Re: [TCML] Pole Pig Cap

["Christoph Bohr" <cb@xxxxxxxxxxxxxxx>]

Hello.

It has bee some years since I read that data sheet, but iirc
it was at 20% voltage reversal max in mainly DC applications.
So you have to seriously derate for TC use. These caps work fine
on small to medium systems with up to 10, maybe 12KV, but with more
you would be pushing things too much. With a pig you would need quite
an array of those caps in series parallel.

regards

Christoph Bohr

> DC -
>
> Once again, the Maxwell datasheet for the Model 37667 cap (.03uF @ 35kV)
> shows a 500 PPS rating.
>
> Herr Zapp
>
> --- On Sun, 6/7/09, DC Cox <resonance@xxxxxxxxxxxx> wrote:
>
> From: DC Cox <resonance@xxxxxxxxxxxx>
> Subject: Re: [TCML] Pole Pig Cap
> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
> Date: Sunday, June 7, 2009, 7:16 PM
>
> The pulse rate of the 35 kV Maxwells is usually around 2-3 pps, not high
> enough for the 400 ppps a large coil operates best at.
>
> The 10 AWG is not large enough.  The xmfr hits peaks drawing approx 7-8
> times the average current value.  You should use
> 6  AWG at 60-70 Amps over it will over heat.  Ask me how I know this ---
> melted windings.
>
> non synchro around 400 pps is the best way for large sparks.
>
> DC
>
>
>
>
> On Sun, Jun 7, 2009 at 3:41 PM, Tyler Pauly <rpggod714@xxxxxxxxx> wrote:
>
>>
>> I'm still brainstorming on my choice of tank cap for my 10 kVA pig.  The
>> goal was to run it around 12-14 kVA  by means of 240V 50-60A.  It will
>> be
>> limited by a ballast inductor of 10 gauge wire wound around a PVC form
>> with
>> individually insulated welding rods inside.  I will soon be testing the
>> ballast to see if the 10 gauge can take short run times without going up
>> in
>> flames.
>>
>> As to the capacitor choice, I'd love to go with one of DC's .1 mfd 80kV
>> caps but I just can't afford one at the moment.  I looked at the
>> standard
>> 37667 Maxwells but I don't think I'm comfortable with running single cap
>> strings, as the 35 kV rating just isn't high enough for comfort, unless
>> someone else has run w/o problems?  MMC's seem to be out of the question
>> as
>> well, unless there is some cap I haven't yet found.
>>
>> However, all of the above thought process was assuming trying to get
>> ~.1mfd.
>>
>> I recently came upon documentation of STR caps.  I was scanning the
>> archive
>> for STR caps with pole pigs, and I can't really find much.  What is the
>> consensus on having a STR cap?  I was hoping for something around
>> .04-.05
>> mfd.  Cres looks to be .092 mfd for 60A input and .0767 mfd for 50A.
>>  However, these C values don't take into account the L of my ballast,
>> which
>> seems to be important.  I don't know how to do this...
>>
>>
>> What I could find on STR's usually associated them with ARSG's; why is
>> that?  I had planned on using a RSG.
>>
>> If STR's are an accepted cap choice, this would really help cut costs;
>> since I'm still technically a poor college student, I can't really drop
>> 750
>> dollars on capacitors.
>>
>> Thanks guys for all the help.
>>
>> Tyler
>>
>>
>>
>>
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