| First, this paper expatiates the definition and development of the contravariant arc welding power supply, and the basic working principle of its key component--the inverter. Contravariant welding power supply is replaced by new ones with the development of power devices. Altogether, the contravariant arc welding power supply has gone through four phases: thyristor, transistor field effect transistor, IGBT contravariant welding power supply.Compared with conventional arc welding power supply, such as arc welding transformer, direct current arc welding generator and arc welding rectifier and so on, contravariant arc welding power supply has many advantages: first, it is small and ethereal with a smaller output reactor and main transformer which consumes less materials; second, it is very dynamic with quick reaction, and its arc efficiency, stability of the arc and control ability of various waveforms are improved greatly, the current waveform of welding is steady; third, high efficiency, nearly 80-90%.It consumes less electricity and the waste is reduced , so the power factor can reach 0.95-0.99. Therefore, it is a new and promising arc welding power supply. It can be foreseen that the contravariant power supply will develop to be digital, environmental, light, voluminous with soft switch.At the same time, to most of the present contravariant welding power supply, diode bridge is used to commutate in the first stage of inverter, which is a combination of non-linear and power deposited components. Although the input voltage is sine wave, the input AC waveform is distorted greatly, just like pulses. Thus it can be seen that with the application of commutate circuit on a large scale the current waveform from the electric network will become seriously distorted sine wave. And the consequence is that the level of noise will rise. In addition, electric network will be damaged because a mass of current harmonic flow back to it. On the one hand,"second domino effect"will be caused; on the other hand, circuit fault will appear and equipment will be damaged.So restraining harmonic and raising power factor are two problems needed to be settled in the development of contravariant welding power supply, which can be perceived from the perspectives of handling environment pollution and preserving green environment. To electric power system, no harmonic is a main sign of"green". In the field of electronic technique, the request for"green electric power"in practice becomes stronger and stronger. As standards become more and more strict, the field of welding is inevitably restricted by harmonic pollution, so now the issue of arc welding power supply harmonic arouses many investigators'interests, and restraining harmonic and heightening power factor of arc welding power supply become important studies.In order to solve the problem of harmonic pollution and power factor, and to make electric equipment meet various standards and requests about harmonic, people introduce the technique of power factor correction to the design of arc welding power supply. On the basis of numerous related literatures, this paper discusses single-phase power factor correction.First, through comparing the advantages and disadvantages of different topologies of PFC converter such as Buck, Boost, Buck-boost and Cuk, this paper expounds the PFC main circuit that it will employ– Cuk PFC converter, and then analyzes the change and waveform of the voltage and current in every phrase and courses. The input and output voltage of the main circuit in this paper is steady direct voltage; Cuk converter can heighten and lower voltage; in TON and TOFF of switch cycle, the power can be transferred from input to output, the efficiency is high; if the voltage lowered of switch transistor and diode which is used to hold on current is small enough, the infection which is made by interfere from electric net can be ignored. At last the parameter of L1, L2, C1, C2, current and voltage adjuster circuits are calculated.The control chip which is used in this paper is produced by Unitrode Company, which is an appropriative control chip for active power factor correction, and contains all the functions that average current control PFC is required to possess. It can be used when the input voltage is 75V-275V, and the frequency is 50-400Hz. Its power factor is near 1, and it is controlled by average current of the fixed frequency. Besides, it has high precision and broad input voltage bound. It has protective measures when the voltage is not enough or the current is too strong, and contains 7.5V fiducial voltage whose precision is 1%, and the star current is very low. It has low noise of the switch, intact function of the PWM power control, and its highest operation frequency is higher than 300 kHz.Controlling system is very important to a power supply. In this paper, the idea of Boost average current control PFC is adopted in Cuk topology to design acontravariant arc welding power supply with PFC and controlled circuit, and calculate the value of every component.The circuit is simulated by Pspice, and the simulative waveform proves that the PFC can be carried out with the parameter of the main circuit, the input current wave can be sine wave as input voltage, and the output voltage can be steady as the power factor is raised.Some practical metrical waveforms are presented, which indicate that the current of input end follows the voltage waveform basically and is sine-wave, the power factor is near 1, and the harmonic is restrained and meets the international standard about harmonic.
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