SIRIUS S2 power contactor for motor loads and resistive switching
The Siemens 3RT1033-1AM20 is a SIRIUS S2-frame power contactor rated for 15 kW at AC-2 duty at 400 V, making it the correct choice for wound-rotor motor switching or slip-ring applications where moderate overcurrent and frequent starts are expected. Screw-type terminals on the main circuit accept stranded wire up to 2x 25 mm², and the auxiliary contacts handle 10 A at 24 V, 6 A at 230 V, and 3 A at 400 V — enough for a control transformer or PLC output interface.
AC-2 and AC-3 motor switching — what the ratings mean
The AC-3 rating (11 kW at 500 V, 9.5 kW at 690 V) covers standard squirrel-cage motors, making and breaking during running. For high-inertia loads or plugging duty, the AC-4 switching frequency is limited to 250 operations per hour, compared to 1 000/h for AC-3 and 1 200/h for AC-1 resistive loads. That frequency ceiling is the real constraint for a machine with rapid cycling — do not exceed it without derating.
Physical fit and wiring constraints
Dimensions are 112 mm height, 55 mm width, 115 mm depth — fits standard 55 mm-wide DIN-rail slot. Front IP20, terminal area IP00. Wire ranges: solid 2x (0.5 … 1.5 mm²) and 2x (0.75 … 2.5 mm²), max 2x (0.75 … 4 mm²); stranded 2x (0.75 … 25 mm²). Pollution degree 3, so suitable for industrial enclosures without additional sealing.