Rated current and breaking capacity — what they mean for panel coordination
The Siemens 3VA1340-7EE42-0AA0 is a SENTRON molded case circuit breaker (MCCB) rated for a continuous current Iu of 400 A at 40 °C through 50 °C, derating to 367 A at 70 °C. That 400 A figure governs the upstream conductor sizing and the downstream load it can carry without nuisance tripping — sized for a main feeder or large motor branch on a 400 V industrial panel. Breaking capacity hits 440 kA at 240 V AC, 242 kA at 415/440 V, and 154 kA at 500 V — numbers that place it squarely in the high-interrupting class for fault-current-heavy installations like transformer secondaries or large motor control centers. The 690 V rating drops to 17 kA, which still covers most low-voltage distribution scenarios where the service voltage stays under 600 V. Rated insulation voltage Ui is 800 V, giving headroom for 690 V systems. The TM220 overcurrent release provides thermal-magnetic protection — thermal element for overload, magnetic for short-circuit. No ground-fault monitoring and no N-conductor protection, so this is a straight line-protection device; add external modules if those functions are required.
Mounting, dimensions, and panel integration
The 3VA1340-7EE42-0AA0 measures 248 mm high by 184 mm wide by 110 mm deep — a 4-pole MCCB footprint that fits standard Siemens SENTRON mounting plates. Front-face protection class IP40 means it is protected against tools and small wires entering the front, but not sealed against water ingress; mount inside an enclosure rated for the environment. Optional motor drive allows remote electrical operation, useful for panels with remote trip/close functionality.
Thermal derating and operating range
The breaker holds its full 400 A rating from 40 °C to 50 °C ambient (–). Above that, derate linearly: 392 A at 55 °C, 384 A at 60 °C, 376 A at 65 °C, 367 A at 70 °C. Operating ambient range spans -25 °C to +70 °C; storage from -40 °C to +80 °C. Maximum power loss at rated current is 92.1 W — factor that into enclosure thermal calculations.