The Siemens 5SL4540-7 is a SENTRON miniature circuit breaker (MCB) with a 1-pole-plus-neutral (1P+N) design, rated 40 A at 230 V AC with a C-curve tripping characteristic.
Temperature derating — the real current rating changes with the panel environment
At 40 °C that drops to 36.96 A; at 45 °C it's 35.2 A; at 55 °C it's 31.85 A. The panel designer should size the load to the derated value at the expected internal temperature, not the 30 °C reference.
The 5SL4540-7 occupies 2 modular width units (36 mm) on a DIN rail, with a depth of 76 mm and an installation depth of 70 mm. It is sealable (e.g., with lead seals or adhesive labels) for tamper-evident installations.
DC rating and single-phase use
While primarily an AC breaker (230 V rated, 50/60 Hz), the 5SL4540-7 carries a DC rating up to 72 V maximum. That covers DC auxiliary circuits in a panel or small PV string combiner boxes, but the DC breaking capacity is not stated — the 10 kA figure applies to AC only. For single-phase AC operation the voltage limit rises to 250 V.