Current derating and thermal budget
The 3RW4426-1BC44: The derating temperature threshold is 40 °C; above that, the thyristor stack and integrated bypass contact system share the thermal load, but the bypass carries the steady-state current once the motor is up to speed. Minimum load is 8 % of the rated current — below that the soft starter may not reliably detect the motor current zero-cross for thyristor gating, so verify the no-load current of the driven motor stays above that floor.
Wiring and termination
Main power circuit uses box terminals accepting 2x (4 … 50 mm²) stranded or 2x (10 … 1/0 AWG) using both clamping points; the front and back clamping points each accept 10 … 2/0 AWG. Maximum motor cable length is 500 m — longer runs increase charging current and may cause nuisance overcurrent trips during start.
Mounting and clearance
Dimensions are 192 mm high, 170 mm wide, 270 mm deep. Fastening is screw fixing to the mounting surface. The mounting position allows vertical surface mounting with ±90° rotation and ±22.5° tilt front-to-back. Clearance requirements: 100 mm upwards, 75 mm downwards, 5 mm at the sides — the upward clearance is critical for convection cooling of the thyristor heatsink.
Inside-delta and adjustable current limit
Inside-delta circuit connection is supported — this reduces the soft starter current rating requirement to 58 % of the motor full-load current, allowing a smaller unit for delta-connected motors. Adjustable current limitation lets the user set the start current between the minimum load threshold and the device rated current, which is useful for limiting supply voltage dip during acceleration of high-inertia loads.