On Apr 26, 4:47 pm, Peter Wieck wrote:
On Apr 26, 1:39 pm, Eeyore
wrote:
Peter Wieck wrote:
Eeyore wrote:
Peter Wieck wrote:
Repeat: You are entirely unencumbered by the thought process. When you
get your meds adjusted and learn to think clearly rather than like a
gerbil on PCP, please do come back and revisit this.
What Phil is quite correctly pointing out is that the use of an isolation transformer means that
you will get no protection from an 'earth leakage current' breaker feeding it.
Your very life might depend on it. Do not use isolation transformers 'willy nilly'. They have their
dangers.
I have no clue as to what sorts of GFIC devices you use, and how they
are configured, but in this country (USA), based on NEC requirements
the Device measures any deviations between input and output and will
trip on any leakage to ground.
It works bt detecting any line-neutral imbalance.
Let's look at the nature of a GFIC device: It is designed to trip when
the current goes anywhere other than from hot to neutral. Can we agree
on that?
Yes.
If that is the case, and you insert yourself into a circuit *between
the hot and the neutral*, whether there is a GFIC device or not, you
will get zapped, as it cannot differentiate between you and a 1/4 watt
10,000 ohm resistor put in the same location.. or a 25 what
incandescent lamp, for that matter.
Which is exactly what happens when you use an isoaltion transformer if you're touching the live and
ground say and the neutral is also grounded. You become a perfectly valid load and get electrocuted
whilst the breaker sees no problem with that. Remove the isolating transformer and the breaker will trip.
Graham- Hide quoted text -
- Show quoted text -
Clearly you do not understand the nature of lab-grade isolation
transformers. ALL power through them is 'above ground', the only valid
path is hot-to-neutral. There is no ground path from the isolated hot
side. Whether the neutral is grounded or not. There is still no path
except between hot and neutral... same as there would (should) be
anyway.
Don't take my word for it. Set it up and test it for yourself. You can
ground the test piece to a good direct ground. And then measure a VOM
from the hot side to it. No current will flow. And you can short the
neutral to the ground and do the same. It still won't go through the
ground. Or, measure current from neutral to ground. Nothing. Connect
your GFIC device. Use a leaky test-probe from a signal generator or
scope not isolated to the test piece... *POP* goes the breaker. As it
should. Lots-O-Speculation here, little actual experience testing from
appearances. It ain't nohow black magic.
This is an unique condition, and isolated (pun intended) to test-bench
conditions, to be used by someone who clearly understands the
limitations of the device with great specificity to what it does NOT
do.
Now, of course, consider your scenario under hospital conditions where
all sorts of wet stuff, machines, needles and monitors are operated
through isolation transformers to protect the patient (and the
machinery) from stray currents that could be anything from life-
threatening to causing the machines to malfunction. If your scenario
obtained, there would be no benefit to their use... which, of course,
is not the case.
http://www.reo.co.uk/files/kbase/Saf...ansformers.pdf
http://www.mhennessy.f9.co.uk/isolating/index.htm
http://www.sussex.ac.uk/Units/safety/sgn/sgn08.pdf
http://www.reo.co.uk/news_article/71/0
http://jobfunctions.bnet.com/whitepa...px?docid=58852
http://www.freelists.org/archives/pc.../msg00012.html
http://www.trft.org/TRFTPix/CHRSSafety.pdf
http://www.wireless-workshop.com/safety.htm
I always see problems in if the people are not aware of what a regular
isolation does and is connected. I was reverifying how they are
connected. For servicing equipment, I make use of a transformer that
has the secondary completely isolated, which is not the case with
approved devices.
By the way, I use variacs, isolation transformers, and light bulbs, as
needed to control power.
According to rules, isolation transformers have one side of the
secondary tied to ground. The ground
goes from input to output. The secondary is ground referenced and can
be hazardous working
on equipment. An isolations transformer is designed to minimize common
mode leakage current from
primary to secondary. It also effectively filters common mode noise.
Drawn like this...............
http://zekfrivolous.com/iso/isozoom.JPG.
Like all these and the medical approved......................
http://www.tripplite.com/products/co...eneral_purpose
The medical units have the better plugs but are otherwise the same.
Operating rooms have a 100 ua limit but even that can be hazardous
with open
tissue.
I found some info from the original stuff from Mark Waller.
http://www.smartpowersystems.com/New...%20article.pdf
greg