What this 400 A MCCB delivers
The Siemens SENTRON 3VA2340-5HN42-0BA0 is a 4-pole molded case circuit breaker rated for 400 A continuous current at 40 °C, with a 187 kA interrupting capacity at 240 V — that is the short-circuit current it can safely clear without welding contacts or rupturing the case, critical for high-fault service-entrance or distribution panels where upstream transformer capacity is large. The ETU350 electronic trip unit provides adjustable long-time, short-time, and instantaneous protection curves, so this breaker can be coordinated with downstream devices to achieve selective tripping — only the faulted branch opens, keeping the rest of the line live.
Breaking capacity across voltage levels
At 415 V and 440 V it still delivers 121 kA; at 500 V it drops to 75.6 kA; and at 690 V it holds 17 kA. That voltage-dependent curve is typical for MCCBs — the arc energy scales with voltage, so the same mechanism interrupts less current at higher potentials. For a 400 V three-phase panel this breaker gives substantial headroom above typical available fault currents.
Thermal derating and panel fit
Full 400 A rating holds through 50 °C ambient; above that it derates linearly to 340 A at 70 °C. In a sealed, uncooled enclosure this matters — if the panel ambient runs 60 °C, you lose 30 A of headroom. The 184 mm width and 248 mm height place it in the standard SENTRON 3VA frame footprint, and the 110 mm depth fits typical distribution board gutters without gland-plate interference.
Integrated undervoltage release
Factory-fitted with an undervoltage release (UVR) — part number 3VA9608-0BB11 — which trips the breaker when control voltage drops below a threshold. This is standard for safety circuits that need to drop power on loss of control supply, or for emergency-stop chains that use a held-in undervoltage coil.