What it is and what it does
The Siemens 3RT7026-1AV05 is a Size S0 three-pole contactor from the SIRIUS family, rated for AC-3 switching up to 690 V. The 3 NO main contacts handle motor loads; the auxiliary contact block is field-addable (product extension auxiliary switch is supported). Coil holding power is 0.24 W at both 50 and 60 Hz, with a closing power of 0.82 W DC — low enough for direct PLC output drive without an interposing relay in many panels.
Where it fits
Mounts via screw or snap-on onto 35 mm DIN rail per EN 50022. The 55 mm width and 91 mm depth fit standard S0 footprint — drops into existing S0 cutouts without panel rework. Side-by-side mounting is permitted, so multiple contactors can pack tightly on the rail. IP20 on the front and terminals means it is suited for enclosed control panels; no washdown rating, so keep it inside the cabinet.
Key ratings and what they mean for your circuit
Rated insulation voltage is 690 V, and surge voltage resistance is 6 kV — that covers the impulse withstand for most 400 V and 480 V industrial networks. The auxiliary contact ratings are 6 A at 230 V, 3 A at 400 V, and 1 A at 690 V; these are the maximums for the built-in auxiliary, so if your PLC feedback loop draws 5 mA at 17 V, the contact reliability is specified for that low-level signal (acceptability for PLC control).
Coordination and protection
For type 2 coordination (no damage to the contactor after a short circuit) the fuse requirement is gL/gG 35 A; for type 1 coordination (contactor may need replacement) it is 80 A. Both use NH 3NA fuses. This matters when you are designing a motor branch circuit to IEC 60947-4-1 — the 35 A limit tells you the maximum upstream protective device that still leaves the contactor reusable after a fault.