What it is and what it does
The Siemens 3RT2028-2NP30 is a SIRIUS power contactor in the compact S0 frame, designed for switching motor and resistive loads in industrial control panels. Its 200-280 V AC coil covers common European and North American control voltages, and the spring-type terminals on the coil side eliminate the need for screwdriver torque checks during commissioning. The main contacts are rated for switching at 24 V up to 10 A, at 48 V and 60 V up to 2 A, and at 110 V up to 1 A. That means this contactor handles low-voltage DC loads common in PLC output circuits or small solenoid valves, but the real work is AC motor duty: the AC-3 switching rate of 750 operations per hour tells you it's built for frequent starting of squirrel-cage motors, not just occasional on/off. Mechanical life is rated at 10 million operations, so in a typical conveyor or pump application cycling a few times per minute, you're looking at years of service before the contactor wears out mechanically.
Mounting and integration
Mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 60715. The S0 footprint is 45 mm wide, 102 mm tall, and 107 mm deep — it fits a standard 45 mm slot in a panel layout. Clearance requirements: 10 mm upwards, 10 mm downwards, 10 mm forwards, and 6 mm at the side to adjacent devices. The mounting position is flexible: +/-180° rotation on a vertical surface, plus +/-22.5° tilt forward/backward, which helps when the panel layout is tight. Main contact terminals accept solid or stranded conductors from 1 to 10 mm², and fine-stranded wire with ferrules up to 2x 0.5-2.5 mm². The spring-type coil terminals are the same style — strip length around 8-10 mm, push to insert.
Operating conditions and switching performance
Rated for ambient operation from -25 to +60 °C, and storage from -55 to +80 °C. The coil picks up at 0.7 times rated voltage and drops out at 1.1 times rated — that's a standard hysteresis for AC contactors, ensuring reliable pull-in and clean drop-out without chatter. Coil holding power is 0.51 VA at 50 Hz and 0.56 VA at 60 Hz, so the control transformer load is minimal. Inrush current peaks at 25 A during coil energization — brief, but worth noting if the control supply is shared with sensitive electronics. Operating time is 30-50 ms for both AC and DC coil variants, and arcing time is a consistent 10 ms. The auxiliary switch is included.