Design And Research On High-reliability Plasma Cutting Power Supply

The plasma cutting technology is developing, and widely applied in the manufacturing and processing industries. Only to improve the cutting quality and efficiency, it is unable to fully meet the needs of the market. The reliability of plasma cutting power supply is also pay close attention to. In this paper, based on the theory of reliability, the plasma cutting power supply is designed and realized.The theory of reliability is introduced into the design of plasma cutting power supply, and this paper analyses the vital factors affecting the plasma cutting power supply system reliability. The contents include the schemes of three-phase rectifier circuit and schemes of the DC-DC converter. In view of the comparison and analysis of the reliability of different kinds of circuit topology, the twelve-pulse uncontrolled rectifier circuit is selected as an AC-DC converter and the phase-shift full-bridge converter as a DC-DC converter. And some advantages and problems which need to be solved are also pointed out.This paper combines the options of circuit reliability with the special plasma cutting power supply equipment’s technical indicators, which include the THD, level of output voltage and so on. It selects a twelve-pulse uncontrolled rectifier circuit with a composite filtering device. The simulation results of twelve-pulse uncontrolled rectifier circuit suggest that the THD exceeds the standard. In order to reduce the main harmonic of the input current, LC filter parameters and reasonable allocation of notch filter are designed. This paper finally designs a twelve-pulse rectifier circuit of 50 k VA with a composite filtering device. At a rated load, the input current THD is less than 3% which satisfies specifications.Based on the power level of special plasma cutting power supply requirements and the results of reliability analysis, this paper selects phase-shift full bridge converter as main DC-DC converter. Firstly, according to the analysis of its working principle, it designs a dual closed-loop control strategy. Meanwhile, the simulation results show that it has high dynamic and static performance. Then, the simple and effective finite state machine(FSM) is high reliability. The control method of FSM is used in software design. This paper designs a 12 k W plasma cutting power. The experimental results verify that the plasma cutting power supply has better dynamic performance and higher reliability.