What It Is and Where It Fits
The Siemens 3RT1034-3BB40-ZX95 is a SIRIUS S2 power contactor, rated for switching motor loads up to 15 kW in AC-2 duty at 400 V, and handling 29 A in AC-4 at 400 V for high-stress reversing or inching applications. The 24 VDC coil draws 10 A at rated voltage. Screw-type terminals on the main circuit accept stranded conductors up to 2x 25 mm², making this a solid choice for panel builds where field wiring needs robust termination. Snap-on mounting onto a 35 mm DIN rail per DIN EN 50022 is standard, with a screw-fastening option for vibration-prone environments. The S2 frame size (55 mm wide, 112 mm tall, 130 mm deep) fits standard cabinet layouts without crowding adjacent devices.
Key Ratings and What They Mean for Your Panel
The AC-2 rating of 15 kW at 400 V means this contactor is sized for slip-ring motor starting and stopping — the kind of moderate-duty cycle found on crane hoists or conveyor drives. The AC-4 rating of 29 A at 400 V covers plugging and inching, where the contactor must interrupt locked-rotor current. For resistive loads (AC-1), the switching rate peaks at 1,200 operations per hour, so it can handle fast cycling in heating or lighting banks. The 24 VDC coil holds reliably at 24 V nominal. Contact arcing time runs 10 to 15 ms, and the DC dropout delay is 20 to 30 ms — useful for sequencing logic where you need predictable off-delay without an external timer. Operating temperature range of -25 to +60 °C covers most indoor panel environments, and the IP20 front / IP00 terminal rating means it's intended for enclosed cabinets — not open washdown zones. Pollution degree 3 suits industrial atmospheres with conductive dust or occasional condensation.