# Re: Latest MMC Calculations...

```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.

For the example you give at
<http://www.peakpeak-dot-com/~terryf/tesla/misc/MMCCalc1.jpg>,
I would say that the total lifetime is more like
1e6 x (Life1/1e6 x Life2/1e6 x Life3/1e6),
which works out to 96 hours instead of 6576 hours which
was the lowest single value (Life1).

I'm not sure if the three factors should be of equal weight.
On the other hand, if you give some weight to the factors,
the product should always be a stronger criteria than any single
factor. As you can't tell which factor is the most important one,
I think the equal weight is most probably the right one, isn't it?
Only other solution could be a weight that depends on the factors
themselfes, such as "if the temperature dependent reduction actor is
below 1/1000, then it is negligible (weight = 0), otherwise the
weight = 1".

This view shortens the predicted life dramatically (in your example from
6576 hours down to 96 hours, which is factor 69.

But as said - I'm not sure here but it seems logical to me (remember
the reduction of the rated AC-voltage with increased frequency due to the
frequency dependent heating of the cap).

Any more thoughts on this?

Cheers, Stefan
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