Design And Research On Digital Chopper Plasma Cutting Machine Power Supply

Power supply is the key component of plasma cutting machines. Meanwhile power electronic technology is one of the crucial technologies of modern plasma cutting devices. So the research of highly efficient, stable and reliable power supply for plasma cutting machine is of great importance to the improvement of efficiency and quality.The plasma cutting principle and the overall diagram of the power supply system were analyzed based on the research situation and development trend of the plasma cutting machine at domestic and abroad. The special requirements of plasma cutting machine were obtained according to the plasma cutting process.Based on the key technical parameters of the power supply system studied, two BUCK circuits parallel output as the main topology of the system was determined. The electrical components of the main circuit were mathematical calculation, analysis and selection. And also, suitable snubber circuit was selected for the system.The BUCK circuit was modeled by the advanced circuit averaging method and nonlinear discrete method respectively. Based on the advanced averaging method simulation results, a compensation network was added to the system to enhance the system’s response speed and phase margin; based on the nonlinear discrete simulation results, the theoretical basis of under-voltage and over-voltage software settings were obtained.TMS320F28335 DSP was selected as the main control chip and it achieved the current-loop control of the power supply system. With the designed hardware in digital control board and the written codes of the digital control system, the paper showed some crucial parts of the hardware schematics and software design flow chart.The power supply of the plasma cutting machine had passed the cutting test with the following results: stable current output, fast dynamic responses and the output met the requirements of dramatic decreasing external characteristics; good communications behaviors among the power supply control board, the gas control box and the CNC module. During the cutting process, the state transformations were in line with the cutting manual and the coordination of different models was also realized. All of these have laid a solid foundation to the further development.