The Siemens 5SL6340-8CC is a SENTRON 3-pole miniature circuit breaker with a D tripping characteristic, rated 40 A at 400 V AC and a breaking capacity of 6 kA per EN 60898. The D-curve means it's built for loads with high inrush currents — motor starters, transformers, welding equipment — where the magnetic trip holds off long enough to let the start surge pass without nuisance tripping. At 40 A and 3 poles, it covers a 3-phase motor circuit or a distribution subfeed where the upstream breaker is already coordinated.
Rated current and thermal derating
The 40 A rating holds at 30 °C ambient. At 40 °C it derates to 37.72 A, at 45 °C to 36.53 A, at 50 °C to 35.3 A, and at 55 °C to 34.02 A. If the panel runs warm — say, a crowded enclosure with drives — the 40 A frame may need to be bumped to the next size up to stay within the thermal curve. Power loss per pole is 4.8 W at rated current in hot operating state, so three poles together dump about 14.4 W into the enclosure; factor that into the thermal budget.
Mechanical fit and environment
Three modular width units wide (54 mm), 76 mm deep, 90 mm tall, with an installation depth of 70 mm. It snaps onto standard DIN rail and can be mounted in any position. The IP20 rating with connected conductors is typical for enclosed panel mount — it's not a standalone outdoor breaker. Vibration resistance is 50 m/s² at 25 to 150 Hz per IEC 60068-2-6, so it holds up on machine-mounted subpanels near rotating equipment. The housing is halogen-free and silicon-free, which matters for clean-room or corrosive-environment installs.
Standards and approvals
Rated per EN 60898 for the 6 kA breaking capacity at 400 V AC. Overvoltage category III, pollution degree 2 — standard for fixed-installation distribution boards. The operating voltage is AC only, 50/60 Hz, with a maximum of 440 V for multi-phase operation. DC rating is limited to 72 V maximum, so it's not a DC distribution breaker. The product designation follows EN 61346-2 and IEC 81346-2 as function letter F.