What it is and where it fits
The Siemens 3RV5921-1M is a short-circuit signalling switch designed to mount directly onto 3RV5 and 3RV6 motor circuit breakers in sizes S2 and S3. It provides remote indication that the breaker has tripped on a short-circuit event, using its two auxiliary contacts to signal back to a PLC or status lamp. The snap-on mounting means it clips onto the breaker body without extra hardware, keeping the DIN-rail layout compact.
Key ratings and what they mean for fit
Rated insulation voltage of 690 V AC at pollution degree 3 means this switch is rated for the full 400/480/690 V industrial panel environment common in motor control centres. The 18.5 mm width and 68 mm depth let it sit flush against the breaker face without protruding past the enclosure gland plate. Operating temperature range of -20 to +60 °C covers unheated plant floors and enclosed cabinets; storage range of -50 to +80 °C covers shipping and warehouse conditions. The 50/60 Hz rating confirms it works on either mains frequency without derating.