The 4.5 kA breaking capacity per EN 60898 covers standard domestic/commercial fault levels; the 6 kA rating per IEC 60947-2 gives headroom for industrial panel applications where prospective short-circuit current is higher. At 400 V AC this breaker handles a 40 A continuous load, so it's sized for branch circuits feeding a 9–10 kW resistive load or a 7.5 kW motor with proper coordination. For DC circuits, the 5SY3140-7 is rated 72 V DC maximum with a 15 kA breaking capacity per IEC 60947-2 — that's a solid DC rating for control power supplies or DC bus protection in a 48–60 V system. The UL 1077 / CSA C22.2 No.235 supplementary protector rating at 5 kA (AC) means it's accepted as a supplementary protector in North American panels, though not a branch-circuit rated device per UL 489.
At 18 mm wide (1 width unit), 90 mm tall, and 76 mm deep (70 mm installation depth), this breaker occupies one standard DIN-rail slot. The combined top and bottom terminals accept 0.75–35 mm² solid or stranded wire — that's up to a 2 AWG conductor, so it handles the full 40 A with no terminal derating.