# Re: Latest MMC Calculations...

Hi Reinhard,

I think I'll agree with you.  If we have three lifetimes that are all 900
hours, My equation would give only 300 hours total.  That is not right.
You assumption would give 900 hours total which is much better.  If we knew
the distribution of the failure functions we would see that it is really a
little less than 900 hours but that detail is meaningless (it is like
figuring all this out to 30 digits of accuracy...).  I think your taking
the lowest number as the life is best.

Cheers,

Terry

At 08:06 PM 7/15/99 +0200, you wrote:
>Hi Terry, all,
>
>I donīt know if I can agree with this. Personally, I think
>one needs to calculate the lifetime for each situation (L1,
>L2, L3) and simply take the lowest number as THE life
>factor. I know this is somewhat pessimistic, but at least
>you wonīt be disapointed. For an analogy lets have a
>look at a normal light switch. Letīs say the life of the
>plastic handle (before it gets brittle and breaks) is 10
>years, the life of the pivot (before it wears out so far
>that it wobbles all around) is 5 years and the life of the
>contacts themselves is around 2 years (Of course these
>are just imaginary numbers). This means the effective
>lifetime of the switch is 2 years and not 1/(1/5+1/10+
>1/2) years. In our cases, I donīt think Life3 (DvDT)
>will ever be a real consideration, simply because (if you
>near or exceed dv/dt) you will also decrease Life1
>(the temp factor) by a much higher rate. Your method
>of seeing them as "parallel resistors" would be a sort
>of statistic value (Iīm not a believer in statistics).
>However, as not every coiler will be using the exact
>same building technique or caps (etc), I donīt think
>this will give more realistic values, then if you simply
>just view the lowest of the 3 lifetime values.
>
>We shouldnīt forget that we are not using the caps in
>a 24 hr/day mode. If this were the case, then I would
>tend to agree that the different lifetime factors affect
>one another (like the temperature factor aggrevating
>the ionization factor and perhaps dv/dt being lowered
>due to the lowering of the ionization factor).
>
>Coiler greets from germany,
>Reinhard
>
>
>
>
>> Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
>> Hi Stefan,
>> I too was wondering how to combine the lifetimes.  I was thinking of
>> combining them like parrallel resitors.  Suppose you have three life
>>times of 10000, 1000, and 5000 hours.  1/(1/10000 + 1/1000 +
>>1/5000) = 769 hours.
>>  Seems reasonable to me...
>
>
>> At 04:39 PM 7/14/99 +0200, you wrote:
>> >Hi Terry, all,
>> >
>> >the "15th_power-law" is a very interesting find. I looked over
>> >the formulas, you posted at
>> ><http://www.peakpeak-dot-com/~terryf/tesla/misc/MMCCalc1.jpg>.
>> >
>> >You wrote:
>> >> These equations have the life estimates for corona, temperature,
>> >> and Dv/Dt
>> >
>> >and you calculate the lifetimes L1, L2, L3.
>> >
>> >But don't you think that all those three major factors play
>> >a role TOGETHER in decreasing the lifetime? In my opinion, the
>> >lifetime reduction factors should be multiplied as each one is
>> >decreasing the lifetime at the same time.
>SNIP
>
>
>
>

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