What it is and what the ratings mean for fit
The Siemens 3VA2340-5JQ42-0AF0 is a SENTRON molded case circuit breaker (MCCB) rated for line protection, with a frame size that carries a full-scale value of 400 A and a minimum setting of 600 A. It's a 4-pole unit designed to sit in a distribution panel or switchboard — the 248 mm height, 184 mm width, and 110 mm depth (9.76 x 7.24 x 4.33 in) tell you the cubicle cutout and busbar spacing needed. The interrupting ratings are what decide whether it clears a fault without upstream damage: 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. At 690 V the capacity drops sharply — that's the voltage class where the arc energy saturates the internal arc chamber; if your system runs 690 V with available fault current above 7.5 kA, this breaker isn't the right fit. The continuous current rating holds 400 A from 40 °C up through 50 °C ambient — no derating needed in a typical 40 °C panel. Above that, it steps down: 375 A at 55 °C, 350 A at 60 °C, 325 A at 65 °C, and 300 A at 70 °C. If your enclosure runs hot (say, a packed MCC lineup near a furnace line), you need to account for that drop. Maximum power loss is 96 W, which adds to the enclosure's thermal load.
Sourcing and lifecycle reality
The 3VA2340-5JQ42-0AF0 carries a communication function, which means it can integrate with monitoring systems — useful for a plant that tracks breaker status or load profiles. The auxiliary switch configuration includes 1 auxiliary switch plus 1 trip alarm switch (HQ design), so you get both a position signal and a trip indication without adding external accessories.
Installation and integration notes
Mounts in a standard switchboard or distribution panel — the 184 mm width and 248 mm height fit common MCCB cubicle cutouts. The 110 mm depth leaves room for rear bus connections and wiring ducts. It's a 4-pole breaker, so it needs four conductors plus a neutral if the system requires it. The basic switch variant is listed as 3VA2340-5JQ42-0AA0, which is the same frame without the communication module; this version adds the comms function on top of the base switch. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. The storage limit is wider because it governs handling and warehousing, not running conditions. No undervoltage release is fitted, and no voltage trigger — if you need undervoltage protection, you'd add an external release module.