What this MCB is and where it fits
The Siemens 5SL3140-7CC is a 1-pole miniature circuit breaker with a C-trip curve, rated 40 A at 230/400 V AC with a 4.5 kA breaking capacity. It snaps onto a standard DIN rail inside a distribution board or control panel — the same footprint as any 1-pole MCB in the 5SL series, so it drops into an existing rail without re-spacing. The C-curve means it trips between 5 and 10 times rated current, which suits moderate inrush loads like small motor starters, lighting banks, or transformer primaries. At 40 A it handles a 9 kW resistive load on a 230 V line or a 17 kW three-phase load when ganged across poles.
What the ratings mean for fit
The 4.5 kA breaking capacity at 400 V is the standard domestic and light-commercial SCCR for this class — it safely interrupts a fault current up to 4.5 kA without welding the contacts or cascading the fault upstream. That is adequate for most final sub-circuits in a TN or TT system; if your available fault current exceeds 4.5 kA, you need a higher-rated breaker (the 5SL series also offers 6 kA and 10 kA variants). The 230/400 V rating covers both single-pole-to-neutral (230 V) and single-pole-to-phase (400 V in a 3-phase system) applications. The 40 A rating is the continuous thermal current — do not load it above 40 A even if the fault rating looks generous.
Panel integration note
Mounts on a 35 mm DIN rail per EN 60715. The 1-pole width is 18 mm per module. Wire termination accepts up to 25 mm² conductor for the line and load sides — torque to 2.5 Nm per the terminal marking. No auxiliary contact slot on this base unit; add a separate 5ST3 auxiliary switch if remote status indication is needed.