The Siemens 3RA1245-4FB44-1AK6 is a non-fused reversing motor starter from the SIRIUS family, size S3, designed to switch and protect three-phase motors in both forward and reverse directions from a single assembly. It combines a reversing contactor pair with a thermal (bimetallic) overload relay in one package, rated for AC-3 switching duty up to 690 V.
At 400 V rated value, this starter is rated for 18,500 W (18.5 kW) motor output. At 480 V it carries 40 A, and at 600 V also 40 A. The control coil is wound for 88–121 V at 50 Hz and 96–132 V at 60 Hz — a dual-frequency coil that covers most 110–120 V control circuits globally. The supplied contactor is a 3RT1044-1AK60, and the link module and busbar adapter (3RA1941-1AA00 and 3RA1942-1AA00) are included, so the reversing interlock and power bus connections are pre-engineered.
Snap-on fastening on 35 mm DIN rail, vertical mounting position only. The dimensions are 150 mm wide, 207 mm deep, and 330 mm tall — size S3 is the largest standard SIRIUS feeder frame, so plan for panel depth. Clearance: 90 mm upwards, 10 mm forwards, 10 mm downwards, 12 mm at the side, 0 mm backwards. Main conductor cross-section accepts stranded 2.5–70 mm² or 2×(10–50 mm²).