Research On A 50KW Digital Inverter Type Plasma Cutting Power Supply

In recent years, with the upscaling of manufacturing industry, China’s steel consumption demand is growing. In 2004, the domestic steel production has been more than 1.1 billion tons. The production among the rest of medium heavy steel plate is as high as 140 million tons, which is mainly used in ships, bridges, pressure vessels and so on. Therefore, the thermal cutting technology and equipment for medium plate with high quality, high efficiency and low cost has become the focus of the industries. Plasma arc cutting owns the features of less thermal deformation and high-speed cutting ability, and it can almost cut all materials. Especially in the medium/thick plate cutting, plasma arc cutting has more efficiency and cost advantages. So that it has a broad application prospect. In order to meet the thermal cutting demands of medium plate, higher requirements which aim at the output power and control performance of cutting power supply are put forward. But now the international and domestic market has not yet seen any high power digital inverter type plasma cutting power supply products because of the limited factors such as technology, material and machining accuracy. Therefore, research on high power plasma cutting power technology has become more and more important and urgent.With the support of the National Natural Science Foundation of China(Project number: E51375173), Guangdong Strategic Emerging Industries Core Technology Research Project(Project number: 2012A032300007) and Guangdong Science and Technology Planning Project(Project number: 2013B010402007), by adopting the method of combining high-frequency inverter technology and digital control technology, this thesis presents a type of 50 k W digital inverter type plasma cutting power supply with energy efficiency and good performance. The thesis firstly introduces backgrounds of issue and analyzes research status as well as development trend of plasma cutting power supply. On the basis of above, according to plasma arc theory and cutting process requirement, develop a 50 k W digital inverter type plasma cutting power supply prototype including main circuit and control circuit. The main circuit of power supply is composed of two 25 k W power electronic building blocks, which adopt full-bridge topology and choose IGBT as the power switch tube of inverter module. The control circuit mainly uses Cortex-M4 ARM microprocessor STM32F405 as the cybernetic core to construct the hardware platform of digital control system by well-designed MCU minimum system, IGBT drive circuit, signal sampling circuit, fault protection circuit and so on. At the same time, according to the workflow and output characteristics of power supply, this paper also develops the software of digital control system based on Free RTOS of real-time kernel. Finally, use the developed plasma cutting power supply prototype as experimental platform and test the machine performance under simulated load, and complete lots of cutting process experiments. Also, use laboratory instruments like power quality analyzer, oscilloscope and digital clamp meter to collect experimental data and waveforms, and then analyze the cutting effect of workpieces under different parameter settings.The result shows that the developed 50 k W digital inverter type plasma cutting power supply has good external characteristics and dynamic response performances and can work stably and reliably. The power supply can also meet the requirements of plasma cutting process with excellent performance, high efficiency, accurate control and good cutting quality. All of these further verify the correctness and feasibility of the design.