What this SIRIUS soft starter delivers
The Siemens 3RW4076-2BB44 is a SIRIUS S12 soft starter rated 432 A at 40 °C, 385 A at 50 °C, and 335 A at 60 °C — so the 40 °C figure is the one to size against unless your panel runs hot. It includes an integrated bypass contact system, which means once the motor is up to speed, the thyristors are shorted out and heat dissipation drops to near zero — a real help in a crowded enclosure. The control supply is 230 V at both 50 Hz and 60 Hz, and the operating frequency range is 50 to 60 Hz. Motor overload protection and intrinsic device protection are built in, and the current limitation is adjustable down to 20% of the rated motor current.
This is a screw-fixed unit, size S12, measuring 230 mm high, 160 mm wide, and 278 mm deep — plan the gland plate and backpanel real estate accordingly. Clearance requirements: 100 mm above, 75 mm below, and 5 mm at the sides for airflow. The main circuit uses busbar connection; the stranded cable range is 70 to 240 mm², finely stranded 50 to 240 mm², and the front clamping point accepts 3/0 to 600 kcmil. Solid conductors for control wiring are 2x 0.25 to 1.5 mm².
Operating temperature range is -25 to +60 °C, storage -40 to +80 °C, with derating starting at 40 °C. Insulation voltage rated at 600 V.