The Siemens 3RV1991-1AA0 is a SIRIUS auxiliary switch designed to snap onto 3RV1 motor-protective circuit breakers in sizes 5, 6, 7, and 8. It provides one signaling changeover contact and one dedicated tripped signal contact, both rated at 250 V AC/DC. This is the part that tells the PLC or HMI whether the breaker is on, off, or tripped — without it, the panel has no status feedback from the motor branch.
The 250 V AC/DC rating covers the control-voltage levels listed in the spec. The signaling changeover provides a normally-open and normally-closed signal from the breaker's on/off state. The separate tripped signal contact closes only when the breaker has tripped on overload or short circuit. This auxiliary switch mounts directly onto the side of the 3RV1 breaker using the integrated snap-on mechanism — no tools needed for attachment, and it shares the breaker's DIN-rail footprint. The wiring terminals accept 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) solid or ferruled stranded wire, torqued to 0.8–1.2 N·m with a Pozidriv size 2 screwdriver.