Pismennyy A. Increasing efficiency of power supply systems of machines for resistance spot welding.

The thesis work is devoted to analysis of problems of electric power supply and operation of machines for resistance spot welding (RSW). The most perspective trends for further work in this area have been analyzed and determined. The thesis contains systematic analysis of the known power supply systems for RSW on the basis of which theoretical and calculation evaluations of the most perspective systems have been done. To develop power supply systems of the power up to 100 kVA with a longitudinal compensation of reactive voltage a program for automatic calculation of the power coefficients, values of relative voltages and currents according to given values of the making angles at different values of voltage active resistance has been created. For RSW machines of a power more than 100 kVA the power supple system with three phase converter and 30 Hz current frequency was found as a perspective one. It is proved that quasisymplectic work of the converter allows receiving profitable current separation at the chain phases without loading of neutral wire and reduction of current operating frequency – increase the power coefficient of machine itself. For welding and micro welding of the parts with small (lower 1 mm) and extra small (lower 0,1 mm) thickness an application of a higher-frequency welding current inverter converter was proposed as an alternative for machines of capacitor type welding. The work contains description of the development and production of an experimental research sample of higher-frequency current inverter power supply source of 500 Hz with developed automatic mode of welding control. This power supply source provides a process of high quality welding of metallic products in a thickness range of 0,05…0,5 mm and models the power source with current frequency 30 Hz for welding of products in a thickness range of 5…8 mm. The experimental investigation results of microwelding of the samples of products on stainless steel 08X118H10T, made by it, are represented.