What this 400 A MCCB is and where it fits
The Siemens 3VA2340-5JQ42-0JL0 is a SENTRON molded case circuit breaker (MCCB) rated for a continuous current Iu of 400 A at 40 °C, with four poles and a line protection version. It carries a breaking capacity of 187 kA at 240 V, 121 kA at 415 V, and 75.6 kA at 500 V — numbers that tell you it can interrupt massive fault currents without letting an arc cascade upstream. That kind of interrupting rating is what you need on the main feeder of a large industrial panel or a motor control center where the available fault current is high. The ETU560 electronic trip unit gives you adjustable long-time, short-time, and instantaneous protection curves, so you can coordinate it with downstream breakers rather than just blasting everything off when a branch faults.
Key ratings and what they mean for your panel
The 400 A rating holds steady from 40 °C up to 50 °C — no derating needed in a warm enclosure. At 55 °C it still carries 375 A, and at 70 °C it's 300 A. That thermal performance matters when you're packing this breaker into a crowded panel with other heat sources; you don't lose headroom just because the ambient creeps up. The rated insulation voltage Ui of 800 V means it's rated for 690 V systems with margin, and the 4-pole design lets you switch all three phases plus neutral in a single unit — common in North American 277/480 V wye or European 400/230 V TN systems. Dimensions of 248 mm high by 184 mm wide by 110 mm deep fit standard MCCB footprints, so it drops into existing switchboard cutouts without panel rework.
Trip unit and auxiliary options
The ETU560 overcurrent release is a programmable electronic trip unit that supports LSI protection (long-time, short-time, instantaneous) and includes ground-fault monitoring via summation current formation on L + N conductors. The breaker also ships with a shunt trip (STL) for remote opening, plus a full auxiliary contact block: two auxiliary switches, one trip alarm switch, and one electrical alarm switch (HQ). That's enough status feedback for a PLC to know whether the breaker is on, off, or tripped — no separate relay interface needed. Communication function is built in, so it can talk to a higher-level system for energy monitoring or remote control without an add-on module.