What this MCCB brings to a hot, dusty panel
The Siemens 3VA1140-4EF32-0AD0 is a SENTRON molded case circuit breaker (MCCB) rated for 40 A continuous at 40 °C, with a thermal-magnetic TM240 release and 3 poles. It's built for line protection — the kind of duty where a breaker sits between a transformer secondary and a distribution bus, not cycling every shift but needing to clear a fault without hesitation when it happens. Interrupting capacity is 121 kA at 240 V AC — that's a serious number for a 40 A frame, meaning it can ride through a high-energy fault on a low-voltage service without rupturing. At 415 V it still holds 75.6 kA, and at 690 V it's rated 11.9 kA. The insulation voltage is rated 800 V, so it's comfortable on 480 V or 600 V class systems as long as the interrupting curve matches the available fault current at that voltage. The TM240 thermal-magnetic release means the thermal element tracks load heating for overload protection, and the magnetic instantaneous element handles short circuits. No ground-fault monitoring, no undervoltage release, no communication module — this is a straightforward, no-frills breaker for a main feeder or large branch circuit where you don't need remote trip signaling.
Thermal derating and panel fit
Rated current holds at 40 A from 40 °C through 50 °C, then drops to 39 A at 55 °C, 38 A at 65 °C, and 37 A at 70 °C. In a cement plant control room that hits 55 °C in summer, you still get 39 A continuous — enough for a 40 A feeder if you're not pushing the thermal limit. The maximum operating temperature is 70 °C, storage from -40 °C to 80 °C. Dimensions are 130 mm height, 76.2 mm width, 70 mm depth. That's a standard 3-pole MCCB footprint for a 40 A frame — fits most DIN-rail or panel-mount enclosures without surprises. Power loss at rated current is 10.8 W maximum, so heat dissipation inside a sealed panel is manageable but not negligible.