280 A at 40 °C — what that means for the motor it starts
The 3RW4074-2BB45 is rated 280 A at 40 °C ambient. That is the continuous current the thyristors can carry with the heatsink at that temperature — not a starting surge, but the steady-state motor current after the ramp is complete. The operating frequency range is 50 to 60 Hz.
Terminal sizing and connection — main circuit
Main circuit connection is via busbar; the terminal range accepts stranded cable 70 to 240 mm² and fine-stranded 50 to 240 mm². For US installations, the range covers 2/0 to 500 kcmil using both clamping points, with a back clamping point accepting 250 to 500 kcmil. That is a big cable fit — this unit expects a serious feeder.
Protection and control features built in
Motor overload protection is integrated — no separate overload relay needed for most applications. Adjustable current limitation lets you set the start current below the locked-rotor value, which reduces mechanical shock and line drop. External reset is supported, and intrinsic device protection covers the soft starter itself against overtemperature and phase imbalance. The minimum load is 20 % of the rated current — below that the motor might not ramp up cleanly. Pollution degree 3 per IEC 60947-4-2 confirms it is rated for conductive-dust industrial environments.
Mounting and thermal management
The mounting position is flexible: with an additional fan, the unit can be mounted vertically with +/-90° rotation and +/-22.5° tilt front/back; without the fan, +/-10° rotation and +/-10° tilt. The derating temperature starts at 40 °C. Overall dimensions: width 160 mm, height 230 mm, depth 278 mm. Clearances: 100 mm upwards, 75 mm downwards, 5 mm at the sides. Storage temperature range -40 to +80 °C; operating range -25 to +60 °C. Maximum motor cable length is 300 m.