The Siemens 5SP3720-3 is a SENTRON main miniature circuit breaker (MCB), single-pole, with an E-trip characteristic. The E-curve (tripping between 10 and 20 times rated current) is a specialty curve for protecting transformers, power supplies, or long cable runs where inrush is higher than a standard C-curve handles. At 1.5 modular width units (roughly 27 mm), it's a bit wider than a standard 1-pole MCB — that extra space houses the higher arc-quenching chamber needed for the 25 kA rating. The enclosure is IP40 with conductors connected, meaning it's splash-proof in a closed panel but not washdown-rated.
The 690 V insulation voltage (Ui) and 6 kV surge voltage resistance give it headroom for transient-heavy environments like industrial supply panels. Saddle terminals and infeed-at-box-terminal design mean the line and load can land on the same side, simplifying busbar routing. The integrated locking slide accepts a padlock, wire seal, or cable tie for lockout/tagout compliance.
Mechanical and environmental
Rated for 20,000 mechanical operating cycles — that's typical for an MCB in distribution duty, not a switching contactor. Shock resistance of 30 g (11 ms half-sine, 3 impacts) and vibration resistance per IEC 60068-2-6 (2 g, 5–150 Hz sweep) mean it holds up in transport or seismic zones.