Re: Bleeder resistors

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

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

Hi,

There is a problem with 1Meg resistors.  If you have 2000 volts across the
resistor when the gap fires, the power dissipation in the resistors is:

P = 1/2 x SQRT(2) x V^2 / R  (it is 1/2 the RMS value since the gap firing
removes half the cycle).

So in our case, 

P = 1/2 x SQRT(2) x 2000^2 / 1e6 = 2.83 watts

So you need maybe 5 watt resistors.

You could use 1/2 watt 10Meg resistors for only .28 watts dissipation.

The discharge time would be:

5 x R x C = 5 x 10e6 x 0.15e-6 = 7.5 seconds.  You could use two 10Meg
resistors in parallel for 3.75 seconds or more for a still shorter time.

Cheers,

	Terry


At 01:53 PM 10/14/2001 -0500, you wrote:
>Vince,
>
>The time it will take for each cap to discharge is related to the product
>of the R and C (called appropriately enough, the RC time constant). For
>your values, RC = 0.15 seconds, and the capacitors will be fully discharged
>in about 5*RC or about 0.75 Seconds.
>
>Good luck on your MMC!
>
>-- Bert --
>-- 
>Bert Hickman
>Stoneridge Engineering
>Email:    bert.hickman-at-aquila-dot-net
>Web Site: http://www.teslamania-dot-com
>
>
>Tesla list wrote:
>> 
>> Original poster: "Vince D'Amore by way of Terry Fritz 
><twftesla-at-qwest-dot-net>" <vincedamore-at-earthlink-dot-net>
>> 
>> Hello People
>> 
>>  I have a question about bleed resistors for my MMC that I am building.
>> I'm going to be using .150uF caps rated at 2kV each.
>> Will a 1meg ohm resistor across each cap be sufficient?
>> Any info on this would be greatly appreciated.
>> 
>> Thanks
>> 
>> Vince
>>
>