400 A MCCB with undervoltage release — what the ratings mean
The Siemens 3VA2340-5HN32-0BA0 is a SENTRON molded case circuit breaker (MCCB) rated for 400 A continuous current, holding that rating from 40 °C up to 50 °C before derating begins — at 55 °C it's still good for 385 A, and at 70 °C it delivers 340 A. That thermal curve matters when the breaker sits in a crowded panel with other heat sources; you don't lose headroom until the ambient pushes past 50 °C. Breaking capacity is 187 kA at 240 V, 121 kA at 415 V and 440 V, 75.6 kA at 500 V, and 7.5 kA at 690 V. For a 400 A frame, those numbers give you serious fault-current headroom on most industrial secondary distribution — the 121 kA at 415 V covers high-fault installations without needing a current-limiting upstream device. This variant ships with an undervoltage release (UVR) fitted — the auxiliary release type is listed as undervoltage release. No auxiliary switch, no ground-fault monitoring. The UVR means the breaker trips automatically when supply voltage drops below a threshold, which is standard for motor feeder protection where you want to prevent automatic reclosure after a dip.
Panel fit and integration
Dimensions are 248 mm high, 138 mm wide, 110 mm deep — a standard 3-pole MCCB footprint for a 400 A frame. Maximum power loss is 98.5 W at rated current. That's the heat you need to vent in the enclosure — factor it into your thermal calculation if the panel is sealed or has multiple breakers in a row.