SIRIUS S2 power contactor — what the ratings mean for your panel
The Siemens 3RT1035-1AH24 is a SIRIUS S2-size power contactor rated for 22 kW at 500 V AC-3 (motor switching) and 18.5 kW at 400 V AC-2 (slip-ring motor / wound-rotor duty). That 22 kW figure at 500 V tells you it handles a standard 30 HP motor on a 480 V line — the AC-3 category covers starting and stopping squirrel-cage motors under load, which is the heavy lifting in most conveyor, pump, and fan applications. The AC-2 rating at 400 V (18.5 kW) matters if you're switching wound-rotor motors where the rotor circuit is opened under load; that duty cycle is harder on the contacts, so the derating from AC-3 is expected. Mechanically rated for 10 million operations typical, with maximum switching rates of 1 200 cycles/hour at AC-1 (resistive), 1 000 at AC-3, and 300 at AC-4 (plugging / inching). The arcing time sits at 10–15 ms, and the coil pick-up / drop-out window is 7–20 ms at AC — let me show you why that matters: if your PLC output cycle time is faster than 20 ms, you need a hold-in interlock or a longer pulse to guarantee the contactor seals. Snap-on mounting onto 35 mm DIN rail per EN 50022, with screw terminals for the main circuit accepting stranded wire up to 2x 25 mm². Side-by-side mounting is allowed — no derating gap required for ambient up to 60 °C, but keep the pollution degree 3 environment in mind: that means conductive pollution or dry non-conductive pollution that becomes conductive due to condensation, typical in industrial panels not sealed to IP54.
Terminal details and wire range
Main circuit screw terminals accept 2x (0.75... 25 mm²) stranded. Solid wire: 2x (0.5... 1.5 mm²) and 2x (0.75... 2.5 mm²), max 2x (0.75... 4 mm²). The auxiliary / coil terminals are not separately listed, but the main circuit range covers the typical power feed. Strip length for screw terminals is not given here — if you are prepping wires, a standard 10–12 mm strip is safe for this class, but verify against the terminal marking on the part itself. The IP20 front means the contactor is finger-safe from the panel face; the terminal area is IP00, so live parts are exposed when the panel door is open — standard for enclosed industrial gear.
Environmental limits and storage
Operating temperature range -25 to +60 °C; storage from -55 to +80 °C. That storage range is the handling limit — the contactor can sit in a cold warehouse or a hot shipping container without damage, but it must be at operating temperature before you energize the coil. The coil itself is rated for 50/60 Hz at 0.8–1.1 x rated voltage (48 V at 50 Hz, 48 V at 60 Hz).