Re: Recent power arc experiments

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

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

Hi Boris,

Water resistors are made not bought... :^)
A water resistor is simply an insulated tube containing an ionic
solution of water and a metal salt (usually copper sulfate) capped with
electrodes on each end. It's sometimes called an electrolytic or copper
sulfate resistor. These are often used in high voltage and pulsed power
work because of their capability to absorb considerable power at high
voltages without breakdown. It can be fabricated using clear flexible
vinyl tubing with properly sized copper electrodes sealing each end. The
electrolyte is simply distilled water and copper sulfate - the more
dissolved CuSO4 or the larger the internal diameter of the tubing, the
lower the resistance, and total resistance simply scales linearly with
length.

When current flows through the resistor, copper is simply electroplated
from the anode to the cathode with little, if any, evolution of gas at
the electrodes. Because of the excellent thermal capacity of water, it
can absorb huge amounts of pulsed power safely and predictably. I was
originally going to water resistors as charging and bleeder resistors on
the Quarter Shrinker before I found a batch of 20k 225 watt power
resistors at the local recycling center (dump!). Some difficulties with
using these: the resistance will slowly change over time as ions leach
from the electrodes, and (in unheated labs) they may tend to freeze
during the winter in northern climates. 

Jim Lux has an excellent article proving specific design information for
these at his site:
  http://home.earthlink-dot-net/~jimlux/hv/rwater.htm

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-net
Web Site: http://www.teslamania-dot-com

Tesla list wrote:
> 
> Original poster: "boris petkovic by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <petkovic7-at-yahoo-dot-com>
> 
> --- Tesla list <tesla-at-pupman-dot-com> wrote:
> > Original poster: "Bert Hickman by way of Terry Fritz
> > <twftesla-at-uswest-dot-net>" <bert.hickman-at-aquila-dot-net>
> >
> > Boris,
> >
<SNIP>
> > It would be interesting to duplicate the resistor
> > experiment with a
> > chain of longer HV resistors capable of withstanding
> > the peak transient
> > voltage. Another alternative might be a long, small
> > diameter water
> > resistor.
> >
> > -- Bert --
> 
> Bert,
> 
> Thanks for your comments and suggestions.
> These were definitely not HV resistors but cheap
> resistors for low voltage  network (yellow body with
> coloured rings on it describing their ohmmage) and
> used in various power electronic devices I guess.
> To our surprise, 9 of them in string survived TC
> arcing experiments without destruction as was checked
> latter!
> Except their possible suspicious behaviour during fast
> transients ,I'm ready to blame extra high frequency
> itself for lack of heating effect to resistors.
> Boy,there could be 20 Mhz or more here..
> Attached arc looked even more brighter when
> 6" long wire (for accepting the arc) was connected to
> the first resistor of the  string instead of 3" long
> wire.
> The structure and colour of that arc surely indicate
> it can not be treated as corona arc ( ~200 k ,1 pF per
> foot).
> 
> Where to look for  small diameter water resistor (I
> haven't seen such thing before)?
> 
> Regards,
> Boris
> 
> 
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