, the optimal values of the modulation parameters - frequency, depth, shape - are provided programmatically in the control unit.

The water supply is carried out through the water supply unit, which provides disconnection and connection of the water supply in each channel. In addition, the temperature and pressure of the cooling water at the inlet to the block are controlled in the supply unit. The control unit ensures the operation of the components of the gas-water console, the operational monitoring of their condition, receives tasks from the control panel and sends the current parameters to the control panel - mass flow rate and pressure in each gas supply channel, inlet pressure in the gas supply manifold, flow rate and water temperature at the discharge each channel, the pressure and temperature of the water in the pressure manifold, in addition, the control unit, in the event of an emergency, opens the contacts of the blocking relay, which can be used for emergency about turning off the power source of the plasma torch.

Using the installation, the proposed method is implemented as follows. The upper and lower limits of the operating plasma torch current, arc voltage, and voltage of each neutrode are set from the control panel of the installation, and the upper and lower limits of the flow rates, pressures, and temperatures of gases and water are set for each channel of the gas-water console. If the sensor signals are within the specified limits, the control unit gives a signal to close the blocking relay and allows the plasma torch to work, and if the signals on any channel go to the specified limits, a signal is sent from the control panel to turn off the plasma torch. The current stabilization is carried out by software in the control unit by comparing the values of the specified operating current with the signal of the analog current sensor. During start-up, at rapidly changing values of the arc current from zero to a given value, the maximum allowable frequency is used, and after the end of transient processes, when the set value of the arc current is reached, the frequency decreases to the minimum possible value, while expanding the arc reference zone by periodically changing flow rate of plasma-forming gas in one of the gas supply channels using a pneumatic modulator of the gas console. Signal from analog the current sensor to the control unit is continuously analyzed in automatic mode, and when the mode of unstable arc burning appears, the maximum allowable switching frequency of the transistor switch is set, and after the end of transient processes, when the arc current reaches the set value, the frequency decreases to the minimum possible value.

The drawing shows a functional diagram of the inventive installation. The power supply installation of the plasma torch consists of an arc current regulator 1, an arc excitation unit 2, a gas-water console 3 and a plant control panel 4. The current controller of the arc 1 consists of an input protection unit 5, the input of which is supplied with a three-phase supply voltage. Next, the supply voltage is supplied to a three-phase rectifier 6, then the rectified direct voltage is smoothed using a capacitor bank 7 and is supplied to a transistor switch 8, the output of which is connected to a diode 9 and a choke 10. A limit current sensor 11 and an analog current sensor 12 are connected in series with the choke 10. The output of the current sensor 12 is connected to the control unit of the current regulator 13. The control input of the transistor switch 8 is connected to the output of the two-input driver 14, one of the inputs of which is connected to the output of the unit 13, and the second input is connected to the output of the current limit sensor 11.

The arc excitation unit 2 consists of a high-voltage transformer 15 connected to a high voltage unit 16, the control input of which is connected to the output of the control unit 17. An arc current sensor 18 is installed in the positive bus, the output of which is connected to the input of the control unit 17. The output of the control unit 17 is connected with the contactor 19. A wire resistor 20 is connected to the capacitor 21 and the terminal of the neutrode. A capacitor bank 22 is connected to the negative bus via a charging resistor 23 and through a series-connected discharge resistor 24 and a diode 25. The output of the control unit 17 is connected to the control winding of the blocking relay 26.

The gas-water remote control consists of a plasma-forming gas supply system, a coolant supply and exhaust system, and an information system. The plasma gas supply system consists of an inlet manifold 27 to which a pressure sensor 28 and flow controllers 29 are connected, each of which contains an electric control valve 30, a flow sensor 31, a pressure sensor 32, a temperature sensor 33, and a computing device 34. In one of pneumatic modulator 35 is installed in the gas supply channels. The coolant supply / removal system consists of a pressure manifold 36, to which a temperature sensor 37, a pressure sensor 38, as well as shut-off valves 39, and a drain manifold 40 are connected to which water flow meters 41 and water temperature sensors 42 are connected. The information system consists of a control unit 43 to which computing devices 34 of each of gas flow regulators 29, as well as water flow meters 41, water temperature sensors 37 and 42, and pressure sensors 28 and 38. In addition, the control unit includes a communication interface 44, a display 45 and a keyboard 46. The output of the control unit 43 is connected connected to the control winding of the interlock relay 47.

The installation control panel 4 consists of a control unit 48 to which a display 49, a keyboard 50, and a communication interface 51 are connected.

A three-phase supply voltage is applied to the input terminals of the arc current regulator 1. The output terminals of the arc current regulator 1 are connected to the input terminals of the arc excitation unit 2. The output terminals of the arc 2 excitation unit are connected to the electrodes of the plasma torch. The installation control panel 4 is connected by information buses to the arc current regulator 1, the arc excitation unit 2 and the gas-water console 3. In addition, the relay contacts of the locks 26 and 47 are connected in series and connected to the control unit 48. The installation works as follows. The control panel of the installation 4 contains a display 49 and a keyboard 50, which allows you to control the installation in manual mode, and to monitor the status of its components. In addition, the control panel 4 includes a communication interface 51, which allows you to include the installation in the ACS TP, and control it remotely.

The control panel 4 is connected to the control units 13, 17 and 43 using the integrated communication interfaces through which the control panel 4 transmits commands and receives response information from the blocks.

An alternating three-phase voltage is supplied to the input protection unit 5, then to a three-phase rectifier 6. The direct voltage rectified by the three-phase rectifier 6 is additionally smoothed using a capacitor bank 7, and supplied to the transistor switch 8. A driver 14 is installed in the control circuit of the transistor switch 8, which provides supply to the input of the transistor switch 8 the necessary voltage levels for its complete unlocking and locking. A feature of the shaper 14 is the presence of a second (locking) input, which provides a quick shutdown of the transistor 8 when the allowed current is exceeded, regardless of the signal at the main input. Transistor switch 8 operates in a pulsed mode, with alternating fully open and completely locked states, which ensures minimal power loss when regulating the arc current. Current regulation is achieved by changing the duty cycle of the pulses - the ratio of the time of the open and locked state of the key. The diode 9 and the inductor 10 ensure the continuity of the current flow in the load (arc), with the pulse nature of the transistor switch 8. When the open state of the switch 8, the diode 9 is locked, the arc current passes through the inductor 10, accumulating magnetic field energy in it. When the transistor switch 8 is locked in the inductor 10, an emf occurs. self-induction, and the accumulated magnetic energy is transferred to the load. In this case, the diode 9 is unlocked, and the arc current passes through it. In series with the load in the negative bus, the limit current sensor 11 is turned on, which ensures the safe operation of the transistor, quickly locking the shaper 14 when the current exceeds the maximum permissible value. Thus, additional inertialess protection of the transistor switch 8 is provided, which is necessary during transients during the start of the plasma torch, or with an unstable character of arc burning. Analog current sensor 12 generates a signal proportional to the current value of the current, which is compared in the control unit 13 with the set current value received from the control panel 4. The difference between the set and current values is a control parameter for the pulse-width modulator included in the control unit 13 In this case, the duty cycle of the pulses at the output of the pulse-width modulator is changed so that the current current value becomes equal to the specified value. This ensures the adjustment and stabilization of the set current value.

The frequency of the pulse-width modulator is not constant. To ensure maximum stability of the feedback loop of the current regulator, it is necessary to increase the switching frequency of the transistor switch. But with an increase in frequency, dynamic losses in the transistor key increase, which leads to its increased heating, a decrease in the reliability of the current regulator, and a decrease in efficiency installation as a whole. Therefore, the frequency is selected by the control unit 13 adaptively, depending on the operating conditions of the current regulator. At start-up, when the value of the arc current rapidly changes from zero to the set value, the maximum allowable frequency is used for more accurate current processing. After the end of transient processes, when the arc current reaches the set value, the frequency, in order to reduce the dynamic losses in the transistor, decreases to the minimum possible value. The minimum frequency value is determined permissible amplitude of ripple current and inductance of the inductor. In addition, the control unit 13 constantly analyzes the signal from the output of the analog current sensor 12, and when an unstable mode of arc burning occurs, it increases the frequency momentarily. The output terminals of the current regulator 1 are connected by cables to the arc excitation unit 2. The primary winding of the step-up high-voltage transformer 15 is connected to the high voltage unit 16. The secondary (step-up) winding of the transformer 15 is connected in series in the negative bus. In order for a high-voltage breakdown to occur in the gap between the cathode and the plasma torch neutrode, a blocking capacitor 21 is installed in the circuit. The control unit 17 monitors the presence of voltage on the negative rail.

The appearance of voltage from the power source serves as a command for the control unit 17 to start the start. To do this, first, the control unit 17 closes the contacts of the contactor 19, and then sends a command to the high voltage unit 16. In this case, the high voltage unit 16 supplies a pulse to the primary winding of the transformer 15, a high-voltage pulse appears on the secondary winding, which is applied to the cathode, and through the capacitor 21 - to the neutrode, and a breakdown of the interelectrode gap of the cathode-neutrode occurs. Conditions are created for the appearance of the arc, and the arc current passes through the circuit: bus (+), contactor 19, resistor 20, neutrode, arc between the neutrode and cathode, cathode, secondary winding of transformer 15, bus (-).

After some time, the arc moves from the neutrode to the anode. At the same time, a current appears in the anode circuit, which is detected by the current sensor 18. The control unit 17 constantly monitors the signal from the output of the current sensor 18, and as soon as the anode current appears, the contacts of the contactor 19 open. This completes the start-up mode. The arc at startup should move from the neutrode to the anode quickly enough. This time is controlled by the control unit 17. If it exceeds the permissible value, and the arc has not reached the anode during this time, the neutrode may be destroyed, the start-up is considered to be unsuccessful, the control unit 17 forcibly opens contactor 19. After this, the mode switches to restart mode. The number of subsequent consecutive starts is controlled by the control unit 17. If it exceeds the permissible value, this means either a malfunction of the plasma torch itself or an incorrectly established mode of supply of plasma-forming gas. In this case, the control unit 17 stops further attempts to start, and goes into emergency stop mode. After the launch was successful, the control unit 17 controls the presence of an arc current in the anode circuit using a current sensor 18 and the voltage at the cathode and neutrode. If there is no signal at the output of the current sensor 18, but there is voltage at the cathode, then the arc has failed, and a transition to the restart mode is required. If there is no arc current, and there is no voltage at the cathode either, then the power source is turned off, and the arc excitation unit goes into standby mode.

During normal operation of the plasma torch, the arc should burn only between the cathode and the anode, without touching the neutrode. The voltage at the neutrode depends on the type of plasma torch and its mode of operation. The resistance of the gaps between the cathode-neutrode and the neutrode-anode is high, so the voltage at the neutrode takes a value close to half the voltage between the anode and cathode. If for some reason the arc begins to burn in the gap between the neutrode and the adjacent electrode, the resistance of this gap decreases sharply, and the voltage at the neutrode becomes close to the voltage of this electrode. Therefore, the voltage difference between adjacent electrodes, for example, a cathode-neutrode or a neutrode-anode, is important. If this difference decreases to a certain value, this means that a breakdown of this interval has occurred. The control unit 17 monitors the duration and frequency of occurrence of such a situation. If the duration exceeds the permissible value, a transition to emergency stop mode occurs.

Emergency stop is performed by opening the contacts of the blocking relay 26, by command from the control unit 17. The opening of the contacts of the relay 26 is monitored by the control panel 4, and can be used for emergency shutdown of the power source of the plasma torch. In addition, the control unit 17 through a communication line transmits to the control panel 4 text information about the cause of the emergency stop, which facilitates the quick elimination of the emergency. The circuit allows you to start the plasma torch, without requiring additional starting switching in the throttle circuit. The inductor at the output of the power source is necessary to smooth current ripples and to increase the stability of arc burning. As the inductance of the inductor increases, the power quality of the arc improves. But at the same time, startup problems increase. A choke with high inductance prevents the rapid increase of the arc current. And the duration of the spark during ignition is very small, so the current in the inductor in such a short time does not have time to reach values sufficient for stable combustion, and the arc goes out.

In the proposed circuit of the arc excitation unit, a capacitor bank 22 is installed, in which enough energy is accumulated to develop and maintain the arc at the start-up time: When applying a supply voltage to the input terminals, the capacitor bank is charged through the charging resistor 23 to the supply voltage. At start-up, when a breakdown of the cathode-neutrode gap occurs, the resistance of this gap decreases sharply, and the charged capacitor bank is discharged along the circuit: lining (+), contactor 19, resistor 20, neutrode, neutron-cathode gap, cathode, transformer secondary winding 15, diode 25, bit resistor 24, plate (-). In this case, as the capacitor bank 22 is discharged, the voltage on the negative bus decreases, which leads to the appearance of current through the power source and the inductor at its output. The capacity of the capacitor bank 22 depends on the inductance of the inductor, and is selected so that the accumulated energy is sufficient to maintain the arc while the current in the inductor reaches a sufficient value. The resistance of the discharge resistor 24 is selected so that the discharge current does not exceed the permissible limits. Diode 25 is needed so that after starting the arc voltage is not shunted by the capacitor bank 22 through a low-impedance resistor 24. This circuit provides a reliable start, and does not require additional configuration and control circuits.

The control unit 43 of the remote control 3 gas-water using the communication interface 44 receives from the remote control 4 installation of the set values of the flow rate of the plasma-forming gas. The control unit 43 transmits the received tasks to the corresponding flow controllers 29. The computing device 34 of the flow control device controls the control valve 30, changing the current value of the flow up or down. While the gas flow passes through the flow sensor 31, the output signal of which is supplied to the computing device 34. In addition, the computing device 34 receives signals from the temperature sensor 33 and the pressure sensor 32. Based on the values of temperature and gas pressure, the computing device 34 corrects the sensor flow rate 31, resulting in the current value of the mass flow rate. Further, the calculated current flow rate value is compared with a predetermined one, and if the difference exceeds the permissible error, a control signal is generated for the control valve, which closes or opens by an amount sufficient to ensure a given flow rate. The current value of the mass flow rate and pressure in each channel is transmitted to the control unit 43.

A feature of the circuit is that in one of the gas supply channels a pneumatic modulator 35 is installed, which is controlled by the control unit 43. Modulator 35 is necessary to reduce wear on the cathode surface, expanding the arc attachment zone by periodically changing the gas flow (modulation) by one of the channels. In this case, the optimal values of the modulation parameters — frequency, depth, shape — are provided programmatically in the control unit 43.

Water was supplied through a pressure manifold 36, at the outlet of which shut-off valves 39 were installed, which provide for switching off and connecting the water supply in each channel. Further, the cooling water, passing through the cooling jacket of the plasma torch, enters the drain manifold 40, after passing through the flow meters 41. In addition, the sensors 42 monitor the temperature of the water at the outlet of each channel. The output signals from the flow meters 41 and temperature sensors 42 are supplied to the control unit 43. In addition, a temperature sensor 37 and a pressure sensor 38 are installed on the pressure manifold, the output signals of which are sent to the control unit 43.

The control unit 43 provides the operation of the components of the gas-water console, the operational monitoring of their condition, through the communication interface 44 receives tasks from the external control panel of the installation, and sends the current parameters to the control panel of the installation - mass flow and pressure in each gas supply channel, inlet pressure a gas supply manifold 27, a flow rate and a water temperature at the discharge of each channel, a pressure and a water temperature in a pressure head manifold. In addition, the control unit 43, by opening the contactors of the interlock relay 47, can carry out an emergency shutdown of the plasma torch or a start interlock in the event of an emergency. Among emergency situations are, for example, the absence or insufficient value of the water flow rate, the inlet water temperature exceeds the permissible value, the gas flow rate differs from the set more acceptable value, etc. In addition, the control unit 43 transmits to the control panel 4 of the installation text information about the cause of the lock, which facilitates the quick elimination of an emergency.

The presence of the display 45 and the keyboard 46 allows you to control the gas-water remote control and monitor its status in automatic and manual mode. This helps to prevent an emergency in case of damage to the communication line with the control panel of the installation, which increases the reliability of the entire plasma torch power supply system as a whole.

The structure of the installation includes an arc current regulator, an arc excitation unit, a gas-water console, a control panel of the installation, and a plasma torch.

From the map of the operating modes of the plasma torch, we select its current-voltage characteristic corresponding to a given power, for example, Wpl ⁼ 350 kW. Based on this, U _D ygi = 1000 V ± 25%, Id _UG and = 350A ± 25%.

According to the current-voltage characteristics, the following gas flow rates through the plasma torch channels correspond to such arc parameters: air, g / s: cathode - 7, cathode-neutrode - 25, neutrode-anode - 6; natural gas, g / s: neutrode - 6; water consumption, l / min: cathode - 20, neutron-anode - 20.

From the control panel of the installation, we set the upper and lower limits of the discharge current:

I _BEPX = 437 A; Wn = 262 A; U _BE pχ = 1250 V; U _H izhn = 750 V. Gas consumption, g / s: cathode - 7-5; cathode-neutrode - 20-30; neutrode anode - 5-8; the neutrode is 6-16. Water consumption, l / min: cathode - 18-25; neutrode anode - 15-22. The voltage at the neutrode for the stable operation of the plasma torch should be: U _BE pχ = 600 V; U _H izhn = 500 V.

Pressure, MPa: inlet air pressure P _BEPX ⁼ 0.75; P _HLH ⁼ 0.45; gas pressure RGA _Z A B _E P _X = 0.25; P _{GAS H} IHH = 0.15; inlet water pressure Discharge _BEPX = 1, 0; PB rows _{HIZHH O} = 0.6.

Enter the values of the external parameters of the atmosphere, for example, Pdtm ⁼ 0.09 MPa; temperature Tdtm ⁼ 25 ° C = 298 K.

температура, ⁰C: катод - T_BEPX

катод-нейтрод - T_BEP_{X KAT HEЙTP}=40; нейтрод-анод - T_BEpχ НЕЙТР AH_OД=40.We introduce the limiting values of pressures and temperatures in the channels of the gas-water console: pressure, MPa: cathode - P _BE Px to _AT = 3.5; P _{LOWER KAT} = 2; cathode-neutrode - РЕРХ.КАТ HEEYTP = 4; RHINE CAT HEYTP = 3; neutron anode - P _BE PX HEEY _{TP AHO} D ⁼ 3; P _LOWER H.H ETP

temperature, ⁰ C: cathode - T _BEPX

cathode-neutrode - T _B EP _{X KAT HEIT} = 40; neutrode anode - T _BE pχ NEUTR AH _O D = 40.

When you enter all the parameters, the previous values are not reset. The plasmatron is launched by pressing the “PUSK” button. In case of successful adjustment, the plasma torch enters normal operation with power: W _PL = 350 ± 87 kW.

The claimed group of inventions meets the requirement of unity of invention, since the group forms a single inventive concept, and one of the claimed objects of the group is a method of automatic regulation the mode of operation of the plasma torch is intended for use in another declared object of the group - the installation, while both objects are aimed at solving the same problem with a single technical result and can only be used together.

Claims

Claim 1. A method for automatically controlling the plasma torch operating mode, in which a constant voltage source is periodically connected to the plasmatron using a transistor switch, the average voltage and current in the plasmatron being controlled by changing the duty cycle of the pulses, and the continuous current in the plasmatron is maintained by installing a choke in the circuit , which in the interval of conductivity of the key stores energy, and during a pause transfers energy through a diode to a plasma torch, characterized in that the upper and lower the limits of the values of the operating current of the plasma torch, arc voltage and voltage of each neutrode from the control panel of the installation and additionally set the upper and lower limits of the flow rates, pressures and temperatures of gases and water for each channel of the gas-water console, while if the sensor signals are within the specified limits, the control unit gives a signal to close the blocking relay and allows the plasma torch to work, if the signals on any channel are outside the specified limits, then a signal to turn off the inspection, and current stabilization is carried out by a software method in the control unit, by comparing the values of the specified operating current with the signal of the analog current sensor, and during startup, at rapidly changing values of the arc current from zero to the specified value, the maximum permissible frequency is used, and after the end of transient processes , upon reaching the set value of the arc current, the frequency decreases to the minimum possible value, while expanding the zone of arc binding by periodically changing the plasma-forming flow rate gas in one of the gas supply channels using a pneumatic modulator of the gas console, while the signal from the analog current sensor to the control unit is continuously analyzed in automatic mode and, when an unstable arc burning occurs, the maximum allowable switching frequency of the transistor switch is set, and after the end of transients, when the arc current reaches a predetermined value, the frequency decreases to the minimum possible value. 2. Installation of automatic control of the plasma torch operation mode, comprising a three-phase rectifier, an arc excitation unit with a high-voltage transformer connected to the cathode and anode of the plasma torch, characterized in that the installation further comprises an arc current regulator, a gas-water console and a control panel of the installation, while the controller output terminals arc current are connected to the output terminals of the arc excitation unit, the output terminals of the unit the excitations are connected to the corresponding electrodes of the plasma torch, and the control panel of the installation is connected by information buses to the current regulator, the arc excitation unit and the gas-water console, and the high-voltage transformer of the arc excitation unit is connected to the high voltage unit, the control input of which is connected to the output of the arc excitation control unit, in positive the bus of which an arc current sensor is installed, the output of which is connected to the input of the control unit, and the output of the control unit is connected to the coil of the contactor, through a resistor with a capacitor and an output terminal of the plasma torch neutron, and additional capacitors are connected to the negative polarity bus through a charging resistor and a series resistor and a diode, and the output of the control unit is connected to the control winding of the interlock relay. 3. Installation according to claim 1, characterized in that the arc current regulator consists of an input protection unit with terminals for connecting the mains supply, a three-phase rectifier, a capacitor, a transistor switch, the output of which is connected to a diode and inductor, in series with which the limit current sensor is connected and the current sensor is analog, and the output of the current sensor is connected to the current regulator control unit, and the control input of the transistor switch is connected to the output of the two-input driver, one of the inputs of which is connected to the output of the unit a systematic way, and the other connected to the output of the limit current sensor. 4. Installation according to claim 1, characterized in that the gas-water console includes a plasma-forming gas supply system, which consists of an input manifold to which a pressure sensor and flow controllers are connected, each of which contains an electric control valve, a flow sensor, a pressure sensor, temperature sensor and computing device, moreover, a pneumatic modulator is installed in one of the gas supply valves, and the coolant supply and removal system consists of a pressure manifold to which the dates are connected a temperature sensor, a pressure sensor and a drain manifold to which water flow meters, temperature sensors are connected, the gas-water console is equipped with an information system consisting of a control unit with computing devices for each gas flow controller, water flow meters, water temperature sensors and pressure sensors, when This control unit contains a communication interface, a display and a keyboard, and the output of the control unit is connected to the control winding of the interlock relay.