What this soft starter does on the line
The Siemens 3RW4455-6BC45 is a SIRIUS soft starter rated 1200 A at 40 °C, sized for large motor loads in a 690 V insulation class system. It uses thyristors to ramp voltage during start, then the integrated bypass contact system takes over for full-speed running — which means the bypass carries the continuous current and the thyristors only dissipate heat during the start cycle, keeping the cabinet cooler and extending service life. The 690 V rated insulation voltage (acc. to IEC 60947-4-2, pollution degree 3) suits it for 400 V and 480 V distribution systems with headroom. The 8% minimum load setting means it can start lightly loaded motors without tripping on undercurrent. Adjustable current limitation is built in, and motor overload protection is integral, so no separate overload relay is needed for most installations.
Mounting and wiring realities for the panel
This unit is big — 640 mm high, 510 mm wide, 290 mm deep — and mounts via screw fixing. Keep 100 mm clearance upwards, 75 mm downwards, and 5 mm at the sides for airflow and cable bending radius. Main current circuit connection uses busbar connection. Main contact wire range accepts 2/0 to 500 kcmil.