ATEX-rated motor starting for hazardous zones
This Siemens 3RW5521-1HA16 soft starter carries ATEX and IECEx certification, meaning it can be specified for motor starting in potentially explosive atmospheres without an additional isolation barrier. The ATEX marking covers gas and dust groups per the ATEX directive; the IECEx listing provides the global equivalent for jurisdictions that follow the IECEx scheme. The wide voltage window means one part number can be stocked for multi-voltage plants.
Trip class and motor protection coordination
The trip class is selectable from CLASS 10A / 10E (default) / 20E / 30E per IEC 60947-4-2. Class 10A is the standard for standard-start applications; Class 20E or 30E accommodates high-inertia loads like centrifuges or crushers where the start time exceeds 10 seconds. The selector is parameterized via the onboard interface. Built-in motor heating and DC braking allow the soft starter to handle both start and stop control without external contactors for the braking function. The voltage ramp and pump ramp down reduce mechanical shock on the load and piping. Accuracy Class 5 per IEC 61557-12 applies to the integrated current measurement — sufficient for motor protection without a separate CT. The service factor of 1.15 means the starter can run the motor at 115% of rated current continuously without tripping, matching typical NEMA motor service factors.
Fieldbus and control integration
The 3RW5521-1HA16 supports PROFIBUS, Modbus RTU, Modbus TCP, and EtherNet/IP natively — no separate communication module required for these protocols. PROFINET with PROFIenergy is available via an optional communication module. This multi-protocol capability lets the starter drop into existing plant networks without a gateway. Analog output configurable as 4-20 mA or 0-10 V provides a real-time motor current signal to a PLC or SCADA. The event list and error logbook store the last several fault events with timestamps, useful for diagnosing intermittent trips without a continuous connection. Firmware update capability via the fieldbus interface means the starter can be upgraded in the field without replacing hardware. Four parameter sets allow quick changeover between different motor configurations or process recipes.
Mounting and clearance for panel layout
The unit measures 185 mm wide, 306 mm high, and 203 mm deep. Required clearances: 100 mm above, 75 mm below, 10 mm in front, 5 mm at the sides, and 0 mm behind. The zero rear clearance means it can be mounted flush against a back panel, saving depth in shallow enclosures. Screw terminals are standard for power and control wiring — no special crimp tooling needed. The terminal layout follows Siemens SIRIUS standard spacing, compatible with common busbar systems and feeder terminals.
Compliance and approvals for global shipments
CE marking covers the EU low-voltage and EMC directives. UL approval and CSA approval cover North American installations. ATEX and IECEx cover hazardous locations. This combination of approvals means the starter can be shipped to most industrial markets without additional certification work.