81 A minimum, 200-600 V — SIRIUS soft starter for motor starting duty
The Siemens 3RW5236-6AC05 is a SIRIUS hybrid soft starter rated for a minimum operating current of 81 A across a 200-600 V supply range. This puts it in the mid-range of the 3RW52 family, sized for motors that draw 81 A or more during start — typically 30-50 kW depending on voltage and load type. Trip class is selectable as CLASS 10A (default), 10E, or 20E per IEC 60947-4-2. For a pump or conveyor with a moderate inertia load, Class 10A gives a 10-second thermal limit at 7.2× Ie; Class 20E doubles that window for high-inertia starts like centrifuges or crushers. The default 10A is fine for most fan and pump applications, but if the motor takes longer than 10 seconds to reach speed, switch to 20E via the parameter set. In a panel with other heat sources — drives, transformers, contactors — the internal temperature rise can push past 40 °C, so the 81 A minimum figure may need to be de-rated. Plan for forced ventilation or a larger enclosure if the panel ambient exceeds 40 °C.
Fieldbus integration and analog output
This soft starter supports PROFIBUS, Modbus RTU, Modbus TCP, EtherNet/IP, and PROFINET — a full industrial Ethernet stack plus the legacy fieldbus. The PROFINET variant also supports PROFIenergy for coordinated energy management during idle phases. No separate communication module is needed for the standard protocols; the unit ships with the interfaces onboard. An analog output is configurable as 4-20 mA (default) or 0-10 V, parameterizable via the High Feature HMI. This lets the PLC read motor current or torque directly without a separate transducer — useful for condition monitoring or load profiling on a conveyor line.
Mounting and panel fit — 306 x 185 x 203 mm
The 3RW5236-6AC05 measures 306 mm high, 185 mm wide, and 203 mm deep — a substantial unit that requires screw fixing to the backplate. Clearance requirements: 100 mm above, 75 mm below, 10 mm forward, 5 mm to the side, and 0 mm backward (flush to the mounting surface). The 100 mm top clearance is critical for natural convection cooling — a common oversight that leads to nuisance thermal trips in enclosed panels.
Compliance and approvals — CE, UL, CSA
The 3RW5236-6AC05 carries CE marking, UL approval, and CSA approval. Shock resistance is 15 g for 11 ms, dropping to 12 g if contact lifting is a concern.