The Siemens SIRIUS 3RU1946-3AA01 is a Size S3 overload relay for stand-alone installation, using screw-type terminals on the main circuit and mounting via screw and snap-on onto 35 mm DIN rail — a standard panel integration for motor protection in control cabinets.
This part is a phased-out product. The official Siemens successor is the SIRIUS 3RU2946-3AA01, which is the preferred replacement.
At 70 mm width, this Size S3 relay fits into a standard DIN-rail enclosure bay. The screw-type terminals accept 1x (2.5... 50 mm²) or 1x (10... 1 AWG) for the main circuit, so it handles motor feeder wiring up to that cross-section without needing lug adapters.
Rated for operation from -20 to +70 °C and storage from -50 to +80 °C, so it can sit in a warm panel or a cold warehouse without derating concerns within that range.