What it is and what it does
The Siemens 3RT1025-1AP00-1AA0 is a SIRIUS power contactor in the S0 frame size, with three normally-open main contacts and screw-type terminals for the main circuit. It mounts via screw or snap-on onto a 35 mm DIN rail per EN 50022.
Key ratings and what they mean for fit
The AC-4 current of 15.5 A at 400 V is the rating that matters most for applications with frequent plugging or jogging — the contactor must interrupt locked-rotor current each cycle. For general motor starting (AC-3), the part is typically applied up to its 7.5 kW (AC-2) or 11 kW (690 V) capability, but the datasheet does not list a separate AC-3 figure; the AC-2 and AC-4 values bound the envelope. The operating voltage range is 0.8 to 1.1 times the rated control supply voltage at 50 Hz, so a 230 V coil holds in from about 184 V to 253 V. The contactor is rated for pollution degree 3 (conductive pollution or dry non-conductive that becomes conductive due to condensation), which is typical for industrial control panels not in sealed enclosures. Mechanical life is 10 million operations, meaning the contactor itself will outlast most applications if the coil and contacts are properly protected.
Mounting and integration
The 45 mm width and 85 mm height fit the standard S0 footprint, and the 91 mm depth leaves room for wiring. Side-by-side mounting is allowed, with 6 mm clearance to adjacent devices on the side.
Coordination and protection
For type 2 coordination (no damage to the contactor after a short circuit), the required upstream fuse is gL/gG 25 A. For type 1 coordination (contactor may need replacement after a fault), use a 63 A gL/gG fuse. The contactor is rated for a maximum altitude of 2000 m without derating, and operates from -25 °C to +60 °C. The rated frequency is 50 Hz.