Siemens 3RW3047-1BB14 SIRIUS soft starter — field-fit and ratings
The Siemens 3RW3047-1BB14 is a SIRIUS soft starter in size S3, built for reduced-voltage starting of three-phase induction motors. It's rated 106 A at 40 °C, derating to 98 A at 50 °C and 90 A at 60 °C — so at line temperature you lose about 8 A per 10 °C rise above 40. That matters when you're stuffing this into a warm panel next to a contactor and a drive. Control supply is 110 to 230 VDC, so it works off a standard DC bus or a separate power supply. The main circuit lands on screw-type terminals accepting 2x (10 to 70 mm²) stranded or 2x (7 to 1/0 AWG) — no special crimp tool needed, just a decent screwdriver. Auxiliary terminals take 2x (20 to 14 AWG). The body is 70 mm wide, 170 mm tall, 190 mm deep — fits a standard 70 mm wide modular slot. Clearance: 60 mm upward, 40 mm downward, 30 mm at the sides for ventilation. Pollution degree 3 (conductive pollution, typical for industrial control panels) per IEC 60947-4-2.
The minimum load is 10 % of the rated current. The thyristor stack is rated for 50/60 Hz line frequency. Maximum motor cable length is 300 m — beyond that you risk reflected-wave spikes on the output. No external reset, no display for fault signals beyond a red LED.