What it is and where it fits
The Siemens 3RT2018-1BG42 is a SIRIUS power contactor in frame size S00, designed for switching motor loads and resistive loads in industrial control panels. It mounts via screw and snap-on onto 35 mm standard mounting rail per DIN EN 60715, with a width of 45 mm, height of 58 mm, and depth of 73 mm — a compact footprint that fits standard enclosure layouts. The magnet coil uses screw-type terminals, accepting solid or stranded conductors from 0.5 to 4 mm², and 2x conductors in the same range. An auxiliary switch is included, rated 10 A at 24 V DC, 2 A at 48 V DC, 1 A at 110 V DC, 0.9 A at 125 V DC, and 0.3 A at 220 V DC — covering common control voltages for PLC and relay logic feedback. Operating temperature range is -25 to +60 °C, storage -55 to +80 °C, with mounting position flexibility: +/-180° rotation on a vertical surface and +/-22.5° tilt forward/backward. Clearance distances required: 10 mm upwards, downwards, and forwards, 6 mm at the side — useful for panel layout planning.
Switching performance and duty cycles
Maximum switching frequency varies by duty: 1 000 operations per hour at AC-1 (resistive loads), 750/h at AC-2 and AC-3 (motor starting and running), and 250/h at AC-4 (plugging and inching). The AC-3e rating also allows 750/h. These limits govern contactor life in cyclic applications — exceeding them accelerates wear. Mechanical service life is typically 30 000 000 operations. DC operating time is 7 to 13 ms; arcing time is 10 to 15 ms. The contactor is rated for motor loads up to 2 hp at 230 V and 3 A at 400 V AC on auxiliary contacts.