What this 4-pole B-curve 6 A MCB is for
The Siemens SENTRON 5SY5406-6 is a 4-pole miniature circuit breaker rated 6 A with a B tripping characteristic, breaking 10 kA per EN 60898 at 400 V AC. The 4-pole version (4P) switches all four conductors, so it fits three-phase plus neutral applications in distribution boards or sub-panels. Rated 880 V DC as well, with a 10 kA DC breaking capacity per EN 60898-2, so it also covers DC combiner boxes or battery circuits.
At 72 mm wide (4 width units of 18 mm), it occupies four adjacent slots in a standard distribution board. Mount in any position; ambient range -40 to +70 °C, storage down to -75 °C.
The 10 kA breaking capacity at 400 V AC (per EN 60898) tells you this MCB can safely interrupt a fault current up to 10,000 A without welding its contacts or exploding — standard for most commercial and light industrial distribution boards where the prospective short-circuit current stays under that threshold. The B-curve (3-5× In) avoids nuisance tripping on resistive loads but will trip fast on a hard short. Energy limiting class 3 means it restricts let-through energy well, protecting downstream equipment.