February 2013
Intermediate to advanced
480 pages
13h 35m
English
Content preview from Power Over Ethernet Interoperability GuideBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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What Happens during the Surge Test
In Fig. 11.4, we monitor the voltage and current associated with the surge. Let us do some simple math around this. If we apply 2 kV across a dead short (say the almost-uncharged caps at the input or output of the PSE), we will get an instantaneous current of I = V/R = 2000/42 ≈ 47 A. Well, this is the simplified upper limit. In reality, we can get much less. There are two related reasons for that. First, the voltage does not reach 2000 V immediately. It takes a few microseconds to get there. And things can change quite dramatically during that brief instant. Which brings us to the second reason: All the surge current must pass through the Y-caps (in series, thus acting as a bottleneck). So if we reduce the ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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