Re: Capacitor Size

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Illicium Verum <sebas@xxxxxxxxxxxxxxxx>


Hello Dirk,

That depends on your mains voltage and frequency.

In Sweden and I think whole Europe this is 230V at 50Hz

In the USA I believe it to bee 110V at 60Hz


I wrote a reply not to long ago on the topic MMC let me quote that reply.

_____________________________________

Most builders make 5

strings to divide the current. High voltage

capacitors don't often come in a high pulse speed

(Vµs) and the ones that do are expensive. This

means a lower voltage lets say you decide to use

the DC rating of capacitors instead of the AC

rating and the capacitor is rated at 1000VDC. The

Transformers peak voltage is 21213V. To require a

minimum safety voltage for your MMC (having your

budget in mind) I would go for 25KV.


Now the Primary capacitance depends on your main

frequency and voltage. This is for a:

110V 60Hz = 5.30nF

A safer capacitance for your transformer is

called LTR (Larger than resonance) and depends on

the type of sparkgap you are planning to build. This is for a:

Static spark gap (SSG) 7.95nF

Rotary spark gap (RSG) 14.85nF

230V 50Hz = 6.36nF

The RTL for 230V 50Hz systems are:

Static spark gap (SSG) 9.54nF

Rotary spark gap (RSG) 17.82nF

_____________________________________


As you can see you will have to choose which kind 
of spark gap you are planning to choose.

If you use a 0.006uF which equals 6.0nF primary 
capacitor on a 110V 60Hz system, you are above 
the minimum required primary capacitance of 
5.30nF. This is fine. But, I don't have any 
experience with doorknob capacitors, about there 
pulsrate and there performance at high frequency, 
so I can not advise you in that. I  do think that 
using just one string in your MMC puts a lot of 
power in your capacitors and they might explode 
if they can not handle the high pulsrate created 
by the spark gap and the amount of current passing true.


Now, if you have a 230V 50Hz system, you are a 
little bit below the minimum, this might give a 
lot of stress  to your NST and you might have to 
adjust your safety spark gaps very accurate to avoid problems for your NST


This all assuming you are going to use a static 
spark gap, as you definitely need more capacitance for a rotary spark gap.


I hope his helped a bit?

Good luck with your wife! ;)

My wife has the tendency not to ask a question as 
I always like to explain in detail what I'm doing 
(I'm a slow talker) But she is positive about the 
Tesla coil (I guess I'm lucky)


Anyway,

Best regards,

Sebas.


Thursday, October 6, 2005, 1:14:40 AM, you wrote:


> Original poster: "Dirk Stubbs" 
<<mailto:dirk@xxxxxxxxxxxxxx>dirk@xxxxxxxxxxxxxx>


> I have a question about sizing of a capacitor. My power supply is a

> NST 15kV at 30mA. I originally planned on using 10 doorknob

> capacitors which are rated at 30kV with 0.006 uF total(each was 620

> pF). However I have a question about the needed capacitance for my

> TC. Most of the references such as websites  and calculators said

> that I need .0053 but I see people saying you need .008-.009 uF.


> What size is correct?



> What will happen if I use my current capacitor setup?




> I would like to use my current setup to save money. The wife has

> about had it with the TC as it is . J





> Thanks,

> Dirk


> -






--

Best regards,

Sebastiaan