What this 125 A C-curve MCB does in the panel
The Siemens 5SP5292-7 is a 2-pole SENTRON miniature circuit breaker rated 125 A at 400 V AC with a C tripping characteristic — meaning it trips between 5 and 10 times rated current, which is the standard choice for motor circuits, transformers, and capacitive loads where inrush is higher than a B-curve would tolerate. On the DC side it breaks 10 kA per EN 60898-2 and 15 kA per IEC 60947-2, so it handles the fault energy on a 440 V DC bus without cascading upstream. The 2-pole form factor (3 width units, 54 mm wide) snaps onto standard mounting rail or accepts screw fixing, and the IP20 rating with connected conductors means it's protected against finger contact once wired — standard for enclosed distribution boards.
Mounting and integration notes
Mounts in any position on standard mounting rail or with screw fixing. Installation depth is 70 mm; the breaker body is 76 mm deep, 54 mm wide, 90 mm tall. Tunnel terminals top and bottom accept the conductors. The part is halogen-free and silicon-free — relevant if the panel is in a clean-air or corrosive environment like a pulp mill wet-end or chemical dosing area. Sealable design allows the panel builder to lock the toggle position after commissioning.
What the ratings mean for fit
The 125 A rating at 400 V AC is the headline number for panel builders sizing feeder breakers. The C-curve (5–10× In) means it will hold through the inrush of a 125 A motor or transformer bank without nuisance tripping, but still clears a short-circuit fast enough to protect downstream cable. On the DC side, the 10 kA (EN 60898-2) and 15 kA (IEC 60947-2) ratings cover most industrial DC bus applications up to 440 V — common in drive DC links or battery backup circuits. The 20 000 mechanical switching cycles typical service life is adequate for a distribution breaker that operates infrequently; this is not a daily-switched load-break device.