SIRIUS S3 power contactor — 77 A AC-3 at 480 V
The Siemens 3RT2045-3AH00 is a SIRIUS S3 power contactor rated for 77 A in AC-3 duty at 480 V, which means it handles motor switching loads up to that current — common for 40–50 hp induction motors on 480 V three-phase lines. Mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 60715, with ±180° rotation on a vertical surface and ±22.5° tilt forward/backward — useful when the panel layout forces an odd orientation. The S3 frame (Size 3) is the physical envelope; at 70 mm wide, 140 mm tall, and 152 mm deep, it occupies a standard DIN-rail footprint with clearance requirements of 10 mm upwards, 10 mm downwards, 20 mm forwards, and 10 mm at the side.
Main power terminals accept solid conductors from 2.5 to 16 mm² or stranded from 6 to 70 mm² — the stranded range covers the heavier cable gauges typical for a 77 A motor circuit. Auxiliary and coil terminals use spring-type connections accepting 2x (0.5 to 2.5 mm²) solid or stranded, which speeds panel wiring compared to screw terminals on the control side. Coil arcing time runs 10–20 ms; switching frequency varies by duty class — up to 1 000 cycles/hour in AC-3, 900 in AC-1, 400 in AC-2, and 300 in AC-4.
Mechanical life is typical at 10 million operations. Coil draws 10 A at 24 V rated value; auxiliary contact ratings span 2 A at 48/60 V down to 0.3 A at 220 V and 0.8 A at 440 V — check the specific control voltage against your PLC output card's sink capacity.