Rated current and thermal derating — the real-world limit
The 3RW4436-2BC36: At 40 °C ambient, the soft starter is rated 281 A continuous. That drops to 251 A at 50 °C and 217 A at 60 °C. The derating is linear over that range — if the panel ambient runs above 40 °C, the load current must be reduced proportionally. The insulation voltage is rated 690 V, and the operating frequency covers 50 to 60 Hz. The minimum load is 8 % of the rated current — below that, the thyristor firing angle may not be reliable for some motor types.
Wiring and termination — what fits the lugs
Main circuit termination accepts stranded wire from 25 to 120 mm², or 4 to 250 kcmil. The main current circuit also supports busbar connection — common in high-current panels where lugging every phase individually is preferred. The depth is 270 mm, width 170 mm, height 200 mm — plan the gland plate and door clearance accordingly.
Protection and control features built in
Motor overload protection and intrinsic device protection are integrated — no separate overload relay needed for most applications. Adjustable current limitation lets you set the starting current between 8 % and the rated value, reducing mechanical stress on the driven load. The soft starter uses thyristors in an inside-delta circuit configuration — common for reducing line-side harmonics and allowing a smaller unit for a given motor current. External reset is supported, and a display shows fault signals for diagnostics.
Environmental and mounting constraints
Storage temperature range is -25 to +80 °C; operation is allowed up to 60 °C ambient. Maximum motor cable length is 500 m — beyond that, capacitive charging current may cause nuisance tripping or reduce the effective starting torque. Clearance requirements: 100 mm upwards, 75 mm downwards, 5 mm at the sides for airflow.