Ron - a word on how the 22.7 multiplier comes about - It is not just
voltage - Illcap says going from 35 volts to 6 volts approximately a 2X
multiplier is valid for voltage . The rest of the multiplier comes for
temperature operation under rated max temp. That multiplier comes from the
Arrhenius relationship of life doubling for each 10 deg C reduction in
temperature from max rated spec. So for a 105 c rated cap operated at max
ripple current with a rated life of 2000 hours , the life would be 2X at 95
, 4X at 85 , 8X at 75 , 16 X at 65 and 32 X at 55 C . For this case if case
temp were 65 C you get 16X times the 2X voltage multiplier times the 2000
hours or 64000 hours .
Another factor that is seldom mentioned in Electrolytic capacitor life is
the below - which says if you get more than a 10 deg C temp rise from
ripple current - you will degrade life. (That is why the Panasonic Engineer
says they simply design for a less than 10 deg C rise at rated ripple
current.)
Per Illcap tech notes.
"The temperature rise formula is the rms AC current( ripple) squared times
the ESR of the capacitor at the operating frequency divided by a thermal
constant multiplied by the surface area of the capacitor."
"IF the calculated temperature rise is greater than 10C then the capacitor
is being overstressed and will eventualy fail sooner than it should."
The "tan" or DF numbers are explained in detail in the following link.
http://www.illinoiscapacitor.com/uploads/papers_application/F8CD49C1EA8E45BDA61D71D903DE2554.pdf
73 Hank K7HP
----- Original Message -----
From: "Ron Castro" <ronc@sonic.net>
To: <geraldj@storm.weather.net>; "Discussion of Ten-Tec Equipment"
<tentec@contesting.com>
Sent: Wednesday, June 25, 2008 3:57 PM
Subject: Re: [TenTec] Orion II A9 Board Failure...Again!
>I hope it will run more than 2,000 hours too! According to Hank, that
> number gets multiplied by a factor for lower temp, in this case 1.7 for 80
> degree C operation (it's actually much cooler than that), times a factor
> for
> running at lower voltage, which is something like 22 x. If I got that
> right, that's 74,800 hours, or 8.5 years of continuous operation, plus the
> factor for an ambient temp of around 50 C instead of 80. I think there is
> an additional factor for running less than the max specified ripple
> current.
>
> According to the specs, dissipation, shown as "TAN (lower case Greek
> 'Delta') at 20 C 120 Hz", is 0.10 for the 50 WV units. I don't know what
> that means, but it sounds better than the 0.16 speced for the 16 WV units.
>
> Ron N6IE
> www.N6IE.com
>
>
> ----- Original Message -----
> From: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
> To: <tentec@contesting.com>
> Sent: Wednesday, June 25, 2008 3:34 PM
> Subject: Re: [TenTec] Orion II A9 Board Failure...Again!
>
>
>> On Wed, 2008-06-25 at 10:36 -0700, Ron Castro wrote:
>>> Whoops... that last link was:
>>>
>>> http://n6ie.com/A9_Fix.html
>>>
>>> Ron N6IE
>>> www.N6IE.com
>>>
>>>
>>> ----- Original Message -----
>>> From: "Ron Castro" <ronc@sonic.net>
>>> To: "Ten Tec List" <tentec@contesting.com>
>>> Sent: Wednesday, June 25, 2008 10:35 AM
>>> Subject: [TenTec] Orion II A9 Board Failure...Again!
>>>
>>>
>>> > Hank: Excellent analysis! Can I please link to that from my page?
>>> >
>>> > I believe, based on this link that there is a direct connection
>>> > between
>>> > ESR
>>> > and ripple ratings:
>>> >
>>> > http://wiki.xtronics.com/index.php/Capacitors_and_ESR
>>> >
>>> > "Ripple Current Rating
>>> > The ripple current is sometimes rated for a capacitor in RMS current.
>>> > Remembering that P = I2R where R in this case is ESR it is plain to
>>> > see
>>> > that
>>> > this is a power dispassion rating. "
>>
>> Almost but it doesn't give a number for the heat transfer capability of
>> the package. That is vitally important, the larger the case, the better
>> that heat will be transfered to the air and environment and that is
>> CRUCIAL for keeping the capacitor temperature in reason.
>>> >
>>> > Here is a link to the data sheet of the caps I used:
>>> >
>>> > http://www.mouser.com/catalog/specsheets/esrl.pdf
>>> >
>>> > I haven't figured out the calculations, but the ripple rating is 1355
>>> > ma
>>> > @
>>> > 100 kHz, 50 Volts, 105 C and a "life test" rating of 2,000 hours.
>>> > What
>>> > kind
>>> > of life could I expect in the C6 application?
>>
>> 2000 hours is only a quarter of a year. I want my radio to run longer
>> than that!
>>> >
>>> > BTW, I didn't test the caps I removed, but as you can see if you look
>>> > carefully on the 'before' picture on my site, C9 has a bulge on the
>>> > top
>>> > of
>>> > its casing.
>>
>> A bulge is a sign of getting hot and expanding the liquid, possibly by
>> boiling it to steam. There are weak points in the case, sometimes that
>> leaking electrolyte eats traces from the board nearby.
>>
>>> TT never told me which caps they replaced the first time
>>> > around. Another interesting thing is that all three original caps
>>> > were
>>> > the
>>> > same specs, but all three were different sizes.
>>> >
>>> > http://n6ie.com/A9_Fix.
>>> >
>>> > Ron N6IE
>>> > www.N6IE.com
>>> >
>> 73, Jerry, K0CQ
>>
>> _______________________________________________
>> TenTec mailing list
>> TenTec@contesting.com
>> http://lists.contesting.com/mailman/listinfo/tentec
>>
>
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
>
>
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|