What it is and where it fits
The Siemens 3RT1017-1AN21 is a SIRIUS S00-frame power contactor rated for 5.5 kW at 400 V in AC-3 duty, meaning it handles squirrel-cage motor switching in control panels up to that load. The 24 VDC coil pulls in reliably across 0.8–1.1× rated voltage at 50 Hz and 0.85–1.1× at 60 Hz, so it stays picked during brownout conditions down to about 19.2 V. Snaps onto 35 mm DIN rail per EN 50022 or screws directly to a backplate — the 45 mm width and 57.5 mm height leave room for auxiliary contact blocks alongside. IP20 on the front and terminals means it's protected against finger contact but needs enclosure for washdown or dust.
Ratings that matter for motor switching
AC-3 rating at 400 V is 5.5 kW — that's the figure for sizing on a standard 400 V three-phase motor. AC-4 at 400 V is 8.5 A, covering plugging and inching duty where the contactor makes and breaks stalled-rotor current. At 690 V it still delivers 5.5 kW in AC-3, so it works on 690 V line supplies without derating the motor power. Auxiliary contacts are rated at 10 A at 24 V, 2 A at 60 V, 1 A at 110 V, and 0.3 A at 220 V — these are the switching limits for the control circuit, not the main poles. The 30 million mechanical cycles typical life means it outlasts most panel refreshes in normal cycling service.
Terminal and wiring detail
Main and auxiliary circuits use screw-type terminals. Solid or stranded wire: 2× (0.5–1.5 mm²), 2× (0.75–2.5 mm²), or max 2× (0.75–4 mm²). AWG equivalents: 2× (20–16), 2× (18–14), or 1× 12. The 72 mm depth includes terminal clearance — factor that into gland-plate planning.
Coordination and compliance
Type 2 coordination requires a gL/gG fuse rated 20 A; Type 1 coordination calls for 35 A. Pollution degree 3 means it's rated for industrial environments with conductive dust or humidity. RoHS compliance date is July 1, 2006 — the part meets the original EU RoHS directive.