What this soft starter carries
The Siemens 3RW5535-6HA14 is a SIRIUS 3RW55 soft starter rated for 200-480 V supply voltage, with selectable trip classes 10A / 10E (default) / 20E / 30E per IEC 60947-4-2. That means you can match the overload protection curve to the motor start profile — CLASS 10A for standard starts, 10E for electronic motor protection, or 20E/30E for high-inertia loads that need a longer ramp. ATEX and IECEx certification (Yes) is the headline here: this unit is approved for use in explosive atmospheres, so it can sit in a Zone 1 or Zone 21 panel feeding a motor in a hazardous area without an external isolation barrier.
Fieldbus and control options
On the communications side, the 3RW5535-6HA14 supports PROFIBUS, Modbus RTU, Modbus TCP, and EtherNet/IP natively — no separate gateway module needed. It also carries PROFIenergy in connection with PROFINET Standard and PROFINET High-Feature communication modules, which lets the drive park the motor during production pauses and save energy on the line. The analog output is configurable as 4-20 mA (default) or 0-10 V, useful for feeding motor current or power data to a PLC or local display. Screw terminals on the power and control side keep wiring straightforward for panel builders.
Dimensions are 306 mm height, 185 mm width, 203 mm depth. Clearance requirements: 100 mm upwards, 75 mm downwards, 10 mm forwards, 5 mm at the side, 0 mm backwards. That side clearance is tight — 5 mm means you can stack units nearly side-by-side on the DIN rail without a spacer, but the 100 mm top gap is non-negotiable for heat dissipation from the thyristor stack. The backwards clearance of 0 mm means it can sit flush against the back panel.
Protection and diagnostics
Beyond the trip class, the unit includes DC braking, voltage ramp, pump ramp down, torque control, breakaway pulse, motor heating, and auto-reset with remote reset capability. Accuracy class 5 per IEC 61557-12 means the current measurement is within 5% of reading — adequate for overload protection but not a precision metering device. The service factor of 1.15 allows the motor to run at 115% of its rated load continuously without tripping, common for pump and fan applications. Event list, error logbook, and trace function are built in for fault isolation.