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.
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.
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).