Re: Current Limiting and Impedence

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Paul B. Brodie" <pbbrodie@xxxxxxxxxxxxx>

Malcolm,
You mention N27 ferrites but the ferrites I have access to are surplus and 
completely unmarked and of unknown origin. The good thing is that I have a 
bucketload of them that have accumulated from various sources over many 
years. I believe that most of them are ferrite beads that were on power 
cords. Would these work in use as you suggested, crushed up in a PVC tube? 
I like this idea as I have ready access to so many ferrite beads. Since it 
sounds so good, I just know you are going to tell me that they are 
completely different from the ferrite used for toroids and transformers and 
therefore useless for this application. {:-(
Regards.
Paul
Think Positive

----- Original Message -----
From: "Tesla list" <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx>
To: <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx>
Sent: Thursday, May 12, 2005 4:46 PM
Subject: Re: Current Limiting and Impedence

> Original poster: "Malcolm Watts" 
<<mailto:m.j.watts@xxxxxxxxxxxx>m.j.watts@xxxxxxxxxxxx>
>
> On 12 May 2005, at 10:27, Tesla list wrote:
>
> > Original poster: "Gerald  Reynolds" 
<<mailto:gerryreynolds@xxxxxxxxxxxxx>gerryreynolds@xxxxxxxxxxxxx>
> >
> > Hi Malcolm,
> >
> > Where can you get Silicon steel?? Do they make welding rods out of
> > this stuff or is there another alloy that would work?? and what
> > diameter rod should we be looking for??
> >
> > Gerry R.
>
> Hi Gerry,
>           Silicon steel is the material used in transformer
> laminations. I can't suggest any shortcuts to getting it any other
> way sorry. I'm suggesting making the core using discarded transformer
> laminations. You just want whatever material you are using to have as
> small a cross-sectional area as small possible to minimize eddy
> currents. A tale was recounted some years ago of someone who made a
> ballast core from varnished welding rods which got so hot that the
> varnish melted. It is questionable whether low-frequency type
> transformer iron is really that suited to the job anyway as the gap
> is going to throw step functions at it. A PVC tube full of smashed up
> N27 ferrites would be a better option. I did this once and built two
> such cores.
>
> Malcolm
>
>
>
> >
> > >Original poster: "Malcolm Watts" 
<<mailto:m.j.watts@xxxxxxxxxxxx>m.j.watts@xxxxxxxxxxxx>
> > >
> > >Hi Paul,
> > >           Whatever rods you purchase for the core, they have to have
> > >a very small x-sectional area. They should also not retain much if
> > >any magnetism after being de-energized (check with a magnet) or they
> > >will have large hysteresis losses resulting in lots of heating.
> > >Silicon steel such as used in transformer cores is preferred if you
> > >can get them.
> > >
> > >Malcolm
> >
> >
> >
> >
> >
>
>