To improve the characteristics of the electric field in a vacuum interrupter with horseshoe-shaped axial magnetic field contacts

the response surface method is employed for optimization. Three contact parameters

i.e.

the outer diameter of the iron plate（d）

the difference between the outer and inner diameters of the iron plate（s）

and the difference of the slot angle between each iron plate（θ）

are chosen as the optimizing parameters. The axial magnetic flux density at current peak

the width of effective magnetic area and the phase shift time are chosen as the optimizing objectives. A 3-D finite element model of the contact is built

and simulation is carried out based on the central composite design method. Simulation results are analyzed by the response surface method

and the magnetic field characteristics are optimized by multiple objective optimization. As a result

the optimal values of d

s and θ are determined as90 mm

55 mm and 8.54°

respectively; the axial magnetic flux density at current peak increases from633.3 to 713.3 m T; the width of effective magnetic area increases from 25.2 to 25.9 mm

and the phase shift time decreases from 1.16 to 0.77 ms.