What this contactor is and where it fits
The Siemens 3RT1017-2BF41 is a SIRIUS power contactor in the size S00 frame — the smallest of the SIRIUS contactor family, built for motor starting and switching loads up to 5.5 kW in AC-3 duty at 500 V or 690 V. The 110 VDC coil draws 3.3 W for both closing and holding, so the control transformer or DC supply needs to deliver that continuously, not just a pickup surge. It mounts by screw or snap-on onto 35 mm DIN rail per DIN EN 50022, which is the standard for most industrial control panels.
Terminals and wiring
Main current circuit terminals are spring-loaded, accepting 2x (0.25 to 2.5 mm²) solid or stranded wire, or 2x (24 to 14 AWG). That's the same cage-clamp style you find on many PLC I/O modules — strip to 8 mm, push the wire in, no screw tightening. The IP20 finger-safe protection on the front and at the terminals means it's safe to touch inside a closed panel, but it's not sealed against dust or moisture; keep it in an enclosure rated for the environment.
Ratings and what they mean for your motor
The AC-3 rating is the one that matters for standard squirrel-cage motors: 5.5 kW at 500 V and the same 5.5 kW at 690 V. That tells you it can handle the inrush and break the running current of a motor up to that power. For AC-4 (plugging, inching, reversing) the current rating drops to 8.5 A at 400 V — the contactor takes more wear from those duty cycles, so size up if your application reverses frequently. The auxiliary contact is a single instantaneous contact (1 NO or 1 NC depending on configuration), which is enough for a basic interlock or status feedback but may need an auxiliary contact block if you need more.
Coordination and protection
For type 2 coordination (no damage to the contactor under short circuit), Siemens specifies a gL/gG fuse rated 20 A. For type 1 coordination (contactor may need replacement after fault), use a 35 A fuse. This matters for panel builders who need to meet IEC 60947-4-1 coordination requirements — pick your fuse size based on whether you want to protect the contactor or just clear the fault.