CN114070117A - Alternating current reversing pilot arc circuit and alternating current welding power supply - Google Patents
Alternating current reversing pilot arc circuit and alternating current welding power supply Download PDFInfo
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- CN114070117A CN114070117A CN202210036122.0A CN202210036122A CN114070117A CN 114070117 A CN114070117 A CN 114070117A CN 202210036122 A CN202210036122 A CN 202210036122A CN 114070117 A CN114070117 A CN 114070117A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
- H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/06—Arrangements or circuits for starting the arc, e.g. by generating ignition voltage, or for stabilising the arc
- B23K9/073—Stabilising the arc
- B23K9/0732—Stabilising of the arc current
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/09—Arrangements or circuits for arc welding with pulsed current or voltage
- B23K9/091—Arrangements or circuits for arc welding with pulsed current or voltage characterised by the circuits
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K9/00—Arc welding or cutting
- B23K9/10—Other electric circuits therefor; Protective circuits; Remote controls
- B23K9/1081—Arc welding by means of accumulated energy
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
- H02M3/33523—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Plasma & Fusion (AREA)
- Mechanical Engineering (AREA)
- Arc Welding Control (AREA)
Abstract
The invention provides an alternating current commutation pilot circuit and an alternating current welding power supply. The first capacitor is connected in series with the output end of the pilot arc alternating current input circuit to limit the output current of the pilot arc alternating current input circuit. The rectification filter circuit comprises a rectifier and a second capacitor, and the pilot arc alternating current input charges the second capacitor through the first capacitor and the rectifier. The output loop comprises a positive connection control switch connected to the output of the rectification filter circuit, and the positive connection control switch is configured to connect or disconnect the alternating current commutation pilot arc circuit into or out of an electrode positive connection loop of the main circuit. When the main circuit is switched from the negative electrode connection to the positive electrode connection, the positive connection control switch is conducted, the charged second capacitor provides pilot arc voltage and pilot arc pulse current for the positive electrode connection loop, and the pilot arc input circuit provides the maintaining current for the positive electrode connection loop.
Description
Technical Field
The invention relates to the field of welding, in particular to an alternating current commutation pilot arc circuit and an alternating current welding power supply.
Background
In the modern industrial construction process, the alternating current argon arc welding power source becomes an ideal choice of aluminum and aluminum alloy in the aspect of welding processing equipment based on the wide application of aluminum and the advantages of the alternating current argon arc welding power source in the processing process of the aluminum and the aluminum alloy. However, when the alternating current argon arc welding is performed at the current zero crossing point or the small current welding, the residual ionization degree is smaller because the temperature of the arc space is lower; the re-ignition is difficult, and the arc breaking phenomenon is easily caused; such as tungsten electrode negative (DCEN) to tungsten electrode positive (DCEP) polarity switching process in TIG welding.
In the existing secondary inverter topology welding power supply with a half-bridge structure, in order to ensure the stability of an arc, power devices such as resistors, capacitors and the like are added to the positive and negative output ends of an inverter main circuit and the center tap of a main transformer to store voltage, and the voltage can be superposed into a welding loop through a current limiting resistor or an inductor in the process of polarity switching from DCEN to DCEP, so that the arc is re-ignited by commutation. In the circuit structure, a second capacitor with larger capacity is needed to store pilot arc energy, and a resistor with larger power is needed in a pilot arc loop to limit the pilot arc current. When the alternating current inversion frequency is increased (such as 500 HZ), the working frequency of the pilot arc device is increased, and in order to ensure the stability of the pilot arc, the capacity of a device for storing pilot arc energy and the power of a current-limiting resistor are increased in multiples, so that the pilot arc circuit has the problems of high cost, large volume, high device power, high heat generation and the like. Based on the problems, the existing pilot arc circuit is difficult to realize high-frequency alternating current welding.
Disclosure of Invention
The invention provides an alternating current commutation pilot arc circuit and an alternating current welding power supply, which are used for high-frequency alternating current welding and have small device capacity, and aims to overcome at least one defect of the prior art.
In order to achieve the above object, the present invention provides an ac commutating pilot circuit connected to a main circuit of an ac welding power supply and including a pilot ac input, a first capacitor, a rectifying-filtering circuit, and an output circuit. The first capacitor is connected in series with the output end of the pilot arc alternating current input circuit to limit the output current of the pilot arc alternating current input circuit. The rectification filter circuit comprises a rectifier and a second capacitor, and the pilot arc alternating current input charges the second capacitor through the first capacitor and the rectifier. The output loop comprises a positive connection control switch connected to the output of the rectification filter circuit, and the positive connection control switch is configured to connect or disconnect the alternating current commutation pilot arc circuit into or out of an electrode positive connection loop of the main circuit. When the main circuit is switched from the negative electrode connection to the positive electrode connection, the positive connection control switch is conducted, the charged second capacitor provides pilot arc voltage and pilot arc pulse current for the positive electrode connection loop, and the pilot arc input circuit provides the maintaining current for the positive electrode connection loop.
According to an embodiment of the invention, when the main circuit is switched from electrode negative connection to electrode positive connection, the positive connection control switch is turned on before the commutation zero crossing point, and the alternating current commutation pilot arc circuit is connected into the main circuit in advance.
According to an embodiment of the present invention, the auxiliary transformer participates in the PI control of the welding power supply based on the welding loop current, and the voltage of the auxiliary transformer is output in a maximum state when the positive control switch is turned on.
According to one embodiment of the present invention, the pilot arc ac input is an auxiliary transformer connected in parallel with the main transformer on the main circuit to the primary inverter output of the welding power supply.
According to an embodiment of the invention, the ac commutating pilot circuit further includes a current limiting element connected to the output end of the rectifying and filtering circuit, and the current limiting element limits the pilot pulse current outputted.
According to an embodiment of the present invention, the current limiting element is an inductor, the ac commutating pilot arc power further includes a discharge loop connected to the inductor, and when the forward control switch is turned off, the flyback voltage of the inductor is discharged through the discharge loop.
According to an embodiment of the present invention, the discharging circuit is a freewheeling diode connected in parallel with two ends of the inductor or an RC absorption circuit connected in parallel with two ends of the inductor.
According to an embodiment of the invention, the alternating current commutation pilot circuit further comprises a diode connected to the output side of the rectification filter circuit, and the diode blocks the voltage and current of the main circuit to be superposed on the alternating current commutation pilot circuit.
According to an embodiment of the invention, the output loop further comprises a negative connection control switch connected to the output of the rectification filter circuit, the negative connection control switch is configured to connect or disconnect the alternating current commutation pilot arc circuit into or out of the electrode negative connection loop of the main circuit; when the main circuit commutates from positive electrode connection to negative electrode connection, the negative connection control switch is conducted and the positive connection control switch is closed.
In another aspect, the present invention also provides an ac welding power supply including a main circuit and the ac commutating pilot arc circuit described above.
According to an embodiment of the present invention, the main circuit is a half-bridge inverter circuit or a full-bridge inverter circuit.
In summary, when the ac commutation pilot arc circuit provided by the present invention is not connected to the main circuit, the high frequency ac power source formed by the pilot arc ac input charges the second capacitor through the first capacitor and the rectifier, and stores pilot arc energy. When the positive control switch is conducted, the charged second capacitor provides pilot arc voltage and pilot arc pulse current for the electrode positive circuit, and provides conditions for reigniting the arc after commutation. As the second capacitor discharges, the pilot arc AC input continuously provides a small holding current to the electrode positive return path through the first capacitor to ensure continuity of the welding arc during polarity switching. The pilot arc condition output of the second capacitor charged based on pilot arc alternating current input is not related to the inversion frequency on the main circuit, the requirement of the inversion frequency of the welding power supply on a capacity device is well removed, and therefore the volume of the second capacitor under high-frequency inversion is reduced. Correspondingly, the power of the device connected to the output end of the second capacitor can be set smaller, so that the miniaturization design of the device under high frequency is realized. Based on the small maintaining current formed by the first capacitor, the pilot arc energy is continuously supplemented after the second capacitor discharges, so that the requirement on the capacity of the second capacitor is further reduced, and the stability of the pilot arc is greatly improved. In addition, the first capacitor is adopted for frequent current limiting, so that energy loss caused by current limiting is greatly reduced, the capacity of the device is small, and the heat productivity of the device is small.
In order to make the aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
Fig. 1 is a schematic structural diagram of an ac commutating pilot circuit according to an embodiment of the present invention.
Fig. 2 is a schematic structural diagram of an ac power supply of the ac commutating pilot arc and half-bridge secondary inverter structure shown in fig. 1.
Fig. 3 is a schematic current flow diagram of the ac commutating pilot arc circuit of fig. 2 in a charging state.
Fig. 4 and 5 are schematic current flow diagrams of the ac commutating pilot arc circuit in fig. 2 in a pilot arc output state.
Fig. 6 is a timing diagram of the main circuit output current, the ac commutating pilot arc circuit output current, and the welding loop arc current in fig. 2.
Fig. 7 is a schematic structural diagram of a main circuit of a half-bridge secondary inverter structure connected to an ac commutating pilot arc according to another embodiment of the present invention.
Detailed Description
In conventional pilot arc circuits based on the main circuit of the welding power supply, the pilot arc energy stored on the capacitor is derived from the charging of the main circuit during a half cycle. When the alternating current inversion frequency is very high, the capacitor after last pilot arc discharge is too late to be charged through the bus, so that the next pilot arc energy is insufficient, and the high-frequency welding requirement cannot be met. To solve this problem, only the capacitance of the capacitor and the power of the corresponding device can be increased, but this causes problems of cost, volume and heat generation. There is also an arc-maintaining device for raising the commutation voltage of the main circuit bus by using a pre-charged capacitor, in which the charged capacitor only plays a role of raising the commutation voltage and does not output current to the welding loop; the establishment of re-arcs by simply relying on the application of voltage has some difficulties due to the low ionization degree of the arc space during commutation.
In view of the above, the present embodiment provides an ac commutating wippen circuit 40, which is connected to the main circuit 30 of the ac welding power source and includes a wippen ac input, a first capacitor C1, a rectifier filter circuit, and an output loop. The first capacitor C1 is connected in series with the output end of the pilot arc AC input to limit the output current of the pilot arc AC input. The rectifier filter circuit comprises a rectifier B1 and a second capacitor C2, and the pilot arc alternating current input charges the second capacitor C2 through the first capacitor C1 and the rectifier B1. The output loop comprises a positive connection control switch Q3 connected to the output of the rectifying and filtering circuit, and the positive connection control switch Q3 is configured to connect or disconnect the alternating current commutation pilot arc circuit into or out of the electrode positive connection loop of the main circuit 30; when the main circuit 30 is switched from the negative electrode connection to the positive electrode connection, the positive connection control switch Q3 is conducted, the charged second capacitor C2 provides a pilot arc voltage and a pilot arc pulse current for the positive electrode connection loop, and the pilot arc input circuit provides a pilot current for the positive electrode connection loop.
Compared with the traditional pilot arc circuit which is obtained by charging a main circuit bus in a half period, the pilot arc energy of the alternating current commutation pilot arc circuit 40 provided by the embodiment is obtained by the second capacitor C2 charged by the pilot arc input circuit and the pilot arc output current of the pilot arc input circuit through the first capacitor C1. Specifically, the second capacitor C2, which is charged when the forward control switch Q3 is open, rapidly provides a sufficiently high pilot voltage and pilot pulse current to the electrode forward loop to establish the reignition arc condition. As the discharge progresses, the voltage and current of the second capacitor C2 gradually decrease. At this time, the pilot arc input circuit will continue to provide a sustaining current for sustaining stable arc for the electrode positive circuit after the current is limited by the first capacitor C1, so as to ensure the arc can sustain combustion.
The pilot arc energy in the ac commutation pilot arc circuit 40 provided by the present embodiment is provided completely independent of the ac inversion frequency on the main circuit 30, so that the limitation of the ac inversion frequency on the device capacity is well removed, and the capacity of the second capacitor C2 does not need to increase with the increase of the inversion frequency. Further, after the second capacitor C2 discharges, the sustaining current output by the pilot arc input circuit through the first capacitor C1 is continuously supplemented, and the supply time of the current required by pilot arc is greatly prolonged. The stability and the continuity after the reestablishment of the commutation arc are ensured, and the capacity requirement on the second capacitor C2 is further reduced, so that the miniaturization design of the second capacitor C2 in the high-frequency inverter circuit is realized.
Due to the zero-crossing commutation, the second capacitor C2 needs to provide a high enough reignition voltage, around 300V, to the positive electrode return. Therefore, it is desirable that the pilot input circuit be capable of providing high voltages of at least 300V or more. The holding current output by the pilot arc input circuit is as small as possible on the premise of meeting the requirement of arc continuity so as to reduce the influence of the holding current superposed on the output current of the main circuit on the welding current characteristic of the main circuit. The sustain current needs to be limited. In this embodiment, the pilot arc input circuit is an auxiliary transformer T2 connected to the output of the primary inverter 20 of the welding power supply. However, the present invention is not limited thereto. In other embodiments, the pilot arc input circuit may also be an auxiliary transformer connected to the secondary side of the main transformer on the main circuit; or an external ac voltage source. In fig. 1, the ac current output from the auxiliary transformer T2 first passes through the first capacitor C1 connected in series in the circuit, and enters the rectifier B1 after being limited by the capacitive reactance of the first capacitor C1. Compared with the traditional resistance current limiting with energy loss, the alternating current is blocked and limited by the first capacitor C1 without energy loss, so that the high-voltage output of the auxiliary transformer T2 can be ensured, the heat productivity of the device is smaller, and the volume of the device is smaller.
Further, the ac commutating and maintaining circuit 40 further includes a current limiting element connected to the output end of the rectifying and filtering circuit, and the current limiting element limits the maintaining arc pulse current output when the second capacitor C2 discharges. As shown in fig. 1, the current limiting element is an inductor L1. After the commutation break is complete, the forward control switch Q3 is turned off to switch the ac commutation break circuit 40 out of the main circuit 30. The inductor L1 is arranged so that when the forward control switch Q3 is turned off, it generates a flyback voltage and applies it to the forward control switch Q3. In order to avoid the damage of the forward connection control switch Q3 by the excessively high flyback voltage, the alternating current commutation pilot arc power device further comprises a discharge loop connected to the inductor L1, and when the forward connection control switch Q3 is turned off, the flyback voltage of the inductor L1 is discharged through the discharge loop. Preferably, as shown in fig. 1, the discharging circuit is a freewheeling diode D2 connected in parallel across the inductor. However, the present invention is not limited thereto. In other embodiments, an RC snubber circuit connected in parallel across the inductor L1 may be used as the discharge loop. Alternatively, when the withstand voltage of the positive connection control switch Q3 is sufficiently high, the discharge circuit may not be provided.
In TIG welding, the aluminum workpiece is a cold cathode, considering that the tungsten electrode is a hot cathode; the tungsten electrode has strong electron thermal emission capability and is made of aluminum. Therefore, during welding, the polarity switching process from tungsten electrode connection plus (DCEP) to tungsten electrode connection minus (DCEN) is much easier than reigniting the tungsten electrode connection minus (DCEN) to tungsten electrode connection plus (DCEP) arc; commutation arcing typically occurs during a polarity switching process from tungsten negative (DCEN) to tungsten positive (DCEP). Therefore, in the present embodiment, the output circuit uses the positive connection control switch Q3 to connect the ac commutating wippen circuit 40 to the electrode positive connection circuit of the main circuit 30. However, the present invention is not limited thereto.
In other embodiments, as shown in fig. 7, the output circuit includes positive control switches Q3, Q4, which are turned on or off synchronously to switch the ac commutating pilot circuit into or out of the electrode positive circuit of the main circuit. Furthermore, the output loop also comprises negative connection control switches Q5 and Q6 which are connected with the output of the rectifying and filtering circuit. The negative connection control switches Q5, Q6 are configured to switch the AC commutating pilot arc circuit into or out of the negative electrode connection loop of the main circuit 30. When the main circuit 30 commutates from positive electrode connection to negative electrode connection, the negative connection control switches Q5, Q6 are turned on and the positive connection control switches Q3, Q4 are turned off. The auxiliary transformer T2, the first capacitor C1, the rectifier B1 and the charged second capacitor C2 provide a pilot arc voltage, a pilot arc pulse current and a sustain voltage for a negative electrode circuit (i.e. a circuit when the switching tube Q1 on the main circuit is turned on) through the negative control switches Q5 and Q6, the inductor L2 and the diode D3, wherein the diode D4 is a freewheeling diode connected in parallel across the inductor L2. The auxiliary arc maintaining circuit comprises positive control switches Q3 and Q4 and a negative control switch Q5, wherein an output loop of the Q6 realizes arc maintaining assistance of the main circuit in zero-crossing commutation in two directions, and the auxiliary arc maintaining circuit can be used for the main circuit of a half-bridge secondary inversion structure and can also be used for the main circuit of a full-bridge secondary inversion structure.
Fig. 2 is a schematic structural diagram of the ac commutating pilot arc circuit applied to a half-bridge secondary inverter welding power supply provided in this embodiment, and the main circuit includes a switching tube Q1, a switching tube Q2, and diodes VD1 and VD 2. The switch tube Q1 and the switch tube Q2 are conducted alternately to form an electrode negative connection loop and an electrode positive connection loop respectively. The arc maintaining process of the ac commutating arc maintaining circuit will be described in detail below with reference to fig. 3 to 6.
In fig. 3, when the main circuit switching tube Q1 is turned on and the switching tube Q2 is turned off, the welding current flows from the main transformer T1 → the diode VD1 or the diode VD2 → the common mode inductor La → the switching tube Q1 → the welding circuit arc + → the welding circuit arc- → the inductor DCL → the center tap of the main transformer T1, and an electrode negative connection circuit is formed, as indicated by the black solid arrow in fig. 3. Meanwhile, an auxiliary transformer T2 in the AC commutation pilot arc circuit 40 generates AC voltage with the same high frequency as the primary inverter 20, a first capacitor C1 is connected in series in an output loop of the auxiliary transformer T2 to limit the output current of the auxiliary transformer T2, and the AC voltage is rectified by a rectifier bridge B1 and then stored in a second capacitor C2 to provide energy for the pilot arc device.
FIG. 4: when the switch Q1 in the main circuit 30 is turned off, the switch Q2 is turned on. The current direction of the AC welding power supply begins to be converted, and the welding current flows to: main transformer T1 center tap → inductor DCL → welding circuit arc- → welding circuit arc + → switching tube Q2 → common mode inductor Lb → diode VD3 or diode VD4 → main transformer T1; an electrode positive connection loop is formed as indicated by the black solid arrow in fig. 4. When the switching tube Q1 is turned off, the switching tube Q2 is turned on and simultaneously the forward control switch Q3 is turned on, and because the voltage of the second capacitor C2 is higher than the voltage of the electrode forward loop, the energy stored in the second capacitor C2 passes through the forward control switch Q3 → inductor L1 → diode D1 → inductor DCL → welding loop arc- → welding loop arc + → switching tube Q2 → common mode inductor Lb → back to the second capacitor C2, as shown by the hollow arrow in FIG. 4. The second capacitor C2 rapidly superposes pilot arc voltage and pilot arc pulse current to the electrode positive connection loop at the moment when the switch tube Q2 and the positive connection control switch Q3 are conducted, provides conditions for reestablishing the arc of the welding loop when the switch tube Q2 is conducted, and ensures the continuity of the arc after commutation. As the second capacitor C2 discharges, the stored energy decreases, at which point the state of fig. 5 will be entered.
FIG. 5: at this time, as shown by the open arrow, the sustain current output by the auxiliary transformer T2 is superimposed on the discharge current of the second capacitor C2 and then output to the positive electrode circuit. At this point, although the stored energy on the second capacitor C2 drops, the holding current output by the auxiliary transformer T2 will continue to provide energy to ensure that the established arc continues to burn, maintaining arc continuity. Since the discharge current of the second capacitor C2 gradually decreases, the superposition of the sustain current appears on the timing diagram to delay the falling speed of the output current of the sustain auxiliary circuit, such as the slope falling rate at the right side of the pilot arc current pulse in fig. 6 (b).
After the current direction of the welding power supply is converted, the positive connection control switch Q3 is turned off, the alternating current commutation pilot arc circuit is cut out from the main circuit 30, the welding voltage and current in the half period after the commutation of the main circuit 30 cannot be influenced, and the main circuit has good voltage and current characteristics. After the positive control switch Q3 is turned off, the auxiliary transformer T2 still continuously generates an ac voltage having a frequency equal to that of the primary inverter 20. The first capacitor C1 is connected in series in the output loop of the auxiliary transformer T2 to limit the output current, and the ac voltage is rectified by the rectifier bridge B1 and then stored in the second capacitor C2 to provide energy for the next pilot arc, as shown in fig. 3.
In fig. 6, (a) is an output current timing chart of the main loop; (b) an output current timing diagram of the alternating current commutation pilot arc circuit is shown; (c) arc current timing diagram for a welding circuit. It can also be seen from fig. 4 that the ac commutation pilot arc circuit outputs a pilot arc pulse current and a sustain current which are superimposed when the main circuit current commutates. After the welding circuit has established sufficient arc current (indicated to reignite) the pulse current rapidly decreases to zero as the positive control switch Q3 closes, thereby no longer affecting the main circuit.
In fig. 1 and 2, when the forward control switch Q3 is turned on, in order to prevent the voltage and current of the main circuit from being superimposed on the ac commutation pilot circuit, the ac commutation pilot circuit further includes a diode D1 connected to the output side of the rectifier filter circuit, and the diode D1 ensures the one-way circulation of the current.
In the present embodiment, the conduction of the positive control switch Q3 is synchronized with the switch Q2. However, the present invention is not limited thereto. In other embodiments, when the main circuit is switched from negative electrode connection to positive electrode connection (the switch Q2 is turned on, the switch Q1 is turned off), the positive connection control switch Q3 is turned on before the commutation zero crossing point, and the ac commutation pilot circuit 40 is connected to the main circuit 30 in advance. The welding current still passes through the electrode negative connection loop before the zero crossing point, the alternating current reversing arc maintaining circuit provides the welding loop with the current from the arc- → arc + of the welding loop, the current is opposite to the current in the electrode negative connection loop in the reverse direction, and the current are mutually counteracted, so that the current reduction rate of the welding loop before the zero crossing is accelerated, and the reignition of the arc after the reversing is facilitated. Furthermore, the pre-connected AC commutation pilot arc circuit can provide pilot arc voltage and pilot arc current pulses for the electrode positive connection loop more quickly when the switching tube Q2 is conducted.
In order to further improve the arc maintenance effect, in the present embodiment, the auxiliary transformer T2 is provided to participate in PI control of the welding power supply based on the welding loop current, and when the positive control switch Q3 is turned on, the voltage of the auxiliary transformer T2 is output in the maximum state. Specifically, when the positive control switch Q3 is turned on, the current in the welding circuit in the main circuit 30 is very small; based on this current, the PI control system of the welding power supply will increase the output voltage of the auxiliary transformer T2 to be at its maximum output (e.g., 300V). Correspondingly, the pilot arc voltage superposed on the positive electrode connecting loop is also at the maximum value, thereby being more beneficial to commutation pilot arc. However, the present invention is not limited thereto. In other embodiments, the auxiliary transformer T2 may also be controlled with a fixed pulse width, when the voltage output by the auxiliary transformer T2 is controlled with a fixed pulse width sufficient to ensure that the main circuit is switched from tungsten negative (DCEN) to tungsten positive (DCEP). Of course, in this control state, the auxiliary transformer T2 is always in the maximum and fixed state output.
Correspondingly, the present embodiment further provides an ac welding power source, as shown in fig. 2, the ac welding power source includes an input rectifying and filtering circuit 1, a primary inverter 20, a main circuit 30, and an ac commutating and pilot arc circuit 40 provided in the present embodiment, where the main circuit 30 is a half-bridge inverter circuit.
In summary, when the ac commutation pilot arc circuit provided by the present invention is not connected to the main circuit, the high frequency ac power source formed by the pilot arc ac input charges the second capacitor through the first capacitor and the rectifier, and stores pilot arc energy. When the positive control switch is conducted, the charged second capacitor provides pilot arc voltage and pilot arc pulse current for the electrode positive circuit, and provides conditions for reigniting the arc after commutation. As the second capacitor discharges, the pilot arc AC input continuously provides a small holding current to the electrode positive return path through the first capacitor to ensure continuity of the welding arc during polarity switching. The pilot arc condition output of the second capacitor charged based on pilot arc alternating current input is not related to the inversion frequency on the main circuit, the requirement of the inversion frequency of the welding power supply on a capacity device is well removed, and therefore the volume of the second capacitor under high-frequency inversion is reduced. Correspondingly, the power of the device connected to the output end of the second capacitor can be set smaller, so that the miniaturization design of the device under high frequency is realized. Based on the small maintaining current formed by the first capacitor, the pilot arc energy is continuously supplemented after the second capacitor discharges, so that the requirement on the capacity of the second capacitor is further reduced, and the stability of the pilot arc is greatly improved. In addition, the first capacitor is adopted for frequent current limiting, so that energy loss caused by current limiting is greatly reduced, the capacity of the device is small, and the heat productivity of the device is small.
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. An ac commutating wippen circuit, for connection to a main circuit of an ac welding power source, comprising:
pilot arc alternating current input;
the first capacitor is connected in series with the output end of the pilot arc alternating current input and used for limiting the output current of the pilot arc alternating current input circuit;
the rectification filter circuit comprises a rectifier and a second capacitor, and the pilot arc alternating current input charges the second capacitor through the first capacitor and the rectifier;
the output loop comprises a positive connection control switch connected to the output of the rectification filter circuit, and the positive connection control switch is configured to connect or disconnect the alternating current commutation pilot arc circuit into or out of an electrode positive connection loop of the main circuit;
when the main circuit is switched from negative electrode connection to positive electrode connection, the positive connection control switch is switched on, the charged second capacitor provides pilot arc voltage and pilot arc pulse current for the positive electrode connection loop, and the pilot arc input circuit provides pilot current for the positive electrode connection loop.
2. The ac commutation wippen circuit of claim 1, wherein when the main circuit switches from negative electrode connection to positive electrode connection, the positive control switch is turned on before the commutation zero crossing point to connect the ac commutation wippen circuit to the main circuit in advance.
3. The ac commutating wive circuit of claim 1 wherein the auxiliary transformer participates in PI control of the welding power supply based on the welding loop current, and the voltage of the auxiliary transformer is output at maximum when the positive control switch is turned on.
4. The ac commutating wive circuit of claim 1 wherein the wive ac input is an auxiliary transformer connected in parallel with the main transformer on the main circuit to the primary inverting output of the welding power supply.
5. The ac commutating wir circuit of claim 1 further comprising a current limiting element connected to the output of the rectifying filter circuit, which limits the output wir pulse current.
6. The ac commutating pilot arc circuit of claim 5 wherein the current limiting element is an inductor and the ac commutating pilot arc further comprises a discharge loop connected to the inductor through which the flyback voltage of the inductor is discharged when the forward control switch is turned off.
7. The ac commutating wive circuit of claim 6, wherein the discharging loop is a freewheeling diode connected in parallel across the inductor or an RC snubber circuit connected in parallel across the inductor.
8. The ac commutation wir circuit of claim 1, further comprising a diode connected to the output side of the rectifier filter circuit, wherein the diode blocks the voltage and current of the main circuit superimposed on the ac commutation wir circuit.
9. The ac commutating wirc circuit of claim 1 wherein the output loop further comprises a negative connection control switch connected to the output of the rectifying and filtering circuit, the negative connection control switch configured to switch the ac commutating wirc circuit into or out of the negative connection loop of the main circuit; when the main circuit commutates from positive electrode connection to negative electrode connection, the negative connection control switch is conducted and the positive connection control switch is closed.
10. An ac welding power supply comprising a main circuit and an ac commutating pilot arc circuit as claimed in any one of claims 1 to 8.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202111398800X | 2021-11-19 | ||
| CN202111398800 | 2021-11-19 |
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| CN202210036122.0A Active CN114070117B (en) | 2021-11-19 | 2022-01-13 | Alternating current reversing pilot arc circuit and alternating current welding power supply |
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| CN (1) | CN114070117B (en) |
| WO (1) | WO2023087743A1 (en) |
Cited By (1)
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| WO2023087743A1 (en) * | 2021-11-19 | 2023-05-25 | 杭州凯尔达电焊机有限公司 | Alternating current commutation pilot arc circuit, and alternating current welding power supply |
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| Publication number | Publication date |
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| CN114070117B (en) | 2022-05-20 |
| WO2023087743A1 (en) | 2023-05-25 |
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