The Siemens SENTRON 3VA2440-6HN32-0AJ0 is a 3-pole molded case circuit breaker (MCCB) rated for 400 A continuous at 40 °C through 70 °C — no derating needed across that range.
At 240 V the breaker interrupts 242 kA symmetrical; at 415 V and 440 V it holds 187 kA; at 500 V it drops to 121 kA; at 690 V it is still rated 9 kA. These are the maximum fault currents the MCCB can safely clear without welding or rupturing. For a 400 A feeder on a 480 V system the 187 kA rating at 415 V gives ample SCCR headroom for most industrial switchboards — coordination studies should verify the upstream transformer impedance and available fault current, but this breaker will not be the weak link in the chain.
The 3-pole footprint is standard for this class; verify the busbar or lug kit spacing matches the 138 mm width before panel layout.