What this MCCB is and what it handles
The Siemens 3VA2340-7HN32-0CH0 is a SENTRON molded case circuit breaker (MCCB) sized for line-protection duty — meaning it sits at the incoming feeder or main distribution point, not downstream on a motor branch. It carries a rated continuous current Iu of 400 A and a rated insulation voltage Ui of 800 V, so it's built for a 400 V or 480 V main bus where you need to clear a fault without taking out the whole switchboard. The interrupting ratings tell the real story: 330 kA at 240 V, 242 kA at 415 V, 242 kA at 440 V, 187 kA at 500 V, and still 52.5 kA at 690 V. That's a high-interrupting-capacity frame — it handles utility-grade fault currents without needing a current-limiting fuse upstream. For a 400 A main breaker in an industrial panel, that's the kind of SCCR that keeps the series rating simple. The electronic trip unit is an ETU350, which gives you adjustable long-time, short-time, instantaneous, and ground-fault protection curves. That matters when you're coordinating with downstream feeders and don't want nuisance trips on motor-start inrush. The undervoltage release (UVR) is built in — it drops the breaker if control power fails, which is a common spec for emergency-stop and safety circuits.
Thermal derating and panel fit
This MCCB is rated for 400 A continuous from 40 °C up to 50 °C ambient — no derating needed in a typical ventilated enclosure. At 55 °C it's 385 A, at 60 °C it's 370 A, at 65 °C it's 355 A, and at 70 °C it's 340 A. If your panel runs hot, that derating curve is what you use to size the breaker correctly, not the 400 A nameplate. Physical dimensions: 248 mm high, 138 mm wide, 110 mm deep. That's a standard 3-pole MCCB footprint for the SENTRON 3VA frame — it mounts on a DIN rail or can be bolted directly to a mounting plate. The 110 mm depth means it fits in a 300 mm deep enclosure with room for rear-connected busbars. Auxiliary contact configuration is 2 auxiliary switches plus 1 trip alarm switch (HQ type). That gives you two form-C contacts for status feedback to a PLC and a dedicated alarm contact that only changes state on a trip, not on manual open. The integrated auxiliary trip is order code 3VA9608-0BB24.
Lifecycle and sourcing posture
Maximum power loss is 98.5 W at rated current — that's the heat you need to vent from the enclosure. It's not a number you see on every listing, but for a panel builder it decides whether you need forced ventilation or a bigger cabinet. Latching endurance is rated at 15,000 operations, which is typical for a main breaker that sees infrequent switching. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. That covers unheated warehouses and outdoor enclosures in most climates. The -40 °C storage minimum is the limit for cold-weather shipping and storage — don't let it sit in a frozen truck for weeks.