The Siemens 5SL3640-7MB is a SENTRON miniature circuit breaker (MCB) with a C tripping characteristic, rated 40 A at 400 V AC, and a 4.5 kA breaking capacity per EN 60898 and IEC 60947-2. This 3P+N (4-pole) unit switches the neutral conductor, which is useful for final circuits where isolating all live conductors is required. The 4.5 kA breaking capacity covers most residential and light commercial distribution board faults; if your available fault current exceeds that, you step up to the 6 kA or 10 kA 5SL variants.
This MCB occupies 4 modular width units (MW) on a DIN rail — 72 mm wide, 90 mm tall, 76 mm deep, with a 70 mm installation depth behind the panel. The sealable design allows panel builders to lock the toggle position after commissioning, preventing unauthorized switching.