What this 400 A MCCB is and what the ratings mean for fit
The Siemens SENTRON 3VA2340-6JQ32-0DA0 is a 3-pole molded case circuit breaker (MCCB) configured for line protection, carrying a rated continuous current Iu of 400 A that holds flat from 40 °C through 50 °C — meaning no derating needed in a typical 40 °C panel environment. Above 50 °C, the current rating steps down: 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C. That thermal curve is the one to check if the breaker sits near transformers or other heat sources inside the enclosure. Breaking capacity is the headline number that decides whether this breaker clears a fault without upstream coordination issues. At 240 V it interrupts 242 kA; at 415 V and 440 V it holds 187 kA; at 500 V it still manages 121 kA; and at 690 V it drops to 40 kA. For a 400 A frame, those are high-interrupting ratings — the kind you spec when the available fault current at the panelboard is known to be stiff, or when you want selectivity headroom downstream. The electronic trip unit is an ETU560, and the breaker includes an undervoltage release (UVR) plus a communication function — so it can be integrated into a monitoring or remote-trip scheme. There is no auxiliary contact on this variant, and no voltage trigger or phase failure detection built in. The ground fault monitoring uses summation current formation on the L-conductor.
Mounting and integration into the panel
The breaker dimensions — 248 mm height, 138 mm width, 110 mm depth — fit the standard SENTRON 3VA frame footprint. It mounts on a DIN rail or can be screw-fixed to a backplate. The 110 mm depth is the dimension to watch when the gland plate or door clearance is tight; the 138 mm width means a 3-pole unit occupies roughly three 45 mm module spaces on the rail. Rated insulation voltage is 800 V, and maximum power loss is 98.5 W — that heat has to be vented or accounted for in the enclosure thermal calculation.