1680 A at 40 °C — the current rating that drives the motor spec
The 3RW4458-2BC44: That 1680 A figure is the continuous motor full-load current the unit can start and run through the bypass — not a transient surge rating. With an integrated bypass contact system, the thyristors are shorted out once the motor reaches full speed, eliminating the heat load on the semiconductors during continuous running. This means the 1680 A rating is sustainable without external bypass contactors or additional panel cooling.
Inside-delta wiring and adjustable current limit — tuning for the supply
Inside-delta circuit connection is supported, which lets the soft starter handle a given motor current with lower-rated thyristors by connecting across the motor windings rather than in the supply lines. This is a panel-wiring decision, not a firmware setting — the motor leads must be brought back to the starter terminals. Adjustable current limitation lets you cap the starting inrush at a percentage of the motor FLA, useful when starting against a weak supply transformer or when the generator set has limited overload capacity. The minimum load threshold is 8 %, meaning the starter can reliably detect and control loads down to that level.
Motor overload and device protection — one unit, fewer relays
Motor overload protection is built in, along with intrinsic device protection that guards the thyristors against over-temperature and over-current. This reduces the component count in the motor control centre — no separate thermal overload relay or electronic motor protection relay needed for most applications. The external reset input and display for fault signals mean the starter can be integrated into a remote reset circuit and the fault code read locally without a separate HMI. Pollution degree 3 per IEC 60947-4-2 confirms the creepage distances are designed for conductive dust environments typical in cement, mining, and steel mills.
Mounting and panel integration — 640 x 510 x 290 mm, screw-fixed
The unit measures 640 mm high, 510 mm wide, and 290 mm deep, with screw fixing to the mounting surface. The mounting position allows vertical surface mounting with +/-90° rotation and +/-22.5° tilt forward/backward — useful when the panel layout forces an angled installation. Clearance requirements: 100 mm above, 75 mm below, and 5 mm at the sides for airflow and cable bending radius.
The SIRIUS brand is Siemens' flagship soft starter family, so the 3RW4458-2BC44 sits in a well-supported product line with ongoing firmware updates and accessory availability.