The Siemens 5SY4404-7CV is a 4-pole miniature circuit breaker (MCB) with a C-curve trip characteristic, rated 4 A. Its headline figure is a 15 kA breaking capacity (Icu) at 400 V AC — that means it can safely interrupt a fault current up to 15,000 amps without welding its contacts or failing catastrophically, which is the spec that determines whether this breaker coordinates with the upstream protective device in a panel.
The C-curve (4 A) means the magnetic trip activates at 5 to 10 times rated current — 20 to 40 A — so it tolerates the inrush of small motor loads, transformers, or lighting ballasts without nuisance tripping, while still clearing a hard short. The 4-pole configuration (all poles switched) is typical for three-phase plus neutral circuits in IEC distribution boards; the 15 kA Icu at 400 V AC is the maximum short-circuit current the breaker can interrupt once.
Panel integration
Snap-on DIN rail mount, standard 18 mm per pole width (72 mm total for 4P). Busbar comb compatible via the tunnel terminals. Fits alongside other 5SY series devices in a Siemens ALPHA or SIVACON distribution board without special adapters.