SIRIUS S0 power contactor — 3RT1025-1AR00
The Siemens 3RT1025-1AR00 is a SIRIUS S0-frame power contactor, three main poles normally open, rated for AC-3 motor switching at 7.5 kW on a 400 V three-phase line. It mounts via screw or snap-on onto a 35 mm DIN rail per EN 50022, taking 45 mm of panel width and 85 mm height, with a 91 mm depth that clears most standard gland plates and enclosure backwalls. The coil is rated for 50 Hz operation at a voltage factor of 0.8 to 1.1 times the rated value, so it holds in during brownout conditions down to 80 % of nominal. For the main circuit, screw-type terminals accept solid or stranded conductors up to 2x 10 mm² or a single 10 mm², with a separate auxiliary contact block wired through 0.5 to 4 mm² terminals — no special crimp tooling needed for panel assembly.
Motor duty ratings — AC-3 and AC-4 at 400 V
At 400 V, the AC-3 duty rating is 7.5 kW, which covers standard squirrel-cage motors up to that power for starting and disconnecting under load. The AC-4 rating at the same voltage is 15.5 A — this is the inching/plugging current the contactor can interrupt repeatedly, relevant for reversing or jogging applications. The AC-2 rating is also 7.5 kW at 400 V, covering slip-ring motor duty. For resistive loads (AC-1), the maximum continuous operating current is 10 A. The auxiliary contacts switch 10 A at 24 V, 6 A at 230 V, and 3 A at 400 V, with lower ratings for DC loads — 2 A at 60 V, 1 A at 110 V, 0.3 A at 220 V. These numbers govern the control-circuit side: a PLC output driving a 24 V DC auxiliary contact sees a 10 A make/break capacity, well above typical pilot-duty requirements.
Panel integration — S0 frame, DIN rail, clearances
The S0 frame is Siemens' compact footprint for contactors up to about 12 kW AC-3. Side-by-side mounting is permitted, with a 6 mm clearance required on the sides for heat dissipation when multiple units are ganged. The IP20 front protection means the contactor is touch-safe from the panel face; the terminal area is IP00, so live parts are exposed at the wiring point — standard for panel interiors where the enclosure provides the outer IP rating. Operating temperature range is -25 °C to +60 °C, with a maximum installation altitude of 2 000 m. Pollution degree 3 classification means it is suited for industrial environments with conductive pollution or dry non-conductive pollution that becomes conductive due to condensation — typical for unsealed control cabinets in factory floors.