The 1N6155A: The 27.4V reverse standoff means it sits across a nominal 24V bus and stays off until a surge pushes it into breakdown at 34.2V min. Bidirectional construction (single channel) lets it clamp both polarities, so it handles AC-coupled transients or bipolar supplies without a series diode. Through-hole axial package (B, Axial) is straightforward to hand-solder or wave-solder into a board or terminal block — no reflow profile to manage.
At the 30.1A peak pulse current the clamp voltage hits 49.9V max. That means a 24V rail (nominal) sees a transient clamped to under 50V, which is safe for most 60V-rated downstream components. The 34.2V min breakdown gives a 7V margin above the 27.4V standoff — enough to avoid nuisance triggering from normal ripple or load dump. No power line protection (the part is not designed for AC mains) — it is a secondary-side transient suppressor for DC buses, signal lines, or low-voltage power inputs. The 30.1A peak current at 10/1000µs is the rated surge; derate for shorter pulses per the datasheet curve.
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Base product number 1N6155 covers the family variants; the 'A' suffix indicates a tighter breakdown tolerance. Package is bulk (tube or loose) in the axial format — no tape-and-reel option listed, so expect hand-loading for through-hole assembly. The B, Axial package case is a standard DO-201 outline; the lead diameter and body length match common through-hole TVS footprints.