Siemens 3RB3133-4UB0 SIRIUS 3RB electronic overload relays. Siemens 3RB3133-4UB0 is the exact printed commercial reference for an electronic overload relay in the SIRIUS 3RB Overload Relays range. Siemens' official product description is: Overload relay 12.5...50 A Electronic For motor protection Size S2, Class 5E..30E Contactor mounting Main circuit: Screw Auxiliary circuit: Screw Manual-Automatic-Reset Internal ground fault detection.