Rated current and thermal derating — what 281 A means on the panel
The 3RW4436-2BC45: Thyristor-based output with adjustable current limitation lets you set the start ramp peak below the motor's locked-rotor draw, reducing mechanical shock on the load train. The inside-delta circuit configuration means the soft starter can be wired in the motor delta loop, reducing the unit's current rating requirement compared to in-line connection.
Mounting and connection — screw-fixed, multi-cable entry
Mounting position allows vertical surface with ±90° rotation and ±22.5° tilt front/back — fits into tight panel layouts where the gland plate orientation is fixed. Fastening method is screw fixing, not DIN rail snap-on, so plan for drilled holes and M6 or M8 hardware. Main current circuit accepts busbar connection or cable: stranded 25–120 mm², finely stranded 16–95 mm², or AWG 4–250 kcmil. The front and back clamping points each handle 6–2/0 AWG; using both clamping points maxes at 2x 1/0 AWG. Clearance spaces: 100 mm upwards, 75 mm downwards, 5 mm at the side — essential for airflow and cable bending radius. Maximum wire length to the motor is 500 m; longer runs increase voltage drop and may cause nuisance overcurrent trips during start.
Protection and diagnostics — built-in overload and fault display
Motor overload protection is integrated, so a separate thermal overload relay is not needed for most installations. Intrinsic device protection (thyristor overtemperature, phase imbalance) is also included, reducing external monitoring hardware. Fault signal is shown on a display (not just a single LED), giving a readable code for troubleshooting — useful when the panel is remote from the operator station. External reset input allows remote clearing after a fault, avoiding a trip to the cabinet. Minimum load is 8% of the rated current — below that the soft starter may not detect the motor current correctly, so verify the no-load or light-load condition.
Compliance documentation includes IEC 60947-4-2 (pollution degree 3), operating frequency 50/60 Hz, and storage temperature range -25 to +80 °C.