The Siemens 3RT2045-1NP30 is a SIRIUS S3 power contactor — the workhorse size for motor loads that need a 70 mm wide footprint on the DIN rail. It's rated for up to 1000 operating cycles per hour in AC-3 duty (direct-on-line motor switching), and 900 cycles per hour in AC-1 (resistive load) service. The coil pulls 3.5 VA at both 50 and 60 Hz, with a rated control voltage range of 175 to 280 V. Inrush peaks at 65 A, so keep that in mind when sizing your control transformer. Mounting is screw-and-snap-on onto standard 35 mm DIN rail per EN 60715. The contactor can be rotated ±180° on a vertical surface, and tilted forward or backward by ±22.5° — useful when you're fitting it into a tight gland plate or a panel with an odd orientation. It carries an auxiliary switch as standard, so you don't need a separate add-on block for basic status feedback.
Ratings and what they mean on the line
The AC-3 rating of 1000 cycles per hour tells you this contactor is built for frequent motor starting — think conveyors, pumps, compressors that cycle regularly. The AC-4 rating of 300 cycles per hour covers plugging and inching duty, where the contactor makes and breaks under full motor current. Arcing time runs 10 to 20 ms, which is typical for this class and short enough that most downstream overload relays won't see a nuisance trip. Wire sizing is straightforward: main power terminals accept stranded cable from 6 to 70 mm², solid from 2.5 to 16 mm². Auxiliary terminals take 2x (0.5 to 1.5 mm²) solid or stranded, or 2x (0.75 to 2.5 mm²). That covers most panel-building wire gauges without needing adapters.
Mounting and integration
The S3 frame is 70 mm wide, 140 mm tall, and 152 mm deep — that's the depth you need to account for behind the panel door or inside the enclosure. Clearance requirements: 10 mm upward, 10 mm downward, 20 mm forward, and 10 mm to the side. Operating temperature range is -25 to +60 °C; storage range is -55 to +80 °C, so it can sit in an unheated warehouse or on a truck in winter without issue.