Rated current and thermal derating — what the numbers mean for the motor circuit
The 3RW4075-2BB35: That 40 °C derating temperature means the full 356 A is only available when the enclosure ambient stays at or below 40 °C — above that, the current must be reduced per the derating curve, not guessed. For a 315 A motor in a 50 °C panel, this unit still delivers the full motor FLA without oversizing. The S12 frame size and 600 V rated insulation voltage place it in the heavy end of the SIRIUS soft starter family, sized for large conveyors, pumps, and compressors where the starting current ramp matters more than a VFD's speed control.
Connection and mounting — what fits in the panel
Main circuit connection accepts busbar or cable: stranded 70–240 mm², finely stranded 50–240 mm², or AWG 2/0–500 kcmil using both clamping points. The back clamping point takes 250–500 kcmil, the front takes 3/0–600 kcmil — so you can land incoming and outgoing conductors on separate points without a splice bar. Screw fixing to the mounting surface, with dimensions 230 mm high by 160 mm wide by 278 mm deep. Clearance requirements: 100 mm upwards, 75 mm downwards, 5 mm at the sides — the side clearance is tight, so adjacent devices can sit close, but the vertical clearance above and below must be kept for airflow and cable bending radius.
Protection and control — built-in overload and adjustable current limit
Motor overload protection is integrated, and the device includes intrinsic device protection — so the soft starter monitors its own thyristor temperature and shuts down before damage. Adjustable current limitation lets you set the starting current between 20% and the rated current, which is useful for soft-starting high-inertia loads without tripping upstream protection. External reset input allows remote fault reset from a PLC or pushbutton, avoiding a trip to the panel. Pollution degree 3 per IEC 60947-4-2 means it's rated for industrial environments with conductive dust or occasional condensation — no need for a sealed enclosure in a typical motor control centre.