I found this relation about the optimum stages and also two examples. However I can not have the same results as they do. Can anyone help me, please ?

1.Ex.

Noptimum = INT[SQRT( Epk * fC/Iload)]
f we drive our CW with an input voltage Epk=10kV and a load of 10mA, running at 70kHz and 390pF capacitors, Noptimum=INT[5.22]=5

2.Ex.
For a generator with Epk=100 kV, f=500 Hz, C=7μF and I=500 mA,
nopt=10.

 

Have you read the Wikipedia article?

It might hold the answer, looking at it.

http://en.wikipedia.org/wiki/Cockcroft–Walton_generator

 

Yes, I've read this article. I found this equation into two books. The problem is when I substitute the numbers given for these two examples I have very different results.