Re: help me put my coil on a diet; its capacitor appetite is expensive!

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "seanick" <edgarsbat@xxxxxxxxxxx>

Hi Gerry (+ others of the list)
Thanks for the reply, and sorry also for taking so long myself. In my 
case, the problem is that I seem not to be getting the digest mail 
anymore (and I am not on the list directly either).
So I had to get this message from the pupman.com archive and paste it 
into a new mail.

Re: the 100 A ballast-
Actually, I was probably confusing things when I said the ballast was 
set to 100A. I meant the secondary (of the welder) was set to 100A 
which means the primary is closer to 35A. Also, my Cp is (now) 60nF, 
in the form of 6 strings of 15 x 942C20P15K. I am still running 120 
BPS sync. My pig's voltage output is 14400V. so I don't think I am 
running it at 80KV... at least I hope not. I have a huge MOV that I 
will be running in parallel with the pig, and a safety gap in 
parallel as well. the MOV is a 27KV (and many KA) that is about 2+ 
feet tall and at least 8 or 9 inches in diameter, contained in a 
porcelain insulator. I figure the combination of those will help 
protect the 30kv rating of the 942C's (which also handle voltage 
reversals well, or so I hear) so this time around my caps should at 
least last for a run or two before dying, I would hope.

I also think the caps were overvolted, but as I mentioed above, 
probably not quite as badly as you might have thought from my 
original statement. It did run for a few minutes without bursting 
immediately into flames.... :)

Thanks!
NICK

---------------------------
Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>Hi Nick,
Sorry about not answering before this. Your email got lost in a sea 
of other email and I just now rediscovered it.

I will presume your 100amp ballast is with 240V so you are running at 
24KVA. If your Cp is 100nf and you are running at 120 BPS sync and 
the timing of the SRSG is set normally, the voltage will be 43KV. 
However, if the timing is incorrectly set, the voltage could go as 
high as 87KV. This is not a case where you adjust for maximum 
voltage. I think it is very likely that the caps were overvolted. 
Cres for a 25KVA PIG is 320nf so if you want to run at 120 BPS sync, 
you will need a Cp of about 900 nf. Alternatively, you could go async 
and shoot for a high BPS. With 100nf and 400BPS, some of the firings 
will get to 39KV. I do think you need to have a larger Cp. With 200nf 
and 400BPS, some of the firings will get to 24KV.
Hope this helps,Gerry R.