What it is and where it fits
The Siemens 3RT1025-1AL20-ZW97 is a SIRIUS power contactor in Size S0, designed for switching motor loads up to 11 kW at 690 V AC-3 (50/60 Hz). It mounts via screw or snap-on onto a 35 mm DIN rail per EN 50022, making it a direct fit into standard industrial control panels.
Key ratings and what they mean for fit
The AC-3 rating of 11 kW at 690 V tells you this contactor handles standard squirrel-cage motor switching at that voltage. The AC-4 rating of 15.5 A at 400 V covers inching and plugging duty where the contactor makes and breaks stalled-rotor current — that's the figure to check for frequent jogging or reversing applications. For resistive or lightly inductive loads (AC-1), the contactor is rated 10 A at 24 V, 6 A at 230 V, and 3 A at 400 V. The auxiliary contact ratings cover 10 A at 24 V, 2 A at 60 V, 1 A at 110 V, and 0.3 A at 220 V — useful for control circuit integration. The 91 mm depth, 45 mm width, and 85 mm height place it in the standard S0 footprint. Side-by-side mounting is permitted, so you can gang multiple units without derating for heat buildup — useful when packing contactors into a tight enclosure. Operating temperature range is -25 to +60 °C, and pollution degree 3 means it's rated for the conductive-dust and condensation environment typical of industrial control rooms. The IP20 front and IP00 terminals mean the enclosure provides finger-safe protection on the front face, but the terminals require a separate touch-safe cover or enclosure.
Wiring and coordination
Main circuit terminals accept screw-type connections: solid 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²), max 2x (0.75 to 4 mm²). Stranded conductors: 2x (1 to 2.5 mm²) or 2x (2.5 to 6 mm²), max 2x 10 mm². AWG equivalents: 2x (16 to 12), 2x (14 to 10), or 1x 8. Strip length and torque spec follow standard Siemens practice for the S0 frame. For type 2 coordination (no-weld protection), the required upstream fuse is 25 A gL/gG. For type 1 coordination (limited damage allowed), the fuse can be 63 A gL/gG. This is the spec to hand to the panel builder when sizing branch protection.