The Siemens SENTRON 5SP4392-6 is a 3-pole miniature circuit breaker rated 125 A with B-curve tripping characteristic, breaking 10 kA per EN 60898 at 400 V AC. This is the part for a 3-phase 125 A feeder where the upstream fault level stays under 10 kA — the B curve means it trips at 3 to 5 times rated current, so it suits resistive or general-purpose loads where inrush is moderate. Installation depth is 70 mm; overall depth 76 mm, width 81 mm (4.5 modular width units).
The B-curve (3-5× In) provides fast response to short circuits while tolerating the modest inrush of resistive loads, lighting, or small transformers. Rated 400 V AC at 50/60 Hz, 3-pole configuration, so it switches all three phases simultaneously — critical for a 3-phase panel where single-pole interruption could cause single-phasing on a motor load.
Fastens via DIN rail or screw fixing — the DIN rail is the standard for panel builders; the screw option helps in retrofit enclosures without a DIN rail. Mounting position any, so vertical or horizontal orientation in the panel is acceptable. The 4.5 modular width units (81 mm) occupy the space of 4.5 standard 18 mm-wide module positions on the rail. Sealable — a lead seal can be fitted to the toggle to lock the breaker in the ON or OFF position for lockout/tagout compliance. IP20 with connected conductors, IP40 in the handle area with a distribution cover — not a washdown rating, but suitable for dry indoor panels.
Shock resistance 150 m/s² at 11 ms half-sine per IEC 60068-2-27; vibration resistance 50 m/s² at 25 to 150 Hz and 60 m/s² at 35 Hz per IEC 60068-2-6 — the breaker holds its calibration under typical industrial vibration.