Re: first post (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Wed, 15 Aug 2007 08:29:08 -0700
From: huil888 <huil888@xxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: first post (fwd)

Terri -

First question is about your HV power supply transformers. These are 
nominally rated at 4500 volts RMS, 400ma. I assume that you intend to 
connect them in series to obtain 9KV RMS AC output? Peak-to-peak voltage 
will be about 12.7KV.  Are you sure that the transformer insulation will 
withstand this? One good flashover at this much current may destroy the 
transformers.

How will you limit secondary the current to 225ma?

Some tesla coil builders have had failures with the  Maxwell 37667 
capacitors (.03uF @ 35KV). They are rated for 25K amps peak current, 20A RMS 
current, but only 15% voltage reversal. Since all of these capacitors appear 
to have been removed from medical lasers as they approached the end of their 
"rated" life, there is some risk involved in using them. Since they usually 
sell for $60-100 each, I think you would be much better off using a 
conservatively-designed MMC using the well-proven Cornell-Dubilier type 942 
film/foil capacitors. These have proven to be very reliable in Tesla coil 
service.

If this is really your first "serious" coil, you might consider starting 
with a single transformer, and using a voltage doubler on the output to 
build a DC resonant-charged coil. Slightly more complex then an AC spark-gap 
coil, but the only added components are a charging inductor (can be made 
from 2 microwave oven transformers, or hand-wound) and a high-voltage 
de-Q'ing diode.(See Richie Burnett's website for a detailed description of 
Tesla coil DC resonant charging.)

400ma secondary current (or your stated 225ma, if you current limit it by 
some means) is a lot of current by Tesla coil standards, and may pose 
quenching problems. You might be better off getting the system running at a 
lower power level with a single transformer, then adding more power later.

Regards,
Scott Hanson
----- Original Message ----- 
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Wednesday, August 15, 2007 5:49 AM
Subject: first post (fwd)



---------- Forwarded message ----------
Date: Wed, 15 Aug 2007 07:34:54 -0500
From: Terri Neeley <neeley_111@xxxxxxx>
To: tesla@xxxxxxxxxx
Subject: first post

Hey guys im new to coiling but I am building my second coil and I need some
help.  I don't want to make the same costly mistakes as I did on the first
coil.  I will have 2 ge 5021g10 wired for 9000v 225ma for a spark gap coil. 
My
question is:  What capacitors should i go with?  I need .06microfarad so I
thought about the maxwell you see floating around ebay?  2 in parallel of 
the
35k .03mF would work but would it survive?  Any suggestions would be great 
Thx
in advance.
Garry Neeley

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