Research On Metal Spraying Inverter-based Power Supply

Metal spraying is a very key production process of capacitor manufacturing, and the quality and performance of capacitor are directly affected by metal spraying quality. Metal spraying power is one of the key links to guarantee the quality, and the quality of metal spraying is related directly to the output parameters of metal spraying power. At present, The majority of power supply for metal spraying process is rectified power, whose dynamic characteristics is poor, and arc control is unstable, and metal spraying quality is bad. So this paper has designed a metal spraying inverter-based power supply to significantly improve the dynamic characteristics and to realize the stable control of arc and to improve the metal spraying coating quality.The paper put forward an overall solution of the power supply, selecting full-bridge as the main circuit topology structure, and completing the design of high frequency transformer and the selection of other key components in the main circuit.The control system based on DSP was designed, including driving circuit, sampling circuited, interactive system and fault protection circuit, etc. The arc of metal spraying was analyzed, and the paper designed arc igniting control strategy with constant current, and arc burning control strategy with constant voltage. The software of the power control system was designed, including the written and debug of the main program and the PWM, A/D sampling, PID control, digital tube display, encoder and other sub-programs.The experimental platform of metal spraying process was built, and the metal spraying inverter-based power was installed and debugged. The two feedback control models, current-constant arc igniting and voltage-constant arc burning, were realized through adjusting PI parameters of different phases in the whole metal spraying process. During the arc igniting phase, the peak current and the current rise speed were high, which could realize stable current control within 1ms. During the arc burning phase, the voltage of the arc was controlled stably, and the arc could continue burning for a long time, realizing the fast and reliable arc igniting and stable arc burning, which met the requirements of metal spraying power. The zinc wire was chosen to conduct metal spraying process experiment, and the results indicated that the particles of metal spraying coating, which adopted the inverted metal spraying power, was small, uniform and shiny, and the particles temperature was low when arriving at the end face, which lead to none scald defects, consequently the coating quality was good. And it was concluded that the higher voltage could make the metal spraying particle smaller, but the metal spraying particle would be oxidized and the metal spraying quality would be poor if voltage would be too high. The metal spraying inverter-based power supply developed in this paper could perfectly meet the requirements of metal spraying process, and had very important practical values.