400 A MCCB with ETU550 — what the ratings mean for your panel
The Siemens 3VA2340-5JP32-0AA0 is a 3-pole SENTRON molded case circuit breaker rated for 400 A continuous current at 40 °C, with the ETU550 electronic trip unit handling line protection. That 400 A holds flat through 50 °C — above that, derate linearly to 300 A at 70 °C, which matters if this breaker sits near transformers or drives in a sealed enclosure. The 800 V rated insulation voltage and IP40 front protection suit it for main distribution panels where finger-safe front access is required but the body is inside a cabinet.
SCCR by voltage — the selectivity story
Short-circuit breaking capacity varies sharply with system voltage: 187 kA at 240 V, 121 kA at 415 V and 440 V, 75.6 kA at 500 V, and 7.5 kA at 690 V. For a 400 V industrial feeder, 121 kA covers most transformer-secondaries up to about 2.5 MVA; at 690 V the 7.5 kA figure limits it to lower-fault-current applications. The ETU550 trip unit communicates via the integrated communication function, so it can report status and current draw to a BMS or PLC — useful for predictive maintenance on critical feeders.
Panel fit — dimensions and mounting
The breaker measures 248 mm high × 138 mm wide × 110 mm deep. That 138 mm width for a 3-pole 400 A frame is typical for this class — it occupies three 45 mm modular spaces on a DIN rail or bolts directly to a mounting plate. The 110 mm depth leaves room for rear-connection busbars or cable lugs in a standard 600 mm deep enclosure.