What it is and where it lands
The Siemens 3RT2018-1BM41 is a SIRIUS power contactor in size S00, built for switching motor loads and resistive circuits inside control panels. It mounts via screw or snap-on onto 35 mm standard mounting rail per DIN EN 60715, so it drops into any DIN-rail enclosure without extra brackets. Rated for continuous operation from -25 to +60 °C, with storage tolerance from -55 to +80 °C — covers most indoor panel environments and unheated warehouses.
Key ratings and what they mean for fit
Mechanical switching frequency varies by duty: up to 1000 cycles per hour at AC-1 (resistive loads), 750 cycles/h at AC-3 (standard motor starting), and 250 cycles/h at AC-4 (plugging/inching). The AC-3e rating also sits at 750 cycles/h. That spread tells you this contactor is sized for moderate-speed motor cycling — not high-speed resistor banks, not continuous jogging. Arcing time runs 10 to 15 ms, and the DC dropout delay is 7 to 13 ms. Those numbers matter when coordinating with upstream protection or sequencing multiple contactors in a star-delta start. Terminals accept solid or stranded conductors from 0.5 to 4 mm², with dual-wire capability up to 2x 2.5 mm². Screw-type terminals on the magnet coil — no spring-cage here, so keep a screwdriver handy for panel wiring.
Mounting and clearances
The 45 mm width and 58 mm height fit the S00 footprint. Clearance requirements: 10 mm upward, 10 mm forward, 10 mm downward, and 6 mm at the side. The mounting position allows +/-180° rotation on a vertical surface and can be tilted forward/backward by +/-22.5° — useful when the panel layout forces an unconventional orientation. Depth measures 73 mm from the mounting surface to the front of the terminals — account for that when sizing the enclosure depth and gland plate clearance.