# Re: Latest MMC Calculations...

```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

```