Re: 2465B power supply - Sprague 290uF/200V big blue caps


vdonisa
 

Not exactly. I'm saying that when trying to find a substitute cap, ESR, ripple current and thermal/size characteristics have priority over exactly matching voltage. Messing those has proven, well documented, dramatic effects. While "undervolting" doesn't.

In fact I'm not even original. Quote from another CDE document:

"Higher rated voltage capacitors may be substituted for lower rated voltage capacitors as long as case size, DF, and ESR ratings are also compatible."

(full document here: http://www.cde.com/resources/catalogs/AEappGUIDE.pdf http://www.cde.com/resources/catalogs/AEappGUIDE.pdf )


---In TekScopes@yahoogroups.com, <david_wise@...> wrote :

I didn't. I remembered it wrong.

You're saying that with a 100V part, 1V is as good as 100V, are you?

Dave Wise

-----Original Message-----
From: TekScopes@yahoogroups.com mailto:TekScopes@yahoogroups.com [mailto:TekScopes@yahoogroups.com mailto:TekScopes@yahoogroups.com]
Sent: Wednesday, October 21, 2015 3:44 PM
To: TekScopes@yahoogroups.com mailto:TekScopes@yahoogroups.com
Subject: RE: [TekScopes] Re: 2465B power supply - Sprague 290uF/200V big blue caps

Where did you see the mention "near rated voltage"? It plainly says:

"In electrolytic capacitors, applying DC voltage actually drives a beneficial, on-going electrochemical reaction that heals defects in the anode dielectric."

Followed shortly by a description of the negative effects of simultaneously maxing out on both voltage and current/temperature.

---In TekScopes@yahoogroups.com mailto:TekScopes@yahoogroups.com, <david_wise@...> wrote :

I read CDE_Multipliers.pdf, and they do claim that operating near rated voltage has the beneficial effect of repairing weak spots in the dielectric. Their graph of voltage life multipliers also stops at half of rated voltage.

I don't know how strongly this correlates with the useful life of a cap operated below rating. I suppose a graph would show a sweet spot with maximum life, with less at each end. I can't begin to guess at the shape of the tails.

The Shelf Life rating is based on storage at rated temperature. We don't know the degree to which thinning is accelerated by heat, although Arrhenius would be a reasonable first guess. A cap stored at comfortable room temperature will last much longer than the rating.

The Shelf Life test also applies rated voltage after storage. If the circuit applies only low voltage, this test will reject caps that operate just fine.

I just can't get righteous over this, but certainly there is *some* effect. We just don't know how much, and the people who research this for a living don't care about this operating point. I'm determined not to lose sleep over it.

Dave Wise

-----Original Message-----
From: TekScopes@yahoogroups.com mailto:TekScopes@yahoogroups.com mailto:TekScopes@yahoogroups.com mailto:TekScopes@yahoogroups.com [mailto:TekScopes@yahoogroups.com mailto:TekScopes@yahoogroups.com mailto:TekScopes@yahoogroups.com mailto:TekScopes@yahoogroups.com]
Sent: Wednesday, October 21, 2015 12:29 PM
To: vdonisa@... mailto:vdonisa@... [TekScopes]
Subject: Re: [TekScopes] Re: 2465B power supply - Sprague 290uF/200V big blue caps

On Tue, 20 Oct 2015, vdonisa@... mailto:vdonisa@... [TekScopes] wrote:

*PLONK*

>
> Thanks.
>
> I suggest in the future you also take it with Cornell Dubillier:
>
> https://www.digikey.com/Web%20Export/Supplier%20Content/CDE_338/PDF/CDE_Multipliers.pdf?redirected=1 https://www.digikey.com/Web%20Export/Supplier%20Content/CDE_338/PDF/CDE_Multipliers.pdf?redirected=1 https://www.digikey.com/Web%20Export/Supplier%20Content/CDE_338/PDF/CDE_Multipliers.pdf?redirected=1 https://www.digikey.com/Web%20Export/Supplier%20Content/CDE_338/PDF/CDE_Multipliers.pdf?redirected=1 https://www.digikey.com/Web%20Export/Supplier%20Content/CDE_338/PDF/CDE_Multipliers.pdf?redirected=1 https://www.digikey.com/Web%20Export/Supplier%20Content/CDE_338/PDF/CDE_Multipliers.pdf?redirected=1 https://www.digikey.com/Web%20Export/Supplier%20Content/CDE_338/PDF/CDE_Multipliers.pdf?redirected=1 https://www.digikey.com/Web%20Export/Supplier%20Content/CDE_338/PDF/CDE_Multipliers.pdf?redirected=1
>
> EPCOS/TDK:
>
> http://en.tdk.eu/designtools/alu_useful_life/Useful_life.swf http://en.tdk.eu/designtools/alu_useful_life/Useful_life.swf http://en.tdk.eu/designtools/alu_useful_life/Useful_life.swf http://en.tdk.eu/designtools/alu_useful_life/Useful_life.swf http://en.tdk.eu/designtools/alu_useful_life/Useful_life.swf http://en.tdk.eu/designtools/alu_useful_life/Useful_life.swf http://en.tdk.eu/designtools/alu_useful_life/Useful_life.swf http://en.tdk.eu/designtools/alu_useful_life/Useful_life.swf
>
> and Illinois Capacitor:
>
> http://www.illinoiscapacitor.com/tech-center/life-calculators.aspx http://www.illinoiscapacitor.com/tech-center/life-calculators.aspx http://www.illinoiscapacitor.com/tech-center/life-calculators.aspx http://www.illinoiscapacitor.com/tech-center/life-calculators.aspx http://www.illinoiscapacitor.com/tech-center/life-calculators.aspx http://www.illinoiscapacitor.com/tech-center/life-calculators.aspx http://www.illinoiscapacitor.com/tech-center/life-calculators.aspx http://www.illinoiscapacitor.com/tech-center/life-calculators.aspx
>
> to name just a few.
>
>







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Posted by: vdonisa@... mailto:vdonisa@...
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