The 3VA frame is the current SENTRON generation, and this variant includes an undervoltage release (UNI universal trigger) plus two HQ auxiliary switches for status feedback. It also has a communication function, meaning it can talk to a higher-level monitoring or control system.
The 400 A rating holds steady from 40 °C up to 50 °C, then derates: 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C. The interrupting curve drops fast at higher voltages: 75.6 kA at 500 V and only 7.5 kA at 690 V. At 690 V this breaker is still useful for a lightly-faulted industrial system, but it's not your main service entrance breaker at that voltage. The 3-pole construction fits standard three-phase distribution.
That 110 mm depth (4.33 inches) is the dimension you check against the enclosure door clearance and bus bar reach. The 138 mm width (5.43 inches) determines the DIN-rail or mounting-plate spacing for a 3-pole MCCB. It ships with two HQ auxiliary switches and a universal trigger (UNI) undervoltage release already integrated — no separate field-assembly of those accessories. The communication function is onboard, so you only need to wire the bus connection.
The breaker includes a voltage trigger (undervoltage release) and a communication function, both of which require their own wiring and coordination with the control system.