What it is and where it lands
The Siemens 3RT1017-1KJ81 is a SIRIUS power contactor in the S00 frame size, built for switching motor loads in control panels. It mounts via screw or snap-on onto a 35 mm DIN rail per EN 50022, and the 45 mm width means it fits standard 8-module enclosure cutouts without crowding adjacent devices.
Coil and control circuit
The magnet coil is rated at 72 V DC and draws a constant 2.3 W for both closing and holding — no inrush spike to size your DC supply around. A built-in varistor suppresses the back-EMF when the coil de-energizes, so you don't need an external snubber across the PLC output driving it.
Main contact ratings — what they mean for motor duty
In AC-3 duty (starting and disconnecting squirrel-cage motors), the contactor handles 5.5 kW at both 500 V and 690 V — that's the rating that governs real motor switching. For AC-4 duty (plugging and inching), it's rated 8.5 A at 400 V, which is the figure to check if your application involves frequent reversing or jogging. The AC-12 maximum operating current is 10 A, covering resistive and low-inductance loads.
Short-circuit coordination and wire termination
For Type 2 coordination (no damage to the contactor after a fault), Siemens specifies a gL/gG fuse rated 20 A. Type 1 coordination (contactor may need replacement) allows a 35 A fuse. The screw-type main terminals accept 2 x (0.5 to 1.5 mm²), 2 x (0.75 to 2.5 mm²), or up to 2 x (0.75 to 4 mm²) — solid or stranded — plus AWG equivalents down to 20 AWG. That covers most panel wiring from control to power circuits.
Auxiliary contact and environmental limits
One instantaneous auxiliary contact is built in (NO or NC configuration depends on the variant ordered). The contactor is rated for pollution degree 3 (industrial environments with conductive or dry non-conductive pollution), operates from -25 °C to +60 °C, and is limited to 2000 m altitude without derating. Enclosure and terminal protection is IP20 — finger-safe but not washdown-rated, so keep it inside the panel.
Mounting and spacing
Side-by-side mounting is permitted with only 6 mm clearance to adjacent devices on either side — no forced air gap. The 57.5 mm height and 72 mm depth fit standard S00 footprint, so it drops into existing panel layouts without re-drilling the backplate.