Abstract: A semi-conductor controlled rectifier (SCR) d.c. interrupter in which any (optional) number m of identical, self-contained and parallel connected phases each form an identical series connection of a semi-conductor controlled retifier (Th.sub.1) . . . (TH.sub.m) and a diodes (D.sub.1 . . . (D.sub.m). An m number of identical, self-contained resonant arms are arranged in star or Y-connection, with any of the arms having an identical series connection of a capacitor (C.sub.1) . . . (C.sub.m) and a reactor (L.sub.1) . . . (L.sub.m) respectively. The star vertices are connected between the cathodes of the semi-conductor controlled rectifiers (Th.sub.1) . . . (Th.sub.m) and the anodes of the diodes (D.sub.1) . . . (D.sub.m). The star neutral is associated with the d.c. power source (BA) positive or negative pole.