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Re: [Amps] Equalising resistors with HV diodes

To: Radio WC6W <wc6w@juno.com>
Subject: Re: [Amps] Equalising resistors with HV diodes
From: R.Measures <r@somis.org>
Date: Sun, 19 Sep 2004 17:13:02 -0700
List-post: <mailto:amps@contesting.com>

On Sep 19, 2004, at 3:51 PM, Radio WC6W wrote:



On Sat, 18 Sep 2004 17:55:33 +0200 (CEST) Roger B <f6fer@yahoo.fr> writes:
Hello to all
I am designing a 2kV PSU for a 1kW amp (bridge not
doubler).
About equalising resistors and capacitors with HV
diodes, some says it is absolutely necessary. Others
say it is a waste of time with modern diodes.
Any comment will be appreciated. 73 Roger

Hi Roger, Depends on which diodes... and how reliable you wish the resulting unit to be...

- Indeed But do "equalizing" resistors increase or decrease reliability? Without equalizing resistors, and provided that all of the rectifiers in a series-string have similar junction-capacitances, the reverse current is the same in each one. Since excessive reverse-current is what typically causes rectifier failure, not having more reverse current in any one rectifier is desirable. Although "equalizing" resistors equalize reverse voltages, they often un-equalize reverse currents. Thus, unless the measured PIVs of the rectifiers are identical, removing equalizing resistors should increase reliability.



Richard L. Measures, AG6K, 805.386.3734. www.somis.org

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