What this breaker is and where it fits
The Siemens SENTRON 3VA2340-5JQ32-0AG0 is a 3-pole molded case circuit breaker rated for a continuous current of 400 A, with an ETU560 electronic trip unit configured for line protection. It handles fault currents up to 187 kA at 240 V and 121 kA at 415 V, which means it can safely interrupt high-energy faults on the secondary side of a distribution transformer or at a main feeder without upstream damage. The 800 V rated insulation voltage (Ui) supports 690 V line-to-line systems — typical for industrial switchboards feeding motor control centers or large HVAC loads.
Thermal derating and real-world current capacity
The breaker carries a full 400 A up to 50 °C ambient, then derates to 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C. For a panel that runs at 55 °C — common in a packed switchroom — you lose 25 A of headroom. If your load is a 380 A continuous draw and the enclosure hits 60 °C, the 350 A rating means you need a larger frame or forced ventilation. The maximum operating ambient is 70 °C; storage range is -40 °C to 80 °C.
Dimensions and panel fit
The breaker measures 110 mm deep, 138 mm wide, and 248 mm tall. It mounts on a DIN rail or directly to a backplate via the fixed screw terminals.
Auxiliary and communication options
The breaker ships with one auxiliary switch and one trip alarm switch (HP type), plus a communication function for remote status monitoring. It does not include an undervoltage release or phase failure detection. The integrated auxiliary trip is order code 3VA9608-0BB11; the basic switch assembly is 3VA2340-5JQ32-0AA0. Maximum power loss is 96 W — account for that in enclosure thermal calculations.