400 A MCCB with ETU550 — line protection for main feeders
The Siemens SENTRON 3VA2340-6JP32-0JA0 is a 3-pole molded case circuit breaker rated for 400 A continuous current, configured for line protection with an ETU550 electronic trip unit. It carries a breaking capacity of 242 kA at 240 V, stepping down through 187 kA at 415 V and 440 V, 121 kA at 500 V, and 40 kA at 690 V — so it handles high-fault main feeders where the upstream transformer can deliver serious short-circuit energy. The thermal derating curve holds full 400 A up to 50 °C, then drops to 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C; if your panel ambient runs hot, size the breaker for the actual enclosure temperature, not the nameplate.
What the ratings mean for your panel
The 400 A rated continuous current (Iu) is the breaker's thermal capacity under normal load — it's the number you match to your feeder ampacity. The ETU550 electronic trip unit gives you adjustable long-time, short-time, instantaneous, and ground-fault protection curves, which means you can coordinate selectivity downstream without nuisance trips. The breaking capacities at each voltage level tell you the maximum fault current the breaker can safely interrupt at that voltage; at 690 V it's still 40 kA, so it works on 480 V or 600 V class systems with headroom. The 800 V rated insulation voltage (Ui) confirms the internal clearance is rated for 690 V nominal systems.
Mounting and panel fit
Dimensions are 248 mm height, 138 mm width, 110 mm depth — a standard SENTRON 3VA2 frame size. It mounts on a DIN rail or can be screw-fixed to a backplate; the 110 mm depth includes the arc chamber and terminals, so allow clearance for cable bending radius below the breaker. The 3-pole block fits a 138 mm wide slot in a distribution panel or motor control center bucket.
Trip unit and auxiliary functions
The ETU550 trip unit includes a voltage trigger function and communication capability, so it can report status or accept a remote trip signal on a digital network. No auxiliary contact is fitted as standard, and there is no undervoltage release or ground-fault monitoring module on this variant — those would need to be ordered as separate accessories if your application requires them. The mechanical endurance is rated at 15,000 operations, which is typical for a main breaker that sees infrequent switching.
Environmental limits
Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. Maximum power loss at rated current is 96 W — that's the heat the breaker dissipates into the enclosure, so factor it into your panel cooling calculation, especially if multiple breakers are ganged in a small cabinet.