954 A at 40 °C — motor sizing anchor
The 3RW4453-6BC45 is rated 954 A at 40 °C ambient. Derating starts above 40 °C, so if your enclosure runs hot, size on the 50 °C or 60 °C column, not the 40 °C figure. Insulation voltage is 690 V rated, covering 400 V, 480 V, and 690 V line-to-line systems. Operating frequency is 50/60 Hz — one unit handles both, no separate variant for 60 Hz markets.
Integrated bypass and inside-delta — panel space savings
This soft starter has an integrated bypass contact system. That means once the motor reaches full speed, the thyristors are shorted out — no external bypass contactor to wire in, no extra heat dissipation from the SCRs during run. The inside-delta circuit reduces the current through each thyristor by about 42% compared to standard in-line connection, so for a given motor current the unit can be smaller than an equivalent in-line soft starter.
Wiring and connection — main and control circuits
Main current circuit connects via busbar — typical for this current class. Acceptable cable sizes: stranded 70-240 mm², finely stranded 50-240 mm², or AWG 2/0-500 kcmil. For auxiliary and control circuits, screw-type terminals accepting solid 0.5-2.5 mm² or 20-14 AWG. Maximum motor cable length is 500 m — beyond that, voltage drop and reflected wave issues may require output reactors. The unit includes a display for fault signals and supports external reset, so you can clear faults remotely without opening the panel door.
Protection and diagnostics — built-in, no add-ons needed
Motor overload protection is integrated — no separate overload relay required. Intrinsic device protection covers overtemperature, overcurrent, and phase-loss on the thyristor stack. Adjustable current limitation lets you set the start current between the minimum load of 8% and the unit's rated current, protecting both motor and driven load during ramp-up. The unit includes a motor brake output — useful for holding loads at standstill without a separate brake contactor. Pollution degree 3 per IEC 60947-4-2 means it's rated for industrial environments with conductive dust or occasional condensation — no derating needed for typical factory floor conditions.