SIRIUS S3 power contactor — what it is and where it fits
The Siemens SIRIUS 3RT2045-1NB30-0CC0 is a size S3 power contactor designed for switching motor loads in industrial control panels. It mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 60715, with a mounting position that allows ±180° rotation on a vertical surface and ±22.5° tilt forward or backward — useful when panel layout forces an unconventional orientation. The coil is rated for 20–33 VDC, with an inrush peak of 6.5 A and a holding draw of 3.5 VA at both 50 Hz and 60 Hz. Auxiliary contacts are integrated, rated at 10 A at 24 V, 2 A at 48 V or 60 V, and 1 A at 110 V — enough for signaling back to a PLC input card or a pilot light.
Switching duty and what the ratings mean for your load
The contactor's maximum operating rate depends on the duty class: 900 cycles per hour for AC-1 (resistive loads), 400 cycles per hour for AC-2 (slip-ring motors), 1,000 cycles per hour for AC-3 (squirrel-cage motors — the most common industrial motor start), and 300 cycles per hour for AC-4 (plugging and inching). The AC-3e rating matches AC-3 at 1,000 cycles per hour. For a packaging line running a 3-phase conveyor motor at 800 starts per hour, the AC-3 rating confirms the contactor is not thermally overstressed. Arcing time is 10–20 ms, and the opening/closing times (including bounce) span 38–57 ms for both AC and DC coil supplies. That timing matters when coordinating with upstream short-circuit protection — the contactor clears the arc before the breaker's instantaneous trip can operate on a moderate fault.
Panel integration — clearances and wiring
Physical footprint: 70 mm wide, 140 mm tall, 152 mm deep. Required clearances for thermal dissipation: 10 mm upward, 10 mm downward, 20 mm forward, and 10 mm at each side. In a crowded enclosure, those gaps must be maintained to stay within the -25 °C to +60 °C operating range. Main circuit terminals accept solid conductors from 2.5 to 16 mm² and stranded conductors from 6 to 70 mm². Auxiliary terminals accept two conductors per clamp: 0.5–1.5 mm² solid or stranded, or 0.75–2.5 mm². All terminals are screw-type, so a standard Pozidriv or slotted driver is all that is needed on the panel build.