Re: The Geek Group High Voltage Capacitors, making a HV switch, (fwd)

["High Voltage list" <hvlist@xxxxxxxxxx>]

Original poster: Steven Roys <sroys@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Wed, 1 Nov 2006 08:27:45 -0800 (PST)
From: C. Sibley <a37chevy@xxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: The Geek Group High Voltage Capacitors, making a HV switch,  (fwd)

With respect to charging, how large of a power supply does one need?  I'm considering two of the geek capacitors in parallel, for 14.8uF.  If I were to charge with a 60mA 15KV NST to a peak voltage of (24500V), I calculate total energy of 4500 Joules.  Assuming a .8 power factor, a 60mA 15K NST puts out about 720W.  Since "Joules" is watt*seconds, is it just as simple as dividing Joules/watts to get seconds of charging time?  With that I get just over 6 seconds, but that seems like a low number.  I assume that I'm doing something wrong, but even with a factor of 10 it's only a minute.  Is an NST a good choice for a charger, or should I look for something bigger?

Curt.

---------- Forwarded message ----------
Date: Mon, 30 Oct 2006 19:29:10 +0800
From: Peter Terren <pterren@xxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: The Geek Group High Voltage Capacitors, making a HV switch, 

You don't have to disconnect the power supply, however, if you were to have 
100% voltage reversal in an inductive load, the power supply has to cope 
with 50kV in the reverse polarity ie not just a short circuit but a full 
reverse voltage.  You need to make your charger able to acomodate this or 
you will lose your diodes to overcurrent. A suitable resistor is needed 
rated at 100kV - easy!. Failure to appreciate this is why I have seen some 
people blow diodes.
Your charge/discharge switch can be very low power connections.
Constructing a switch to do what you have specified really only needs to 
have one heavy contact with a 4-6 inch travel for safety with big brass 
contacts.  I dampen my contact with neoprene behind the contact to avoid 
bounce and make the gap more efficient. At those voltages though, much of 
the the energy will have gone by the time the contact is made as the spark 
will probably strike when the contacts are a bit less than 1 inch apart..
You need to have a very positive device controlled by a long string. I use a 
simple spacer holding the electrodes apart and the heavy trampoline springs 
do the rest.  You don't want to be close when wires are exploding.

My switch here http://tesladownunder.com/PulseCapsSwitch.jpg
The relevant pages for my cap bank
http://tesladownunder.com/CanCrushing.htm#Can%20crusher%204
and exploding wires.
http://tesladownunder.com/Pulse_Power.htm

Peter

> ---------- Forwarded message ----------
> Date: Thu, 26 Oct 2006 19:15:31 -0700
> From: Jim Mora <jmora@xxxxxxxxxxx>
> To: 'High Voltage list' <hvlist@xxxxxxxxxx>
> Subject: The Geek Group High Voltage Capacitors, making a HV switch,
>     or HV switch gear
>
> Hello all,
>
> I would like to start a thread on the large number of The Geek Group HV
> capacitors recently sent to them from Lawrence - Livermore. They typically
> are 7.2uf 50KV 9000 Joules.
>
> I need some suggestions to create a High voltage double pole triple throw
> switch that could handle an exploding wire demonstration in the several KJ
> range at say 30-40KV.
>
> One position would be for charging, one for standby, and one for fire. 
> This
> could be two switches one to disconnect the PS and one to close the 
> business
> end. A third could be a final absolute bleeder. Anyone who has done this
> sort of experience please chime in.
>
> I have some HV pole switches but they surely can't take this abuse.
>
> This forum seems more appropriately posted here then on the Tesla list.
> Please invite us if that is acceptable with you.
>
> Best Regards,
> Jim Mora
> Ojai, Ca.