I. Introduction
Vacuum interrupters (VIs) are favored in medium power systems for their environmental benefits and excellent insulation. With increasing demand for higher transmission voltages, efforts to enhance interruption capacity of VIs have intensified [1], [2]. A key approach is the vacuum arc control strategy, where the contact structure influences the axial magnetic field (AMF), an effective method to control arcing mode [3]. The AMF, generated by current through cup-type AMF contacts (CACs), helps maintain the vacuum arc in a diffuse mode, boosting interrupting capacity [4], [5]. Z. Liu et al. [6] focused on enhancing AMF characteristics by incorporating various iron cores in CACs, such as iron plates, ring iron cores, and asymmetric iron cores. Y. Zheng et al. [7], [8] explored the impact of iron core types on AMF characteristics, highlighting that ring iron cores and their derivative asymmetric designs exhibit superior magnetic enhancement effects. Y. Huang et al. [9], [10] indicated that the dimensions of iron cores, particularly slot depth and angle, critically impact the AMF characteristics.