What this 748 A soft starter means for your line
The Siemens 3RW4447-2BC46 is a SIRIUS soft starter rated 748 A at 40 °C, 667 A at 50 °C, and 580 A at 60 °C — so at typical panel ambient you get the full 748 A, but if your enclosure runs hot you need to account for the derating curve. Insulation voltage is 690 V, operating frequency 50/60 Hz, and it uses thyristors for the ramp-down and current-limiting start, which means no mechanical contacts to weld on a stalled motor. It includes motor overload protection and adjustable current limitation, so you can set the start current to match the load without an external overload relay. The inside-delta circuit option lets you wire the soft starter inside the motor delta connection, reducing the current the device sees by a factor of 1.73 — useful for large motors where you want to spec a smaller frame.
Mounting and wiring — what fits in the panel
Dimensions are 230 mm high, 210 mm wide, 298 mm deep — that depth matters for shallow backpanels; allow 100 mm clearance above and 75 mm below for air circulation, and 5 mm at the sides. Main current circuit connections are busbar or cable: stranded 70–240 mm², finely stranded 50–240 mm², or kcmil 2/0–500 using both clamping points. The back clamping point takes 250–500 kcmil, the front takes 3/0–600 kcmil. Auxiliary contacts accept 24–16 AWG solid. Maximum wire length to the motor is 500 m — keep that in mind for remote installations.