[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Question on bleed off resistor



Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>

Hi Tim,

For bleeder resistors, R = 1 / C is a nice value.  That drains the cap in 
about 5 seconds.  In your case:

R = 1 / 0.02e-6 = 50,000,000 ohms.  The resistors you have now won't work.

The power dissipated in the resistors is P = V^2 / R.  In this case that 
would be:

7500^2 / 50e6 = 1.125 watts.  No problem at all there.

For the voltage standoff, I would use 1000V / 10Meg resistor for a long 
string.  If the voltage gets uneven across the string due to corona or 
something, that will give more headroom than in the more stable MMC where 
we go up to 2000V / resistor.

I would use two strings of resistors just for redundancy.

So you could use 20  10Meg 1/2 watt MMC resistors in a 2 x 10 array which 
would give 50Meg ohms at 10kV and 20 watts.

Be sure to keep the resistors far clear of other stuff by at least an inch 
or so.

I have a bunch here, so send me your address and I would be happy to send 
you a bunch.

Cheers,

         Terry
         terrellf-at-qwest-dot-net


At 02:29 PM 7/21/2003 -0500, you wrote:

>I have a single .02MFD (80KVDC) capacitor I will be connecting to a 
>7500/60 NST as part of a tesla coil tank circuit.  The output of the 
>transformer is 540 Watts.

I think you meant 450 watts ;-))


>My question is, what size resistor can I safely get away with to bleed off 
>the charge in the capacitor?  I have 3 or 4 500 Ohm 100 Watt resistors 
>lying around I would like to make use of.
>
>Thanks in advance,
>
>Tim M.