What it is and what it does
The Siemens 3VA1340-4EF32-0AF0 is a SENTRON molded case circuit breaker (MCCB) rated for line protection, meaning its primary job is to protect cables and busbars from overloads and short circuits in a distribution panel — not motor protection, which requires a different trip curve. It carries a continuous current rating of 400 A at 40 °C, and that figure holds steady up to 50 °C before derating begins — at 55 °C it's still good for 392 A, at 70 °C it drops to 367 A, so the thermal margin is generous for most panel environments. The TM240 overcurrent release is a thermal-magnetic type — the thermal element handles overloads, the magnetic element handles short circuits — tuned for line protection duty, not motor starting.
Breaking capacity — what the ratings mean for your fault level
Breaking capacity is the maximum fault current the breaker can safely interrupt without welding contacts or rupturing the case. This MCCB delivers 121 kA at 240 V, 76 kA at 415 V and 440 V, 53 kA at 500 V, and 10.5 kA at 690 V — so it handles high available fault currents at the lower voltages common in North American and some European distribution, while the 690 V figure still covers most industrial service-entrance requirements. Rated insulation voltage is 800 V, which means the internal clearances and creepage distances are designed for systems up to that level — the 690 V breaking capacity is the practical limit for a fault interruption, but the insulation path is rated higher.
Lifecycle and sourcing reality
The auxiliary contact configuration is 1 auxiliary switch + 1 trip alarm switch (HQ version), which gives you both a status mirror and a separate alarm contact for remote fault indication — useful for PLC or SCADA integration without adding external relays. Power loss at rated current is 92.1 W maximum — factor that into your panel thermal budget, especially if the breaker is enclosed or mounted in a densely packed switchboard.
Panel fit and integration
Dimensions are 248 mm high, 138 mm wide, 110 mm deep. Depth of 110 mm fits most enclosures with room for rear cable access. Operating temperature range is -25 °C to 70 °C, storage from -40 °C to 80 °C.