Application Scenarios

On a 33 kV wind farm collection feeder in Northern China, each box-type substation houses a Siemens S7-300 RTU and a handful of SM331 analog input modules reading winding temperature, oil level, and tap-changer position. The site’s DC auxiliary bus runs at 110 V DC from a station battery backed by a solar charge controller—convenient for tripping circuits, but problematic for the RTU: the original solution used a string of linear dropper resistors plus a 7824 regulator to get 24 V for the PLC, and every summer the regulator cooked itself inside the sealed cabinet, triggering RTU brownouts during peak telemetry windows. During the mid-life retrofit, the maintenance crew replaced the dropper assembly with a single Siemens 6EP1731-2BA00​ mounted on the DIN rail beside the PS307. Because the 6EP1731-2BA00​ covers 48–220 V DC input in one SKU, the same part works on both the 110 V DC bus of the wind farm and the 220 V DC bus of the main step-up substation—no need to stock two different AC/DC variants. The soft-start characteristic (no output overshoot) meant the SM331 modules saw a clean 24 V ramp rather than the old dropper’s slow decay, eliminating the false “sensor fault” alarms that used to fire on every battery load-test. For the SCADA engineer, the green “24 V OK” LED on the 6EP1731-2BA00​ became the first thing he checked during remote fault calls—and it was lit every time.

h2 Parameter

h2 Technical Principles and Innovative Values

Innovation Point 1: Single-SKU DC Wide-Range Coverage 48–220 V. Most compact DC/DC bricks are locked to one nominal—12 V, 24 V, or 48 V input—forcing spares inventory to multiply across rail (110 V DC), telecom (48 V DC), and industrial (220 V DC) sites. The 6EP1731-2BA00​ absorbs the entire span in one 22.5 mm footprint. For EPCs that standardize a control panel drawing across multiple continents, this is a bill-of-materials simplifier.

Innovation Point 2: SELV Isolation with EN 60950-1 Compliance. The input/output galvanic isolation isn’t just a nice-to-have—on 220 V DC battery strings (common in substations), a non-isolated dropper can float the 24 V rail at dangerous potential relative to PE. The 6EP1731-2BA00​ delivers a proper SELV output, protecting both field technicians and downstream 24 V electronics.

Innovation Point 3: Soft-Start, Zero Overshoot. Unlike linear regulators that sag on load step, the 6EP1731-2BA00​ ramps output in ~90 ms with no overshoot (per Siemens datasheet spec “Vout no overshoot, soft start”). For sensitive analog front-ends—SM331, ultrasonic level transmitters, PROFIBUS repeaters—this prevents spurious startup alarms that mimic sensor failures.

Innovation Point 4: Electronic Short-Circuit with Auto-Restart. When a field tech accidentally shorts a 24 V sensor loop, the 6EP1731-2BA00​ latches off electronically (~0.9 A continuous short current, 200 ms timeout) then retries automatically once the fault clears. No fuse to hunt for in a dark cabinet.

h2 Application Cases and Industry Value

A metro signaling depot in Southeast Asia standardized the Siemens 6EP1731-2BA00​ across 14 trackside equipment rooms where the station DC screen ran at 220 V DC (old 1950s vintage rectifier set, still going). Each room housed an ET 200M remote I/O rack serving track-circuit relays and axle-counter interfaces—total 24 V load under 300 mA, perfectly sized for the 6EP1731-2BA00‘s 375 mA rating. Previously the depot used repurposed telecom 48→24 V bricks with external buck boards, which failed at a rate of ~18 %/year in the tropical humidity. After the swap to 6EP1731-2BA00, two full years passed with zero PSU-related signaling faults. The depot’s maintenance chief noted two practical wins: first, the 22.5 mm width let them squeeze the DC/DC onto panels originally drawn for the fatter AC/DC SITOP Smart; second, because the 6EP1731-2BA00​ shares the same screw-terminal layout as the rest of the SITOP family, the junior techs didn’t need a new torque chart. The module paid for itself in one avoided “wrong-side failure” incident during monsoon season.

h2 Related Product Combination Solutions

When specifying around the Siemens 6EP1731-2BA00, these sibling and successor units commonly appear:

• Siemens 6EP3332-0TA00-0AY0:​ The official successor (PSU3400 24 V / 2.5 A), accepts both 88–264 V AC and 18–264 V DC input—an upgrade path if you’re retiring the 6EP1731-2BA00​ from active designs.
• Siemens 6EP1961-3BA10:​ Signaling module that clips onto the 6EP1731-2BA00​ to add a “Power Good” relay contact and 0–2.5 V current monitor signal—useful for SCADA telemetry of PSU health.
• Siemens 6EP1321-5BA00:​ The AC/DC counterpart (120/230 V AC → 24 V DC, 0.3 A class), for sites where you have AC mains and want the same SITOP form factor.
• Siemens 6ES7305-1BA80-0AA0 (SIMATIC PS305):​ S7-300 rack-mounted DC/DC PSU, 24–110 V DC in / 24 V 2 A out—closer to the 6EP1731-2BA00‘s application space but lives inside the S7-300 chassis instead of on the DIN rail.
• Siemens 6EP1457-3BA00:​ SITOP modular 48 V / 20 A three-phase unit—don’t confuse this with the 6EP1731-2BA00; the -2BA00 is the tiny 0.375 A DC/DC, the -3BA00 is the heavy 20 A 48 V brick. Both share catalog space in the “alternative voltages” chapter.
• Siemens 6EP1961-2BA31 / 6EP1962-2BA00:​ SITOP buffer modules and redundancy modules—often mounted adjacent when the 6EP1731-2BA00​ feeds critical loops that need ride-through.