What it is and what it does
The Siemens 3RT1016-1KJ81 is a SIRIUS size S00 power contactor with a 72 V DC coil, rated for motor switching up to 5.5 kW at 690 V AC-3. It handles 10 A at 24 V and 6 A at 230 V, so it fits small-to-medium motor loads like conveyors, pumps, and fans in a control panel.
Key ratings and what they mean for fit
The AC-3 motor rating of 5.5 kW at 690 V tells you this contactor can switch a 5.5 kW induction motor on a 690 V line — that's the real-world load it's designed for, not just a resistive bench number. At 400 V AC-3, it's rated 4.5 kW; at 500 V, still 4.5 kW. The AC-4 rating of 8.5 A at 400 V covers reversing or inching duty where the contactor makes and breaks full current under load. Coil is 72 V DC with a closing and holding power of 2.3 W — a constant-hold DC coil that doesn't hum and runs cool. The built-in varistor surge suppressor means you don't need to add an external snubber across the coil for DC switching. Type 2 coordination (no-weld) requires a 20 A gL/gG fuse upstream; Type 1 (weld-allowed) can use a 35 A fuse. That's the short-circuit protection the contactor expects to survive a fault without welding its main contacts.
Mounting and integration
Snap-on mounting onto 35 mm DIN rail per EN 50022, or screw-mount if you prefer. The S00 frame is compact at 45 mm wide, 57.5 mm tall, and 72 mm deep — fits a standard 8-module enclosure row with room for a motor starter or auxiliary contact block alongside. Side-by-side mounting is allowed with 6 mm spacing to adjacent devices for heat dissipation. Screw terminals on the main circuit 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 — covers standard control wiring up to 4 mm² for the power path. AWG equivalents: 2x (20 to 16), 2x (18 to 14), 1x 12. IP20 on the front and terminals means it's protected against finger contact but not washdown — standard for enclosed panel use.