Re: [Amps] HV SAFETY QUESTION

["David A. Pruett" <k8cc@comcast.net>]

At 06:35 PM 1/22/04 -0700, Jim Homer wrote:
> I have an old Ham acquaintance that can testify to 8 inches of a
> medium-weight plastic-handled screwdriver being reduced in length by about 
> 3 inches while using it to ground a 40 ufd 6.6 kv HV power supply that had 
> an open bleeder string.

I see a lot of power supply designs where the HV metering circuit is 
connected across a relatively small (~500 ohms) power resistor at the low 
end of the bleeder string.  This has the advantage of economy in avoiding 
the need for HV meter multiplier resistors.

I would suggest that a safer approach is to have the metering circuit 
separate with it's own string of resistors.  This way, if the bleeders 
open, the metering current will still discharge the filter capacitors.  It 
*MAY* take a while (depending on the impedance of your HV meter circuit) 
but it will discharge.  This approach also has the safety advantage that 
the HV meter still works if the bleeder opens.

Dave/K8CC


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