The Siemens 3RT1044-1AK64 is a SIRIUS power contactor in size S3, screw-type terminals, rated for AC-3 motor switching at 37 kW at 500 V and 18.6 kW at 690 V. It mounts on 35 mm or 75 mm standard DIN rail via screw and snap-on fastening.
The AC-3 motor rating of 37 kW at 500 V is the load figure that governs most industrial conveyor, pump, and fan applications — that's the rating to match against your motor nameplate. At 690 V the same contactor is rated 18.6 kW (AC-3). The screw terminals accept solid conductors up to 2x 4 mm² and stranded up to 2x 50 mm², covering most panel wire sizes up to 4 AWG. Coil draw at 24 V DC is 10 A inrush; that's the pick-up current, not the hold — factor it into your 24 V DC supply sizing if multiple contactors pull in simultaneously. The contactor is rated for side-by-side mounting with no derating, which keeps panel width tight.
Size S3 means a 70 mm wide footprint on the DIN rail — plan for that in your panel layout. Depth is 188 mm, height 146 mm. The screw-type terminals are the main-circuit connection; auxiliary blocks snap on the front. The IP20 front cover stays on during operation, protecting live terminals from accidental contact.