1680 A at 40 °C — what that means for a motor line
The 3RW4458-2BC35 is a SIRIUS soft starter rated 1680 A at 40 °C in standard duty. That current rating drops to 1472 A at 50 °C and 1316 A at 60 °C, so the panel ambient temperature directly governs the motor current it can handle — if the enclosure runs hot, you lose headroom. The insulation voltage ceiling is 690 V, and it runs on 50 or 60 Hz supply. The integrated bypass contact system means the thyristors are shorted out once the motor is up to speed, cutting heat dissipation in the cabinet.
Inside-delta wiring and protection features
This unit supports inside-delta circuit wiring, which lets you use a smaller-rated soft starter for a given motor by connecting the thyristors in the delta legs rather than the line. The minimum load threshold is 8 % of the rated current — below that the starter may not detect the load correctly. Motor overload protection and intrinsic device protection are built in, with adjustable current limitation. An external reset input and a display for fault signals make commissioning and troubleshooting straightforward. The control and auxiliary wiring uses spring-loaded terminals; the main current circuit is busbar connection. Stranded cable from 70 to 240 mm² and finely stranded from 50 to 240 mm² are accepted on the power side, with a kcmil range of 2/0 to 500 for North American builds.
Mounting and panel fit
Clearance requirements: 100 mm upwards, 75 mm downwards, 5 mm at the sides. The pollution degree is 3 per IEC 60947-4-2, meaning it's rated for conductive pollution environments typical in industrial panels. Maximum motor cable length is 500 m — beyond that, reflected wave voltage spikes may stress the motor insulation. The operating temperature range is up to 60 °C during operation, with storage from -25 to +80 °C.