What this SIRIUS S0 contactor is built for
The Siemens 3RT1025-1BB44-0AA1-ZX95 is a SIRIUS S0 power contactor with a 24 V DC coil, screw-type terminals on the main circuit, and a footprint that snaps onto 35 mm DIN rail per DIN EN 50022. This is the S0 frame — the middle size in the SIRIUS contactor family, designed for motor loads up to 11 kW at 690 V and 10 kW at 500 V. The AC-4 rating of 15.5 A at 400 V tells you this contactor is built for reversing, plugging, and inching duty — the kind of cycle that eats standard AC-3 contacts. If your application involves frequent jogging or reversing, the AC-4 number is the one that governs contact life.
The DC coil pulls 5.4 W on closing and holds at 5.4 W — no power reduction after pick-up, so the coil stays fully energized. The holding power equals the closing power, which means the coil runs warm but predictably. The auxiliary contact block carries 2 instantaneous contacts, rated for 10 A at 24 V DC, 2 A at 60 V, 1 A at 110 V, and 0.3 A at 220 V — enough for standard PLC or relay interposing.
Short-circuit coordination and wiring
Type 2 coordination requires a 25 A gL/gG fuse; Type 1 coordination allows up to 63 A gL/gG. If you're specifying for a panel that needs Type 2 — meaning the contactor must remain serviceable after a short — the 25 A fuse limit is the one to design around. Main circuit wiring accepts 2x (1...2.5 mm²) solid or 2x (2.5...6 mm²) stranded, max 2x 10 mm². The auxiliary terminals take 2x (0.5...1.5 mm²) solid or 2x (0.75...2.5 mm²) stranded, max 2x 4 mm².
Rated for pollution degree 3 — that's the industrial environment where conductive dust or moisture is expected. The front face carries IP20 (finger-safe), the terminals are IP00 (touch-hazard when live — cover them in the panel). Side-by-side mounting is allowed with a 6 mm gap at the side. Dimensions: 85 mm high, 45 mm wide, 150 mm deep — a compact S0 footprint that fits standard 45 mm-wide DIN-rail slots.