Current ratings that decide the motor size
The 3RW4427-3BC46: Rated 161 A at 40 °C, derating to 142 A at 50 °C and 125 A at 60 °C — the thermal budget in the enclosure determines which current column applies. At 40 °C ambient this unit handles a 75–90 kW motor at 230 V; push the ambient to 60 °C and the same unit covers about 55 kW. The integrated bypass contact system carries the full motor current after start-up, taking the heat out of the thyristors. This means the derating curve matters less for continuous running than for the start duty cycle — the bypass handles the steady-state load.
Inside-delta wiring and adjustable current limit
Supports inside-delta circuit connection, which lets the soft starter handle a motor with a lower line current than the full-winding current — common on larger motors where the starter sits in the delta leg rather than the line. The adjustable current limitation sets the start current anywhere from 0 to the unit's rated maximum, so you can tune the ramp to the load without swapping hardware. Minimum load is 8 % of the rated current — below that the thyristors may not fire cleanly. If the motor no-load current is under ~13 A at 40 °C, the unit might not commutate properly.
Mounting and wiring — panel fit
Screw fixing to a vertical mounting surface, rotatable ±90° and tiltable ±22.5° front-to-back. Dimensions are 170 mm wide, 192 mm high, 270 mm deep — it needs 100 mm clearance above and 75 mm below for airflow, and only 5 mm at the sides. Main current circuit uses box terminals accepting 2x (4 … 50 mm²) stranded or 2x (10 … 1/0) AWG using both clamping points. Maximum wire length to the motor is 500 m — beyond that the cable capacitance can cause nuisance thyristor firing.
Protection and diagnostics
Built-in motor overload protection and intrinsic device protection — the soft starter monitors its own thyristor temperature and line-side conditions. External reset via a display for fault signal shows the error code directly on the unit, no extra HMI needed.