Re: Suggestion for current limiting

To: tesla-at-poodle.pupman-dot-com
Subject: Re: Suggestion for current limiting
From: Tesla List <tesla-at-stic-dot-net>
Date: Wed, 28 May 1997 07:39:33 -0500
Approved: tesla-at-stic-dot-net
Subject:  Re: Suggestion for current limiting
  Date:   Tue, 27 May 1997 13:58:13 -0600
  From:   "DR.RESONANCE" <DR.RESONANCE-at-next-wave-dot-net>
    To:   "Tesla List" <tesla-at-pupman-dot-com>


To: Rodney Davis

Good idea Bill but it doesn't work in practice as well as in theory. 
Large
water resistors have been used for years to limit charging current in
large
Marx generators.  A small amount of blue copper sulfate crystals are
usually added to make the liquid slightly conductive but still have a
value
of 100K or so for charging.

The problem actually isn't the liquid --- it's the electrodes.  It seems
after a few weeks the ions begin drifting off the metal electrodes and
make
the water highly conductive.  This system works only if very pure
materials
such as platinum are used for the electrodes otherwise the value keeps
changing and usually only requires a few weeks to become too conductive
to
provide effective current limiting and as William pointed out there is a
great danger of steam forming.

A good quality high silicone C core reactor with a cross sectional area
of 
9-11 in. squared seems to work the best without a lot of mess.  120-160
turns tapped every 10 turns on this reactor works well.  Use a quality
10
KW  1/2 Ohm series resistor to prevent rapid saturation with this
reactor.

DR.RESONANCE-at-next-wave-dot-net


----------

> 
> 
> good idea, but beware of 2 things:
> 1. steam production - if you seal the pipe it may well explode
> 2. I wouldn't be too suprised to see the resistance decrease with time
> as ions 
> are pulled off of the electrical contacts, but it would be an
> interesting 
> experiment.  If the resistance did decrease with time, then the circuit
> could 
> "run away" and that could be a problem.
> 

> 
> Hi all,
> 
> Ever thought of current-limiting that 10KVA pig-pole transformer with
> water?
> 
> Since water in it's pure (distilled) form is a perfect insulator, since
> there are no impurities or free ions to conduct electrons.
> 
> I built a resistor out of 1" diam PVC pipe, about 6 feet in length, 
> plugged at each end with feed-thru conductors, where I filled the pipe
> with distilled water, then added tap water to give it conduction.
> While adding the tap water, I was continuously measuring the resistance. 
> Once I reached the required resistance, I plugged it up.
> 
> The beauty of this resistor is that it can dissapate heat very well, so
> it's ideal for current limiting and I haven't had any problems at all
> with
> operation.
> 
> The costs was < $10 as I mostly had all the parts lying around the
> house...
> 
> Well, there's a cheap solution if you don't have an arc-welder! :-)
> 
> My suggestions for the day...
> 
> Catchya!
> Rod