What this 400 A MCCB does and where it fits
The Siemens 3VA1340-5GE42-0AA0 is a 4-pole SENTRON molded case circuit breaker rated 400 A continuous at 40 °C with a TM220 thermal-magnetic trip unit. It interrupts 187 kA at 240 V and 121 kA at 415 V, so it handles high-fault-current service-entrance or distribution applications where the available short-circuit current is substantial. The 400 A frame carries full current up to 50 °C before derating begins — at 55 °C it's still 392 A, at 70 °C it's 367 A — which gives you thermal headroom in a warm enclosure. The TM220 designation means a thermal-magnetic overcurrent release with a fixed thermal pickup and magnetic short-circuit trip. No undervoltage release, no voltage trigger, no ground-fault monitoring, no communication function — this is a straight line-protection breaker for a main or feeder circuit where you don't need auxiliary electronics.
Mounting and integration
The 3VA1340-5GE42-0AA0 measures 248 mm high by 184 mm wide by 110 mm deep. It mounts on a DIN rail or can be bolted to a backplate in a standard distribution panel. The 4-pole footprint with 100 % N-conductor protection means the neutral pole is fully rated and switches with the phases — no derating for the neutral path. Front IP40 protection keeps dust and tools out of the mechanism. Power loss is 92.1 W at full load, so factor that into enclosure thermal calculations — a 400 A breaker dumping nearly 100 W needs ventilation or a larger cabinet than a lower-rated frame.
Interrupting capacity by voltage — what the numbers mean
The 187 kA at 240 V is the highest interrupting rating on this breaker — it's sized for 240 V distribution where fault currents can be extreme (large transformers, utility tie points). At 415/440 V it's still 121 kA, which covers most industrial low-voltage switchgear. At 500 V it drops to 75.6 kA, and at 690 V to 11.9 kA — still adequate for 690 V motor circuits but not for high-fault 690 V buswork. The rated insulation voltage is 800 V, so the breaker itself is insulated for 690 V systems.