SIRIUS Size S2 Power Contactor, 30 kW at 500 V
The Siemens SIRIUS 3RT1036-3XB40-0LA2 is a Size S2 power contactor rated for 30 kW at 500 V in AC-3 duty — the motor-switching curve that governs most induction-motor loads up to that power. The 24 V DC coil pulls in at 0.7x rated (about 16.8 V) and drops out with a 20–25 ms delay, which is long enough to ride through brief sags but fast enough to clear a fault before the main breaker reacts. Screw-type terminals on the main circuit accept up to 16 mm² stranded, and the auxiliary circuit takes 2.5 mm² solid. Side-by-side mounting is permitted, so you can gang several units without derating for heat buildup — useful in a dense motor-control center. Mechanical life is rated at 10 million operations typical, and the operating temperature range of -40 to +70 °C covers most indoor and sheltered outdoor installations. Storage range extends to -55 to +80 °C, which governs handling and warehousing, not running conditions.
Duty Ratings and Switching Frequency
This contactor carries separate switching-frequency limits per duty class: 1 000 cycles/hour at AC-1 (resistive), 800 at AC-3 (motor start/run), 400 at AC-2 (slip-ring motor), and 300 at AC-4 (plugging/inching). The AC-3 figure is the one that matters for standard squirrel-cage motors — 800 cycles/hour means it can cycle a conveyor drive every 4.5 seconds without exceeding the thermal design. At 400 V AC-2 the unit is rated for 22 kW, and at 690 V AC-3 it delivers 11.4 kW. The arcing time of 10–15 ms is consistent across these loads, which helps when coordinating with upstream short-circuit protection.
Mounting and Panel Integration
Fastening is by screw or snap-on onto 35 mm standard mounting rail per DIN EN 50022. The 55 mm width and 142 mm height fit a standard 8-module DIN-rail footprint, leaving room for a thermal overload relay alongside. Clearance requirements: 10 mm upwards, 10 mm forwards, 10 mm downwards, and 10 mm at the side — no special ventilation gaps needed beyond those.