Development Of The Variable Polarity Plasma Arc Welding Power Source

This paper firstly makes an attempt to introduce the characteristics of variable polarity plasma arc welding source and present research situation in domestic and international welding field.According to the request of the aluminum alloy welding and the development tendency of variable polarity plasma arc welding source,the design scheme includes main circuit and control system.The build-up and control principle of the VPPAW source are introduced in this paper. Full-bridge dual inverter configuration by main circuit which is supplied by single power source.The operation frequency of the first inverter is 20 kHz and the maximum output current is 500 A.The main circuit is made up of input rectifier & filter circuit,first inverter circuit,second inverter circuit,output rectifier & filter circuit,high frequency striking arc circuit.The design process and device parameters are discussed at length in this paper where the realization.The control system uses the PWM pattern control mode,voltage PWM integrated circuit in the first inverter controlling system is chosen of SG3525A,peripheral circuit is designed.The impulse signals,which are used to trigger power switch tube,are amplificated by EXB841.The chip has the properties of test of over-voltage,over-current and the soft-shut off.SG3526 is chosen in the second inverter,peripheral circuit and the driver circuits are also designed.The impulse,which trigger power switch tube,is amplificated by TLP250.The changes of current wave are realized to shutoff and breakover.The AC square wave of welding process command is satisfied.The emulating mode of main circuit is built by simulink of matlab.The designing scheme and the processing of test are adjusted on time.The VPPAW power wave is realized.The key factor which affects the welding power wave is presented.The design rationality is certificated.The design cost is reduced.Worked efficiency is improved.This paper design one VPPAW power according to theoretical calculation simulation. Through online debugging,test data and results are attained and analyzed.The experiment results indicate that the VPPAW power source gains asymmetrical square-wave whose current frequency,amplitude,DCEN/DCEP ratio can be adjusted separately.Therefore, VPPAW power source runs stably,with high reliability.