The Siemens SIRIUS 3RT2018-1CP04-3MA0 is a Size S00 power contactor — the smallest frame in the SIRIUS contactor family, built for switching motor loads and resistive loads in control panels up to about 5.5 kW at 400 V. The Size S00 footprint (45 mm wide, 58 mm tall, 117 mm deep) is the one you reach for when panel space is tight and the load is a small pump, fan, or conveyor drive. The AC-3 switching frequency of 750 operations per hour tells you this contactor is rated for the start-stop duty cycle of a typical induction motor; the AC-4 rating of 250 operations per hour covers plugging and inching, which is harder on the contacts. The 24 V coil draws 0.25 A at 50 or 60 Hz, and the coil terminals are screw-type — no push-in or cage-clamp here, so factor in the screwdriver time if you're used to spring terminals on the auxiliary side.
That means you can orient it to fit cable entries or gland plates without worrying about the contactor's internal mechanics — the arc chamber and magnet are designed for that range. That side clearance is tighter than the front-to-back gap — if you're packing multiple contactors side-by-side, the 6 mm is the binding constraint for heat dissipation and arc flash separation.
Wiring and conductor range
For multiple conductors, the terminal can take 2x (0.5...1.5 mm²), 2x (0.75...2.5 mm²), or 2x 4 mm². That covers common control wiring (1.5 mm² for coil and auxiliary circuits) and power wiring up to 4 mm² for the main poles — adequate for the rated currents this contactor handles.
That is the normal state for a SIRIUS Size S00 contactor; the series is a workhorse in European panel designs and is not near end-of-life.
Temperature and mechanical endurance
Storage range is -55 °C to +80 °C, which is the handling and shipping limit, not the running limit. Mechanical life is 10,000,000 cycles typical, so the contactor itself will outlast the panel's service life in most duty cycles; the electrical life depends on the load category and switching frequency, but the mechanical figure gives you confidence in the actuator and spring set.