Re: bleeding caps

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>

Hi Matt,

I try and get caps to bleed down in 2 to 10 seconds.  That is fast enough
to be safe but does not load the coil down or waste power.  The time it
takes for a cap to drain is:

t = 5 x R x C

So a 10M resistor and a 0.02uF cap will drain down in 1 second.

If we shoot for 5 seconds we get:

5 = 5 x R x 0.02e-6  so R = 50Meg.  You also need that resistor to take 15kV.

The 1/2 watt 10Meg resistors take 2kV.  So one could use two strings of 10
resistors (or one string for a 10 second drain time) on each cap.  Since
the resistors only cost $0.01 each it is no big deal to use a lot of them.
Of corse, other high voltage resistors would work to if you can find them.
I get the 10Meg ones buy the thousands so if you need any let me know.

Cheers,

	Terry


At 08:19 AM 1/30/2001 -0800, you wrote:
>hi, 
>i just got 5 15KvDC 0.02 uf caps for $10. i was going to use 3 or 4 of
>these in series to obtain the desired capacitance for my coil. my question
>is, since i will more be using as many caps as a normal MMC would use, how
>would i go about bleeding these? i didnt think that 1 10 Mohm resistor
>across each cap would do it. maybe 2 or 4 resistors? or even make a small
>board with man resistors in paralell and then use that to bleed the
>resistors. and if all my caps blow up it wont be a big loss.
>
>im also trying to figure out how to make an NST filter on a budget. i dont
>have enough money to make terry's excellent protection, so im trying to
>think of other ways to accomplish this.
>
>-fox
>