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Re: [TCML] Need new cap(s) for my coil
First of all, there may be some confusion about the correct capacitor value
you need. What type of spark gap are you using with your 15/30 NST?
If you are using a simple static spark gap, the correct capacitor value is
around .008uF, not .015uF.
If you are using a synchronous rotary spark gap, then you will need a
capacitor value around .014-.015uF.
You also need to learn how capacitance and voltage ratings are calculated
change when individual capacitors are connected in series or parallel. See:
for an easily understood explanation.
The film capacitors you have found at tedss.com are NOT suitable for Tesla
coil use because:
1) They use polyester dielectric that is very "lossy" at high frequencies
and will quickly overheat and fail;
2. They cannot handle the high current pulses present in a Tesla coil
circuit and will quickly "burn up" internally.
There is a tremendous amount of information on Tesla coil capacitors in the
TCML archives at www.pupman.com. Use the "Search the archives" option.
The bottom line is that the simplest, least-expensive and most-reliable
capacitors you can use in an MMC for a small Tesla coil are Cornell-Dubilier
942 series hybrid film-foil capacitors. For a Tesla coil using a 15/30 NST
with a static spark gap, and using the C-D .15uF, 2000V capacitors, you will
need a series string of ~19 capacitors (at about $3.50 each). The .15uF, 2kV
caps are the easiest to find; they are frequently offered on eBay. Other
capacitance values of the 942 series can be used that may require fewer
total capacitors, but you need to know how to calculate the capacitance
value of series-connected caps.
----- Original Message -----
From: "Brandon Hendershot" <mrbrandman@xxxxxxx>
Sent: Saturday, October 24, 2009 11:05 AM
Subject: [TCML] Need new cap(s) for my coil
I'm running a 15/30 NST. the recommended capacitor farad rating for that is
0.015uF. I've found this capacitor; 0.015uF 10,000V Film Capacitor
(http://www.tedss.com/MPE11H-.015-10000-10/). Could I wire 4 of these in
series to get a total voltage rating of 40,000V ( 2.6 times the NST output
voltage) and still have a 0.015uF capacitance rating?
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