In the paper some results regarding electro-magnetic processes investigation in the single-phase transformer based AC pulse modulation mode regulated system of network voltage stabilization are presented. The main attention is paid to the mathematical description of switching electro-magnetic processes of transformer windings, which influence output parameters of device. Switching processes are regarded to application of transistor switches with proper snubbering circuits. Computer simulation of the processes above mentioned as well experimental investigation of a model are done and its outcomes are presented.