What this MCCB delivers on the line
The Siemens 3VA2340-6JQ32-0BH0 is a SENTRON molded case circuit breaker rated for 400 A continuous at 40–50 °C, with a 3-pole design and an adjustable trip unit spanning 80 A to 400 A full-scale. It carries a breaking capacity of 242 kA at 240 V and 187 kA at 415 V, so it handles high-fault scenarios without cascading upstream — a solid choice for main or large feeder breakers in industrial switchgear. This is a line-protection device, meaning it's designed to guard cables and busbars against overloads and short circuits, not motor protection — so don't spec it for direct motor starting duty. It ships with an undervoltage release (UVR) pre-installed and provisions for two auxiliary switches plus one trip alarm switch, which covers most panel interlocking and remote-status needs without adding external relays.
Temperature derating curve — the real-world current rating
The 400 A rating holds flat from 40 °C up to 50 °C ambient. Above that, it derates linearly: 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C. If your panel enclosure runs hot — say, a packed MCC lineup near a furnace line — factor in that 300 A ceiling at 70 °C before you size the breaker. Power loss at full load is 98.5 W max. That's not trivial in a sealed enclosure; make sure your ventilation or cooling plan accounts for it, especially if you're stacking multiple breakers in the same section.
Breaking capacity — where it clears faults cleanly
Breaking capacity drops sharply above 500 V: 121 kA at 500 V, then only 7.5 kA at 690 V. On a 690 V system this breaker won't handle high-fault scenarios — it's really a 240–500 V device for serious fault duty. Below that range it's overkill for most sub-feeders; it belongs at the main or a heavy bus riser.
Physical fit and panel integration
Dimensions are 248 mm high, 138 mm wide, 110 mm deep. That's a standard SENTRON 3VA frame size for this current class — mounts via screw terminals onto a backplate or DIN rail adapter (not included). Verify the gland plate knockout pattern against your existing panel cutout before ordering; the 138 mm width typically fits a 4-module-wide slot in a Siemens 8MF enclosure, but third-party panels may differ.