Tham khảo tài liệu 'advanced welding processes episode 1 part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 46 Advanced Welding Processes This type of circuit was initially used for MMA power sources but it is now being employed for GT AW and pulsed GM AW units. It has particularly good electrical efficiency and a comparison of inverter and conventional power sources at current settings of 250 A has shown that idle power consumption is only one-tenth of that of a conventional machine and during welding the efficiency is around 86 compared with 52 for a conventional unit 29 . Transformer Output Mains Input Output Control Figure Primary rectifier-inverter. Hybrid designs It is possible to combine the electronic control techniques outlined above to improve the performance and cost effectiveness of the Welding Power Source Technology 47 power source. For example the use of a secondary chopper to preregulate the supply followed by a small air-cooled transistor series regulator for final control of the output has been described 30 the circuit is shown schematically in figure and the advantages of this approach are summarized in table . Hybrid designs may also be adopted to produce a square-wave AC output by adding a secondary inverter to the output of a DC phase-controlled unit. SCR phase-controlled power sources may be used in conjunction with an SCR inverter 31 or alternatively the system may be based on an integrated primary rectifier inverter design. Sophisticated experimental hybrid units have been developed for example for high-frequency AC plasma welding 32 in order to investigate potential improvements in process control. Alternative power devices such as asymmetrical SCRS ASCRs 33 or metal oxide-silicon field-effect transistors MOSFETs may also be used to improve the efficiency of conventional electronic and hybrid systems. Features of electronic power source designs The electronic designs all share a capability for remote control and are easily interfaced with system controllers within the power supply or from an external source. The output .
