What it is and what it does
The Siemens 3RT1035-3KJ84-0LA0 is a SIRIUS S2-frame power contactor rated for motor switching at 22 kW on 500 V AC-3 duty, and 18.5 kW at 400 V AC-2. In the heavier AC-4 category (plugging, inching) it handles 35 A at 400 V. That AC-4 number is the one to watch if your application does frequent reversing or jogging — the contactor is sized for it, not just the AC-3 motor-start rating. The S2 frame is the middle size in the SIRIUS contactor family, sitting between the compact S0 and the larger S3. It mounts on 35 mm DIN rail per EN 50022, with screw and snap-on fastening. Side-by-side mounting is permitted, so you can gang multiple contactors on the same rail without a gap. Main circuit connections are screw-type terminals. Wire ranges: solid 2x (0.25 to 2.5 mm²), stranded 2x (0.75 to 25 mm²), and a second stranded range 2x (0.75 to 16 mm²). The 25 mm² stranded capacity is the one that matters for the main power wiring at the 22 kW level.
Where it goes in the panel
This is a panel-mount component — IP00 on the front and at the terminals, so it lives inside an enclosure, not out in the weather. Pollution degree 3 means it's rated for industrial environments with conductive dust or occasional condensation, which is the normal condition inside a control cabinet. Dimensions: 80 mm wide, 110 mm high, 167 mm deep. The 167 mm depth is the dimension that determines how deep your enclosure needs to be — measure from the DIN rail back to the gland plate. Operating temperature range is -40 to +70 °C, storage -55 to +80 °C, so it handles unheated warehouses and hot panels alike. Mechanical life is 10 million operating cycles typical. Switching frequencies: 1200 cycles/hour at AC-1 (resistive), 1000 at AC-3 (motor start), 600 at AC-2, and 300 at AC-4. The AC-4 limit is the binding constraint for high-duty reversing applications.
Control circuit and aux contacts
The coil is rated 72 V. Pickup and dropout timing: DC operate time 20 to 25 ms, arcing time 10 to 15 ms. The auxiliary contact block (integrated or add-on) carries 10 A at 24 V, 2 A at 60 V, 1 A at 110 V, 0.3 A at 220 V, 6 A at 230 V, and 3 A at 400 V. The 24 V 10 A rating is the one to note for PLC output interfacing. Control supply threshold: initial value 0.7, full-scale value 1.25 — these are the pickup and dropout ratios relative to the rated control supply voltage. The contactor picks up at 70% of rated voltage and drops out at 125% (overvoltage release).