What it is and what the ratings mean
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.
Mounting and integration
Mounts via screw or snap-on onto a 35 mm DIN rail per DIN EN 60715. The mounting position is flexible: +/-180° rotation on a vertical surface, and can be tilted forward/backward by +/-22.5° on a vertical surface. 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. Clearance requirements: 10 mm upwards, downwards, and forwards; 6 mm at the sides. 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
Accepts solid or stranded conductors from 0.5 mm² up to 4 mm². 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. No auxiliary switch is included on this variant (the order code suffix -3MA0 indicates that), so if you need a mirror contact or a feedback signal for a PLC, you'll add a separate auxiliary contact block that snaps onto the front.
Lifecycle and sourcing
The lifecycle stage is marked as current — meaning Siemens still actively produces this order code, and it has not been announced for discontinuation. 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. For a BOM freeze or a long-term project, this part is a safe line item. Sourcing is through the standard Siemens distribution channel; we quote it to order against an RFQ.
Temperature and mechanical endurance
Rated for operation from -25 °C to +60 °C ambient — that covers most indoor panel environments and even outdoor cabinets in moderate climates. 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.