400 A MCCB with ETU550 — what the ratings mean for fit
The Siemens 3VA2340-5JP32-0DH0 is a 3-pole SENTRON molded case circuit breaker (MCCB) rated for 400 A continuous current (Iu) with an 800 V rated insulation voltage (Ui). The breaking capacity tells you where this breaker can safely interrupt a fault without upstream damage. At 240 V it clears 187 kA; at 415 V and 440 V it holds 121 kA; at 500 V it drops to 75.6 kA; at 690 V it is 17 kA. For a typical 400 V industrial service with a transformer rating that yields a 50–65 kA prospective fault current, this breaker has comfortable margin. At 690 V the 17 kA figure is low — verify your system's available fault current before specifying it on a 690 V line. The ETU550 electronic trip unit provides adjustable overload and short-circuit protection with a communications interface. This is the version with line protection firmware, meaning it is optimized for feeder protection rather than motor or generator duty. An undervoltage release (UVR) is built in — when control voltage drops, the breaker trips, which is standard for emergency-stop or loss-of-mains schemes. The auxiliary contact package is 2 auxiliary switches plus 1 trip alarm switch (HQ configuration), enough to signal breaker status back to a PLC or DCS without an external relay.
Mounting and panel integration
The breaker measures 138 mm wide, 248 mm high, and 110 mm deep. That 110 mm depth is the dimension that matters for enclosure depth selection. Maximum power loss is 98.5 W. In a sealed enclosure this heat must be managed — at 400 A continuous load, the breaker dissipates nearly 100 W. Ensure the enclosure has adequate ventilation or forced cooling to keep internal ambient below 50 °C if you want to hold the full 400 A rating. Mechanical endurance is rated at 15 000 operations, which is standard for a fixed-mounted MCCB in a distribution panel — not a switching duty cycle, but fine for occasional on-load switching and fault isolation.