What it is and where it lands
The Siemens 3RT1044-3AX00-0AA3 is a SIRIUS power contactor in frame size S3, designed for switching motor loads and resistive loads in industrial control panels. It mounts on 35 mm or 75 mm DIN rail via the screw-and-snap-on method, or directly to a backplate with screws. The IP20 rating on the front with cover or box terminal means the live parts are finger-safe once the panel door is closed — standard for enclosed industrial gear. The terminal area itself is IP00, so keep the panel locked during operation.
Key ratings and what they mean for your motor
The AC-4 rating of 55 A at 400 V is the one that matters for reversing or inching duty — plugging and jogging cycles where the contactor makes and breaks stalled-rotor current. That is the heavy-use rating; at 55 A it handles frequent reversals on a motor up to roughly 30 kW at 400 V without welding the main contacts. For standard across-the-line starting (AC-3), the contactor is sized for 37 kW at 500 V and 18.6 kW at 690 V. The 500 V figure covers most 480 V北美 installations with headroom; the 690 V rating suits 600 V Canadian or 690 V European industrial networks. AC-2 duty (slip-ring motor starting) is rated at 30 kW at 400 V — a lower switching frequency than AC-3 because the rotor circuit sees higher making current.
Terminal wiring and panel integration
Main power terminals are screw-type, accepting 2x (10... 50 mm²) stranded or 2x (2.5... 16 mm²) solid/stranded. The control circuit (coil) terminals take 2x (0.25... 2.5 mm²) solid. Strip lengths and torque values follow standard Siemens practice for S3 frame — no special tooling needed. Dimensions are 146 mm high, 70 mm wide, 139 mm deep. The 70 mm width matches the S3 footprint; side-by-side mounting is permitted without derating for AC-3 duty, though AC-4 cycling may need a 10 mm gap depending on ambient. Check the thermal derating curve above 40 °C.
Lifecycle and compliance posture
RoHS compliance date is 05/01/2012, meaning it meets the EU RoHS directive for substances of concern. The pollution degree rating of 3 suits industrial environments with conductive pollution (condensation, light dust).