Re: high voltage resistors

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

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

Hi Mark,

20,000 volts across a 35kOhm resistor is a stunning 11.5kW of power =:O

I guess it is "pulsed", but beware that kind of power can rip a resistor to 
shreds over time.  Good thing Malcolm is on his long vacation, or he would 
be all over our cases :o)))

For the voltage, you need about 2 inches between the terminals to be 
"really" safe.  For the power, you needs lots of surface area.  But it is 
less than one amp, so we are in the thick film region.  DigiKey page 734 
and 725 has thick film resistors.  Something like two SM204J15K-ND's may do 
it (page 725 of current cat.).

However, huge power pulses can be messy, so beware...  You may be best off 
with a bunch of cheap 1/2 watt resistors like we use in MMCs...

Cheers,

         Terry



At 08:50 PM 1/20/2003 -0600, you wrote:
>Hello, all!
>
>I'm looking for some inexpensive resistors that will stand off 20kV 
>pulses.  I have
>no objections to using two or three in series.  I need a value of 
>30-40kohm.  I am
>currently using 3 1/2W resistors in series, but question the longterm 
>standoff
>ability.  I have been considering the Ohmite OY series - 2W ceramic 
>composition
>that are about .75" long and .3"diameter, available from Digikey.  But at 
>about a
>buck each, I'd rather not spend $40 to discover they won't work!
>
>Thanks,
>
>Mark Broker
>Chief Engineer, The Geek Group