The S803S-B50 is a 3-pole miniature circuit breaker (MCB) rated 50 A continuous with a B trip curve, meaning it trips at 3–5× rated current for short-circuit protection.
The 3-pole format covers three-phase loads (L1–L2–L3) or three independent single-phase circuits sharing a common trip. Rated 230/400 VAC — line-to-neutral or line-to-line in a 400 V three-phase system. Keep the 50 A continuous rating in mind when sizing upstream protective devices and conductor cross-section; the B curve's magnetic trip threshold (150–250 A) means it coordinates well with downstream C-curve MCBs on motor-starting branches where you want selectivity.