SIRIUS S0 power contactor for motor loads
The Siemens 3RT1026-3AP04-1AA0 is a SIRIUS power contactor in the compact S0 frame size, designed for switching three-phase motor loads in industrial control panels. It carries 3 NO main contacts rated for AC-3 duty at 11 kW on both 500 V and 690 V supplies, so it handles standard 400 V motors with headroom for higher-voltage installations. The contactor mounts on a 35 mm DIN rail per DIN EN 50022, using either screw-clamp or snap-on fixing, and occupies 45 mm of panel width.
Ratings and what they mean for fit
The AC-3 motor-switching rating of 11 kW at both 500 V and 690 V means this contactor is sized for a typical 15 hp (11 kW) induction motor on a 400 V line, with enough margin to cover the same motor if the supply is 690 V. The AC-4 rating of 15.5 A at 400 V covers inching or plug-reverse duty, where the contactor makes and breaks stalled-rotor current — a common requirement on crane or conveyor applications. For resistive loads (AC-1), the contactor can handle up to the same 10 A continuous as its AC-12 auxiliary rating. The contactor is rated for pollution degree 3, meaning it is suited for industrial environments with conductive dust or occasional condensation — typical for unsealed control cabinets. Front-side protection is IP20, so finger-safe when installed, while the terminal area is IP00 (no protection), which is standard for panel-mount contactors where the enclosure provides the outer seal. Operating temperature spans -25 to +60 °C, covering most indoor industrial installations without derating. The maximum operating altitude of 2 000 m matches standard low-voltage switchgear limits; above that, dielectric strength and air clearance derate apply.
Coordination and protection
For type 1 coordination (no damage to the enclosure, contactor may need replacement after a fault), the maximum backup fuse is 100 A gL/gG. For type 2 coordination (contactor remains usable after a fault), the fuse limit drops to 35 A gL/gG. These values matter when sizing upstream protection for a motor starter combination — the 35 A limit is the one to design around if you want to avoid replacing the contactor after a short circuit.
Termination and wiring
Main circuit terminals are screw-type, accepting 2x (1 to 2.5 mm²) stranded, 2x (2.5 to 6 mm²), or up to 2x 10 mm². AWG equivalents are 2x (16 to 12), 2x (14 to 10), or 1x 8. The auxiliary contact block uses 2x (0.25 to 2.5 mm²) solid or stranded. Side-by-side mounting is permitted without derating, which keeps the panel layout dense.