Soft starter for heavy motor loads
The Siemens 3RW4458-2BC45 is a SIRIUS soft starter rated 1680 A at 40 °C, dropping to 1472 A at 50 °C and 1316 A at 60 °C — so it handles a 1680 A motor start at a 40 °C ambient, but you need to derate if the panel runs hotter. Insulation voltage is 690 V, operating frequency 50 to 60 Hz, with a minimum load of 8% of the rated current, meaning it won't soft-start a motor that's too small for its range.
Inside-delta wiring and bypass
This unit supports inside-delta circuit connection, which lets you wire the soft starter in the delta leg of a six-lead motor — that reduces the current the soft starter sees to 58% of the line current, so you can size the unit smaller for a given motor. It also has an integrated bypass contact system, so after the motor reaches full speed, the bypass contacts close and the thyristors are taken out of circuit — no heat dissipation from the power semiconductors during run, which keeps the enclosure cooler and extends thyristor life. The main current circuit uses busbar connection; the auxiliary and control circuit uses spring-loaded terminals, which is faster to wire than screw clamps and doesn't loosen under vibration.
Clearances: 100 mm upwards, 75 mm downwards, 5 mm at the side. Dimensions are 510 mm wide by 640 mm high by 290 mm deep — it's a large unit, so check the backpanel space before cutting the gland plate. Stranded cable goes 70 to 240 mm²; finely stranded 50 to 240 mm²; for main contacts it also accepts 2/0 to 500 kcmil. Solid wire is 2x (0.25 to 1.5 mm²) for the auxiliary contacts only.
Protection and control features
Motor overload protection is built in, along with intrinsic device protection — it monitors the thyristor junction temperature and shuts down before the semiconductors overheat. Adjustable current limitation lets you set the start current between 8% and the full rated current, which is useful for limiting inrush on weak lines or soft-load conveyors. External reset is supported, so you can wire a remote reset button to clear a fault without opening the panel door. A display shows the fault signal, which speeds up diagnostics on the floor. There's also a motor brake output component, so it can control a DC injection brake if the motor is equipped.
This is a current-production part in the SIRIUS family — no obsolescence notice on record. For volume or BOM-freeze purchases, submit an RFQ and we'll pull the latest factory lead time and price.