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Re: [TCML] Looking for Pole Pig Capacitors

Hey---
In a resonant charging system, the storage cap only sees a small voltage change. The problem with this system is that the storage cap stores a huge amount of energy, so if something bad happens it can result in an only slightly nonnuclear explosion. Also, the whole voltage swing across the primary cap has to be significantly lower than the cap's voltage rating, especially for repetitive discharge. You might consider a full-bridge rectifier instead--no excess stored energy and you can adjust the turns of the primary to match the voltage. It still has the advantage of the wide range of repetition rates. More diodes to acquire, of course. 

---Carl






Travis,

Yea, the DC Res charging allows the versatility of a widely variable bps rate. I think you would also need a de-Q-ing diode between the storage cap and the primary cap as well. I have personally never built a DC Res charging
power supply so you may do better seeking the advice of someone who has actual experience with this type of coil system. I know Roger Smith's big coil is a DC Res system. Maybe he could chip in on this?

David Rieben

On Nov 28, 2011, at 10:52 AM, Travis Tabbal<travis@xxxxxxxxxx>  wrote:


Thanks for the great info. I wondered if I would be able to charge a .3uF
with my 10kVA 14.4KV pig. LTR is an option, but I don't have a sync
motor... DC resonant looked interesting to me though. Other than needing a
big cap rated for the transformer voltage, and diodes along with the
inductor, anything to look out for? I think one of my pigs can do 7.2Kv, so
the DC resonant mode would kick it up to 14.4 if I'm reading properly. Does
the DC filter cap see the inductive kick? I know the primary cap does.
Designing for 28kV sounds.... interesting... not sure I want to go there...


On Sat, Nov 26, 2011 at 2:33 PM, drieben<drieben@xxxxxxx>  wrote:


Hi Travis,

No, I suppose there really isn't a reason, other
than that it would take a power supply of con-
siderable magnitude to be able to fully charge
a .3 uFd cap, at 14.4 kV (maybe more than the
typical residential, single phase electrical service could
reliably provide), especially with an ARSG churning
out several hundred breaks per second. This is
the typical way in which a classic SG driven, 14.4 kV
pole pig powered coil system is operated. If one was
so inclined to operate their pig powered system
LTR, with an SRSG at 120 BPS, or a DC resonant
charging power supply with a pole pig (ala - Roger Smith),
OR, if you are operating with a lower voltage output pole
pig, then a single unit of this persuation may be your ticket
to success ;^) Amir Mojarradi was looking for a suitable
capacitor in the 0.1 to 0.2 uFd range (and rightfully so
for the size and specs of his coil system, as his coil was
running great w/ 0.14 uFd), so that was the reason for
my suggestion as to the feasability of two of these units
in a series configuration.

Also, I would consider a 50 kV(DC) rating on a commercial
pulse cap to be on the very low end of the acceptable spec limit
for a suitable primary cap in a coil system driven by a 14,400
volt pole pig (especially with the high charge/discharge BPS
duty cycle of an ARSG). As Amir can now handily attest, a
35 kVDC rating is certainly NOT sufficient for a 14.4 kVAC
pole pig power supply! I have also personally experienced
a failure of a 0.1 uFd, 50 kV rated Hipotronics pulse cap
in my Green Monster Tesla coil system and I probably
only got 2-3 hours of total run time out of it before failure.
My GM coil also utilizes a 10 kVA, 240V/14.4 kV pig.
An autopsy revealed that the failure mode of the Hipotronics
cap was strickly dielectric breakdown, due to overvoltage -
NOT over current. The cap unit had no external signs of
internal failure - no case rupture or external bulging/swelling,
and the Hipotronics unit didn't get warm during operation.
I am currently using a 31885 Maxwell 0.1 uFd, 75 kVDC
rated Maxwell pulse cap and have had no more problems.
The 100 kV rating of two 50 kV rated units, in series, should
prove nearly bullet-proof for a 14.4 kV driven system. ;^)

Happy Sparkin',
David


----- Original Message ----- From: "Travis Tabbal"<travis@xxxxxxxxxx>
To: "Tesla Coil Mailing List"<tesla@xxxxxxxxxx>
Sent: Friday, November 25, 2011 9:45 PM
Subject: Re: [TCML] Looking for Pole Pig Capacitors


I've been considering one of those for a coil with similar power input.

Any
reason .3uf wouldn't work with a properly tuned primary and top load?
On Nov 25, 2011 8:31 PM, "Roger Smith"<rwsmith@xxxxxxxxxxxxxx>  wrote:

On 11/25/2011 5:53 PM, Amir Mojarradi wrote:



Hello everyone!

I recently destroyed a 0.03 uFd  35kv Maxwell capacitor (#37667) of
which
I was using (4) in parallel to achieve 0.15 uFd at 35kv. I am running a
10kva 14.7kv pole pig powered coil with a 12in diameter, 57" winding
length
secondary, and a 60in major/ 12in minor diameter toroid. The single
capacitor cracked in half and splashed oil for a good 8 feet.
Evidently, my
configuration was poorly designed to handle the ~ 15 kv input.
Apparently,
people have had this issue before and I was previously warned by David
Rieben.

David suggested 2 of these Aerovox 0.305 uFd 50KV Capacitors in series,
but that would be a bit pricey given the shipping for about152 lbs!
Yet, I
am considering them.
http://www.ebay.com/itm/****Aerovox-Tesla-50KV-High-**<http://www.ebay.com/itm/**Aerovox-Tesla-50KV-High-**>
Voltage-Aerostor-Pulse-****Capacitor-/200679608603?pt=LH_****
DefaultDomain_0&hash=****item2eb96fd11b<http://www.**
ebay.com/itm/Aerovox-Tesla-**50KV-High-Voltage-Aerostor-**
Pulse-Capacitor-/200679608603?**pt=LH_DefaultDomain_0&hash=**
item2eb96fd11b<http://www.ebay.com/itm/Aerovox-Tesla-50KV-High-Voltage-Aerostor-Pulse-Capacitor-/200679608603?pt=LH_DefaultDomain_0&hash=item2eb96fd11b>

Is anyone willing to sell pole pig suitable capacitors, either single
unit or several, for approximately a 0.15uFd  50KV + rated capacitor
bank?
I'm a student and my budget is around $100-200 and I will of course pay
for
shipping and handling; I live near Pasadena, California. Please let me
know
if you have any comments or suggestions regarding possible capacitor
choices; they will be greatly appreciated.

Thank you for your kindness,

Amir Mojarradi



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Those Aerovox capacitors sound like a good deal to me.   Im tempted to


get a couple myself but if I made my coil any more powerful I would have
to
take it outside to run it.    Your set up sounds pretty awesome.  Do you
have any pictures?

Roger
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