The Siemens 5SL6640-6 is a 4-pole (3P+N) SENTRON miniature circuit breaker from the 5SL6 series, rated 40 A with a B tripping characteristic.
The 5SL6640-6 occupies 4 width units (72 mm) on a DIN rail, with a depth of 76 mm and an installation depth of 70 mm. Terminals accept solid or stranded conductors from 0.75 to 25 mm², with a tightening torque of 2.5 to 3 N·m. The neutral pole is switched (3P+N), and the unit is sealable — useful for installations requiring tamper-proofing after commissioning.