What this SIRIUS soft starter delivers
The Siemens 3RW4447-6BC44 is a SIRIUS-brand soft starter rated 748 A at 40 °C, derating to 667 A at 50 °C and 580 A at 60 °C. At 690 V insulation voltage and 50/60 Hz, it uses thyristors to ramp motor voltage, with adjustable current limitation and integrated motor overload protection. The 8% minimum load setting means it can handle lightly loaded motors without dropping out — useful for pumps or conveyors that start near-empty.
Fastened by screw fixing to a vertical mounting surface, the unit is rotatable ±90° and tiltable ±22.5° front-to-back. Clearance requirements: 100 mm upwards, 75 mm downwards, 5 mm at the sides. Main current circuit uses busbar connection; main contact wire range is 2/0 to 500 kcmil, with both clamping points accepting 2x 2/0 to 2x 500 kcmil. Stranded cable: 70–240 mm²; finely stranded: 50–240 mm². Auxiliary contacts accept 2x (0.5–2.5 mm²) solid or 2x (20–14) AWG. Max wire length to motor: 500 m. Pollution degree 3 per IEC 60947-4-2 — suitable for industrial enclosures with conductive dust.
Inside-delta circuit and external reset
Supports inside-delta circuit wiring, which reduces the current through the soft starter to 58% of line current — useful for larger motors where the starter's amp rating becomes the constraint. External reset input allows remote fault recovery without opening the panel door. Fault signal shown on the built-in display. Intrinsic device protection guards the thyristors against over-temperature and short-duration overcurrent.