[AMPS] Electrolytics

[Steve Thompson]

-----Original Message-----
From: nospam4me@juno.com <nospam4me@juno.com>
To: amps@contesting.com <amps@contesting.com>
Date: 24 May 2001 06:48
Subject: [AMPS] re: Dayton and Emtron

>The capacitors were also mounted right next to each other.
>Cap cooling is something less than desired. In my opinion,
>an issue that should be looked at.  Although I wasn't able
>to check the values, the capacitor bank looked "rather light
>duty" for the power supply level so these close spaced caps
>will get at least very warm with significant ripple current.


This got me thinking, and I wonder if we are overly pessimistic about
electrolytics, maybe based on the poor quality components of the past.

Based on a 3kV supply with a stack of 10 x 330u 450V ordinary (not special
computer grade) 85C caps, rms ripple current rating is 1.5-2A (depending on
brand) with dissipation about 2W at maximum ripple. 2W doesn't seem a huge
amount for the size of can to dissipate.

Roughly, rms ripple is around 2xdc for a bridge, and 2.5xdc for a doubler,
so these caps would be inside rating for, say, 7-800mA dc in a typical psu.

The Siemens version I looked at quotes 10,000 hours life at full ripple at
85C ambient. If we work on 65C ambient, 50% tx duty and 50% loading for
ssb/cw use, then the lifetime prediction is 160,000 hours (18 years)
continuous operation.

Steve


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