Integrator's first look
The Siemens 3RT1045-1BW44 is a Size S3 SIRIUS power contactor rated for 45 kW at 500 V, with a 37 kW rating at AC-2, 400 V. The enclosure carries IP20 on the front with the cover installed; the terminal area itself is IP00, so panel builders need to account for clearance and finger-safe shrouding in the layout.
The 45 kW at 500 V rating tells you this contactor is sized for medium motor loads — think 50–60 hp class in 480 V markets. The AC-2 rating of 37 kW at 400 V covers slip-ring motor duty where starting current is moderate. The AC-4 rating of 66 A at 400 V handles reversing or inching duty with higher switching stress.
Main circuit terminals accept solid wire in multiple combinations: 2x (0.5–1.5 mm²), 2x (0.75–2.5 mm²), or max 2x (0.75–4 mm²). For stranded wire, the main terminals take 2x (10–50 mm²). The auxiliary/control terminals accept 2x (2.5–16 mm²) solid or stranded. This range covers everything from control wiring up to the main power feed for a 45 kW motor.
The contactor measures 146 mm high, 70 mm wide, and 201 mm deep. Side-by-side mounting is supported, which saves rail space in multi-contactor groups. The screw-and-snap-on mounting works on both 35 mm and 75 mm standard mounting rails — the 75 mm option is useful for high-current panels where the rail needs extra mechanical support. The arcing time of 10–15 ms and DC operating time of 14–20 ms are within typical ranges for coordinating with upstream short-circuit protection.
Compliance documentation
The part carries a RoHS compliance date of 05/01/2012, meaning it meets the EU RoHS directive for substances. As a Siemens SIRIUS product, it is designed to meet IEC/EN 60947-4-1 for contactors and motor starters. UL and CSA listings are standard for this series, though specific file numbers should be confirmed from the nameplate marking on the unit received.