What this 1-pole MCCB does in the panel
The Siemens SENTRON 3VM1140-3ED12-0AA0 is a 1-pole molded case circuit breaker (MCCB) rated for line protection — it sits on a DIN rail in a distribution or control panel, protecting a single phase of a 40 A circuit. The TM210 thermal-magnetic release gives fixed thermal pickup at 40 A and a fixed magnetic trip at 400 A (10× Ir), so there is no adjustment dial to set; what you see on the nameplate is what the breaker will do. At 240 V it interrupts faults up to 53 kA, which covers most secondary-side distribution in North American panels; at 415 V the breaking capacity drops to 7.5 kA, still adequate for European 400 V branch circuits behind a larger upstream breaker.
Thermal derating and what it means for a 40 A circuit
The breaker holds its full 40 A rating from 40 °C up to 50 °C — no derating needed in a typical ventilated enclosure. At 55 °C it drops to 39 A, at 65 °C to 38 A, and at the maximum operating temperature of 70 °C it still carries 37 A. That thermal curve matters if the breaker is packed into a high-density panel or mounted near heat sources like transformers or drives; you can run it at 40 A continuous up to 50 °C without second-guessing the nameplate.
Physical fit and panel integration
The breaker occupies a single 25.4 mm (1 in) width on the DIN rail — standard 1-pole modular footprint. Depth is 70 mm (2.8 in), height 130 mm (5.1 in). Front protection is IP40, so it is fine for a dry indoor panel but not for washdown areas. The TM210 release is non-interchangeable; the breaker ships as a sealed unit with no user-accessible trip adjustment.