AbSmi-Over 55kV/p, high voltage r k u p rated pulses have been sucegFfuDy applied betweeu the anode to the cathode of the 4kVBOOA Static Induction Thyristor (SlThy) at t u m 4 actions by applying the Induction Energy Storage 0 eimCit invented in 2002 111. SlThys were bmken d e n the high dv/dt value, over 2kV/p, is applied f o m r d between the anode and tbe cathode at the tum-off action by the conventional opening switching technique. We simulated the electric field SbpngU~ inside of the SlThy on the IES eirmit; consequently the electric field applied in front of the wmitter at the tum-off action b absolutely low. lhis is consided to be the Fesson of the high tolerance for "tum-off dvldt" of SlTbys ou the IES c h i t .