What it is and what it does
The Siemens SIRIUS 3RT1017-2CB04-ZW95 is a size S00 power contactor rated for motor switching up to 5.5 kW at 400 V in AC-2 duty (slip-ring motors, wound-rotor applications) and 8.5 A in AC-4 (plugging, inching, reversing). The coil is a 24 V 50/60 Hz unit with an integrated varistor surge suppressor, so you don't need to add an external snubber for the control circuit. It mounts via screw or snap-on onto a 35 mm DIN rail per EN 50022, and the spring-loaded terminals accept 2x (0.25... 2.5 mm²) solid or stranded wire — no screwdriver torque check needed, which speeds up panel wiring.
Key ratings and what they mean for fit
The AC-2 rating of 5.5 kW at 400 V is the number that governs motor switching for wound-rotor or slip-ring motors — the contactor handles the higher inrush and longer arc time of those loads. For reversing or jogging duty (AC-4), the limit drops to 8.5 A at 400 V, so size accordingly if your application cycles the motor under load. The AC-12 rating of 10 A covers resistive and solid-state loads, useful for switching heaters or power supplies. The short-circuit protection requirement is a gL/gG fuse rated 20 A (type 2 coordination), so your panel designer needs to account for that in the feeder. Operating temperature range is -25 to +60 °C, and pollution degree 3 means it's suited for industrial environments with conductive dust or humidity — no need for a sealed enclosure in a typical panel.
Mounting and integration
The S00 frame is compact at 45 mm wide, 60 mm tall, and 114 mm deep — it fits a standard 45 mm DIN-rail slot and leaves room for auxiliary contact blocks on the side. Side-by-side mounting is allowed with no derating, so you can pack multiple contactors in a row without spacing gaps. The spring-loaded terminals accept 2x (0.25... 2.5 mm²) or 2x (24... 14 AWG) conductors. Strip length is not specified here, but standard practice for spring-cage terminals on this class is 8-10 mm. The front and terminal areas are IP20, so finger-safe in a closed panel.