Plasma arc torch and method of starting an arc

Abstract

The application provides an arc striking control system and method of a plasma cutting machine, and belongs to the technical field of plasma cutting machines.The system comprises a switch panel, an electronic controller, a high-frequency arc striking control device, a low-frequency arc striking control device, a cutting torch head and a workpiece; the high-frequency arc striking control device is integrated with an arc transfer control circuit, a high-frequency arc striking circuit and a plasma power output unit; the high-frequency arc striking circuit is used for generating high-frequency high-voltage input into the arc transfer control circuit based on an input power voltage and a high-frequency arc striking control signal; the arc transfer control circuit is used for transferring the electric arc between the electrode and the nozzle to the workpiece to form a stable plasma electric arc between the workpiece and the electrode; and the low-frequency arc striking control device comprises a signal receiving unit, a plasma gas control module, a PID control module and a high-pressure gas module. The high-frequency arc striking mode and the low-frequency arc striking mode are arranged in the system and can be randomly switched, so that the application range of the plasma cutting machine is wider.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of plasma cutting machines, in particular to an arc striking control system and method of a plasma cutting machine. BACKGROUND

[0002] The arc striking modes of the plasma cutting machine currently mainly include a high-frequency arc striking mode and a low-frequency arc striking mode. The high-frequency arc striking mode is suitable for large-current and large-power plasma cutting. The low-frequency arc striking mode is limited by the installation mode of vulnerable parts and is only suitable for small-power plasma cutting equipment below 200A. The high-frequency arc striking mode is easy to cause large high-frequency and high-voltage interference, which affects the arc striking success rate, interferes with power grid equipment, and the like. The low-frequency arc striking mode will not cause high-frequency and high-voltage interference, and the arc striking success rate will be relatively high, but the use range and the service life of the vulnerable parts will be affected. Currently, the market has only two arc striking modes of high frequency and low frequency, but there is no random switching mode. Customers will select different cutting torches to match different arc striking modes.

[0003] The low-frequency arc striking mode belongs to a contact type arc striking mode. Its principle is as follows. When there is no arc striking, the electrode (negative pole of the power supply output) and the nozzle (positive pole of the power supply output) are in a short-circuit state. When an arc striking signal is given, the half-bridge IGBT and the arc striking IGBT are driven, and the gas circuit electromagnetic valve is turned on. Due to the time delay of the gas circuit, the power supply works in an approximate short-circuit state in the previous stage. At this time, the short-circuit current is controlled at a constant value through the control loop. When the gas flow reaches the nozzle, the high-pressure gas thrust is used to blow the nozzle and the electrode apart from the short-circuit state in an instant. At this time, a small arc will be generated on the inner wall of the cutting torch. The arc slides outward along the gas flow and is finally sprayed out of the nozzle to form a sustainable plasma arc. There is a short-circuit process in the arc striking process. If the control precision is not enough, a small control deviation will cause a large current fluctuation, resulting in system overcurrent. The arc striking process belongs to a load mutation process. If the control speed is not fast enough in this stage, the current will drop too much, and the arc striking process will also fail.

[0004] The above problems are urgent to be solved. SUMMARY

[0005] The present application aims to overcome at least one technical problem existing in the prior art. In a first aspect, the present application provides an arc striking control system of a plasma cutting machine, the system comprising a switch panel, an electronic controller, a high-frequency arc striking control device, a low-frequency arc striking control device, a cutting torch head and a workpiece; the switch panel is electrically connected to the electronic controller, the electronic controller is electrically connected to the high-frequency arc striking control device and the low-frequency arc striking control device respectively, and the high-frequency arc striking control device and the low-frequency arc striking device are both electrically connected to the cutting torch head; the switch panel controls the working mode of the system through the electronic controller; the high-frequency arc striking control device is integrated with an arc transfer control circuit, a high-frequency arc striking circuit and a plasma power output unit, one end of the high-frequency arc striking circuit is used for receiving a high-frequency arc striking control signal, the other end is connected to a first end of the arc transfer control circuit, a second end of the arc transfer control circuit is connected to a first end of the plasma output unit, a third end of the arc transfer control circuit is connected to the workpiece, a fourth end of the arc transfer control circuit is connected to a nozzle of the cutting torch head, and a second end of the plasma output unit is connected to an electrode of the cutting torch head; the high-frequency arc striking circuit is used for generating a high-frequency high-voltage input into the arc transfer control circuit based on an input power voltage and a high-frequency arc striking control signal, the arc transfer control circuit is used for transferring an electric arc between the electrode and the nozzle to the workpiece to form a stable plasma arc between the workpiece and the electrode; the low-frequency arc striking control device comprises a signal receiving unit, a plasma gas control module, a PID control module and a high-pressure gas module, a first end of the signal receiving unit is electrically connected to the electronic controller, a second end is electrically connected to a first end of the plasma gas control module, a second end of the plasma gas control module is electrically connected to a first end of the PID control module, a second end of the PID control module is electrically connected to a first end of the high-pressure gas module, and a second end of the high-pressure gas module is electrically connected to the cutting torch head; the plasma gas control module is used for controlling plasma gas and gas passage closure based on a control signal sent by the signal receiving unit, and discharging residual gas in the plasma gas passage to make the electrode and the nozzle completely contact; the PID control module is used for controlling a cutting machine main circuit and a plasma gas passage, and an incremental PID control algorithm is adopted to realize the transition of a load mutation process by a sudden increase in control amount when the load mutation is detected to generate a voltage between the electrode and the nozzle; and the high-pressure gas module is used for providing high pressure to make the closed electrode and nozzle pop open to form a non-transfer arc between the electrode and the nozzle.

[0006] Further, the working mode comprises a high-frequency arc striking mode and a low-frequency arc striking mode.

[0007] Further, the high-frequency arc striking circuit comprises a first transformer T1, a discharge tube, a first capacitor C1, a second capacitor C2, a third capacitor C3 and a second transformer T2, the primary coil of the first transformer T1 is connected to the main power supply, the secondary coil of the first transformer T1 is connected to the discharge tube, the discharge tube is connected to the first capacitor C1, the second capacitor C2 and the third capacitor C3, the first capacitor C1, the second capacitor C2 and the third capacitor C3 are connected to the secondary coil of the second transformer T2 in parallel, and the primary coil of the second transformer T2 is connected to the arc transfer control circuit.

[0008] Further, the arc transfer control circuit comprises a first resistor R1, a second resistor R2, a fourth capacitor C4 and an insulated gate bipolar transistor IGBT, the first resistor R1 is connected to the IGBT in parallel, the emitter of the IGBT is connected to the second resistor R2, the collector of the IGBT is connected to the primary coil of the second transformer T2, the fourth capacitor C4 is connected to the first resistor R1, the second resistor R2 and the IGBT in parallel, and the primary coil of the second transformer T2 is also connected to the nozzle.

[0009] Further, the primary coil of the second transformer T2 and the fourth capacitor C4 form a high-frequency oscillation loop, the generated high-frequency high voltage is transmitted to the high-frequency arc striking circuit through the secondary coil of the second transformer T2, and the air gap between the nozzle and the electrode is broken to form a plasma arc.

[0010] Further, the arc transfer control circuit is connected to the plasma power output unit and the workpiece through a relay respectively, so that the system determines that the arc transfer is successful when the transferred arc current is greater than a set value, and the relay is disconnected.

[0011] Further, the low-frequency arc striking control device further comprises a gas exhaust module for exhausting the remaining gas in the plasma gas channel, so that the electrode and the nozzle are completely contacted, and the gas exhaust time is delayed for 500ms-1s.

[0012] Further, the low-frequency arc striking control device is used for determining whether air load appears based on a preset error threshold value when the current rises to a given arc striking value after the low-frequency arc striking switch on the switch panel is pressed, and realizing the transition of the load mutation process through the method of sudden increase control amount when the load mutation is detected.

[0013] Further, the incremental PID control algorithm comprises:

[0014] ;

[0015] ;

[0016] ;

[0017] In the formula, is the output current value, is a proportional coefficient, is a fine powder coefficient, is a differential coefficient, and e is a deviation.

[0018] In a second aspect, the present application provides an arc striking control method of a plasma cutting machine, which is applied to the arc striking control system of the plasma cutting machine.

[0019] In a third aspect, the present application further provides a computer readable storage medium, which stores one or more instructions, and the computer instructions are used to make the computer execute the arc striking control method of the plasma cutting machine.

[0020] In a fourth aspect, the present application provides an electronic device, which comprises a memory and a processor; the memory stores at least one program instruction; and the processor loads and executes the at least one program instruction to realize the arc striking control method of the plasma cutting machine.

[0021] The beneficial effects of the present application are: the present application provides a plasma cutting machine arc striking control system, the system includes switch panel, electronic controller, high frequency arc striking control device, low frequency arc striking control device, cutting torch head and workpiece; the switch panel is electrically connected with the electronic controller, the electronic controller is electrically connected with the high frequency arc striking control device and low frequency arc striking control device respectively, the high frequency arc striking control device and low frequency arc striking device are electrically connected with the cutting torch head; the switch panel controls the working mode of the system through the electronic controller; the high frequency arc striking control device is integrated with arc transfer control circuit, high frequency arc striking circuit and plasma power output unit, one end of the high frequency arc striking circuit is used for receiving high frequency arc striking control signal, the other end is connected with the first end of the arc transfer control circuit, the second end of the arc transfer control circuit is connected with the first end of the plasma output unit, the third end of the transfer arc control circuit is connected with the workpiece, the fourth end of the transfer arc control circuit is connected with the nozzle of the cutting torch head, the second end of the plasma output unit is connected with the electrode of the cutting torch head; the high frequency arc striking circuit is used for generating high frequency high voltage input into the arc transfer control circuit based on the input power voltage and high frequency arc striking control signal, the arc transfer control circuit is used for transferring the arc between the electrode and the nozzle to the workpiece to form a stable plasma arc between the workpiece and the electrode; the low frequency arc striking control device includes signal receiving unit, plasma gas control module, PID control module and high pressure gas module, the first end of the signal receiving unit is electrically connected with the electronic controller, the second end is electrically connected with the first end of the plasma gas control module, the second end of the plasma gas control module is electrically connected with the first end of the PID control module, the second end of the PID control module is electrically connected with the first end of the high pressure gas module, the second end of the high pressure gas module is electrically connected with the cutting torch head; the plasma gas control module is used for controlling plasma gas and gas passage closing based on the control signal sent by the signal receiving unit, and discharging the remaining gas in the plasma gas passage, so that the electrode and the nozzle are completely contacted; the PID control module is used for controlling the cutting machine main circuit and the plasma gas passage, and the incremental PID control algorithm is adopted to realize the transition of load mutation process by sudden increase of control amount when the load mutation is detected, so as to generate voltage between the electrode and the nozzle; the high pressure gas module is used for providing high pressure to make the closed electrode and nozzle pop up to form non transfer arc between the electrode and the nozzle. On the one hand, the high frequency arc striking mode and the low frequency arc striking mode can be randomly switched by arranging in the system, so that the application range of the plasma cutting machine is wider. On the second aspect, by integrating the arc striking transfer control circuit and the high frequency filter circuit in the high frequency arc striking control device, the success rate of the arc striking circuit can be improved to meet the reliability technical index of the system. On the third aspect, by integrating the PID control module in the low frequency arc striking control device, the improved PID algorithm can effectively solve the current discontinuity problem when the load mutates, and the success rate of arc striking is improved. Attached Figure Description

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] Figure 1 This is a schematic diagram of the arc ignition control system for a plasma cutting machine provided in Embodiment 1 of the present invention.

[0024] Figure 2 This is a circuit topology diagram of the high-frequency arc ignition control device provided in Embodiment 1 of the present invention.

[0025] Figure 3a This is a waveform diagram of the arc ignition current and half-bridge IGBT drive voltage using a common PID algorithm in the low-frequency arc ignition mode provided in Embodiment 1 of the present invention.

[0026] Figure 3b This is a waveform diagram of arc ignition voltage and current using an improved PID algorithm in the low-frequency arc ignition mode provided in Embodiment 1 of the present invention.

[0027] Figure 4 This is a schematic diagram of the fuzzy PID control principle provided in Embodiment 1 of the present invention.

[0028] Figures 5a-5e The e, ec, and e provided in Embodiment 1 of this invention , and A schematic diagram of the membership function.

[0029] Figure 6 This is a partial block diagram of the electronic device provided in Embodiment 4 of the present invention. Detailed Implementation

[0030] Before discussing the exemplary embodiments in more detail, it should be noted that some exemplary embodiments are described as processes or methods depicted as flowcharts. Although the flowcharts describe the operations as sequential processes, many of these operations can be performed in parallel, concurrently, or simultaneously. Furthermore, the order of the operations can be rearranged. The process can be terminated when its operation is completed, but may also have additional steps not included in the figures. The process can correspond to a method, function, procedure, subroutine, subroutine, etc.

[0031] It should be understood that although the terms "first," "second," etc., may be used herein to describe various units, these units should not be limited by these terms. These terms are used merely to distinguish one unit from another. For example, without departing from the scope of the exemplary embodiments, a first unit may be referred to as a second unit, and similarly, a second unit may be referred to as a first unit. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0032] The present invention will now be described in detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0033] Example 1

[0034] like Figure 1 The diagram shown is a schematic diagram of the arc ignition control system for a plasma cutting machine provided by the present invention.

[0035] As an example, the system comprises a switch panel 1, an electronic controller 2, a high-frequency arc striking control device 3, a low-frequency arc striking control device 4, a cutting torch head 5 and a workpiece 6; the switch panel 1 is electrically connected with the electronic controller 2, the electronic controller 2 is electrically connected with the high-frequency arc striking control device 3 and the low-frequency arc striking control device 4 respectively, and the high-frequency arc striking control device 3 and the low-frequency arc striking control device 4 are electrically connected with the cutting torch head 5; the switch panel 1 controls the working mode of the system through the electronic controller 2; the high-frequency arc striking control device 3 is integrated with an arc transfer control circuit 310, a high-frequency arc striking circuit 320 and a plasma power output unit 330, one end of the high-frequency arc striking circuit 320 is used for receiving a high-frequency arc striking control signal, the other end is connected with a first end of the arc transfer control circuit 310, a second end of the arc transfer control circuit 310 is connected with a first end of the plasma output unit 330, a third end of the arc transfer control circuit 310 is connected with the workpiece, a fourth end of the arc transfer control circuit 310 is connected with a nozzle 510 of the cutting torch head 5, and a second end of the plasma output unit 330 is connected with an electrode 520 of the cutting torch head 5; the high-frequency arc striking circuit 320 is used for generating a high-frequency high-voltage input into the arc transfer control circuit 310 based on an input power voltage and a high-frequency arc striking control signal, and the arc transfer control circuit 310 is used for transferring an electric arc between the electrode 520 and the nozzle 510 to the workpiece 6 to form a stable plasma arc between the workpiece 6 and the electrode 520; the low-frequency arc striking control device 4 comprises a signal receiving unit 410, a plasma gas control module 420, a PID control module 430 and a high-pressure gas module 440, a first end of the signal receiving unit 410 is electrically connected with the electronic controller 2, a second end is electrically connected with a first end of the plasma gas control module 420, a second end of the plasma gas control module 420 is electrically connected with a first end of the PID control module 430, a second end of the PID control module 430 is electrically connected with a first end of the high-pressure gas module 440, and a second end of the high-pressure gas module 440 is electrically connected with the cutting torch head 5; the plasma gas control module 420 is used for controlling plasma gas and gas passage to be closed based on a control signal sent by the signal receiving unit 410, and discharging residual gas in a plasma gas passage to make the electrode 520 and the nozzle 510 completely contact; the PID control module 430 is used for controlling a cutting machine main circuit and a plasma gas passage, and adopts an incremental PID control algorithm to realize a transition of a load mutation process by a sudden increase of a control amount when a load mutation is detected to generate a voltage between the electrode 520 and the nozzle 510; and the high-pressure gas module 440 is used for providing high pressure to make the closed electrode 520 and the nozzle 510 pop open to form a non-transfer arc between the electrode 520 and the nozzle 510.

[0036] Preferably, the working mode comprises a high-frequency arc striking mode and a low-frequency arc striking mode.

[0037] Preferred, such as Figure 2 As shown, the high-frequency arc-initiating circuit 320 includes a first transformer T1, a discharge tube, a first capacitor C1, a second capacitor C2, a third capacitor C3, and a second transformer T2. The primary coil of the first transformer T1 is connected to the main power supply, and the secondary coil of the first transformer T1 is connected to the discharge tube. The discharge tube is connected to the first capacitor C1, the second capacitor C2, and the third capacitor C3. The first capacitor C1, the second capacitor C2, and the third capacitor C3 are connected in parallel to each other and then connected to the secondary coil of the second transformer T2. The primary coil of the second transformer T2 is connected to the arc transfer control circuit 310. The arc transfer control circuit 310 includes a first resistor R1, a second resistor R2, a fourth capacitor C4, and an insulated gate bipolar transistor (IGBT). The first resistor R1 is connected in parallel with the IGBT. The emitter of the IGBT is connected to the second resistor R2, and the collector of the IGBT is connected to the primary coil of the second transformer T2. The fourth capacitor C4 is connected in parallel with the first resistor R1, the second resistor R2, and the IGBT. The primary coil of the second transformer T2 is also connected to the nozzle 510. The primary coil of the second transformer T2 and the fourth capacitor C4 form a high-frequency oscillation circuit. The high-frequency high voltage generated is transmitted to the high-frequency arc ignition circuit through the secondary coil of the second transformer T2, breaking down the air gap between the nozzle 510 and the electrode 520 to form a plasma arc.

[0038] Specifically, the workflow of the high-frequency arc ignition control device includes: A 120V mains power input voltage is stepped up to 5KV by the first transformer T1. This voltage charges three parallel capacitor banks (C1, C2, and C3), increasing the voltage difference across the discharge tube until the tube is broken down. After breakdown, the discharge tube's resistance is almost zero, effectively short-circuiting the first transformer. The first transformer T1 is a high-leakage reactance type; its high secondary inductance limits the short-circuit current, allowing it to operate normally. Simultaneously, the second transformer T2 is a high-frequency coupling transformer. Its primary coil and capacitor C4 form a high-frequency oscillation circuit. The generated high-frequency high voltage flows through the secondary coil of the second transformer T2 to the arc ignition circuit, breaking down the air gap between the nozzle and electrode to form a plasma arc. Since the plasma arc between the nozzle and electrode needs to stabilize before forming a circuit with the mains power supply for cutting operations, an arc transfer control circuit is required to transfer the arc between the electrode and nozzle to the workpiece, forming a stable plasma arc between the workpiece and the electrode. Among them, the IGBT (Insulated Gate Bipolar Transistor) is a composite, fully controllable, voltage-driven power semiconductor device composed of a bipolar transistor and an insulated gate field-effect transistor, characterized by low drive power and low saturation voltage. (Capacitor voltage) The sampled value is compared with the reference value through an operational amplifier. When the voltage is less than the reference value, the IGBT is turned off, C4 is connected in parallel with R1 and R2, and the capacitor is charged, and the voltage is raised. When the voltage exceeds the reference value, the IGBT is turned on, R2 is short-circuited, the capacitor is rapidly discharged, and the capacitor voltage is lowered until the IGBT is turned off. R2 is switched into the circuit continuously, forming a high-frequency impact current of 0-80 A that is continuously changing. When the impact current is on the rising edge, an arc is formed between the electrode and the workpiece, and the main circuit of the power supply is connected. When the transferred arc current i2 is greater than the set value, the system determines that the arc transfer is successful, and the relay is turned off to prepare for cutting. The non-contact high-frequency arc transfer mode is used, and by designing the arc transfer control circuit and the high-frequency filter circuit, the arc transfer success rate of the arc transfer circuit can be improved to meet the reliability technical indicators of the system.

[0039] Preferably, the low-frequency arc transfer control device further comprises a gas exhaust module for exhausting the remaining gas in the plasma gas channel, so that the electrode and the nozzle are in complete contact, and the gas exhaust time is delayed by 500 ms-1 s.

[0040] Preferably, the low-frequency arc transfer control device 4 is used to determine whether an air load occurs based on a preset error threshold when the current rises to a given arc transfer value after the low-frequency arc transfer switch on the switch panel is pressed. When a load mutation is detected, the transition of the load mutation process is realized by the method of sudden increase of the control amount. The incremental PID control algorithm includes:

[0041] ;

[0042] ;

[0043] ;

[0044] Specifically, refer to Figure 4 The fuzzy PID control diagram is shown in FIG. 1, and the membership functions of e, ec, Figures 5a-5e , , and are shown in FIGS. 2-5, respectively. The incremental PID control algorithm can use a fuzzy PID control algorithm, and the three parameter values of the PID include:

[0045] ;

[0046] ;

[0047] ;

[0048] In the formula, is a proportional parameter, is an integral parameter, is a differential parameter, an initial value of a proportional parameter, an initial value of an integral parameter, an initial value of a differential parameter, an increment value of a proportional parameter, an increment value of an integral parameter, an increment value of a differential parameter. The fuzzy control rule table is shown in Table 1:

[0049] Table 1:

[0050]

[0051] The fuzzy control rule table is shown in Table 2:

[0052] Table 2:

[0053]

[0054] The fuzzy control rule table is shown in Table 3:

[0055] Table 3:

[0056]

[0057] In one aspect of the above-mentioned embodiments, the high-frequency arc striking mode and the low-frequency arc striking mode are arranged in the system and can be switched randomly, so that the application range of the plasma cutting machine is wider. In a second aspect, the arc striking transfer control circuit and the high-frequency filter loop are integrated in the high-frequency arc striking control device, so that the arc striking success rate of the arc striking circuit is improved, and the reliability technical index required by the system is achieved. In a third aspect, the PID control module is integrated in the low-frequency arc striking control device, so that the improved PID algorithm is used to effectively solve the current discontinuity problem when the load suddenly changes, and the arc striking success rate is improved.

[0058] Embodiment 2

[0059] As an example, the embodiments of the present application provide a plasma cutting machine arc striking control method. The method is applied to the plasma cutting machine arc striking control system described in Embodiment 1.

[0060] It can be found that the present embodiment is a method embodiment corresponding to the first embodiment, and the present embodiment can be implemented in cooperation with the first embodiment. The related technical details mentioned in the first embodiment are still valid in the present embodiment. In order to reduce repetition, they will not be described here. Correspondingly, the related technical details mentioned in the present embodiment can also be applied in the first embodiment.

[0061] Embodiment 3

[0062] The application further provides a storage medium, and the storage medium stores the plasma cutting machine arc striking control method. The plasma cutting machine arc striking control program is executed by the processor to realize the steps of the plasma cutting machine arc striking control method. The storage medium adopts all the technical solutions of the above embodiments, and thus has all the beneficial effects of the technical solutions of the above embodiments, which will not be repeated here.

[0063] Embodiment 4

[0064] Please refer to Figure 6 The application further provides an electronic device, which comprises a memory and a processor. The memory stores at least one program instruction. The processor loads and executes the at least one program instruction to realize the plasma cutting machine arc striking control method provided in Embodiment 2.

[0065] The memory 602 and the processor 601 are connected in a bus mode. The bus can comprise any number of interconnected buses and bridges. The bus connects various circuits of one or more processors 601 and memories 602 together. The bus can also connect various other circuits such as peripheral devices, voltage stabilizers and power management circuits together, which are well known in the art, and thus will not be further described herein. The bus interface provides an interface between the bus and the transceiver. The transceiver can be one element or multiple elements such as multiple receivers and transmitters, which provide a unit for communicating with various other devices on a transmission medium. Data processed by the processor 601 is transmitted on a wireless medium through an antenna, and further, the antenna also receives data and transmits the data to the processor 601.

[0066] The processor 601 is responsible for managing the bus and general processing, and can also provide various functions including timing, peripheral interface, voltage regulation, power management and other control functions. The memory 602 can be used to store data used by the processor 601 in performing operations.

[0067] The above-mentioned are only embodiments of the present application, and the common knowledge of specific structures and characteristics in the scheme is not described too much herein. The ordinary skilled person in the art knows all the ordinary technical knowledge in the field of the present application before the application date or the priority date, can know all the prior art in the field, and has the ability to apply conventional experimental means before that date. The ordinary skilled person in the art can perfect and implement the present scheme under the guidance of the present application, combined with their own ability. Some typical known structures or known methods should not be an obstacle for the ordinary skilled person in the art to implement the present application. It should be noted that, for those skilled in the art, without departing from the structure of the present application, a number of modifications and improvements can be made, which should also be considered as the protection scope of the present application. The protection scope of the present application should be subject to the content of its claims, and the specific implementation mode and the like in the specification can be used to explain the content of the claims.

Claims

1. A plasma cutting machine arc ignition control system, characterized in that, The system includes a switch panel, an electronic controller, a high-frequency arc ignition control device, a low-frequency arc ignition control device, a cutting torch head, and a workpiece; The switch panel is electrically connected to the electronic controller, the electronic controller is electrically connected to the high-frequency arc ignition control device and the low-frequency arc ignition control device respectively, and both the high-frequency arc ignition control device and the low-frequency arc ignition device are electrically connected to the cutting gun head. The switch panel controls the high-frequency arc-starting mode and low-frequency arc-starting mode of the system via an electronic controller. The high-frequency arc ignition control device integrates an arc transfer control circuit, a high-frequency arc ignition circuit, and a plasma power output unit. One end of the high-frequency arc ignition circuit is used to receive a high-frequency arc ignition control signal, and the other end is connected to the first end of the arc transfer control circuit. The second end of the arc transfer control circuit is connected to the first end of the plasma output unit. The third end of the arc transfer control circuit is connected to the workpiece. The fourth end of the arc transfer control circuit is connected to the nozzle of the cutting torch head. The second end of the plasma output unit is connected to the electrode of the cutting torch head. The high-frequency arc ignition circuit is used to generate a high-frequency high voltage input to the arc transfer control circuit based on the input power supply voltage and the high-frequency arc ignition control signal. The arc transfer control circuit is used to transfer the arc between the electrode and the nozzle to the workpiece to form a stable plasma arc between the workpiece and the electrode. The low-frequency arc ignition control device includes a signal receiving unit, a plasma gas control module, a PID control module, and a high-pressure gas module. The first end of the signal receiving unit is electrically connected to the electronic controller, and the second end is electrically connected to the first end of the plasma gas control module. The second end of the plasma gas control module is electrically connected to the first end of the PID control module, the second end of the PID control module is electrically connected to the first end of the high-pressure gas module, and the second end of the high-pressure gas module is electrically connected to the cutting torch head. The plasma gas control module is used to control the plasma gas and the gas passage to close based on the control signal sent by the signal receiving unit, and to discharge the residual gas in the plasma gas passage so that the electrode and the nozzle are in complete contact. The PID control module is used to control the main circuit of the cutting machine and the plasma gas channel. It adopts an incremental PID control algorithm to realize the transition of the load change process by suddenly increasing the control quantity when a load change is detected, so as to generate voltage between the electrode and the nozzle. The high-pressure gas module is used to provide high pressure, causing the closed electrode and nozzle to spring open to form a non-transfer arc between the electrode and nozzle.

2. The plasma cutting machine arc ignition control system according to claim 1, characterized in that, The high-frequency arc-initiating circuit includes a first transformer T1, a discharge tube, a first capacitor C1, a second capacitor C2, a third capacitor C3, and a second transformer T2. The primary coil of the first transformer T1 is connected to the main power supply, and the secondary coil of the first transformer T1 is connected to the discharge tube. The discharge tube is connected to the first capacitor C1, the second capacitor C2, and the third capacitor C3. The first capacitor C1, the second capacitor C2, and the third capacitor C3 are connected in parallel to each other and then connected to the secondary coil of the second transformer T2. The primary coil of the second transformer T2 is connected to the arc transfer control circuit.

3. The plasma cutting machine arc ignition control system according to claim 2, characterized in that, The arc transfer control circuit includes a first resistor R1, a second resistor R2, a fourth capacitor C4, and an insulated gate bipolar transistor (IGBT). The first resistor R1 is connected in parallel with the IGBT. The emitter of the IGBT is connected to the second resistor R2. The collector of the IGBT is connected to the primary coil of the second transformer T2. The fourth capacitor C4 is connected in parallel with the first resistor R1, the second resistor R2, and the IGBT. The primary coil of the second transformer T2 is also connected to the nozzle.

4. The plasma cutting machine arc ignition control system according to claim 2, characterized in that, The primary coil of the second transformer T2 and the fourth capacitor C4 form a high-frequency oscillation circuit. The high-frequency high voltage generated is transmitted to the high-frequency arc ignition circuit through the secondary coil of the second transformer T2, breaking down the air gap between the nozzle and the electrode to form a plasma arc.

5. The plasma cutting machine arc ignition control system according to claim 1, characterized in that, The arc transfer control circuit is connected to the plasma power output unit and the workpiece via relays respectively. When the transferred arc current is greater than the set value, the system recognizes that the arc transfer is successful and disconnects the relay.

6. The plasma cutting machine arc ignition control system according to claim 1, characterized in that, The low-frequency arc ignition control device also includes a venting module, which is used to discharge the residual gas in the plasma gas channel so that the electrode and the nozzle are in complete contact, with a venting time delay of 500ms-1s.

7. The plasma cutting machine arc ignition control system according to claim 1, characterized in that, The low-frequency arc ignition control device is used to determine whether an air load occurs when the current rises to a given arc ignition value after the low-frequency arc ignition switch is pressed on the switch panel, based on a preset error threshold. When a load change is detected, the device achieves the transition of the load change process by suddenly increasing the control quantity.

8. The plasma cutting machine arc ignition control system according to claim 7, characterized in that, The incremental PID control algorithm includes: ； ； ； In the formula, The output current value. For proportionality coefficient, For micron coefficient, Let be the differential coefficient, and e be the deviation.

9. A method for controlling arc ignition in a plasma cutting machine, characterized in that, The method is applied to the plasma cutting machine arc ignition control system according to any one of claims 1-8.

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