The 5SL6204-7YA: The C-curve (5–10× In) means it's designed for moderate inrush loads — think small motors, transformers, or lighting banks — where the magnetic trip won't nuisance-trip on startup but still clears fast on a hard fault. The 4 A rating governs the continuous load the breaker can carry; size it for the branch circuit's full-load current, not the wire ampacity.
Deployment context
The 2-pole format handles single-phase 230 V line-and-neutral or two legs of a three-phase system for 400 V line-to-line applications where the voltage stays within the 230 V rating (phase-to-neutral).