Re: [TCML] Need new cap(s) for my coil

["Quarkster" <quarkster@xxxxxxx>]

Brandon -

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: 
http://www.allaboutcircuits.com/vol_1/chpt_13/4.html

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.

Regards,
Herr Zapp


----- Original Message ----- 
From: "Brandon Hendershot" <mrbrandman@xxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Saturday, October 24, 2009 11:05 AM
Subject: [TCML] Need new cap(s) for my coil


Hi,
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?
Thanks,
Brandon
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