Abstract: As an important power device for suppressing overvoltage, filtering, and reactive power compensation in power grids, the air-core reactor faces higher requirements for its long-term stable performance in stringent operational environments. Due to the differences in traditional reactor design methods and manufacturing processes, some designed reactors may experience circulating currents between their encapsulation. It is necessary to add external regulating winding coils, which will result in additional weak points in the reactor, and will increase the cracking risk of encapsulation insulation in high-cold regions and large-temperature-difference operating environments. To fundamentally solve the technical challenges of circulating currents in encapsulation and insulation cracking, this paper starts from optimizing the electromagnetic structure of reactors. The conventional perspective of winding small circular wires in parallel was transitioned to the structural approach of single combination wire winding in series. The new nonlinear equation system for calculating the inductance value of reactors was constructed. Under isothermal constraint conditions and by using a multi-terminal lead configuration, the design of a spatially symmetric electromagnetic structure for a non-circulating current reactor was achieved. Finally, the electromagnetic structure design of the first set of non-circulating current reactors was achieved through an equally long winding line, strengthening inter-turn insulation, and weakening encapsulated insulation. The first designed 10 kV series air-core reactor has passed type and special tests and successfully been put into operation on the grid in winter in Northeast China. Compared with traditional reactors, the novel non-circulating current reactor has a 40% smaller volume and a 32% lower temperature-rise. The design method of a novel non-circulating current reactor in this paper will provide a new design form for the high-end manufacturing of air-core reactors in China, which is of great significance for ensuring the long-term reliability of air-core reactors in high-cold regions.