Soft starter for motor starting in hazardous areas
The Siemens 3RW5074-2TB15 is a SIRIUS soft starter with a minimum operating current of 135 A and a rated voltage of 200 to 600 V. It carries ATEX and IECEx certification. Trip class is configurable as CLASS 10A, 10E (preset), or 20E per IEC 60947-4-2, giving the commissioning engineer flexibility to match the motor thermal model: CLASS 10E for standard squirrel-cage motors, CLASS 20E for high-inertia loads like centrifuges or crushers that need a longer acceleration ramp without nuisance tripping. Fieldbus connectivity includes Modbus RTU, Modbus TCP, and EtherNet/IP, so it drops into most common automation architectures without a gateway. PROFIBUS is also listed, though the Modbus TCP and EtherNet/IP options are the more common choices for new installations.
Mounting is by screw fixing; the unit measures 282 mm deep, 160 mm wide, and 230 mm high. Clearance requirements: 100 mm upwards, 10 mm forwards, 75 mm downwards, 5 mm at the sides, and 0 mm backwards — so it can sit flush against the back panel, but needs breathing space above and below for convection cooling. In a non-air-conditioned enclosure on a hot plant floor, that derating curve matters: the 135 A minimum rating may need to be up-sized if ambient exceeds 40 °C. Shock resistance is 15 g / 11 ms, dropping to 12 g / 11 ms if contact lifting is a concern. For mobile or vibrating equipment (e.g., mining conveyors), the lower figure governs.