SIRIUS S12 — what the frame size means for your panel
The 3RT1075-6AD36 is a Size S12 power contactor in the Siemens SIRIUS family, designed for screw fixing to a mounting surface — not DIN-rail snap-on, so budget the panel backplate for four M8 bolts through 11 mm holes on a 160 mm wide footprint. Mounting position is flexible: vertical surface with ±90° rotation and ±22.5° tilt front-to-back, which helps when the gland plate or busbar layout forces an odd orientation. Clearance distances are tight — 10 mm upwards, 10 mm downwards, 10 mm at the side, 20 mm forwards — so you can pack contactors closer than many IEC designs allow, but the arc chute needs that forward gap for arc extinction (arcing time 10–15 ms).
Coil and auxiliary contact ratings — the switching limits
Coil voltage is 42–48 V AC/DC, with a pickup threshold of 0.8× rated value — meaning the contactor pulls in at about 34 V on a 42 V rail, which gives some headroom on a sagging control supply. The magnet coil terminates at screw-type terminals, and the built-in auxiliary switch is rated 10 A at 24 V, 2 A at 48 V, 2 A at 60 V, and 1 A at 110 V — enough to drive a PLC input or a small relay directly without an interposing block. Operating time is 60–100 ms on both AC and DC, consistent across the voltage range, so timing coordination with upstream breakers or soft-starters is predictable.
Switching frequency and mechanical endurance — duty-cycle reality
Maximum switching rates vary by duty: 700 operations/hour in AC-1 (resistive), 500/h in AC-3 (motor start/run), 200/h in AC-2 (slip-ring motor), and 130/h in AC-4 (plugging/inching). The AC-3e rating matches AC-3 at 500/h. Mechanical life is 10 million operations typical — that is the contactor body, not the contacts. In a high-cycle application like a conveyor jog station, the electrical wear in AC-4 will limit service life well before the mechanism wears out. The overload factor is 1.1× full-scale, so the contactor can sustain 110 % rated current briefly without welding — useful for motor inrush coordination.
Wire terminations and thermal limits
Main power circuit accepts stranded wire from 70 to 240 mm² — that is a heavy cable range, typical for a Size S12 contactor handling 250+ A motor loads. The control circuit (auxiliary) takes solid or stranded 2× (0.5–1.5 mm²), 2× (0.75–2.5 mm²), or max 2× (0.75–4 mm²). Operating ambient is –25 to +60 °C, storage –55 to +80 °C — the contactor lives in a warm panel but can sit in a cold warehouse without damage. Power factor rating is 0.9 at both 50 Hz and 60 Hz, so the contactor is equally at home on 50 Hz or 60 Hz networks without derating.