[Milsurplus] [ARC5] Cool New DC-DC Converter

[W2HX]

ESR is a different beast than leakage. Leakage is modeled with an R parallel to the C. ESR is an R in series with the C.  leakage occurs at any frequency even DC. With very low frequency, the C is an open circuit and thus the ESR plays no role. However, at 60/120 Hz for power supplies, you want the ESR minimized to reduce losses/heating.

73

-----Original Message-----
From: milsurplus-bounces at mailman.qth.net [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of Bruce Gentry
Sent: Sunday, March 18, 2018 5:07 PM
To: milsurplus at mailman.qth.net
Subject: Re: [Milsurplus] [ARC5] Cool New DC-DC Converter

I'm showing my age!   I think the term today is ESR. It's the aggregate 
stray resistances between the pure capacitance and the "outside world" 
of the condensor.

        Bruce Gentry, KA2IVY

On 3/18/18 2:51 PM, Peter Gottlieb wrote:
> What do you mean by "power factor" in this context?
>
> I have heard (can't remember sources) that the best way to revive old 
> electrolytics was to apply the current limited voltage, starting low 
> (maybe 1/3 of rated) and gradually increasing to rated as current 
> decreases then letting sit at rated until current stabilizes, a day or 
> so.  I think there is an applications booklet from an electrolytic 
> manufacturer floating around which gives a good description of the 
> process, can't remember if what is described is closer to your method 
> or what I described.
>
> A lot of the older stuff I've recently been resurrecting doesn't even 
> use electrolytics, just oil caps, and the low voltage stuff just has 
> tantalums which are their own nightmare in terms of reliability.
>
> Peter
> kb2vtl
>
>
> On 3/18/2018 2:40 PM, Bruce Gentry wrote:
>> Does anyone know how manufacturers assign or condition new 
>> electrolytics for their working voltage?   As long as the power 
>> factor is good to begin with, I have had very good results reviving 
>> electrolytics that had excessive leakage at or below their operating 
>> voltage by applying the rated voltage through a current limiting 
>> resistor.  I use no more than 2 milliamps and am patient, reducing 
>> the current if needed to prevent heating beyond a temperature 
>> pleasent to hold.  A multi section condensor may take a few days to 
>> reform, but once they do, the power factor/ESR usually improves as 
>> well as capacitance and leakage.
>>
>>      Bruce Gentry, KA2IVY
>>
>>
>> On 3/18/18 1:08 PM, Dennis Monticelli wrote:
>>>   All 'lytics pass current (we call it leakage) as part of their 
>>> natural ongoing process of oxide decomposition and reformation.
>>> Operate a 450V cap at 50V for a long period of time and it will 
>>> reach a new equilibrium, eventually becoming a 50V cap.  To use that 
>>> cap at much higher than 50V safely would require slowly reforming
>>> (re-thickening) of the now very thin oxide layer until an new (high
>>> voltage) equilibrium is reached.
>>>
>>> We see a version of this situation whenever we power up an old piece 
>>> of equipment whose lytics have been dormant for years. If they 
>>> haven't dried out they will properly reform if given the chance.
>>> That is why we are careful to severely limit the current into those 
>>> caps while we allow the oxides to slowly reform. Slow growth creates 
>>> a better quality of oxide and insures that the negative affects of 
>>> self-heating are keep at a minimum.
>>>
>>> Dennis AE6C
>>>
>>
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