The Siemens 3RW4426-1BC45 is a SIRIUS-brand soft starter, rated 133 A at 40 °C (derated to 118 A at 50 °C and 102 A at 60 °C), with an insulation voltage of 690 V and operating frequency of 50 to 60 Hz. It includes an integrated bypass contact system and supports inside-delta wiring. The thyristor-based ramp-up and adjustable current limitation let you tune the starting torque to the load — pumps, fans, conveyors — without the mechanical shock of a direct-on-line start. Minimum load is 8% of the rated current, so it handles lightly loaded motors without nuisance tripping.
Fastening is screw fixing; the unit measures 192 mm high, 170 mm wide, and 270 mm deep. Clearances: 100 mm above, 75 mm below, 5 mm at the sides. Storage temperature -25 to +80 °C; during operation the ambient limit is 60 °C, with derating starting at 40 °C.
Main current circuit uses box terminals accepting stranded 2x (4 to 50 mm²) and solid 2x (0.5 to 2.5 mm²). The back and front clamping points each accept 10 to 2/0 AWG. Auxiliary and control circuits use screw-type terminals for 2x (20 to 14 AWG). Maximum wire length to the motor is 500 m — enough for remote pumps but watch voltage drop at full load.
Protection and diagnostics
Motor overload protection and intrinsic device protection are built in — no separate overload relay needed in most installations. An external reset input and a display for fault signals speed up troubleshooting on the line. The integrated bypass contact system also reduces heat dissipation in the panel after the motor reaches full speed.