Research On High-performance Plasma Cutting Power Supply System

Power supply is the power source of plasma cutting, power conversion technology is one of the core technologies of modern plasma cutting equipments, reseaching the plasma cutting power supply has important significance for improving the cutting efficiency and quality.A plasma cutting power supply based on two parallel Buck converter with passive low lossy snubber is designed in this paper, especially the parameter design of the passive low lossy snubber is researched in detail and deeply. Based on the analysis of the passive low lossy snubber, this paper also researchs a passive lossless snubber with coupled-inductor applicable to high-power situation. The operation process of the snubber and the optimization of the resonance parameters are analyzed in detail. A prototype is built to verify the correctness of the theory analysis and design methodology.Arc ignition is an important step to form the plasma arc when the plasma cutting power supply is working, this paper analyzes the working principle and mathematic modle of the arc ignition circuit, discusses the realize conditions of the high frequency oscillator. Also the simulation modle of the high frequency oscillator for arc ignition is built, and the design principle of key parameters is analyzed.For the dramatic decreasing external characteristics of the plasma cutting power supply, the current closed-loop control system is designed through small signal model of the plasma cutting power supply, which is in accordance with the external characteristics. The design of control parameters, microprocessor control system, PWM control circuit, and drive circuit are respectively analyzed.Combined with designed parameters, the simulation model of the plasma cutting power supply system is built. Based on the theory analysis and simulation, a 30kW plasma cutting power supply prototype is built. The static full-load and cutting experiments are finished, and the relevant performance parameters are tested. The experimental results show that the built prototype possesses high efficiency, high reliability and meets the requirements of dramatic decreasing external characteristics.