Re: New Maxwell on ebay

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Sean Taylor" <sstaylor-at-uiuc.edu> 

Scot,

Voltage is a huge factor in lifetime of a pulse cap - something like a 
fourth power.  If you seriously derate the voltage of the cap (which it 
sounds like you are doing) it will last MUCH longer.  Also, I don't know 
exactly where you're getting the numbers for your total capacitance, but 
keep in mind that if each cap is different, you'll end up not sharing the 
voltage evenly!  The voltage reversal is related to the Q of the system, 
and there is a formula to determine one from the other, but I can't 
remember it, is was posted a while back.  Typically, though, a TC gives a 
cap a near 100% voltage reversal.  The reason that the Maxwell caps survive 
this is the voltage underrating.  The VR rating is kind of like an AC 
rating vs. DC rating.  If you don't use the cap to the full DC rating, you 
can get away with much more voltage reversal.

Sean Taylor
Urbana, IL


On Fri, 06 Aug 2004 07:41:26 -0600, Tesla list <tesla-at-pupman-dot-com> wrote:

>Original poster: "BunnyKiller" <bunikllr-at-bellsouth-dot-net> did a web check on 
>maxwell caps   didnt find too much but did find a page to General 
>Atomics  and they have a list of caps ( suppose they are a continuance of 
>maxwell)  with specs on the caps in question...   also rechecked my coil 
>and found that I had switched out 2 of the 31160's for 2   31231 caps  ( 
>50KV -at- .144uF)  that brings my total cap system to
>200KV -at- .0427uF   I also have sitting on the shelf a  31173 cap  ( 50KV -at- 
>.10uF)   neither of the 31231 or the 31173 are listed at General Atomics 
>site... but the 31160 is posted...
>what I am now wondering about is that the caps I have and compared to GA's 
>numbers, mine should have bit the dust a LONG time ago...  GA 
>quotes   1X10^5 pulses   thats only 100,000  pulses.   So how do my caps 
>last for almost 5 years with about 100+ hours running time on them in 
>T-Coil operation and not blow up?       What do they consider a pulse?
>a voltage reversal??  I always thought that the primary system saw a 
>complete voltage reversal at 60 times per second   ;)
>
>so if their numbers hold true   thats about a 30 minute life time  ;)
>
>things that make you go hmmmm...
>
>
>Scot D
>
>
>
>Tesla list wrote:
>
>>Original poster: "BunnyKiller" <bunikllr-at-bellsouth-dot-net>
>>I should never answer emails when tired..  :)
>>just went out and checked the numbers on the caps...
>>I have the 31160 series        50KV   .114uF caps   4 in series   =
>>200kv -at- .0285 uf
>>
>>same case style as the one in question  but taller by about 3-4 inches
>>
>>the smaller cubical shaped ones with the terminals on the sides are ( 
>>IIRC) what we see so often on Ebay, are the ones used in defibulators....
>>dont know what series they are....   thought those were the 37's
>>anyway...    I guess having 4 in series has been the protective edge I 
>>have going for me...   the coil ran well even with 2 in series...
>>
>>Scot D
>>
>>
>>
>>Tesla list wrote:
>>
>>>Original poster: DRIEBEN-at-midsouth.rr-dot-com
>>>Scot,
>>>
>>>You may be correct about the 35xxx sereis Maxwell caps but
>>>I think that you may have the 37xxx series caps confused w/
>>>the 31xxx sereis caps. The #37667 35 kV -at- .03 uFD that many
>>>of us have employed into our smaller coils is rated for 500
>>>pps and some of the 37xxx series caps are rated for up to
>>>1000 pps. OTH, the Maxwell 31xxx series caps are generally
>>>rated for low pps, usually 1 pps.
>>>
>>>David Rieben
>>>
>>>----- Original Message -----
>>>From: Tesla list <tesla-at-pupman-dot-com>
>>>Date: Thursday, August 5, 2004 9:08 am
>>>Subject: Re: New Maxwell on ebay
>>>
>>> > Original poster: "BunnyKiller" <bunikllr-at-bellsouth-dot-net>
>>> >
>>> > its a 35XXX series cap   thats the one you want for tesla coil use
>>> >    I
>>> > have 4 of them on mine and have no problems in 5 yrs...
>>> >
>>> > the 37XXX series are used for slow pulse units   ....
>>> >
>>> > go for it...   when you get it make sure it has oil in it...
>>> >
>>> > Scot D
>>> >
>>> >
>>> >
>>
>>
>>
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