![<?echo $_SERVER['SERVER_NAME'];?>](/template/twentyseventeen/skin/images/header.jpg)
In the 1990s, domestic and foreign power semiconductor devices and inverter technologies continued to develop in the direction of power, rapid, modular, combined, intelligent, inexpensive and high reliability. New high-power FETs were used for arc welding. The fast switching of the inverter is superior to the ordinary bipolar high power transistor. To this end, this new type of arc welding inverter has been developed. Power semiconductor devices and inverter technologies based on IGBTs and field-effect transistors will lead the rapid development of power electronic devices and power supplies, making them revolutionary, energy-efficient, material-saving, lightweight, and high-performance. Reliability is becoming more and more prominent in its superiority.
The emergence of new high-power electronic components has promoted the development of arc welding power supplies, and the emergence of thyristor welding inverters is an example. It has the outstanding advantages of small size, light weight, efficiency and power factor, and good process performance. The advent of bipolar high-power transistors has further boosted the frequency and performance of inverters.
From the perspective of power device commutation process and its control, the current inverter technology is moving from traditional pulse width modulation hard switching technology and frequency modulation resonance technology to pulse width modulation soft switching technology. In the 1950s, with the advent of pulse width modulation hard switching technology, the prelude of inverter technology development was unveiled. Many countries are striving for research in power electronics, magnetic materials, control integrated chips, and circuit topologies. The pulse width modulation hard switching technology has been widely used until the growth period of the 1960s, the development period of the 1970s, and the mature period of the 1980s. However, its switching frequency can not be too high, there are problems such as slow commutation, relatively large switching loss, high du/dt and di/dt, etc., which are poor in safety and reliability, and will produce significant Electromagnetic interference [6].
In view of the problems in the hard switching process, in the mid-1970s, the frequency modulation resonance technology came into being. The key of the technology lies in the application of the resonant principle of the inductor-capacitor network, forcing the current or voltage of the power switching device to change according to the sine law. When the current or voltage crosses zero, the device is turned on and off, thus solving the problems of switching dynamic loss, current surge, voltage stress and electromagnetic interference. It fundamentally overcomes the shortcomings of the traditional pulse width modulation hard switching converter, and thus quickly becomes a new development direction and research hotspot of power electronics. However, the frequency modulation resonance conversion technology also brings the following new problems: 1 The output voltage is related to the frequency. In order to keep the output voltage substantially constant under various operating conditions, variable frequency control must be adopted, and the adaptability to load changes is poor. Therefore, it is often used in applications where the load is basically constant or does not change much; 2 the capacity of the power device needs to be larger; 3 the wide range of switching frequency causes the design of magnetic devices such as filters and transformers to be difficult to optimize [7].
In the late 1980s, the advent of pulse width modulation soft-switching technology (SPWM) pushed the research and application level of high-power inverter technology to a new level. Pulse width modulation soft switching technology combines the advantages of traditional pulse width modulation technology and resonance technology. It only uses the resonance principle to achieve zero voltage or zero current conversion when the power device is commutating, and uses constant frequency pulse width modulation for most of the rest. The method completes the control of the output voltage or current of the power supply, so the switching device is subjected to less current or voltage stress. In the past 10 years, pulse width modulation soft switching technology has gradually dominated the power inverter circuit [8-10]. At present, pulse width modulation soft switching technology is still one of the most important research contents of power electronics, and its application prospect is very broad.
3 AC and DC arc welding power control digitalization
Digital welding refers to the use of computer technology to control the operating state of the welding equipment to meet and meet the requirements of the welding process to obtain a fully qualified weld. The arc welding inverter power control system mainly experienced two stages of the analog control system and the digital control system in the implementation. The traditional analog control system has limited ability to perform complex processing, and the number of components is large. The parameters of the control system are determined by the parameters of discrete components such as resistors and capacitors. The control system has complex scheduling and poor flexibility. At the same time, the parameter distribution of resistance and capacitance affects the control. The consistency of the system, the stability of the parameters is poor, such as temperature drift affects the stability of the control system; in addition, due to limitations in hardware implementation, the control algorithm can only use PID adjustment methods, some advanced control algorithms cannot be realized by analog circuits. Or it is very difficult to implement and is not used, so it greatly limits the development of arc welding inverter power supply.
In recent years, with the application and development of new semiconductor devices such as large-scale integrated circuit ASIC, digital signal processor DSP, complex programmable logic device CPLD, field programmable gate display FPGA, the control circuit of arc welding power source has been separated from the original Components and simple integrated circuits have been developed into digital control circuits based on single-chip microcomputers, DSPs, CPLDs and FPGAs. The digitization of the main circuit has greatly reduced the power loss of the welding power supply, and the efficiency can reach 90% [11]. In addition, due to the increase of the operating frequency, the ripple of the loop output current is smaller, the response speed is faster, and the welder can obtain better dynamic response characteristics.
At present, the digital control system of arc welding power supply mainly includes: single chip control system, programmable logic device PLD control system, ARM chip control system, DSP based control system and so on.
With its high flexibility and cost performance, single-chip microcomputer is widely used in the digital control of arc welding power supply. The arc welding power source controlled by the single chip microcomputer mainly uses the single chip microcomputer of MCS-51 series or MCS-96 series as the central processing unit, with a small number of interface circuits and peripheral circuits. Because the single-chip microcomputer can not complete real-time calculation and high-precision control tasks, it is generally used in simple control systems. In addition, the MCU control system is only partially digitalized, and its feedback signal and PWM still use analog control circuit. Therefore, the digital characteristics are not fully reflected in the arc welding inverter power supply controlled by single chip microcomputer.
Compared with single-chip microcomputer, DSP-based control system has strong data processing capability, can complete complex calculations in real time, single-cycle multi-function instructions, high PWM resolution, high cost performance, and can achieve more ideal digital control. FRONIU's Transplus synergic2700/4000/5000 series products implement a variety of arc welding methods on the welder, which can store dozens of welding programs, display welding parameters in real time, and give welding parameters and current waveform parameters through a single knob. Precise control of droplet transfer and arc length changes. This type of welding power supply can also be used for process management and control software upgrades over the network.
In [12], based on the AC-DC welding power source controlled by single-chip microcomputer, a multi-function AC/DC square wave power supply controlled by single-chip AT89C51 is designed. With the development of modular circuits combining analog and digital circuits, it will gradually replace discrete analog circuits.
In [13], TI's TMS320F240 DSP was used as the core chip of the control system. The digital IGBT inverter AC/DC square wave pulse TIG welder was developed based on digital signal processor (DSP).
The application of digital control technology in arc welding power source enables advanced control algorithms to be realized in arc welding power supply. Arc welding power supply can adopt more advanced control algorithms to make its output power quality good, high reliability and easy to realize intelligence. control.
Digitization is the development direction of arc welding power supplies. The application of inverter technology realizes the digitization of the main circuit of the power supply. The control system of the new semiconductor device based on single chip microcomputer, DSP and CPLD/FPGA realizes the digitization of the control circuit. DSP, PLD/FPGA will have broad application prospects and advantages in the arc welding power digital control system due to its powerful performance and great flexibility. It is foreseeable that the research on digital control technology of high-precision and high-performance arc welding inverter power supply using DSP and CPLD/FPGA will be the mainstream of arc welding power supply in the future, and will be greatly developed.
Previous Next
Performance advantages:
1.Strong water absorption capacity
2.Increase the collection and release of samples
3.Good abrasion resistance
4.Do not scratch the wiped device
5.No chip drop
6.100% sterilization and disinfection
Operating Steps:
1 Touch the swab to the surface where it is aimed to obtain the sample.
2 Remove the tube cap and put the swab into the transport medium.
3 Break the shaft of the swab so that it will fit in the tube.
4 Close the cap securely.Write on the tube the necessary information about the patient and sample.
VTM Tube,Tube VTM,VTM Tube Price,VTM Test,VTM Test Tube,Lab Test Tube,Small Test Tube,VTM Sampling Tube
Yong Yue Medical Technology(Kunshan) Co.,Ltd , https://www.yonyue.com