Believe or not Resistors have a voltage limit and rating. The standard 2
watt carbon film resistor is only rated for 300 or 400 volts DC. They can
be pushed higher but not by a lot. The same is true for Carbon Comp.
resistors. If you put several thousand volts across a standard carbon film
or comp resistor you may get some exciting fireworks even thought you have
not exceeded their power ratings. A series string is the best choice for
high voltage applications. They do make special high voltage resistors.
They are much longer than ordinary resistors. We have some carbon comp HV
resistors that are almost a foot long.
73
Bill wa4lav
At 11:11 AM 4/27/2005 -0700, aborg wrote:
>What about using 10 2 Meg 2 Watt resistors in
>parallel ? The math indicates it should work.
>****************************************************
>--- Phil Clements <philc@texascellnet.com> wrote:
> > Your bleeder is too small. All you need a bleeder
> > for on a C input filter
> > P.S. is to drain the HV after shut-down. Your
> > 100,000 ohm resistor is
> > flowing 160 ma of current, and just heating itself,
> > your components, and
> > your ham shack. I would use at least 200 k to 400k
> > ohms. In all my 4 kv+
> > power supplies here, I use 4 X 100k ohm @ 100 watt
> > units in series. (225
> > watt units will be better) Even these get really
> > warm, but do the job just
> > fine. I always double the wattage on the bleeder
> > resistors as a safety
> > factor. You don't want one of these babies to go
> > open on you!
> >
> > (((73)))
> > Phil Clements, K5PC
> >
> >
> > -----Original Message-----
> > From: amps-bounces@contesting.com
> > [mailto:amps-bounces@contesting.com] On
> > Behalf Of aborg
> > Sent: Sunday, April 24, 2005 7:44 AM
> > To: Amps Amps
> > Subject: [Amps] Bleeder Resistor Inquiry
> >
> > I am currenty building a HV Power Supply using a
> > 4800vac pole pig, 40uF 5kv oil filled cap , 10kv PIV
> > rectifier board, 20 amp variac and a 100k 225watt
> > bleeder.
> >
> > The initial power up started well without the
> > bleeder
> > connected to the circuit after 30 min burn-in no
> > problems. Discharged the circuit and added the 100k
> > bleeder and 5 mins the bleeder starts to smell and
> > the
> > exterior paint starts to bubble. Shut it down and
> > examined the circuit, all seem accurate.
> >
> > Question : Is my bleeder to small ?
> >
> > P.S. : The variac was set at 4KV at all times.
> >
> > Mike-KK4MS
> > a_borg@yahoo.com
> >
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> >
> >
> >
>
>Mike-KK4MS
>a_borg@yahoo.com
>
>
>
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