Power Supply Fit: Ratings and Derating
The Siemens 6AG1433-2BA20-7AA0 is a 24 V DC switched-mode power supply with a maximum output of 8 A and a typical load of 6.6 A. The continuous rated current is 5 A at 25 °C, but you can pull 6 A up to 45 °C without derating. Above 60 °C, reduce output by 5% per Kelvin—plan your panel thermal budget accordingly. Output voltage adjusts from 24 to 28 V DC. Load step recovery is 4 ms typical. The '24 V OK' relay (NO contact, 60 V DC / 0.3 A) signals status to controls. Isolation is safety extra-low voltage (SELV) per EN 60950-1 and EN 50178, with a transformer meeting EN 61558-2-16.
Feeder Protection Required
The input must be protected by a 3-pole connected miniature circuit breaker, 3–16 A, characteristic C, or a Siemens 3RV2011-1DA10 set at 3 A (or UL 489-listed 3RV2711-1DD10). Don't skip this—it's listed as required. Input connections:, L2, L3, and PE each take one screw terminal for 0.05–2.5 mm² single-core or finely stranded wire. Output (+/-) gets two terminals each for 0.2–2.5 mm². The alarm contact (13, 14) uses one terminal each for 0.2–2.5 mm².
Mounting and Accessories
Snaps onto DIN rail EN 60715 35×7.5/15. Enclosure is 125 mm high × 50 mm wide × 120 mm deep, IP20. For auxiliary functions, compatible redundancy, buffer, selectivity modules, and DC UPS are available. Optional identification label: Siemens 3RT1900-1SB20 (20 mm × 7 mm, pale turquoise).