[TCML] Looking for Pole Pig Capacitors

Tue Nov 29 17:26:49 MST 2011

Hey---

Without a de-Qing diode the voltage on the storage cap fluctuates in a 
sort of random manner above and below zero, and you can't get a full 
charge in a larger cap.  With the diode the voltageclimbs to a max and 
stays there until the switch gap is triggered, then the sequence starts 
again, and if you want you can use a cap of any size.  However, 40ish kV 
sounds hairy.  With a full bridge rectifier on a 14.4 xfmr, you get 
about 20 kV, which with full reversal is still within the ratings of a 
50 kV cap.  With a resonant system, you need a storage cap about 5x the 
primary gap, although it doesn't need to be a pulse cap.  With the full 
bridge, you only need the primary cap.

---Carl

> On 11/28/2011 1:12 PM, David Rieben wrote:
>> 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 at tabbal.net>  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 at att.net>  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 at tabbal.net>
>>>> To: "Tesla Coil Mailing List"<tesla at pupman.com>
>>>> 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 at roadrunner.com>  
>>>>> 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
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> ______________________________****_________________
>>>>>>> Tesla mailing list
>>>>>>> Tesla at pupman.com
>>>>>>> http://www.pupman.com/mailman/****listinfo/tesla<http://www.pupman.com/mailman/**listinfo/tesla> 
>>>>>>>
>>>>>>> <http://www.**pupman.com/mailman/listinfo/**tesla<http://www.pupman.com/mailman/listinfo/tesla> 
>>>>>>>
>>>>>>>
>>>>>>> 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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>>>>>>
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>>>>>>
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>>>>>
>>>>>
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>>>>
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> Travis,   When I first built my big DC resonant charging Tesla coil I 
> was using 7200 volt pole pig with a voltage double and I used a 5uF 
> filter capacitor.  The important thing about your filter capacitor is 
> that it protects the diodes in your voltage doubler.  If you have a 
> little ripple in your supply voltage you wont notice it.    One nice 
> thing about about the voltage doubler is that you can regulate the 
> output by changing the size of the shifter capacitor.   Most people 
> don't have variacs that can handle a pole pig system these days.
>
>   As for the voltage doubling effect at the primary capacitor, you 
> don't have to worry about that.     The same thing goes on with an AC 
> system to some degree and remember the peak voltage of 14.5 KV 
> transformer is 20.5 KV  .       I have upgraded from the 7.2 KV  pole 
> pig to a 19.5 KV pole pig that I am using with a full wave rectifier 
> and a 1 uF filter capacitor and I haven't blown any capacitors yet and 
> that's running it with 230V going directly to the pig with no 
> ballasting !      I do believe I'm on thin ice though.   I haven't put 
> on a lot of run time running it this way.
>
>  As for the deQing diode , I would say you will probably want that .  
> Some smaller DC resonant Tesla coils I have built didn't need them but 
> my big one dose need it.     I haven't done much running with low 
> break rates.   My big coil runs at about 400 breaks per second but on 
> one of the first DC coils I ever built I got the longest sparks 
> running at a real low break rate because I had a limited power supply 
> .   It was some kind of a MOT with voltage doubler arrangement.
>
> Roger
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