The 3RW4426-1BC34: That 40 °C figure is the baseline — if your panel ambient runs hotter, the continuous current ceiling drops by about 11 % per 10 °C rise. For a motor with a 125 A FLA, this starter has headroom at 40 °C but gets tight at 50 °C unless the load is intermittent. The operating frequency is 50/60 Hz, so it works on either line frequency without adjustment.
Integrated bypass and inside-delta wiring
This soft starter includes an integrated bypass contact system, meaning the thyristors are shorted out once the motor is up to speed. That eliminates continuous heat dissipation in the power semiconductors during run — the bypass carries the full load current, not the SCRs. It supports inside-delta circuit configuration, which lets you connect the soft starter in the delta leg of a six-lead motor. Inside-delta wiring reduces the current through the starter to 58 % of the line current, effectively extending the current range of the unit for a given motor FLA.
Protection and control features
Motor overload protection is built in, along with intrinsic device protection that guards the thyristors against overtemperature and phase imbalance. Adjustable current limitation lets you set the starting current between 0 and the rated value — useful for limiting inrush on weak supply lines or for gentle starts on conveyors. The minimum load threshold is 8 % of the rated current, so it can start lightly loaded motors without dropping out. External reset input is provided for remote fault recovery, and the display shows fault codes directly on the unit.
Mounting and panel integration
Dimensions are 170 mm wide, 192 mm high, and 270 mm deep. Mounting position allows vertical surface with +/-90° rotation and +/-22.5° tilt front-to-back, giving flexibility in tight cabinets. Clearance requirements: 100 mm above, 75 mm below, and 5 mm at the sides. The side clearance is minimal, but the vertical clearance is substantial — plan for it in the cabinet layout to maintain airflow for the derating curve. Main circuit terminals are box terminals accepting 2x (4... 50 mm²) stranded or 2x (10... 1/0) AWG using both clamping points. Maximum wire length to the motor is 500 m — beyond that, voltage drop and cable capacitance may affect operation.
Environmental and compliance ratings
Pollution degree 3 per IEC 60947-4-2, meaning it's rated for conductive pollution environments typical in industrial panels. Operating temperature range is up to 60 °C ambient; storage range is -25 to +80 °C.