Overview
The 6AG1931-2FC21-7AA0 is a Siemens SIPLUS PS DC UPS module rated for 40 A continuous current, accepting a 24 V DC input and delivering a buffered output with a switching current of 42 A. It is designed for DIN-rail mounting in IP20 enclosures and operates across an ambient temperature range of -40 to +85 °C.
Function & operation
This module bridges a 24 V DC power supply and a battery energy storage, providing uninterrupted DC power during mains dips or failures. In normal operation the green OK LED and the floating changeover contact indicate the supply voltage is above the cut-in threshold. When the input drops, the module switches to buffered mode — the yellow Bat LED and the OK/Bat contact signal the transition. A prewarning threshold at 20.4 V DC triggers the red alarm LED and the Alarm/Bat contact, giving the control system time for an orderly shutdown. The module also reports energy storage above 85% via a dedicated green LED and a normally-open contact. Rated at 40 A continuous input current with a 42 A switching capability, the module handles the inrush of downstream loads and battery charging simultaneously. The output voltage follows the input minus approximately 0.5 V, so the load sees nearly the same rail voltage during normal operation. A typical startup delay of 1000 ms allows the upstream supply to stabilise before the module engages the load.
Integration & mounting
The module snaps onto a DIN rail per EN 60715 (35 x 7.5/15) and uses screw-type terminals for field wiring. Its enclosure measures 13.5 x 15.00 x 11.00 cm and weighs 1100 g, occupying a single unit width on the rail. The IP20 rating suits clean, dry cabinet environments. Ambient temperature range of -40 to +85 °C and 100% humidity tolerance (including diesel and oil droplets in the air) make it suitable for harsh industrial and outdoor-adjacent installations. Altitude derating applies above 6000 m.