In order to solve the problems of excessive current and voltage sag during the starting of large capacity induction motors under severe conditions

a novel topology structure based on autotransformer and magnetic control（ATMC） is proposed. The structure combines the merits of auto-transformer starting and magnetic-control starting

which can realize the smooth starting of large motor in harsh environment. Through the analysis of the electromagnetic principle of the system

the transient model expressed with space vector is established

and the transient characteristics of the mechanical and electromagnetic physical quantities of the starting process are analyzed. The correctness of the transient model and its characteristics is verified with the simulation and experimental results. By adopting an improved topology structure which can be switched smoothly and its control strategy

the system effectively solves the high spike of auto-transformer starting without magnetic-control link. Moreover

the system improves the starting current

grid voltage sag and other operating characteristics. The system has the advantages of auto-transformer starting and magnetic control starting

high reliability

low cost

and maintenance-free.