Power source for resistance welding machine with increased electromagnetic compatibility

The aim of the work is to develop a power source for a resistance welding machine with improved technical and economic properties. Based on the analysis of existing circuit topologies of three-phase power supplies of resistance welding machines, a new circuit topology of the power supply based on the use of a direct matrix converter is proposed. Transistor-diode circuits are used as power switches in the developed power supply. Each switch consists of a transistor and four diodes. This topology makes it possible to reduce the cost of the supply, and to simplify its control system. To solve the problem of the energy dissipation of the leakage field of a transformer when the polarity of the output voltage is changed, due to the fact that the converter is non-recuperative, the authors proposed an original scheme of a non-dissipative quasi-resonant voltage limiter. It consists of a series-connected capacitor and a bi-directional switch. Its application results in power losses reduction. Switch control algorithms have been developed that make it possible to ensure electromagnetic compatibility of the source with the network and to increase its power factor