12 Nov
2011
12 Nov
'11
7:32 a.m.
On Sat, 12 Nov 2011, Mouse wrote:
Date: Sat, 12 Nov 2011 06:23:11 -0500 (EST)
From: Mouse <mouse at rodents-montreal.org>
Reply-To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
To: cctalk at classiccmp.org
Subject: Re: galvanic isolation (was Re: CMD CQD-220TM problems)
No...but the transformer is not going to pass very much power at mains
frequency; it's designed for much higher frequencies.
Also, "let's test that isolation" calls for different wiring than
"let's apply mains power across the output of the transformer".
Absolutely, once you fry the Ethernet transformer, you dont have _any_
isolation (carbon and copper vapor make poor insulators)
Note that though Ethernet is isolated it is very poorly isolated. Both
primary and secondary are jumble wound together on Ethernet isolation
transformers, the isolation depending entirely on the wire varnish
(which wont last long with an overload)
This is why small isolation transformers and OPTOs need current limiting
devices in their power supplies if failure could present shock hazard, a
carbonized isolator doesn't
I think
the original BOFH "joke" was "Let's see if that 10KV
isolation really works!"
10KV of galvanic isolation won't necessarily
help you much keeping
120VAC or 240VAC across an Ethernet transformer from resulting in
damage to the circuitry on the other side of the transformer.
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