What it is and what it does
The Siemens SIRIUS 3RT1025-3BB40-1AA0 is a size S0 power contactor with a 24 V DC coil. It's designed for switching motor loads in control panels, with screw-type terminals on the main circuit and spring-loaded terminals on the auxiliary and control circuits. The 24 V DC coil pulls 5.4 W on closing and holds at 5.4 W — a continuous-duty coil, so no external holding-current economizer needed. Rated operational current at AC-12 (resistive) is 10 A maximum. For motor duty, it's rated 7.5 kW at 400 V in AC-2 (slip-ring motor starting), and 15.5 A at 400 V in AC-4 (plugging/reversing/inching). At 500 V it handles 10 kW; at 690 V, 11 kW. That AC-4 rating is the one to watch for frequent jogging or reversing applications — it's the thermal limit under those conditions.
Mounting and integration
Mounts via screw or snap-on onto 35 mm standard rail per DIN EN 50022. Side-by-side mounting is allowed. Dimensions: 45 mm wide, 85 mm tall, 101 mm deep. Front face is IP20 (finger-safe); the terminal area is IP00 (open) — so panel builders need to guard live parts if the contactor is mounted near an open door or operator access. Pollution degree 3 rating means it's suited for industrial environments with conductive dust or occasional condensation.
Wiring and coordination
Main circuit terminals accept solid or stranded wire: 2x (0.25–2.5 mm²), 2x (1–2.5 mm²), 2x (2.5–6 mm²), or max 2x 10 mm². AWG equivalents: 2x (16–12), 2x (14–10), 1x 8. Auxiliary terminals accept 2x (24–14) AWG. For type 2 coordination ('no damage' under short circuit), use a gL/gG fuse rated 25 A. For type 1 coordination ('may need replacement after fault'), use a 63 A gL/gG fuse. Operating temperature range is -25 to +60 °C during operation — no special derating needed for most panel environments. Mechanical endurance is typical 10 million operations, so it'll outlast most machines in normal cycling.
Lifecycle and sourcing
Compliance: RoHS substance prohibition date is 2006-07-01, so it meets the original RoHS directive. No UL or CSA listing is explicitly stated in the evidence, but the IEC ratings (AC-2, AC-4, pollution degree 3) are standard for European-spec panels.