SENTRON 5SY6340-8 — D-curve 40 A, 3-pole MCB for industrial branch circuits
Siemens SENTRON 5SY6 series miniature circuit breaker, D tripping characteristic, rated 40 A at 400 V AC, 3 poles. Occupies 3 width units (54 mm) on DIN rail. At DC, the IEC 60947-2 rating reaches 15 kA at 72 V. For UL 1077 / CSA C22.2 No. 235 applications, the interrupting rating is 5 kA. That spread means the same part covers IEC panels and UL-recognized supplementary protection — one BOM line for both regimes.
D-curve selectivity and coordination in the panel
The D-curve holds magnetic trip to 10–20× rated current (400–800 A instantaneous). That delay lets downstream motor-starting inrush pass without clearing the branch. Upstream, a higher-rated SENTRON or SITOR fuse must coordinate for full selectivity — typical rule: upstream device rated ≥ 1.6× the 40 A for overload discrimination, and the instantaneous thresholds must not overlap. The IP20 rating (with conductors connected) means it belongs inside a closed enclosure, not in washdown or outdoor exposure.
Mechanical integration — DIN rail, 3 MW, any position
Any mounting position is permitted — horizontal, vertical, or inverted — no derating required for orientation. The 54 mm width (3 module widths) matches the standard 18 mm/module grid; adjacent breakers or accessories (shunt trip, auxiliary switch) occupy adjacent slots without special spacing. Installation depth is 70 mm to the DIN rail surface; overall depth 76 mm includes the toggle and terminal screws. Ambient temperature range -40 °C to 75 °C, with derating for humidity: max 95% RH at 55 °C, 55% at 70 °C, 35% at 75 °C. That covers cold storage, unheated enclosures, and transformer cabinets.