MCCB with ETU350 — interrupting capacity and thermal derating
The Siemens 3VA2340-5HN32-0KF0 is a SENTRON 3VA2 molded case circuit breaker rated for 400 A continuous current at 40 °C, 45 °C, and 50 °C — no derating needed up to that point. Above 50 °C the curve steps down: 385 A at 55 °C, 370 A at 60 °C, 355 A at 65 °C, and 340 A at 70 °C. Interrupting capacity varies sharply with system voltage: 187 kA at 240 V, 121 kA at 415 V, 55 kA at 440 V, 36 kA at 500 V, and 7.5 kA at 690 V. The electronic trip unit is an ETU350, adjustable for long-time delay (tr) from 0.5 s to 17 s and short-time delay (tsd) from 0.02 s to 0.4 s. That range gives selectivity flexibility downstream — you can set tsd long enough to ride through a feeder breaker's clearing time without nuisance tripping.
The 138 mm width (5.4 in) is a three-pole MCCB footprint. Front-face protection is IP40 — suitable for a closed electrical enclosure where tools are required to access live parts.
Electrical ratings and operating limits
Maximum power loss is 96 W at rated current. Mechanical endurance is 20,000 operations. The ETU350 is a basic electronic trip with adjustable time-current curves but no Modbus or PROFIBUS interface. If remote trip indication or energy metering is needed, a different 3VA2 variant with the communication option would be required.