The Siemens 3VA1340-4EE42-0AA0-ZD00 is a 4-pole IEC frame 400 molded case circuit breaker with a 36 kA interrupting capacity at 415 V (breaking capacity class S). It's fitted with a TM220 thermal-magnetic trip unit — the thermal element adjustable from 280 A to 400 A, the magnetic pickup fixed at 10× In (4000 A). The neutral pole is unprotected, which means it tracks the phase poles thermally but doesn't have its own overload or short-circuit sensing; that's standard for 3VA1 line-protection breakers where the neutral is a switched-only pole.
The 36 kA Icu at 415 V tells you this breaker can safely clear a fault up to 36,000 A symmetrical without welding or rupturing — that's class S in the 3VA1 family, sitting between the standard (25 kA) and higher (50 kA) tiers. For a 400 A frame, that's enough for most industrial secondary-distribution panels fed from a transformer in the 1–2 MVA range. The TM220 thermal-magnetic trip gives you a fixed short-circuit pickup at 10× In (4000 A), so it coordinates well downstream of a larger feeder breaker with a higher Ii setting. The adjustable Ir band (280–400 A) lets you match the continuous load without swapping the trip unit — set it to 320 A for a 300 A continuous load, for example.
Mounts in a standard IEC frame 400 footprint — four-pole version takes the same panel cutout as the three-pole plus one neutral pole width. The nut keeper kit on the line-side terminals is already fitted for the DC Power OEM build; if you're landing aluminum conductors, the keeper prevents the nut from backing off during thermal cycling. No special DIN-rail adapter — this is a bolt-on breaker, intended for a mounting plate or backpanel.