The Siemens 6EP4137-3AB00-1AY0 is a DC UPS module that sits between a 24 V DC power supply and the load, providing buffered backup when the input voltage drops. It's rated for a continuous 40 A and accepts an input range of 21 to 29 V DC. The module snaps onto a standard DIN rail EN 60715 35x7.5/15 and measures 70 mm wide by 139 mm high by 150 mm deep.
The 40 A rated current is the continuous pass-through capacity — it's not a surge rating. The peak current of 120 A handles inrush from downstream loads during transfer to battery, but the module itself doesn't store energy; it relies on an external battery module (type of energy storage: with batteries). The buffered mode LED logic is straightforward: yellow LED and changeover contact indicate buffered mode, red LED and separate contact signal prewarning below 20.4 V DC, and a green LED plus NO contact confirm energy storage above 85%. The floating changeover contacts are rated for DC 60 V / 1 A or AC 30 V / 1 A — fine for signaling a PLC input, but don't try to switch a contactor coil directly off these contacts.
Snaps onto DIN rail EN 60715 35x7.5/15. The enclosure is IP20 — fine for a clean control cabinet, not for washdown areas. The top clearance of 50 mm and bottom clearance of 50 mm are the minimum free air space for convection — if you stack modules tighter than that, expect derating. Left and right clearance is 0 mm, so you can butt it against adjacent units on the rail.
Carries CE, UL (cULus-Listed per UL 508 and CSA C22.2 No. 107.1, File E197259), CSA, EAC, C-Tick, and shipbuilding approvals including ABS and DNV GL. Emission limits meet EN 55022 Class B, immunity per EN 61000-6-2. The ATEX field is marked No — this is not certified for explosive atmospheres. The MTBF at 40 °C is 330,515 hours, which is about 38 years — a solid number for a non-rotating component in a conditioned environment.