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 16:53:37 -0500
From: Mike <mike.marcum@xxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: The Geek Group High Voltage Capacitors, making a HV switch,  (fwd)

Cap charging is the reverse of the RC time constant (draining thru a 
resistor), so the charge rises rapidly at first then slows down as the 
24500v is reached. Ideally a 25kV meter on it would let you see what's going 
on (as opposed to "guessing" what the voltage/energy level is, which is 
scary with this kind of power). Depending on nst manufacturer the effective 
R of the reverse RC time can vary (as well as the R of the rest of the 
circuit to a lesser degree). I'd personally rely on a meter to see what's 
happening and avoid accidents (ex: if the nst resonates with something not 
obvious and puts out more than 24500v but you weren't prepared for the extra 
energy, or if the actual charge time to that is shorter than calculated, 
etc).

Mike
----- Original Message ----- 
From: "High Voltage list" <hvlist@xxxxxxxxxx>
To: "hvlist" <hvlist@xxxxxxxxxx>
Sent: Wednesday, November 01, 2006 4:34 PM
Subject: Re: The Geek Group High Voltage Capacitors, making a HV switch, 
(fwd)


> 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.
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