Abstract: The invention relates to a method of constructing and launching an offshore semi-submersible platform, comprising: a) making said semi-submersible platform in a dry environment by dividing it into a plurality of sub-assemblies each of which comprises at least one of the floating columns and at least one semi-arm of a respective lower structural connection arm; b) providing each sub-assembly in a dry environment with at least one temporary thrust box; c) separately launching in water the individual sub-assemblies; d) adjusting for each sub-assembly the ballast of the respective temporary thrust box so as to obtain a balanced floatation of the sub-assembly; e) bringing the sub-assemblies at the free ends of the respective semi-arms close to each other two-by-two until they are aligned; f) connecting the temporary thrust boxes to each other two-by-two; g) welding the free ends of the semi-arms together; h) removing the temporary thrust boxes.

Abstract: A generator for arc welder, of the type composed of a rectifier stage followed by a PFC stage and by an inverter stage, both of the high-frequency type, the latter stage supplying power to a final rectifier stage for a welding arc, the PFC stage being composed of two inductors that are mutually magnetically coupled, two diodes with opposite conduction directions, two leveling capacitors and means for controlling the succession of the on and off switchings of the two first switches, so as to shape the current absorbed by the rectifier stage by correlating it to the waveform of the line voltage. The inverter stage comprises four triads of second controlled switches, diodes and capacitors, and there is also a control device for the four second switches and for the current for the final stage that supplies power to the welding arc.

Abstract: A generator for arc welder, of the type composed of a rectifier stage followed by a PFC stage and by an inverter stage, both of the high-frequency type, the latter stage supplying power to a final rectifier stage for a welding arc, the PFC stage being composed of two inductors that are mutually magnetically coupled, two diodes with opposite conduction directions, two leveling capacitors and means for controlling the succession of the on and off switchings of the two first switches, so as to shape the current absorbed by the rectifier stage by correlating it to the waveform of the line voltage. The inverter stage comprises four triads of second controlled switches, diodes and capacitors, and there is also a control device for the four second switches and for the current for the final stage that supplies power to the welding arc.