The influence of external axial magnetic fields on the interruption capacities of laser triggered vacuum switch

Magnetic fields across vacuum gap have important effects on the interruption process of vacuum switch. To improve the high-frequency interruption capacity of laser triggered vacuum switch (LTVS), influences of different external axial magnetic fields (AMF) on the interruption capacities of LTVS are studied in this paper. The three-dimensional simulation models of vacuum gap with Cup-type AMF electrode and Helmholtz coils, which is employed to generate external AMF, are built up. The magnetic field distributions in vacuum gap are calculated and analyzed. The test platform is set up based on a detachable vacuum chamber. The influences external AMF strength, applied moments, and directions on the interruption capacity of LTVS are studied and analyzed. The test results prove that, compared to other applied moments, the LTVS with external AMF applied at current-zero point presents larger current interruption capacity. And the interruption capacity of LTVS increases with the increase of the AMF strength. As the frequency of LTVS increases, the effect of AMF increases. The LTVS with AMF under a reverse direction shows better interruption capacity compared to a positive direction. Under the following conditions: the frequency of LTVS1 and LTVS2 is 3.9kHz and 13.9kHz, the amplitude of external reverse AMF is 35mT, the current starting point of LTVS1 leading the current starting point of LTVS2 by 108μs. Then the interruption capacity of LTVS1 increases from 517A to 680A.