Effects of current asymmetry on the electron sheath of magnetically-insulated induction voltage adders

The current asymmetry resulting from the special injection manner of cavities in magnetically-insulated induction voltage adders (MIVA) would affect the electron sheath and power flow of the magnetically-insulated transmission lines (MITL). In this article, based on the two-dimensional Creedon equilibrium flow of the magnetic insulation, the effects of current asymmetry on the electron sheath are evaluated. It is found that, the current asymmetry affects the electron sheath more greatly than the charge centroid and flow impedance. For the given parameters of MITL (e.g., the line voltage V0 is 4.1 MV, and the minimal anode current Iamin is 132 kA), the asymmetric coefficient of the electron sheath is about 79.4% when the asymmetric coefficient of cathode currents, δc, is 35%. And the flow impedance decreases by 5.6% compared with the case of no current asymmetry. As the δc increases to 69.5%, the AK gap is short circuit at some positions due to the off-center electron sheath. It is also found that, the lower of the line voltage V0 and the minimal anode current Iamin are, the larger of the influence extent of current asymmetry is. As the line voltage decreases from the 4.2 to 1.4 MV, the critical value of asymmetric coefficients of cathode currents leading to the gap closure, decreases from 69.5% to 35%.