The Siemens 3RT2045-1AP04 is a SIRIUS power contactor, size S3, rated 77 A at 480 V for AC-3 motor switching duty. That 77 A figure at 480 V is the load-breaking current under motor starting conditions — the rating that governs whether this contactor holds on a 40–60 hp motor at 480 V three-phase.
Depth is 195 mm, width 70 mm, height 140 mm.
Thermal and operational limits
That storage ceiling matters if this sits in a warehouse or unheated container before commissioning — it's fine down to -55 °C in storage, but don't attempt to switch loads below -25 °C ambient. Main contacts rated for 10 million typical mechanical operations; electrical life depends on load and switching frequency: 1,000 cycles/hour at AC-3 maximum, 300 at AC-4 maximum. Arcing time runs 10–20 ms at 50 Hz.