The Siemens 3RW4423-3BC45 is a SIRIUS-brand soft starter, designed to ramp motor loads up gradually rather than slamming them across the line. It carries a rated current of 62 A at 40 °C, derating to 55 A at 50 °C and 50 A at 60 °C, so the real-world capacity depends on your enclosure's internal temperature. The insulation voltage is rated 690 V, and it operates on 50 or 60 Hz supplies at 230 V control voltage.
The 62 A rating at 40 °C is the headline number, but the derating curve tells the real story: at 50 °C it drops to 55 A, and at 60 °C to 50 A. If your panel runs hot, size up or plan for forced ventilation. The minimum load of 8 % means it won't reliably start a motor drawing less than about 5 A — small pumps or fans may need a different starting method. Pollution degree 3 per IEC 60947-4-2 means the unit tolerates conductive pollution and occasional condensation — typical for industrial control panels not in a climate-controlled room. The integrated bypass contact system shunts the thyristors after start, eliminating heat-sink losses during run; the inside-delta circuit allows a six-wire motor connection that reduces the starter's per-phase current draw by about 42 % compared to standard-in-line wiring.
Where this class of part is used
Soft starters like this one go into motor control centers and individual motor starters for pumps, conveyors, compressors, and fans where a reduced-voltage start protects the driven load and the supply network from mechanical shock and voltage dips. The 3RW4423-3BC45 is a panel-mount unit with screw fixing, sized for a standard enclosure backplate.
Dimensions are 170 mm wide, 192 mm high, 270 mm deep. Clearance requirements: 100 mm above, 75 mm below, 5 mm at the sides. Main circuit connections use box terminals; the auxiliary and control circuit uses spring-loaded terminals. Stranded wire capacity on the main terminals is 2x (4 to 50 mm²).