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In this paper, the high-current vacuum arc characteristics of the single coil-type AMF contacts, under axial magnetic field (AMF) generated by a sinusoidal current following, were investigated at a long contact gap of 40 and 60 mm. The distributing characteristics of AMF in contact gap were studied by a finite element method, taking eddy current effect into account. Vacuum arcs appearance was observed by a high-speed charge-coupled device video camera. Vacuum arc voltage was measured using a high-voltage probe. Dependence of arc voltage and vacuum arc appearance upon the self-generated AMF characteristics was investigated. The research results show that anode melting phenomena without arc voltage noises could occur both in an unstable arc and in a diffuse arc in a wide range of arc current and AMF strength at a long contact gap. Also, both many small-scale transient spots and several small luminous melting regions on anode could be observed with a diffuse arc column and a quiescent arc voltage.