Siemens sirius 3rf2x solid state relays siemens 3rf2050 1aa22 this 50a single phase solid state relay is from the sirius 3rf2x series from siemens the relay has a switching voltage of 24 to 230v ac and a normally open contact additional features include zero crossing and high power thyristors with high reverse voltage capability siemens 3rf2050 1aa22 semiconductor relay 24 230 vac 50a