Capacitor-Backed Ride-Through for 24V DC Rails
The Siemens 6EP1933-2EC51 is a SITOP UPS500S uninterruptible power supply module that bridges short mains dips on a 24V DC control bus. It takes 22 to 29 V DC input and delivers a regulated 24 V ± 3 % output at up to 15 A continuous, 360 W. The energy storage is capacitor-based, not battery — meaning no replacement cycle on the storage element and no cold-weather derating, but the buffer time is measured in seconds, not minutes.
Rated Output and Buffer Dynamics
Rated output current is 15 A in normal operation, with a peak capability of 25 A for short-duration loads. The module signals buffer status through three LED indicators and floating relay contacts: green OK when the input supply is above the cut-in threshold, yellow BAT when buffering, and red ALARM when the buffer is below 80 % remaining. A separate floating NO contact closes when the capacitor bank is above 85 % charged. The charging current is selectable at 1 A or 2 A, letting the installer match the inrush draw to the upstream power supply's headroom. Startup delay is 0.6 s typical, and the module meets EN 55022 Class B for conducted emissions and EN 61000-6-2 for industrial immunity.
DIN Rail Mounting and Approvals
The 125 × 120 × 125 mm (H × W × D) enclosure snaps onto 35 mm DIN rail per EN 60715. IP20 rated — intended for dry, enclosed control panels. Input and output connections are screw terminals: 2 terminals at input for 1 to 4 mm² / 17 to 11 AWG, and 4 terminals at output for the same range. Approvals include cULus-Listed to UL 508 and CSA C22.2 No. 107.1, cCSAus to UL 60950-1, CE, EAC, C-Tick, and shipbuilding approvals from ABS and DNV GL. MTBF at 40 °C is calculated at 459,137 hours.