Expect a 225W resistor dissipating 160W to become quite hot...
On a more serious turn, good engineering practice has been to overrate
any bleeder with a safety factor of 4.
The current 100 k bleeder resistor results in a discharge time constant of
about 4 seconds,
and if you increase the bleeder resistance the trade-off will be a prolonged
discharge time.
If you series connect another 100 k resistor with the present, the discharge
time constant
will be 8 seconds, and the safety factor about 3. Also, the maximum voltage
gradient across the
resistor is less likely to be exceeded.
Finally, bleeders should never be trusted, so a grounding switch or preferably
a grounding interlock
should be used to securely short-circuit the HV output before any access moves
are made to
the equipment interiors.
The life you save may be your own.
73/
Karl-Arne
SM0AOM
----- Original Message -----
From: "aborg" <a_borg@yahoo.com>
To: "Amps Amps" <amps@contesting.com>
Sent: Sunday, April 24, 2005 3:44 PM
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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