Re: 4800V 1kVA PTs for sale. CT Question

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-qwest-dot-net>" <bert.hickman-at-aquila-dot-net>

Chris,

A current transformer (CT) is another type of "instrument transformer",
and it's used to measure current passing through a conductor that's run
through the center opening of the transformer, forming a single turn
"primary" for the CT. A CT is used to accurately transform a high
current to a low one that can then be measured remotely at a safe
potential. It is used to meter current flow, or may be used to protect
systems from excessive current (such as a trip for a circuit breaker).
In normal use, a 0-5 Amp full scale AC Ammeter is connected to the
output of the CT, but the "scale" of the meter is set to be the same
full scale rating as the CT. 

For example, a 1000:5 CT would "mate" with a meter whose scale is set to
0-1000 amps even though, at full scale, the meter was actually only
"measuring" 5 amps full scale. An ammeter that's meant to run this way
often has a small "1000:5" somewhere on the scale of the meter, telling
you that it's meant to run with a 1000:5 CT. When 1000 amps is flowing
through the center wire going through the CT, 5 amps would flow through
the CT's secondary, driving the meter to full scale. The meter scale
would read 1000 amps even though it was "really" only seeing 5 amps.
You'll find that virtually all CT's are rated at XXXX:5, implying that
they want to work with a 5A full scale AC ammeter.  

CT's are the "current" equivalent to Voltage Transformers or Potential
Transformers (PT's). BTW, NEVER disconnect a CT secondary from the meter
while it has current passing through the center conductor... the high
voltage that's developed can injure or kill you!

Safe coilin' to you!

-- Bert --

Tesla list wrote:
> 
> Original poster: "Christopher Boden by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <chrisboden-at-hotmail-dot-com>
> 
> As promiced I got a couple more PTs in srock today. The Geek Group is
> selling 4800V 1kVA PT's, Mint condition. I have a matched pair.
> 
> Could somebody please explain to me what a Current Transformer is, does, and
> in detail, how it works? I have the ability to easily scrounge about a dozen
> or more in various sizes if they're worth my time. Would anyone be
> interested in some?
> 
> duck
> 
> Christopher A. Boden Geek#1
> President / C.E.O. / Alpha Geek
> The Geek Group
> www.thegeekgroup-dot-org
> Because the Geek shall inherit the Earth!
> 
> _________________________________________________________________
> Get your FREE download of MSN Explorer at http://explorer.msn-dot-com