What it is and what it fits
The Siemens 3RT1017-1AP05 is a SIRIUS power contactor in the compact S00 frame size, designed for switching motor loads and resistive loads in industrial control panels. It snaps onto a 35 mm DIN rail per DIN EN 50022, and its 45 mm width lets you pack several units side by side without extra spacing — side-by-side mounting is allowed. The coil is rated for 24 V DC, and the contactor carries a rated operational current of 10 A at AC-12 (resistive) and 8.5 A at AC-4 (motor starting/plugging) at 400 V. That AC-4 rating is the one to watch if you're cycling a motor on and off frequently — it's the duty that stresses the contacts hardest.
Panel fit and wiring
At 57.5 mm high and 114 mm deep, this contactor fits standard enclosures with room for wiring ducts. The screw terminals accept 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), or a single 4 mm². Pollution degree 3 rating means it's suited for industrial environments where conductive dust or condensation may occur — typical for a panel in a factory hall, not a climate-controlled server room. The terminals themselves are IP20, so tools and fingers stay safe during commissioning.
Short-circuit coordination and protection
For Type 2 coordination (no damage to the contactor after a short circuit), Siemens specifies a gL/gG fuse rated at 20 A. For Type 1 coordination (contactor may need replacement but the rest of the panel survives), the fuse can go up to 35 A. This is critical for selectivity studies — the fuse size determines whether your upstream breaker holds or trips.