What it is and what it does
The Siemens 3RT1036-1AH20 is a SIRIUS power contactor, Size S2, designed for switching motor loads in control panels. It mounts on a 35 mm DIN rail per EN 50022, with screw terminals for the main circuit. Its AC-2 rating at 400 V is 22 kW, which covers wound-rotor motor switching — the duty class that matters for slip-ring or reversing applications where the contactor makes and breaks under load. At 500 V it handles 30 kW, and at 690 V it's rated 11.4 kW.
Key ratings and what they mean for fit
The AC-3 maximum switching frequency is 800 cycles per hour — that's the mechanical endurance limit for standard induction motor starting. AC-4 drops to 300 cycles per hour, reflecting the heavier duty of plugging or inching. If your application cycles faster than these numbers, the contactor will overheat or wear prematurely. The auxiliary contact ratings at 24 V DC are 10 A, dropping to 0.3 A at 220 V DC. For DC control circuits, check the voltage-specific rating — the 24 V figure is generous, but at higher DC voltages the current capability falls off sharply due to arc extinction limits. Ambient operating range is -25 to +60 °C, with storage down to -55 °C. Pollution degree 3 means it's suitable for industrial environments with conductive dust or occasional condensation — standard for an enclosed panel, but not for direct outdoor exposure without a cabinet.
Mounting and wiring
Screw and snap-on mounting onto 35 mm DIN rail. Side-by-side mounting is permitted — no derating required for adjacent units, which simplifies panel layout. The Size S2 footprint is 55 mm wide, 112 mm high, 115 mm deep. Main circuit terminals accept solid wire from 2x 0.5 mm² up to 2x 4 mm², or stranded from 2x 0.75 mm² up to 2x 25 mm². That range covers most motor feeder cables up to about 6 AWG. The front face is IP20 — safe for finger contact in an enclosed panel.