The Siemens 3RT2015-2BG42-0CC0 is a SIRIUS 3RT2 contactor rated for AC-3 duty at 3 kW on a 400 V three-phase line, with one normally-closed auxiliary contact and a DC 125 V coil.
What the ratings mean for your panel
The AC-3 3 kW / 400 V rating is the one that governs motor switching: it tells you this contactor can make and break the inrush of a squirrel-cage induction motor up to that power, without welding the main poles. The DC 125 V coil means the pickup and dropout characteristics are tuned for a 125 VDC control bus — common in older industrial plants or systems with battery-backed DC supplies. The single NC auxiliary (1NC) is wired into a safety circuit or a status feedback loop, not the main power path. Spring-loaded terminals accept solid or ferruled stranded copper up to the S00 frame rating.