Panel fit and thermal budget — the 230 A rating in context
The 3RW4073-6BB34 is a SIRIUS soft starter from Siemens, Size S12 frame, designed for in-line motor starting with thyristor-based voltage ramp and current limit. It's rated 230 A at 40 °C, derating to 205 A at 50 °C and 180 A at 60 °C — that derating curve is the first thing to check when sizing the panel ambient. If your enclosure runs at 50 °C, you lose about 11% of the continuous rating; at 60 °C it's a 22% drop. The mounting position has limits: with an additional fan you can rotate ±90° or tilt ±22.5° front/back; without the fan, rotation is limited to ±10° and no tilt. That matters if you're shoehorning this into an existing panel with restricted airflow — you need the fan for flexible orientation. Clearance around the unit: 100 mm above, 75 mm below, and just 5 mm at the sides. The 5 mm side gap is tight — make sure no cable bundles or busbars run alongside. The overall dimensions are 230 mm high, 160 mm wide, 278 mm deep.
Wiring — main circuit and control connections
Main circuit connection is via busbar, not cable lugs. The starter accepts stranded cable from 70 to 240 mm², or finely stranded from 50 to 240 mm². For North American practice, it takes 2/0 to 500 kcmil at the front clamping point, and 250 to 500 kcmil at the back. There are two clamping points, each accepting up to 2x 500 kcmil — useful for paralleled feeds or looping through. Operating frequency is 50-60 Hz, so it works on either. Maximum motor cable length is 300 m — if your run is longer, you may need an output reactor or filter. The starter is not designed for inside-delta (six-wire) connection; it's standard in-line wiring only.
Protection and control features
The 3RW4073-6BB34 includes motor overload protection and intrinsic device protection (monitoring the thyristor junction temperature and supply conditions). The current limitation is adjustable — you set the maximum inrush current as a percentage of the motor FLA, which is the main tool for coordinating with upstream breakers and contactors. Minimum load is 20% of the rated current — below that the thyristor firing may become erratic. If you're starting a very small motor relative to the starter size, you'll need to check that the motor FLA is above 46 A (20% of 230 A). External reset is supported — you can wire a remote pushbutton or PLC output to clear a fault without opening the panel. Pollution degree 3 per IEC 60947-4-2 means it's rated for industrial environments with conductive dust and occasional condensation. Rated insulation voltage is 600 V, so it's comfortable on 480 V systems with margin.