Rated current and thermal derating
The 3RW4426-3BC46: This derating curve is the primary selection gate — a 40 °C panel environment buys the full 133 A, but a 50 °C enclosure drops available current by over 11 %. The 8 % minimum load setting means it handles lightly loaded motors without tripping on undercurrent.
Integrated bypass and inside-delta wiring
An integrated bypass contact system and thyristor stack mean the soft starter runs the motor through the SCRs only during start and stop; once at speed, the bypass closes and the SCRs cool. This reduces heat dissipation in the enclosure and extends thyristor life. The inside-delta circuit option allows wiring the soft starter in the motor delta loop, reducing the unit's current rating requirement by about 42 % compared to in-line connection — a common trick for larger motors where panel space is tight.
Mounting, clearances, and terminations
Screw fixing to a vertical mounting surface; the unit can be rotated ±90° or tilted ±22.5° front-to-back. Minimum clearance: 100 mm above, 75 mm below, 5 mm at the sides. The 270 mm depth and 170 mm width fit a standard 600 mm deep enclosure with room for gland plates.
Protection and control features
Motor overload protection and intrinsic device protection are built in — no separate overload relay needed for most applications. Adjustable current limitation lets you set the start current between the minimum load threshold and the unit's rated maximum. External reset supports remote restart after a fault. The display shows fault codes, which speeds troubleshooting on the line.