What this 400 A MCCB delivers in a panel
The Siemens SENTRON 3VA2440-7HL32-0DL0 is a 3-pole molded case circuit breaker rated for 400 A continuous current (Iu) with an ETU320 electronic trip unit. Its 330 kA breaking capacity at 240 V means it can safely interrupt very high fault currents typical of large transformer secondaries or busway feeds — a spec that governs whether the breaker holds under a bolted fault or vents upstream. The 800 V rated insulation voltage (Ui) covers 480/600 V class distribution panels with margin. This is a line-protection variant (no voltage trigger, no phase-failure detection), so it's intended for main feeder or large branch protection where the trip curve handles overloads and short-circuits, not motor protection with phase-loss sensitivity.
Breaking capacity across voltage levels
The interrupting rating drops as system voltage rises: 330 kA at 240 V, 242 kA at 415/440 V, 187 kA at 500 V, and 52.5 kA at 690 V. For a 480 V panel fed from a 500 kVA transformer, the available fault current typically lands between 30–65 kA — this breaker clears that with headroom. At 690 V (common in mining or marine distribution), the 52.5 kA rating still covers most installations, but confirm the calculated SCCR before specifying.
Thermal derating and real-world current
The 400 A rating holds at ambient up to 50 °C. Above that, it derates: 384 A at 55 °C, 376 A at 60 °C, 368 A at 65 °C, 360 A at 70 °C. In a crowded panel with multiple breakers and drives, the internal temperature often hits 55–60 °C — plan for the derated value, not the nameplate 400 A. The maximum power loss is 66 W, which factors into enclosure cooling calculations. Dimensions are 138 mm wide, 248 mm high, 110 mm deep — fits a standard MCCB cutout; verify the mounting footprint against the existing panel's backplate layout.
Auxiliary contacts and releases
This unit ships with an integrated undervoltage release (UVR) and a full auxiliary contact complement: 2 auxiliary switches (NO/NC), 1 trip alarm switch, and 1 electrical alarm switch (HQ type). The UVR ensures the breaker drops out on loss of control voltage — mandatory in safety circuits where a power failure must disconnect loads. The alarm switches signal trip events to a PLC or annunciator panel. The base switch is order code 3VA2440-7HL32-0AA0; the auxiliary trip module is 3VA9608-0BB25.
Environmental and storage limits
Operating ambient range is -25 °C to 70 °C; storage range extends from -40 °C to 80 °C. The storage limit governs handling and warehousing, not running conditions. The breaker carries 15,000 mechanical endurance cycles (latching endurance) — sufficient for infrequent switching applications like main disconnects or backup generator feeders, not for daily motor starting.