What it is and where it fits
The Siemens 3RT1017-1AN04 is a SIRIUS power contactor in the S00 frame size — the smallest footprint in the SIRIUS family, meant for motor loads up to about 5.5 kW at 400 V. Screw-type terminals on the main circuit, snap-on or screw-fixed to a 35 mm DIN rail per EN 50022. Front face is IP20, so it's panel-safe with the cover on; pollution degree 3 means it's rated for industrial atmospheres with conductive dust or occasional condensation.
What the ratings mean on the line
AC-4 at 400 V is 8.5 A — that's the plugging / inching duty rating, the one that matters for frequent reversing or jogging. AC-2 at 400 V carries 5.5 kW, which covers slip-ring motor starting. For standard AC-3 squirrel-cage duty at 400 V, it's also 5.5 kW. The coil holds between 0.8 and 1.1 times rated voltage at 50 Hz (0.85 to 1.1 at 60 Hz), so it stays pulled in through brownouts down to about 176 V on a 220 V coil. Operating temperature range is -25 to +60 °C during operation, which covers most unheated plant floors and outdoor cabinets in moderate climates.
Mounting and wiring
45 mm wide, 57.5 mm tall, 111 mm deep — it's a compact block that fits tight DIN-rail rows. Side-by-side mounting is allowed with no gap, but if you're stacking contactors in a high-ambient enclosure, derate per the thermal curve. Screw terminals accept 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), or max 2x (0.75 to 4 mm²) solid/stranded, plus 1x 12 AWG. The auxiliary contact block has 2 normally-open instantaneous contacts, rated 10 A at 24 V, 6 A at 230 V, and 3 A at 400 V. For type 2 coordination, the required upstream fuse is gL/gG 20 A; type 1 coordination allows 35 A.