What it is and what it does
The Siemens SENTRON 3VA1140-5ED16-0AA0 is a 1-pole molded case circuit breaker (MCCB) rated for 40 A continuous current at 40 °C ambient, with a TM210 thermal-magnetic overcurrent release. It's built for line protection — meaning it sits on the feeder side of a distribution panel, protecting cables and buswork from overloads and short circuits. The key number here is the 121 kA breaking capacity at 240 V AC: that's the fault current it can safely interrupt without welding contacts or venting plasma. At 415 V AC the rating drops to 9 kA, which still covers most industrial secondary-side faults. The thermal derating curve is tight — it holds 40 A all the way to 50 °C, then drops only 1 A per 5 °C step up to 70 °C, so you don't lose headroom in a hot panel.
Where it fits
At 25.4 mm wide (1 inch) and 70 mm deep, this breaker snaps into a standard DIN-rail mount and takes up one pole position in a SENTRON distribution board. The IP40 front protection means it's fine inside a clean indoor panel but not for washdown areas. Power loss is 3.6 W maximum — negligible for thermal budgeting in a crowded enclosure. Insulation voltage is rated 500 V, so it can sit on a 480 V system with margin.