The Siemens 3RW4457-6BC44 is a SIRIUS soft starter rated 1524 A at 40 °C, derating to 1351 A at 50 °C and 1200 A at 60 °C. That 1524 A figure is the current it can handle continuously through the thyristor stack at a 40 °C ambient — above that, you need to derate by roughly 10 A per degree. The integrated bypass contact system means the thyristors are shorted out once the motor is up to speed, so the bypass contactors carry the full load current and the thyristors only see the start transient. This keeps the thermal stress on the thyristors low and extends service life in high-duty-cycle applications. Insulation voltage is rated 690 V, operating frequency 50 to 60 Hz. Motor overload protection is built in, and adjustable current limitation sets start current from 8% to full rated current. The inside-delta circuit configuration is worth noting: this starter can be wired in the delta legs of a six-lead motor, which reduces the current the starter sees to 58% of the line current. That means a 1524 A starter in inside-delta can handle a motor with a line current up to about 2628 A — a significant cost saving on larger drives. The external reset and display for fault signals simplify troubleshooting on the line.
Fastening is screw fixing. The main current circuit connects via busbar; auxiliary and control circuits use screw-type terminals accepting 2x (0.5 to 2.5 mm²) solid or 2x (20 to 14 AWG) for auxiliary contacts. Power wiring accepts stranded 70 to 240 mm² or finely stranded 50 to 240 mm², and for North American practice, 2/0 to 500 kcmil. Dimensions: 640 mm height, 510 mm width, 290 mm depth. Clearance requirements: 100 mm upwards, 75 mm downwards, 5 mm at the sides. The wire length maximum of 500 m from starter to motor should be respected to avoid voltage drop issues during the start ramp. Storage temperature range -25 to +80 °C; during operation the ambient limit is 60 °C with derating starting at 40 °C. The product component includes a motor brake output, which is useful for applications requiring controlled stopping.