The Siemens SIRIUS 3RT2037-3NB30-0CC0 is a Size S2 power contactor with a 20-33 V coil, spring-type terminals, and a main contact configuration of 18 normally open and 1 normally closed. It mounts via screw or snap-on onto 35 mm DIN rail per EN 60715, making it a direct panel fit for standard industrial control cabinets.
What the ratings mean for fit
The 20-33 V coil range covers nominal 24 VDC control circuits with margin — the 0.8 initial dropout factor means it releases reliably at about 16 V, so a sagging bus won't leave it welded closed. Coil inrush peaks at 3 A, steady-state draw is 2 VA at 50 or 60 Hz, which a standard 24 VDC power supply handles without oversizing. Switching frequency limits define the duty cycle: 800 operations/hour at AC-1 (resistive), 700 at AC-3 (motor start/run), 400 at AC-2 (slip-ring motors), and 200 at AC-4 (plugging/inching). For a conveyor running AC-3 duty at 700 ops/h, that's one cycle every ~5 seconds — adequate for most material-handling lines but not for high-speed pick-and-place. Mechanical life is rated at 10 million operations. The arcing time of 10-20 ms and total operating time of 30-55 ms are typical for this contactor class — fast enough for motor sequencing but not for semiconductor switching.
Mounting and integration
Dimensions are 114 mm high, 55 mm wide, 130 mm deep. Clearance distances: 10 mm upwards, 10 mm forwards, 10 mm downwards, 6 mm at the side. The mounting position allows +/-180° rotation on a vertical surface and +/-22.5° tilt forward/backward, so it fits in tight enclosures where the rail is oriented unusually. Spring-type terminals accept 2x 0.5-2.5 mm² solid or stranded wire — no screw torque to verify, just strip and push. The auxiliary switch is built in, with contact ratings: 10 A at 24 V, 2 A at 48/60 V, 1 A at 110 V, 0.9 A at 125 V, 0.3 A at 220 V. That covers most PLC output and relay interface loads.