Cutting machine drive circuit, cutting machine control device and plasma cutting machine

Abstract

The present invention is applicable to the technical field of cutting machines, and in particular relates to a cutting machine drive circuit, a cutting machine control device and a plasma cutting machine, wherein the cutting machine drive circuit includes an inverter circuit, a power conversion circuit, an arc pilot drive circuit, a first current detection circuit, a second current detection circuit and a control circuit. When the cutting machine drive circuit is powered on, the arc pilot drive circuit works. When the arc pilot ignites the main arc, a workpiece, a nozzle and a power conversion circuit form a loop. According to the different time intervals of igniting the main arc of edge arc starting and perforation arc starting, it is determined whether the current cutting machine is edge arc starting or perforation arc starting, and the power conversion circuit is controlled to output different arc starting currents, so as to adapt to edge arc starting and perforation arc starting, improve the arc starting efficiency of edge arc starting, and reduce metal splashing during perforation arc starting.

Description

Technical Field

[0001] The present invention belongs to the technical field of cutting machines, and in particular relates to a cutting machine driving circuit, a cutting machine control device and a plasma cutting machine. Background Art

[0002] Plasma technology has been widely used in the fields of industry, chemistry, national defense and communications. Plasma cutting is a high-speed and high-precision metal material cutting method. Compared with traditional flame cutting, plasma cutting has the advantages of fast cutting speed and good cutting quality, and is increasingly widely used in the field of metal cutting.

[0003] Air plasma cutting machines on the market all use a fixed arc starting control scheme. This arc starting scheme uses the same control scheme regardless of whether the plasma cutting gun nozzle starts the arc from the edge of the workpiece or the plasma cutting gun nozzle starts the arc by punching a hole in the middle of the workpiece.

[0004] Since the plasma cutting machine uses the same control scheme for both edge arcing and perforation arcing, it is difficult to meet the arcing control requirements of two completely different arcing points. If the control scheme meets the requirements of perforation arcing, the arcing may be slow and inefficient when the edge is started; if the control scheme meets the requirements of edge arcing, the arcing current may be large, the molten metal may splash a lot, and even the outgoing wire splashing metal may cause the nozzle and the workpiece to short-circuit and burn. Therefore, the control scheme generally chooses a compromise solution to be compatible with the two arcing methods. Although this compromise solution can avoid major defects, it cannot fully adapt to the two arcing methods.

[0005] Therefore, the traditional arc starting control has the problem of being incompatible with edge arc starting and perforation arc starting. Summary of the invention

[0006] The object of the present invention is to provide a cutting machine driving circuit, aiming to solve the problem that traditional arc starting control is incompatible with edge arc starting and perforation arc starting.

[0007] A first aspect of an embodiment of the present invention provides a cutting machine driving circuit, the cutting machine driving circuit comprising an inverter circuit, a power conversion circuit, an arc driving circuit, a first current detection circuit, a second current detection circuit and a control circuit;

[0008] The inverter circuit is used to convert the received external power into AC power and output it to the power conversion circuit, the negative electrode of the output end of the power conversion circuit is connected to the electrode of the cutting gun head, and the positive electrode of the output end of the power conversion circuit is connected to the workpiece, the arc driving circuit is electrically connected to the nozzle of the cutting gun head and the control circuit respectively, and the control circuit is also electrically connected to the inverter circuit, the first current detection circuit and the second current detection circuit respectively;

[0009] The first current detection circuit is used to detect the current of the AC power supply and feed back a first current detection signal to the control circuit;

[0010] The second current detection circuit is used to detect the current flowing through the workpiece and feed back a second current detection signal to the control circuit;

[0011] The control circuit is used for:

[0012] controlling the arc pilot drive circuit to establish an arc pilot current between the electrode and the nozzle when the first current detection signal is received, and controlling the arc pilot drive circuit to stop the arc pilot when the second current detection signal is received;

[0013] detecting a time interval between receiving the second current detection signal and receiving the first current detection signal;

[0014] When the time interval is detected to be greater than a preset time interval, it is determined that the cutting machine edge is arcing, and a first control signal is output to the inverter circuit so that the power conversion circuit outputs a first arcing current to the electrode and the workpiece;

[0015] When the time interval is detected to be less than the preset time interval, it is determined that the cutting machine is perforating and arcing, and a second control signal is output to the inverter circuit so that the power conversion circuit outputs a second arcing current to the electrode and the workpiece;

[0016] When the first arc starting current or the second arc starting current reaches a set current, the power conversion circuit is controlled to output the set current to the electrode and the workpiece; wherein an initial current value of the first arc starting current is greater than an initial current value of the second arc starting current, and a current rising speed of the first arc starting current is greater than a current rising speed of the second arc starting current.

[0017] In one embodiment, the power conversion circuit includes a main transformer coupling circuit and a rectifier output circuit connected in sequence;

[0018] The main transformer coupling circuit is used to perform voltage conversion on the AC power supply and output the converted AC power supply to the rectifier output circuit;

[0019] The rectifier output circuit is used to rectify and convert the AC power output by the main transformer coupling circuit and output a DC power.

[0020] In one embodiment, the control circuit includes a controller and a PI regulation circuit;

[0021] The signal end of the first current detection circuit is connected to the first signal input end of the PI regulation circuit, the second signal input end of the PI regulation circuit is connected to the signal end of the controller, and the signal output end of the PI regulation circuit is connected to the controlled end of the inverter circuit;

[0022] The controller is used to output a first reference current signal to the PI regulation circuit;

[0023] The PI regulation circuit is used to output a PWM signal whose pulse width is inversely proportional to the current size of the first current detection signal to the inverter circuit according to the first reference current signal and the first current detection signal.

[0024] In one embodiment, the PI adjustment circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a first operational amplifier, a second operational amplifier, a third operational amplifier, a first capacitor, a second capacitor, a third capacitor and a fourth capacitor;

[0025] The first end of the first resistor is the second signal input end of the PI regulation circuit, the second end of the first resistor, the first end of the first capacitor, the first end of the second resistor and the inverting input end of the first operational amplifier are interconnected, the second end of the first capacitor and the first end of the third resistor are grounded, the second end of the third resistor is connected to the non-inverting input end of the first operational amplifier, the second end of the second resistor, the output end of the first operational amplifier and the first end of the fourth resistor are interconnected, the second end of the fourth resistor, the first end of the fifth resistor, the first end of the sixth resistor and the inverting input end of the second operational amplifier are interconnected, the first end of the sixth resistor is the first signal input end of the PI regulation circuit, the second end of the fifth resistor is connected to the output end of the first operational amplifier, and the first end of the sixth resistor is connected to the inverting input end of the second operational amplifier. The first end of the second capacitor is connected, the second end of the seventh resistor is grounded, the second end of the seventh resistor is connected to the non-inverting input terminal of the second operational amplifier, the output terminal of the second operational amplifier, the second end of the second capacitor and the first end of the eighth resistor are interconnected, the second end of the eighth resistor, the first end of the ninth resistor, the first end of the third capacitor and the inverting input terminal of the third operational amplifier are interconnected, the second end of the ninth resistor and the second end of the third capacitor are both grounded, the non-inverting input terminal of the third operational amplifier, the output terminal of the third operational amplifier and the first end of the tenth resistor are interconnected, the second end of the tenth resistor and the first end of the fourth capacitor are connected together to form the signal output terminal of the PI regulation circuit, and the second end of the fourth capacitor is grounded.

[0026] In one embodiment, the arc pilot driving circuit includes an arc pilot control circuit and an arc pilot switch circuit;

[0027] The signal end of the arc pilot control circuit is connected to the signal end of the control circuit and the controlled end of the arc pilot switch circuit respectively, the input end of the arc pilot switch circuit is connected to the positive electrode of the output end of the power conversion circuit, and the output end of the arc pilot switch circuit is connected to the nozzle;

[0028] The control circuit is configured to output a first control signal to the arc pilot control circuit upon receiving the first current detection signal, and output a second control signal to the arc pilot control circuit upon receiving the second current detection signal;

[0029] The arc pilot control circuit is used for:

[0030] When receiving the first control signal, the arc pilot switch circuit is controlled to be turned on, and an arc pilot current is established between the electrode and the nozzle;

[0031] When the second control signal is received, the arc pilot switch circuit is controlled to be turned off to stop the arc pilot.

[0032] In one embodiment, the arc pilot control circuit comprises an optocoupler, an input end of the optocoupler is connected to a signal end of the control circuit, and an output end of the optocoupler is connected to a controlled end of the arc pilot switch circuit.

[0033] In one embodiment, the first current detection circuit includes a current transformer and a rectifier and buck circuit;

[0034] The primary coil of the current transformer is connected to the front stage of the power input terminal of the power conversion circuit, the secondary coil of the current transformer is connected to the power input terminal of the rectifier and buck circuit, and the power output terminal of the rectifier and buck circuit is connected to the signal terminal of the control circuit.

[0035] In one embodiment, the second current detection circuit includes a current sensor.

[0036] A second aspect of an embodiment of the present invention provides a cutting machine control device, which includes an air valve and the cutting machine drive circuit as described above, wherein the air valve is connected to the cutting gun head through an air pipe.

[0037] A third aspect of an embodiment of the present invention provides a plasma cutting machine, which includes a cutting gun head and the cutting machine control device as described above.

[0038] The embodiment of the present invention forms a cutting machine drive circuit by adopting an inverter circuit, a power conversion circuit, an arc pilot drive circuit, a first current detection circuit, a second current detection circuit and a control circuit. When the cutting machine drive circuit is powered on, the arc pilot drive circuit works. When the arc pilot ignites the main arc, the workpiece, the nozzle and the power conversion circuit form a loop. According to the different time intervals of igniting the main arc of edge arc starting and perforation arc starting, it is determined whether the current cutting machine is edge arc starting or perforation arc starting, and the power conversion circuit is controlled to output different arc starting currents, so as to adapt to edge arc starting and perforation arc starting, improve the arc starting efficiency of edge arc starting, and reduce metal splashing during perforation arc starting. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic diagram of a first structure of a cutting machine driving circuit provided by an embodiment of the present invention;

[0040] Figure 2 A schematic diagram of a current waveform of a cutting machine driving circuit provided by an embodiment of the present invention;

[0041] Figure 3 A second structural schematic diagram of a cutting machine driving circuit provided by an embodiment of the present invention;

[0042] Figure 4 A third structural schematic diagram of a cutting machine driving circuit provided by an embodiment of the present invention;

[0043] Figure 5 for Figure 4 A schematic diagram of the structure of a PI regulation circuit provided in an embodiment;

[0044] Figure 6 A fourth structural schematic diagram of a cutting machine driving circuit provided by an embodiment of the present invention;

[0045] Figure 7 A fifth structural schematic diagram of a cutting machine driving circuit provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0047] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0048] A first aspect of an embodiment of the present invention provides a cutting machine driving circuit 100 .

[0049] like Figure 1 As shown, Figure 1 A first structural schematic diagram of a cutting machine driving circuit 100 provided in an embodiment of the present invention. In this embodiment, the cutting machine driving circuit 100 includes an inverter circuit 10, a power conversion circuit 20, an arc driving circuit 30, a first current detection circuit 40, a second current detection circuit 50 and a control circuit 60;

[0050] The inverter circuit 10 is used to convert the received external power into AC power and output it to the power conversion circuit 20. The negative electrode of the output end of the power conversion circuit 20 is connected to the electrode 210 of the cutting gun head 200, and the positive electrode of the output end of the power conversion circuit 20 is connected to the workpiece 300. The arc driving circuit 30 is electrically connected to the nozzle 220 of the cutting gun head 200 and the control circuit 60 respectively. The control circuit 60 is also electrically connected to the inverter circuit 10, the first current detection circuit 40 and the second current detection circuit 50 respectively.

[0051] The first current detection circuit 40 is used to detect the current of the AC power supply and feed back a first current detection signal to the control circuit 60;

[0052] The second current detection circuit 50 is used to detect the current flowing through the workpiece 300 and feed back a second current detection signal to the control circuit 60;

[0053] The control circuit 60 is used for:

[0054] When receiving the first current detection signal, the arc pilot driving circuit 30 is controlled to establish the arc pilot current between the electrode 210 and the nozzle 220, and when receiving the second current detection signal, the arc pilot driving circuit 30 is controlled to stop the arc pilot;

[0055] detecting a time interval between receiving a second current detection signal and receiving a first current detection signal;

[0056] When the detection time interval is greater than the preset time interval, it is determined that the cutting machine edge arcs, and a first control signal is output to the inverter circuit 10, so that the power conversion circuit 20 outputs a first arcing current I1 to the electrode 210 and the workpiece 300;

[0057] When the detection time interval is less than the preset time interval, it is determined that the cutting machine is perforating and arcing, and a second control signal is output to the inverter circuit 10, so that the power conversion circuit 20 outputs a second arcing current I2 to the electrode 210 and the workpiece 300;

[0058] When the first arc-starting current I1 or the second arc-starting current I2 reaches the set current I0, the control power conversion circuit 20 outputs the set current I0 to the electrode 210 and the workpiece 300; wherein the initial current value of the first arc-starting current I1 is greater than the initial current value of the second arc-starting current I2, and the current rising speed of the first arc-starting current I1 is greater than the current rising speed of the second arc-starting current I2.

[0059] In this embodiment, the external power supply is a DC power supply. The inverter circuit 10 performs an inverting conversion on the received external power supply and performs an AC-DC conversion through the power conversion circuit 20. The power conversion circuit 20 may include a step-up and step-down circuit, a rectifier circuit, etc., which are specifically set according to the cutting requirements of the cutting machine.

[0060] When initially powered on, the inverter circuit 10 is powered on. At this time, the nozzle 220 and the electrode 210 are short-circuited. The control circuit 60 first controls the arc pilot drive circuit 30 to work and applies a maintenance current between the nozzle 220 and the electrode 210. Then, the air valve is controlled to open, and the compressed air reaches the cutting gun head 200 through the air pipe, and the nozzle 220 and the electrode 210 are controlled to separate. The arc pilot current draws an arc between the electrode 210 and the nozzle 220 and is ejected from the nozzle 220 with the compressed air to form a pilot arc. The pilot arc contacts the workpiece 300 to ignite the main arc, and the cutting current forms a loop with the electrode 210 and the workpiece 300 to perform normal cutting operations. At this time, when the control circuit 60 receives the second current detection signal, it controls the arc pilot drive circuit 30 to stop working, and the output current of the power conversion circuit 20 is switched from the arc pilot current to the cutting current.

[0061] The time when the pilot arc contacts the workpiece 300 is different, and the time point when the cutting current of the workpiece 300 appears is different. When the cutting machine is edge-starting, the pilot arc slowly approaches the workpiece 300 until it contacts the workpiece 300 to ignite the main arc to form current. The time interval from initial power-on to the formation of the cutting current is longer. When the cutting machine is perforation-starting, the distance between the pilot arc and the workpiece 300 is short, and the pilot arc directly contacts and ignites the main arc. The time interval from initial power-on to the formation of the cutting current is short. Therefore, according to the time when the cutting current is formed and the time interval between the initial power-on, it can be judged whether the cutting machine is currently edge-starting or perforation-starting, and different arc starting control strategies can be adapted accordingly.

[0062] The control circuit 60 receives the first current detection signal and the second current detection signal before and after. When the time interval between the second current detection signal and the first current detection signal is greater than the preset time interval, it can be determined that the current cutting machine is edge-starting arcing, and the inverter circuit 10 is controlled to output the first AC power supply, so that the power conversion circuit 20 outputs the first arc-starting current I1 to the electrode 210 and the workpiece 300 to start the arc. Figure 2As shown, the first arc starting current I1 has a large initial current value and a high current rising speed, so that the set current I0 can be quickly reached at time point t1, thereby improving the arc starting speed and efficiency of edge arc starting.

[0063] When the time interval between the second current detection signal and the first current detection signal is less than the preset time interval, it can be determined that the current cutting machine is in the perforation arcing state, and the control circuit 60 controls the inverter circuit 10 to output the second AC power supply, so that the power conversion circuit 20 outputs the second arcing current I2 to the electrode 210 and the workpiece 300 to start the arc. Figure 2 As shown, the second arc starting current I2 has a small initial current value and a low current rising speed, thereby slowly reaching the set current I0 at time point t2, thereby avoiding the problem of molten metal splashing due to the large arc starting current during perforation arc starting, causing short circuit and burning of the nozzle 220 and the workpiece 300, thereby improving the safety of arc starting.

[0064] When the arc starting current reaches the set current I0, the control circuit 60 controls the cutting current output by the power conversion circuit 20 to remain at the set current I0 and perform normal cutting work.

[0065] The inverter circuit 10 may adopt an inverter bridge composed of IGBT tubes, and may be a full-bridge inverter circuit 10 or a half-bridge inverter circuit 10, and the specific structure is not limited.

[0066] The embodiment of the present invention forms a cutting machine drive circuit 100 by adopting an inverter circuit 10, a power conversion circuit 20, an arc pilot drive circuit 30, a first current detection circuit 40, a second current detection circuit 50 and a control circuit 60. When the cutting machine drive circuit 100 is powered on, the arc pilot drive circuit 30 works. When the arc pilot ignites the main arc, the workpiece 300, the nozzle 220 and the power conversion circuit 20 form a loop. According to the different time intervals of igniting the main arc of edge arc starting and perforation arc starting, it is determined whether the current cutting machine is edge arc starting or perforation arc starting, and the power conversion circuit 20 is controlled to output different arc starting currents, so as to adapt to edge arc starting and perforation arc starting, improve the arc starting efficiency of edge arc starting, and reduce metal splashing during perforation arc starting.

[0067] like Figure 3 As shown, in one embodiment, the power conversion circuit 20 includes a main transformer coupling circuit 21 and a rectifier output circuit 22 connected in sequence;

[0068] The main transformer coupling circuit 21 is used to convert the voltage of the AC power supply and output the converted AC power supply to the rectifier output circuit 22;

[0069] The rectifier output circuit 22 is used to rectify and convert the AC power output by the main transformer coupling circuit 21 and output a DC power.

[0070] In this embodiment, the inverter circuit 10 inputs an external power supply, and outputs a high-voltage DC power supply to the subsequent cutting gun head 200 and the workpiece 300 after being inverted by the inverter circuit 10, coupled and boosted by the main transformer coupling circuit 21, and rectified by the rectifier output circuit 22. The main transformer coupling circuit 21 can use a transformer with different coil ratios, and the rectifier output circuit 2230 can use a full-wave rectifier circuit or a half-wave rectifier circuit. The specific structures of the main transformer coupling circuit 21 and the rectifier output circuit 22 can be set according to the needs, and no specific restrictions are made here.

[0071] like Figure 4 As shown, in one embodiment, the control circuit 60 includes a controller 61 and a PI adjustment circuit 62;

[0072] The signal end of the first current detection circuit 40 is connected to the first signal input end of the PI regulation circuit 62, the second signal input end of the PI regulation circuit 62 is connected to the signal end of the controller 61, and the signal output end of the PI regulation circuit 62 is connected to the controlled end of the inverter circuit 10;

[0073] The controller 61 is used to output a first reference current signal to the PI regulation circuit 62;

[0074] The PI regulating circuit 62 is used to output a PWM signal having a pulse width inversely proportional to the current magnitude of the first current detection signal to the inverter circuit 10 according to the first reference current signal and the first current detection signal.

[0075] In this embodiment, the PI regulation circuit 62 outputs a PWM signal of a corresponding pulse width to the inverter circuit 10 according to the first reference current signal provided by the controller 61 and the detected primary current, thereby realizing constant current output control, wherein, when the primary current is larger, the pulse width of the PWM signal is smaller, and when the primary current is smaller, the pulse width of the PWM signal is larger, thereby realizing a rapid current rise when the current is small, and gradually reducing the pulse width to gradually control the current to rise to the current threshold, thereby realizing constant current control.

[0076] The controller 61 can be a single chip microcomputer, MCU, CPU and other control elements, and the specific structure is not limited. The PI adjustment circuit 62 can be a PI regulator or a corresponding combination circuit, such as Figure 5 As shown, in one embodiment, the PI adjustment circuit 62 includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, a first operational amplifier U1, a second operational amplifier U2, a third operational amplifier U3, a first capacitor C1, a second capacitor C2, a third capacitor C3 and a fourth capacitor C4;

[0077] The first end of the first resistor R1 is the second signal input end of the PI adjustment circuit 62, the second end of the first resistor R1, the first end of the first capacitor C1, the first end of the second resistor R2 and the inverting input end of the first operational amplifier U1 are interconnected, the second end of the first capacitor C1 and the first end of the third resistor R3 are grounded, the second end of the third resistor R3 is connected to the non-inverting input end of the first operational amplifier U1, the second end of the second resistor R2, the output end of the first operational amplifier U1 and the first end of the fourth resistor R4 are interconnected, the second end of the fourth resistor R4, the first end of the fifth resistor R5, the first end of the sixth resistor R6 and the inverting input end of the second operational amplifier U2 are interconnected, the first end of the sixth resistor R6 is the first signal input end of the PI adjustment circuit 62, the second end of the fifth resistor R5 is connected to the second The first end of the capacitor C2 is connected, the second end of the seventh resistor R7 is grounded, the second end of the seventh resistor R7 is connected to the non-inverting input end of the second operational amplifier U2, the output end of the second operational amplifier U2, the second end of the second capacitor C2 and the first end of the eighth resistor R8 are interconnected, the second end of the eighth resistor R8, the first end of the ninth resistor R9, the first end of the third capacitor C3 and the inverting input end of the third operational amplifier U3 are interconnected, the second end of the ninth resistor R9 and the second end of the third capacitor C3 are both grounded, the non-inverting input end of the third operational amplifier U3, the output end of the third operational amplifier U3 and the first end of the tenth resistor R10 are interconnected, the second end of the tenth resistor R10 and the first end of the fourth capacitor C4 are connected together to form a signal output end of the PI adjustment circuit 62, and the second end of the fourth capacitor C4 is grounded.

[0078] The first resistor R1 receives the first reference circuit signal, the sixth resistor R6 receives the third current detection signal, and the operational amplifiers proportionally amplify the signals to implement PI regulation and perform pulse width modulation output to control the inverter circuit 10 to output a constant current.

[0079] like Figure 6 As shown, in one embodiment, the pilot arc driving circuit 30 includes a pilot arc control circuit 31 and a pilot arc switch circuit 32;

[0080] The signal end of the arc pilot control circuit 31 is connected to the signal end of the control circuit 60 and the controlled end of the arc pilot switch circuit 32 respectively, the input end of the arc pilot switch circuit 32 is connected to the positive electrode of the output end of the power conversion circuit 20, and the output end of the arc pilot switch circuit 32 is connected to the nozzle 220;

[0081] The control circuit 60 is used to output a first control signal to the arc-maintaining control circuit 31 when receiving the first current detection signal, and to output a second control signal to the arc-maintaining control circuit 31 when receiving the second current detection signal;

[0082] The arc pilot control circuit 31 is used for:

[0083] When receiving the first control signal, the arc pilot switch circuit 32 is controlled to be turned on, and an arc pilot current is established between the electrode 210 and the nozzle 220;

[0084] When receiving the second control signal, the arc pilot switch circuit 32 is controlled to be turned off to stop the arc pilot.

[0085] In this embodiment, when the arc is not struck normally, no current passes between the positive pole of the output end of the power conversion circuit 20 and the workpiece 300. During normal operation, when the pilot arc current draws an arc between the electrode 210 and the nozzle 220 and is ejected from the nozzle 220 with compressed air to form a pilot arc, the pilot arc contacts the workpiece 300 to ignite the main arc. When the arc is struck normally, the current forms a loop through the electrode 210 and the workpiece 300 to perform normal cutting operations. At this time, the control circuit 60 receives the second current detection signal and outputs a second control signal to control the arc pilot control circuit 31 to stop working, the arc pilot switch circuit 32 is turned off, there is no arc pilot current between the electrode 210 and the nozzle 220, and the cutting machine switches to cutting operation.

[0086] The arc pilot control circuit 31 is used to convert the switch control signal output by the control circuit 60, and can adopt a signal amplification circuit, an isolation circuit, etc. In one embodiment, the arc pilot control circuit 31 includes an optocoupler, the input end of the optocoupler is connected to the signal end of the controller 61, and the output end of the optocoupler is connected to the controlled end of the arc pilot switch circuit 32. The optocoupler performs signal isolation and feeds back the switch control signal to the arc pilot switch circuit 32.

[0087] The arc pilot switch circuit 32 may use a switch tube with a controlled function, such as any one of an IGBT tube, a triode, a MOS tube, etc.

[0088] like Figure 7 As shown, in one embodiment, the first current detection circuit 40 includes a current transformer T1 and a rectifier and buck circuit 41;

[0089] The primary coil of the current transformer T1 is connected to the front stage of the power input terminal of the power conversion circuit 20, the secondary coil of the current transformer T1 is connected to the power input terminal of the rectifier and buck circuit 41, and the power output terminal of the rectifier and buck circuit 41 is connected to the signal terminal of the control circuit 60.

[0090] In this embodiment, the inverter circuit 10 outputs AC power. Therefore, in order to realize current detection, the first current detection circuit 40 includes a current transformer T1 and a rectifier-step-down circuit 41. The current transformer T1 proportionally outputs AC power to the rectifier-step-down circuit 41, and at the same time, the rectifier-step-down circuit 41 performs rectification and step-down conversion to obtain a first current detection signal. The rectifier-step-down circuit 41 may include a rectifier circuit, a step-down circuit, a current limiting circuit, etc., and the specific structure is not limited. At the same time, the current flowing through the workpiece 300 is a DC power supply. Therefore, the second current detection circuit 50 can realize current detection by using a current sensor. In one embodiment, the second current detection circuit 50 includes a current sensor.

[0091] The present invention also provides a cutting machine control device, which includes an air valve and a cutting machine drive circuit 100. The specific structure of the cutting machine drive circuit 100 refers to the above embodiment. Since the present cutting machine control device adopts all the technical solutions of all the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here. Among them, the air valve is connected to the cutting gun head 200 through an air pipe.

[0092] In this embodiment, the cutting machine driving circuit 100 performs arc piloting, and the air valve outputs compressed air at the same time, thereby realizing the arc piloting and igniting main arc operation. The cutting machine driving circuit 100 determines the arc starting mode of the cutting machine, and adapts different arc starting currents to improve the arc starting efficiency of edge arc starting, while reducing metal splashing during perforation arc starting.

[0093] The present invention also proposes a plasma cutting machine, which includes a cutting gun head 200 and a cutting machine control device. The specific structure of the cutting machine control device refers to the above-mentioned embodiment. Since the plasma cutting machine adopts all the technical solutions of all the above-mentioned embodiments, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here one by one.

[0094] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A cutting machine driving circuit, characterized in that: It includes an inverter circuit, a power conversion circuit, an arc driving circuit, a first current detection circuit, a second current detection circuit and a control circuit; The inverter circuit is used to convert the received external power into AC power and output it to the power conversion circuit, the negative electrode of the output end of the power conversion circuit is connected to the electrode of the cutting gun head, and the positive electrode of the output end of the power conversion circuit is connected to the workpiece, the arc driving circuit is electrically connected to the nozzle of the cutting gun head and the control circuit respectively, and the control circuit is also electrically connected to the inverter circuit, the first current detection circuit and the second current detection circuit respectively; The first current detection circuit is used to detect the current of the AC power supply and feed back a first current detection signal to the control circuit; The second current detection circuit is used to detect the current flowing through the workpiece and feed back a second current detection signal to the control circuit; The control circuit is used for: controlling the arc pilot drive circuit to establish an arc pilot current between the electrode and the nozzle when the first current detection signal is received, and controlling the arc pilot drive circuit to stop the arc pilot when the second current detection signal is received; detecting a time interval between receiving the second current detection signal and receiving the first current detection signal; When the time interval is detected to be greater than a preset time interval, it is determined that the cutting machine edge is arcing, and a first control signal is output to the inverter circuit so that the power conversion circuit outputs a first arcing current to the electrode and the workpiece; When the time interval is detected to be less than the preset time interval, it is determined that the cutting machine is perforating and arcing, and a second control signal is output to the inverter circuit so that the power conversion circuit outputs a second arcing current to the electrode and the workpiece; When the first arc starting current or the second arc starting current reaches a set current, the power conversion circuit is controlled to output the set current to the electrode and the workpiece; wherein an initial current value of the first arc starting current is greater than an initial current value of the second arc starting current, and a current rising speed of the first arc starting current is greater than a current rising speed of the second arc starting current.

2. The cutting machine driving circuit according to claim 1, characterized in that: The power conversion circuit comprises a main transformer coupling circuit and a rectifier output circuit connected in sequence; The main transformer coupling circuit is used to perform voltage conversion on the AC power supply and output the converted AC power supply to the rectifier output circuit; The rectifier output circuit is used to rectify and convert the AC power output by the main transformer coupling circuit and output a DC power.

3. The cutting machine driving circuit according to claim 2, characterized in that: The control circuit includes a controller and a PI adjustment circuit; The signal end of the first current detection circuit is connected to the first signal input end of the PI regulation circuit, the second signal input end of the PI regulation circuit is connected to the signal end of the controller, and the signal output end of the PI regulation circuit is connected to the controlled end of the inverter circuit; The controller is used to output a first reference current signal to the PI regulation circuit; The PI regulation circuit is used to output a PWM signal whose pulse width is inversely proportional to the current size of the first current detection signal to the inverter circuit according to the first reference current signal and the first current detection signal.

4. The cutting machine driving circuit according to claim 3, characterized in that: The PI adjustment circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a first operational amplifier, a second operational amplifier, a third operational amplifier, a first capacitor, a second capacitor, a third capacitor and a fourth capacitor; The first end of the first resistor is the second signal input end of the PI regulation circuit, the second end of the first resistor, the first end of the first capacitor, the first end of the second resistor and the inverting input end of the first operational amplifier are interconnected, the second end of the first capacitor and the first end of the third resistor are grounded, the second end of the third resistor is connected to the non-inverting input end of the first operational amplifier, the second end of the second resistor, the output end of the first operational amplifier and the first end of the fourth resistor are interconnected, the second end of the fourth resistor, the first end of the fifth resistor, the first end of the sixth resistor and the inverting input end of the second operational amplifier are interconnected, the first end of the sixth resistor is the first signal input end of the PI regulation circuit, the second end of the fifth resistor is connected to the output end of the first operational amplifier, and the first end of the sixth resistor is connected to the inverting input end of the second operational amplifier. The first end of the second capacitor is connected, the second end of the seventh resistor is grounded, the second end of the seventh resistor is connected to the non-inverting input terminal of the second operational amplifier, the output terminal of the second operational amplifier, the second end of the second capacitor and the first end of the eighth resistor are interconnected, the second end of the eighth resistor, the first end of the ninth resistor, the first end of the third capacitor and the inverting input terminal of the third operational amplifier are interconnected, the second end of the ninth resistor and the second end of the third capacitor are both grounded, the non-inverting input terminal of the third operational amplifier, the output terminal of the third operational amplifier and the first end of the tenth resistor are interconnected, the second end of the tenth resistor and the first end of the fourth capacitor are connected together to form the signal output terminal of the PI regulation circuit, and the second end of the fourth capacitor is grounded.

5. The cutting machine driving circuit according to claim 1, characterized in that: The arc pilot driving circuit includes an arc pilot control circuit and an arc pilot switch circuit; The signal end of the arc pilot control circuit is respectively connected to the signal end of the control circuit and the controlled end of the arc pilot switch circuit, the input end of the arc pilot switch circuit is connected to the positive electrode of the output end of the power conversion circuit, and the output end of the arc pilot switch circuit is connected to the nozzle; The control circuit is configured to output a first control signal to the arc pilot control circuit upon receiving the first current detection signal, and output a second control signal to the arc pilot control circuit upon receiving the second current detection signal; The arc pilot control circuit is used for: When receiving the first control signal, the arc pilot switch circuit is controlled to be turned on, and an arc pilot current is established between the electrode and the nozzle; When the second control signal is received, the arc pilot switch circuit is controlled to be turned off to stop the arc pilot.

6. The cutting machine driving circuit according to claim 5, characterized in that: The arc pilot control circuit comprises an optocoupler, an input end of the optocoupler is connected to a signal end of the control circuit, and an output end of the optocoupler is connected to a controlled end of the arc pilot switch circuit.

7. The cutting machine driving circuit according to claim 1, characterized in that: The first current detection circuit includes a current transformer and a rectifier and step-down circuit; The primary coil of the current transformer is connected to the front stage of the power input terminal of the power conversion circuit, the secondary coil of the current transformer is connected to the power input terminal of the rectifier and buck circuit, and the power output terminal of the rectifier and buck circuit is connected to the signal terminal of the control circuit.

8. The cutting machine driving circuit according to claim 1, characterized in that: The second current detection circuit includes a current sensor.

9. A cutting machine control device, characterized in that: It comprises an air valve and a cutting machine driving circuit as claimed in any one of claims 1 to 8, wherein the air valve is connected to the cutting gun head through an air pipe.

10. A plasma cutting machine, characterized in that: It comprises a cutting gun head and a cutting machine control device as claimed in claim 9.

Images