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Re: HV power supply

Original poster: "Shaun Epp by way of Terry Fritz <twftesla-at-qwest-dot-net>" <scepp-at-mts-dot-net>

Makes sense to me,  I've seen your idea in plans before.  A capacitor
charger for high energy use that produces a much higher voltage than the
caps could handle to speed up charging.  The control for it either had a
voltmeter, variac, and switches so that YOU monitor the cap voltage and YOU
turn down/ shut off the charging supply when the voltage is high enough.
Or, Another approach used a comparator set up, obviously with voltage
dividers and sense circuit.  The charger would automatically charge up the
capacitors to a preset voltage, if in leaked off some, the charger circuit
would start charging again.  I've seen these in books and plans from
Information Unlimited.

BTW:  I'll be working on one of these soon too, I just have muster up the
guts to go high energy.

Shaun Epp

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, May 12, 2002 3:55 PM
Subject: Re: HV power supply

> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> In a message dated 5/12/02 11:01:24 AM Pacific Daylight Time,
> tesla-at-pupman-dot-com writes:
> << I may be wrong, but isn't overvolting any type of capicitor
>  a BAD thing?
>  Coiling In Pittsburgh
>  Ben McMillen
>   >>
> Hi Ben, all
> Yes, overvolting a capacitor is bad, but a large capacitor imparts
> a big load on the power supply so until the capacitor begins to get
> fully charged, the power supply will see the capacitor's low impe-
> dance as a near short which will make the actual voltage across
> the capacitor much lower than the rated output of the power supply.
> As the capacitor gradually charges, the voltage across the capa-
> citor will gradually rise. I used to charge large electrolytic capaci-
> tors (400 volt, 2500 uFD) with the rectified output of an MOT. MOTs
> usually put out ~2000 volts, but a discharged cap of this size is ba-
> sically a dead short until it begins to take on a charge. I had the
> input of the MOT controlled thru a variac but would turn the variac
> up to at least 30% (probably 700 volts or so). I of course had a
> volt meter at the terminals of the capacitor(s) and when the volt-
> age measurement at the cap's terminals reached the rated 400
> volts, i would simply shut off the power from the MOT. That's basic-
> ally what I'm trying to do with my 10 kV,10 kJ quarter shrinker/ can
> crusher capacitor bank now. If the supply voltage is only say 10
> kV, then since it takes 5 RC constants for the cap to completely
> charge to the supply voltage, it takes a looong time for the capa-
> citor's charge to to completely equal the voltage of the power sup-
> ply. The caps charge voltage can reach 80% of the power supply
> voltage pretty quickly, but it takes almost forever for it to reach
> > 99%. If the supply voltage is say only 20% higher than the cap
> voltage rating, the cap could be charged relatively quickly to its
> rated voltage and then removed from the power once its rated
> voltage has been reached. Of course, the impedance and current
> capacity of the power supply would also have a bearing on how
> quickly the cap could be charged, too (a 50 mA supply will charge
> faster than a 20 mA supply, assuming all other factors equal)
> Does any of this make sense :-)??
> David Rieben