Here's an example photo of what I'm talking about.
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| Modeling PDUs https://brainfiller.com/arcflashforum/viewtopic.php?f=23&t=6468 |
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| Author: | NeDCE [ Fri Jul 31, 2026 8:59 am ] |
| Post subject: | Modeling PDUs |
How do you guys typically model PDUs? Do you model each component like an individual component? do you model the wiring in-between? For example, a recent project includes an IT floor with CRACs, PDUs, and server equipment. A typical trunk might include a distribution panel feeding a number of PDUs, which comprise a 480V, 200A breaker>few feet of conductor>transformer>two "panel" main 225A breakers>misc. branch circuit breakers, including one 3-pole 100a breaker which feeds a subsequent panel 20'-150' away. I'm inclined to model each component, however the PDU transformers have no impedance numbers on their nameplates. I know transformers of that size typically range from 2-5%, but I've also heard that PDU transformers tend to have lower impedances. Do you guys typically model every component or treat them as a single component? |
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| Author: | mparenteau [ Fri Jul 31, 2026 12:47 pm ] |
| Post subject: | Re: Modeling PDUs |
Every component... Mike |
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| Author: | jmoore284@gmail.com [ Fri Aug 07, 2026 1:31 pm ] |
| Post subject: | Re: Modeling PDUs |
Every component. I've not seen a PDU with isolation so you'll likely label with the worst case IE and the highest voltage. |
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| Author: | NeDCE [ Wed Aug 12, 2026 12:07 pm ] |
| Post subject: | Re: Modeling PDUs |
jmoore284@gmail.com wrote: Every component. I've not seen a PDU with isolation so you'll likely label with the worst case IE and the highest voltage. Thanks, guys. So question: What do you consider an appropriate estimation for impedance? Despite being a well-known brand of PDU, the transformers do not list impedance. I'm hesitant to estimate for impedance because it has such an outsized effect on incident energy. |
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| Author: | NeDCE [ Wed Aug 12, 2026 12:14 pm ] | ||
| Post subject: | Re: Modeling PDUs | ||
Here's an example photo of what I'm talking about.
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| Author: | mparenteau [ Thu Aug 13, 2026 5:49 am ] |
| Post subject: | Re: Modeling PDUs |
What I've done in these cases is either: 1) Ask the customer for a submittal. If that is a dead end; 2) Assume an impedance and document that in the report. There are a number of references for impedance estimates you can use for dry types. Mike |
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