The Siemens 3RT1934-5BD42 is a SIRIUS-brand magnet coil designed for Size S2 contactors. It's a 42 V DC coil with spring-loaded connection technology — the kind of replaceable coil you swap when the control voltage changes or the old one lets go out here in the grease.
This part is listed as a phased-out product. The official successor is the SIRIUS 3RT2 series — same Size S2 footprint, same spring-loaded connection, but the 3RT2 coil family. Availability and current pricing get confirmed at quote time.
This coil snaps into a SIRIUS Size S2 contactor — the same frame that carries the 3RT1044 and similar power contactors. The 42 V DC rating means it pulls in clean on a 48 V nominal bus with a drop-out below about 34 V; verify your control transformer tap before committing the line.
Why This Coil Matters on the Route
A magnet coil is the part that takes the hit — every time the contactor cycles, that coil takes the inrush and the heat. On a conveyor line or a pump panel that cycles a few hundred times an hour, having the right DC coil voltage (42 V here) keeps the contactor from chattering or dropping out early. The spring-loaded connection means you're not fighting screw terminals when you swap it in a tight enclosure; strip 8 mm, push it in, done.