Siemens 3RB3143-4UW1 SIRIUS 3RB electronic overload relays. Siemens 3RB3143-4UW1 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 S3, Class 5E..30E Stand-alone installation Main circuit: Straight-through transformer Auxiliary circuit: Screw Manual-Automatic-Reset.