81 A at 40 °C — derating governs the real load
The 3RW4424-1BC45: That derating curve is the first check when sizing for a motor load in a warm enclosure — the 81 A figure is the ceiling at 40 °C, not a blanket rating. The integrated bypass contact system switches the thyristors out after start, eliminating semiconductor conduction losses during run — that's the efficiency advantage over a non-bypassed soft starter.
Current limitation and motor protection — adjustable, not fixed
Adjustable current limitation lets you set the start current between 8 % and roughly 400 % of the motor FLA — the 8 % minimum load means it handles lightly loaded motors without dropping out. Motor overload protection and intrinsic device protection are built in, so you don't need a separate overload relay in most installations. The inside-delta circuit option reduces line current by about 42 % compared to standard in-line connection — useful when retrofitting into an existing starter panel where the supply cable or contactor is already sized for a lower current. Maximum motor cable length is 500 m — beyond that, reflected-wave overvoltage can stress the motor winding insulation. For longer runs, an output dV/dt filter should be considered.
Mounting, clearance, and terminal wiring
Dimensions are 170 mm wide, 192 mm high, 270 mm deep. Screw fixing to a vertical mounting surface; the unit can be rotated ±90° or tilted ±22.5° front/back, giving flexibility in tight cabinets. Required clearances: 100 mm above, 75 mm below, 5 mm at the sides — the vertical gap is for thyristor heat dissipation; skimping on it derates the unit below the 40 °C curve. Power circuit uses box terminals accepting 2x (4–50 mm²) stranded or 2x (10–1/0 AWG) using both clamping points. Pollution degree 3 means it's rated for conductive-dust environments — typical in cement plants, sawmills, and similar heavy-industrial settings.