DC UPS Module for 24 V Control Power
This Siemens 6AG1931-2EC21-2AA0 is a DC uninterruptible power supply module designed to buffer 24 V DC control and instrumentation loads. Rated for 15 A continuous (peak 15.7 A), it takes a 22...29 V DC input and delivers output voltage equal to input minus 0.5 V typical, or 19...28.5 V in buffered mode. The module snaps onto a DIN rail EN 60715 and measures 50 mm wide by 125 mm high by 125 mm deep, with screw terminals for power and signaling.
Key Ratings and What They Mean
The 15 A continuous rating is the maximum load current under normal operation; the module can supply this indefinitely at rated input voltage. The charging current is selectable between 0.35 A and 0.7 A, so match the battery module size to the buffer time you need. The buffered mode output range (19...28.5 V) covers the voltage window from a discharged to fully charged battery, important for downstream equipment with narrow voltage tolerance. Status is reported via floating contacts and LEDs: a green LED indicates normal operation with input above cut-in threshold; a yellow LED signals buffered mode; a red LED and flashing alarm indicate low battery (<20.4 V) or battery replacement needed. The floating changeover contacts (DC 60 V/1 A or AC 30 V/1 A) give the PLC a reliable indication of system health.
Mounting and Panel Fit
The enclosure is 50 mm wide with 0 mm left/right clearance and 50 mm top/bottom clearance. Screw terminals accept 1...4 mm² for power (2 input, 4 output) and 0.5...2.5 mm² for control (10 terminals).