Active production — 240 A soft starter with ATEX
The Siemens 3RW5077-6TB05 is an active-production soft starter rated for a minimum operating current of 240 A and a control supply voltage range of 200–600 V. It carries ATEX and IECEx certification, so it is approved for installation in potentially explosive atmospheres — a critical spec for chemical, petrochemical, or grain-handling lines where a standard soft starter would not pass site safety audit. Trip class is configurable among CLASS 10A, 10E (preset), and 20E per IEC 60947-4-2. CLASS 20E extends the ramp window for heavy starts on conveyors or mixers.
Fieldbus and control integration
Onboard fieldbus options cover PROFIBUS, Modbus RTU, Modbus TCP, EtherNet/IP, and PROFINET with PROFIenergy support. That means this soft starter slots directly into a Siemens S7-1500 or S7-1200 network without a gateway — the PROFINET standard module handles cyclic process data and acyclic parameterization over the same cable. Remote reset is supported by cycling the 24 V DC control supply off and back on — no fieldbus command required for a simple fault clear. The error logbook is available, but only with the special accessory module; if you need fault history logging on the soft starter itself, order the communication module separately.
Mounting dimensions and panel fit
The unit measures 282 mm deep, 160 mm wide, and 230 mm high. Clearance requirements: 100 mm upwards, 75 mm downwards, 10 mm forwards, 5 mm at the sides, and 0 mm backwards — the rear face sits flush against the panel. The 160 mm width fits standard 19-inch rack spacing with room for cable ducts on either side. Mounting position is flexible: vertical mounting surface with ±90° rotation and ±22.5° tilt front-to-back. This allows the soft starter to be oriented to match cable entry direction or to fit an existing gland-plate layout without re-drilling.
Environmental and compliance
Shock resistance is 15 g / 11 ms (12 g / 11 ms with potential contact lifting), so it survives vibration on a pump skid or conveyor drive base. Approvals: CE, UL, CSA, ATEX, and IECEx. The ATEX marking (Yes) means it is certified for use in Zone 1 or Zone 2 gas atmospheres and Zone 21 or Zone 22 dust atmospheres — check the specific gas group and temperature class on the nameplate before installation. No analog output or torque control on this variant — those are available on the 3RW5077 high-feature HMI version.
Soft starting features
Three ramp profiles are built in: voltage ramp (standard), soft torque (for pump start to reduce pressure surge), and pump ramp down (for controlled deceleration on pump stop to prevent water hammer). The minimum load setting is 15 % of the smallest settable Ie — useful when starting a partially loaded motor or a motor that is smaller than the soft starter's 240 A minimum. Auto-reset is available (yes), so after a fault clears the soft starter can restart without operator intervention — typical for remote or unmanned pump stations. Service factor is 1.0, meaning no built-in overload margin beyond the nameplate rating.