What it is and what it does
The Siemens SENTRON 5SL6540-7 is a 1P+N miniature circuit breaker (MCB) with a C tripping characteristic, rated 40 A at 230 V AC and a 6 kA breaking capacity per EN 60898. It switches the neutral conductor along with the line, so it's a single-module-width (2 MW) unit that fits standard DIN-rail distribution boards in residential and light commercial infrastructure.
What the ratings mean for fit
The C-curve means the magnetic trip activates at 5–10× rated current — designed for loads with moderate inrush like small motors, fluorescent lighting banks, or transformer-coupled circuits. At 40 A and 6 kA SCCR, it handles typical residential and light commercial fault levels; the same 6 kA rating applies under IEC 60947-2 for industrial panel applications where the standard demands it. Thermal derating is published: full 40 A at 30 °C ambient, 37.57 A at 40 °C, 36.8 A at 45 °C, and 33.61 A at 55 °C (–). If your panel ambient runs above 30 °C, size the upstream protection for the derated figure — the breaker will hold at its published curve, not the nameplate 40 A. Mechanical service life is 10,000 switching cycles — fine for a distribution board where the breaker is rarely operated, but not rated for frequent switching duty like a motor-disconnect application.
Panel fit and mounting
Width is 36 mm (2 modular units), depth 76 mm, height 90 mm, installation depth 70 mm. Snaps onto standard 35 mm DIN rail; mounting position is unrestricted. The housing is halogen-free and silicon-free — relevant for panels in clean-room or semiconductor-adjacent environments where outgassing is a concern. IP20 with connected conductors — protected against finger contact but not water ingress; install inside a sealed enclosure if washdown or outdoor exposure is expected. Overvoltage category III and pollution degree 2 cover fixed-installation distribution panels.