What this 5SP3440-3 is
The Siemens 5SP3440-3 is a SENTRON main miniature circuit breaker (MCB) in a 4-pole (4P) configuration, rated 40 A at 30 °C and carrying a tripping characteristic E — a curve designed for protection of circuits with high inrush currents, such as motor starters or transformer primaries, where a standard B or C curve would nuisance-trip on startup. Its rated breaking capacity is 25 kA per EN 60898 at 400 V AC, with an insulation voltage of 690 V and overvoltage category IV — meaning it can safely interrupt fault currents up to 25 kA in a 400 V three-phase network, and is rated for the highest overvoltage stress at the service entrance.
Tripping characteristic E — what it means for your circuit
Characteristic E is the least common of the standard MCB curves, sitting between C (5–10× In) and D (10–20× In). It typically trips at 10–20× rated current, so a 40 A E-curve breaker will hold through the magnetizing inrush of a 30 kVA transformer or a large contactor coil pull-in, while still providing short-circuit protection. This makes the 5SP3440-3 a better fit for industrial sub-distribution or infrastructure panels than for general-purpose socket circuits — the E curve avoids nuisance trips on motorized loads that a C-curve might not handle.
Mounting and environment
Snap-on mounting on standard 35 mm DIN rail (EN 60715). The 4-pole body occupies 6 modular width units (MW). Conductor cross-section: solid or stranded from 2.5 mm² up to 50 mm², with saddle terminals and infeed at box terminal — so it accepts large incoming cables without piggyback lugs. IP40 with connected conductors, pollution degree 3 (industrial environment with conductive dust), shock resistance 30 g for 11 ms impacts. Ambient temperature range -40 °C to +70 °C, with derated current at elevated temperatures: 38 A at 40 °C, 36 A at 50 °C, 35 A at 55 °C.
Locking and sealing
Integrated locking slide accepts a padlock, wire seal, or cable ties — sealable for safety isolation verification. The part is also sealable per the spec, and the supply cord position is any (top or bottom feed).