The 5SY4320-8CV is a 3-pole miniature circuit breaker with a D20 trip curve and a rated ultimate breaking capacity (Icu) of 15 kA at 400 VAC. It's a current-production part, so no last-time-buy scramble yet.
Deployment context
The 3-pole format covers three-phase motor circuits or three-phase distribution feeders. The D20 rating (20 A thermal-magnetic, D curve) is sized for moderate motor loads — think small conveyors, pumps, or compressors where the start current hits 10–14× full load for a few cycles.