Current derating — the real operating envelope
The 3RW4457-2BC36: Rated 1524 A at 40 °C, derated to 1351 A at 50 °C, and 1200 A at 60 °C. The 324 A drop between 40 °C and 60 °C means panel ambient temperature directly governs the usable motor FLA. If the enclosure runs at 50 °C, budget 1351 A as the ceiling — not the 40 °C figure. Derating temperature threshold is 40 °C; above that the current must be reduced per the datasheet curve. The 690 V rated insulation voltage (IEC 60947-4-2) and pollution degree 3 environment suit industrial panels with conductive dust or humidity.
Inside-delta wiring and integrated bypass
Supports inside-delta circuit configuration — the thyristors are wired inside the motor delta connection, reducing the current through each device to 58% of the line current. This lets a 1524 A unit handle motors with a higher locked-rotor current than a standard line-connected soft starter of the same rating. Integrated bypass contact system means the thyristors are shorted out after the start ramp, eliminating continuous conduction losses. The bypass contactor is built into the unit — no external bypass contactor or wiring needed.
Terminal sizing and panel fit
Main circuit connection is busbar only — no cable lugs. The busbar interface accepts 2/0 to 500 kcmil conductors. Stranded power wiring is 70–240 mm²; finely stranded 50–240 mm². Mounting is screw fixing with a vertical mounting surface. The unit can be rotated ±90° or tilted ±22.5° forward/backward. Dimensions are 640 mm high, 510 mm wide, 290 mm deep — plan the gland plate and busbar clearance accordingly. Minimum clearance: 100 mm upward, 75 mm downward, 5 mm at the sides.
Protection and control features
Built-in motor overload protection and intrinsic device protection (thyristor overtemperature, phase imbalance, etc.). Adjustable current limitation lets you set the start current between 8% and the rated current. External reset input allows remote fault clearing. Display for fault signals on the unit. Includes a motor brake output component — the unit can control a DC injection brake or mechanical brake coil directly. Maximum motor cable length is 500 m.