What it is and what it does
The Siemens 3RT1035-1AP08-0MA0 is a SIRIUS power contactor in frame size S2, built for switching three-phase motors and resistive loads in control panels. It mounts on a 35 mm DIN rail per EN 50022 — screw and snap-on both supported, so you can pre-wire a subplate and clip it in. Rated 18.5 kW at 400 V in AC-2 duty, it handles wound-rotor motors and slip-ring applications where the load current stays high during acceleration. For reversing or inching duty (AC-4), it's rated 35 A at 400 V — enough for frequent plugging or jogging on a conveyor or hoist. The coil draws 10 A at 24 V (inrush) and holds at 2 A at 60 V, with a drop-out time of 7 to 20 ms and arcing time of 10 to 15 ms. That arc time matters for coordination with upstream fuses or breakers — short enough to let a fast semiconductor fuse clear a fault without welding the main contacts.
Mounting and wiring constraints
Occupies 55 mm width on the rail, 112 mm tall, 164 mm deep — the depth is the dimension that often catches panel layouts when replacing an older contactor with a deeper arc chamber. Side-by-side mounting is allowed without derating, so you can gang multiple contactors on a common busbar. Main circuit terminals accept 2x (0.5 to 1.5 mm²) solid, 2x (0.75 to 2.5 mm²) solid, or up to 4 mm² solid per clamp. Stranded goes up to 2x (0.75 to 25 mm²) — plenty for the 16 mm² minimum at 40 °C. Screw-type terminals, so torque to the value on the nameplate.
Lifecycle and compliance
Operating temperature range is -25 to +60 °C; storage goes from -55 to +80 °C. The IP20 front and IP00 terminal block mean it's for enclosure mounting — not for washdown or outdoor exposure without a cabinet.
How it compares to the 3RT1044-1FB46
The 3RT1044-1FB46 is a larger frame (S3 vs S2) with higher motor ratings — typically 30 kW AC-3 at 400 V. The 3RT1035-1AP08-0MA0 tops out at 18.5 kW AC-2. If your BOM calls for the S3 frame, the S2 won't fit the same mounting hole pattern or busbar spacing. Stick with the S2 if your load is under 18.5 kW and you want the narrower 55 mm width.