What this SIRIUS soft starter delivers
The unit works on 50 or 60 Hz supplies at 115 V control voltage. An integrated bypass contact system means the thyristors are shorted out once the motor is at speed, dropping heat dissipation in the enclosure and improving overall efficiency. For applications needing a tighter footprint, the 3RW4453-2BC36 supports inside-delta wiring, which lets the starter handle a given motor current with lower-rated thyristors — a common trick on larger frames. Mounting is screw-fixed with a vertical surface orientation, rotatable ±90° or tiltable ±22.5° front/back. Clearance requirements are 100 mm upward, 75 mm downward, and 5 mm at the sides — tight enough for most MCC buckets.
Current derating and real-world fit
The 954 A rating at 40 °C drops to 856 A at 50 °C and 759 A at 60 °C. Minimum load is 8 % of rated current, so it handles lightly loaded motors or soft-start-only applications without nuisance tripping. Adjustable current limitation is built in, along with motor overload protection and intrinsic device protection (thyristor overtemperature, phase loss).
Wiring and connection details
Main current circuit connections use busbar connection. Stranded cable range is 70 to 240 mm²; finely stranded accepts 50 to 240 mm². For North American builds, the main contacts accept 2/0 to 500 kcmil. Auxiliary and control circuits terminate on spring-loaded terminals accepting 2x (0.25 to 1.5 mm²) solid or 2x (24 to 16 AWG). Maximum wire length from starter to motor is 500 m.