The Siemens 3RT2047-1AG20 is a SIRIUS S3-frame power contactor rated for 20 hp at 230 V — that's the motor load it can switch continuously in AC-3 duty, which covers standard squirrel-cage induction motors on conveyors, pumps, and fans. The S3 frame size tells you the physical envelope: 70 mm wide, 140 mm tall, 152 mm deep, so it occupies a standard three-module-wide DIN-rail footprint (per DIN EN 60715) with screw and snap-on mounting. The main contacts are configured as 10 normally open and 2 normally closed, and an auxiliary switch is included on the unit. Wire termination accepts solid conductors from 2.5 to 16 mm² and stranded from 6 to 70 mm² on the main circuit, with the coil terminals being screw-type. For fine-stranded control wiring, the auxiliary terminals accept 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²).
Duty-cycle and switching frequency
Maximum switching frequency varies by duty class: 900 operations per hour in AC-1 (resistive loads), 850 in AC-3 and AC-3e (motor starting/running), 350 in AC-2 (slip-ring motors), and 200 in AC-4 (plugging/inching). For a line running a conveyor at 850 cycles/hour, the contactor keeps pace without derating. Operating time is 10 to 21 ms, arcing time 10 to 20 ms — both within the expected range for this frame class.
A 152 mm depth means the contactor body extends that far from the rail; verify the gland plate or enclosure depth accommodates it plus wiring bend radius.