The Siemens 3RW5055-6AB14 is a SIRIUS soft starter, a hybrid switching device that ramps motor voltage up and down to limit inrush current and mechanical stress on startup and stop. It is rated for a minimum motor current setting of 68 A and a supply voltage of 200... 480 V, making it suitable for medium-sized induction motors in pump, fan, and conveyor applications where controlled acceleration and deceleration are needed. It also holds UL, CSA, and CE approvals, covering North American and European regulatory jurisdictions for panel builders and OEMs shipping globally.
The minimum settable current is 68 A, which means the soft starter can be adjusted down to protect smaller motors within its range — useful when the BOM calls for a single starter size across slightly different motor ratings. The rated voltage of 200... 480 V covers common three-phase supplies from 208 V North American to 400 V European without needing a different variant. Trip class is selectable between CLASS 10A, 10E (preset), and 20E per IEC 60947-4-2. CLASS 10A suits standard motor starts with short acceleration times; CLASS 20E gives extra headroom for high-inertia loads like centrifuges or long conveyors that take longer to reach speed. The preset 10E is a common middle ground for general-purpose duty. Operating temperature range is -25... +60 °C, but derating is required at 40 °C or above.
Communication and control features
The 3RW5055-6AB14 supports PROFIBUS, Modbus RTU, Modbus TCP, and EtherNet/IP, giving flexibility to integrate into existing fieldbus architectures without a separate gateway. PROFIenergy is available when used with a PROFINET communication module, allowing energy management functions during idle periods. Soft Torque, Voltage Ramp, and Pump Ramp Down are built-in starting and stopping profiles. Soft Torque reduces mechanical shock on geared loads; Pump Ramp Down minimizes water hammer in pumping systems by gradually reducing voltage rather than coasting to a stop. An analog output is configurable as 4... 20 mA (default) or 0... 10 V via the High Feature HMI, providing a real-time current or motor load signal to a PLC or panel meter. Remote reset is possible by cycling the control supply voltage.
Mounting and mechanical integration
Mounting is by screw fixing, not DIN rail. The unit measures 120 mm wide, 198 mm high, and 249 mm deep, with specified clearance requirements: 100 mm upwards, 10 mm forwards, 75 mm downwards, 5 mm at the sides, and 0 mm backwards. These clearances must be maintained for airflow and to prevent contact lifting under shock — the shock resistance rating is 15 g / 11 ms, dropping to 12 g / 11 ms if contact lifting is a concern.
Given the multi-protocol communication and ATEX/UKEX certifications, this is a specified-into-the-BOM part for many OEMs and panel builders.