Developing electric drive with adaptive algorithm for soft switching between frequency converter and three-phase mains

The paper presents a new approach for induction motor (IM) soft switching from frequency converter (FC) to mains and vice versa. Industrial companies' and municipal services' proper operating require numerous complex systems interconnection and cooperation the structure of which depends on the company's type. The frequency control station (FCS) is one of the abovementioned systems. The FCS application for industrial unit group control is usually a technically and economically reasonable solution. Despite all the advantages, the solution provides a dangerous mode which could appear while operating. The article deals with AC electric drive transient at supply voltage loss. The reason for particular attention paid to the voltage loss's processes stands for its connection with FCS operating. The paper conducts detailed investigation of the IM switching processes between FC and mains. Besides, it considers the probable risk estimation. The technique proposed in the article intends to eliminate probable emergency operation while switching. The authors suggest soft switching technique, its schematic circuit implementation and a closed-loop control system designing and calculation. Schematic circuit components' selection guideline is also proposed.