The Siemens 3RT1025-1AN20 is a SIRIUS power contactor in the Size S0 frame, rated for 7.5 kW at AC-2 duty on a 400 V line and 15.5 A at AC-4 on the same voltage. That AC-4 rating is the one that matters for reversing or inching applications where the contactor makes and breaks stalled rotor current — the AC-2 figure covers slip-ring motor starting. Screw-type terminals on both the main and auxiliary/control circuits, with a fastening method that accepts screw fixing or snap-on mounting onto 35 mm standard mounting rail per DIN EN 50022.
Coordination and mounting
Type 1 coordination requires a 63 A gL/gG fuse upstream; Type 2 coordination calls for a 25 A gL/gG fuse. Side-by-side mounting is permitted, which keeps the panel fill factor tight — the 45 mm width per contactor stacks cleanly on the DIN rail. Pollution degree 3 (conductive pollution or dry non-conductive that becomes conductive) means this contactor is suited for industrial control panels where the environment isn't climate-controlled. Operating temperature range -25 to +60 °C, with the IP20 front enclosure protecting the operator side and IP00 at the terminals (finger-safe wiring is on the installer).
Terminal capacity
Main circuit screw terminals accept solid or stranded: 2x (1... 2.5 mm²), 2x (2.5... 6 mm²), max. 2x 10 mm². Auxiliary and control circuit terminals take 2x (0.5... 1.5 mm²), 2x (0.75... 2.5 mm²), max. 2x (0.75... 4 mm²). AWG equivalents: main contacts 2x (16... 12), 2x (14... 10), 1x 8; auxiliary contacts 2x (20... 16), 2x (18... 14), 1x 12.