Re: Current Transformer problems

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

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
> 
> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Mddeming-at-aol-dot-com>
> 
> Hi All,
>          This question is for anyone with experience in use of current
> transformers and O-scopes.
> I made a quick current transformer by winding 20 ft (~150 turns) of #20
magnet
> wire around a 1-inch ID ferrite toroid When I hook it to my scope I get a
wave
> pattern that is very distorted with overtones, 2f, 4f, etc., and pulses of HF
> ringing.
> This is on the inlet side of the control box without the coil or cap
attached.
> The entire lab is lined with grounded wire mesh except the front door.
> 1. What am I doing wrong?
> 2. How can I fix it?
> Matt D.

	Could be a lot of problems, probably resonance in the transformer
winding itself; that's a lot of inductance.  Of course, some of what you
see is probably real. In order to measure current, rather than the rate
of change of current, you need to load the coil with a suitable value of
resistance.  If you didn't do that you were accentuating the harmonics,
as the output of the transformer would increase with frequency.  If
you'll do a Google search on "current transformers" you'll find a lot of
good tutorial material, as well as descriptions of many commercial
devices.

Ed