Three easily underestimated issues with data center PDUs ( Part 3)

An easily overlooked detail: AC/DC compatibility

The power supply links inside data center racks feature both AC and DC power. Generators and UPS output AC power, while the input of server power modules may be AC (such as 220V AC) or DC (such as 240V DC or 270V DC) – depending on the power supply architecture design of the data center .

If the PDU verification load can only support AC or only DC, then testing will require two sets of equipment—increasing costs and adding complexity to on-site operations.

Fude Electronics’ rackmount product line covers multiple power standards: pure AC, pure DC, and AC/DC compatible. For example, the LB-8kW-AC220V/DC270V-J supports dual AC220V and DC270V inputs, allowing switching between AC and DC load simulation. The LB-36kW-AC220V/DC270V-J liquid-cooled rackmount also supports dual power inputs. This AC/DC compatibility allows the same equipment to be reused in data centers with different power supply architectures, improving equipment versatility and asset utilization.

The common logic behind the three questions

The three issues in PDU verification—connection point heating, branch voltage drop, and multiple branches under simultaneous load—have a common characteristic: they show almost no abnormalities in no-load or light-load tests, and only become apparent under full load.

This is precisely why PDU verification loads are irreplaceable. They are not used to “prove that the PDU is good,” but to “find where the PDU has problems.” A PDU that exhibits normal temperature rise during full-load testing, voltage drop within allowable limits, and the ability to operate without tripping when all branches are simultaneously loaded—that is a PDU that is truly ready for delivery and use.

Conclusion

Acceptance testing of data center PDUs should not stop at the three steps of “powering on under no-load, measuring voltage, and signing off”. Overheating at connection points, voltage drop in branch circuits, and multiple branches under simultaneous load—these three issues will only appear under full-load conditions, and can only be verified under full-load conditions.

The value of data center PDU verification workloads lies in expanding the verification scenario from “no load” to “full load”—using a controlled current load to discover hidden problems that would never surface during light load testing. The purchase cost of a single PDU may only be a few thousand yuan, but the loss from an unplanned downtime due to a PDU failure could be hundreds of times that amount. Conducting a complete full-load PDU verification using rack-mounted dummy loads before racking servers is a worthwhile “cost of problem discovery.”