That NST would probably be adequate although your spark gap will have to be set very close to insure reliable firing at only 9 KV. At least a 12 KV transformer would be better. As far as your other questions, I strongly suggest that you use the JAVATC design program. Become familiar with all of the parameters. This program predicts very accurately how your coil will perform if built to high quality standards.
As to your capacitor bank question, let JAVATC help you pick the right value. Start by picking a reasonable size that your transformer is capable of charging. Try something like 10 NF for a start. Enter this into JAVATC and see what percentage the capacitor bank will be charged. This is one of the many outputs of JAVATC. Your goal should be something close to 100% charge on the capacitor bank. If it less than 100%, everything will still work but this indicates that your capacitor bank is incapable of being fully charged by your transformer and you have probably spent more on capacitors than you need. Once you have found the correct capacitor bank value then you can proceed on to how to implement this with a MMC. The MMC is just a series-parallel combination of capacitors to achieve your total capacitance value. You can do this relatively simple calculation by hand or there are computer programs that can do it for you. The first step is to determine the maximum voltage that you want your MMC to be able to safely withstand. JAVATC will give a suggested value which is something like 3.5 times your peak transformer voltage. Many have suggested that this much safety margin is not necessary for MMC arrays using the CD (Cornel Dubilier)capacitors because they are self-healing. I will let others comment on that as I have no actual experience with MMCs based on CD capacitors.
Believe it or not my first coil was a large coil using an 8.5" secondary with about 1400 turns topped by a spun aluminum 8" x 30" toroid. The primary is a 12-turn flat archimedes spiral using 3/8" copper tubing. It uses 45 NF of capacitance using 6 Maxwell pulse capacitors in a series-parallel combination. It uses a synchronous rotary spark gap at 3600 RPM. The primary power source is a 14 KV pole transformer capable of 10 KVA. This coil worked the first time I powered it up with only minor primary tuning required. It produces 8 foot sparks. I attribute my first-time success for such a large coil to 4 things:
1. The extensive use of JAVATC to predict all parameters
2. I read the TCML archives extensively before building or buying anything otherwise you will end up wasting money on things that will not work
3. Look at pictures of how others have constructed their coils to get ideas and to avoid construction mistakes
4. Pay very careful attention to construction details
----- Original Message -----
From: "YESN via Tesla" <tesla@xxxxxxxxxx>
To: tesla@xxxxxxxxxx
Sent: Monday, December 11, 2017 4:19:06 PM
Subject: [TCML] First Tesla Coil
Hi all
I am (still) busy designing my first Tesla Coil.
I have found a reasonable 9kV 60mA NST for 195 eur. Is this reasonable for a first build?
Or is it way too much to begin with?
I have been sent this website for designing my MMC. Bart Anderson uses 150uf 2kV caps.
How exactly is the capacity of a cap chosen? Are there formulas to calculate the total capacitance of your MMC? If so it does depend on the amount of strings you use right?
(The one that in my mind were reasonable were hese: https://nl.mouser.com/ProductDetail/Cornell-Dubilier-CDE/940C20P15K-F/?qs=11kF6y5Z3OhbthK%252bpYczHA%3D%3D)
Also how is the resonant frequency between the two circuits calculated? I have also heard about tapping your primary coil, (much like finding the frequency with an old radio right?) does anyone have a description of how this process is done? About the spark gap. As someone on this list luckily pointed me out placing the spark gap too wide can cause your NST to overvolt and die. How do you decide the starting width of the spark gap? (Do you gradually increase it or leave it at a certain length?)
I recently came across a static spark gap which where multiple ones across copper tubes. Is this advisable for a beginner?
The PVC pipe I have already bought is 11,5 cm in diameter. Therefore it's length should be around 58 cm right?
I really care about the state of the components and do not want them to be harmed? Therefore a Terry-Filter is necessary right?
P.S. Are these questions normal for someone starting?
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