SPED means a superconducting power electronics device. We made some thermally controlled S-PED which is normally-on device. They work up to 100 Hz as a full wave rectifier. For the power supply of superconducting magnets, the flux pump can be used as SPEED (Superconducting Power Electronics Excitation Device). In this paper, we describe the turn off characteristics of one of the S-PED (type d). The relations between generated resistance, gatetrigger energy and channel current were obtained.