What This Part Is and Where It Fits
The Siemens 3RT1055-6AT36 is a SIRIUS power contactor in the Size S6 frame. It's the main switching device for motor loads and resistive heating banks in industrial control panels — the sort of thing you'd find on a MCC bucket or a standalone motor starter enclosure. The coil is rated for 575 to 600 VAC at 50/60 Hz, which means it's built for 600 V class control circuits common in North American and some export panels. Coil termination is screw-type, so you're landing ring or fork terminals, not spring cages.
Mounting and Clearance — What the Panel Guy Needs
Mounting is screw-fixing through a single 9 mm hole, not DIN rail — plan for a drilled backplate. The contactor can sit on a vertical surface and be rotated ±90° or tilted ±22.5° front-to-back, which gives some flexibility for cable entry orientation. Keep at least 10 mm clearance above and below, 10 mm to the sides, and 20 mm in front for arc flash and cooling. That's tighter than some older S6 frames, so check your existing gland plate layout if you're retrofitting.
Ratings That Drive the Application
The main power path accepts stranded conductors from 25 to 120 mm² — that's good for motor feeds up to around 200-250 A depending on duty cycle and ambient. The auxiliary switch (built-in) handles 10 A at 24 V, 2 A at 48 V or 60 V, and 1 A at 110 V. That's enough to drive a PLC input or a small relay directly, but if you're switching a 120 VAC pilot light, watch the 1 A limit. Mechanical endurance is rated at 10 million operations typical — that's a lot of cycles for a motor starter, but the electrical life depends on the load. For resistive loads (AC-1), you can cycle it up to 800 times per hour. For standard motor starting (AC-3), it's 750 cycles per hour. Heavy inching or plugging (AC-4) drops that to 130 cycles per hour. The arcing time is 10 to 15 ms, and the coil pull-in and drop-out times are 40 to 60 ms on both AC and DC — fast enough for most sequencing but not a high-speed transfer switch. The operating temperature range is -25 to +60 °C, which covers most indoor panel environments. Storage range is -55 to +80 °C — fine for warehouse or truck transit. The rated power factor at operational current is 0.8 at both 50 and 60 Hz, so it's designed for typical induction motor loads.