Properties of intermediate frequency vacuum arc under axial magnetic field

This paper presents the study of intermediate frequency vacuum arc under an axial magnetic field (AMF). Arc voltage noise at the first current half-cycle is inconspicuous even if the current is not interrupted successfully, it can be attributed to the application of a sufficiently strong AMF provided by the current in a short vacuum gap. The influence of current frequency on peak arc voltage and the rate of rise of arc voltage are investigated. Interrupting capacity of a CuCr50 cup-type vacuum interrupter (VI) with AMF is examined; the current interruption limit is inversely proportional to frequency from 400 Hz-800 Hz, in agreement with the experimental and theoretical results achieved by other scholars. The eddy current field of a CuCr50 cup-type VI with AMF is studied by the finite-element method based on a simplified axial symmetric model; the results show that the phase shift angle increases conspicuously with the increase of current frequency, and besides the rate of change of current (di/dt) when the current passes zero, phase shift angle also influences the intermediate frequency current interrupting capacity of the VI.