[Amps] (no subject)

[Frank Goenninger DG1SBG <frank_goenninger@t-online.de>]

Hi all:

For my big power supply (see my recent posts) I have found an  
equation for calculating suitable equalizing Rs for the caps:

My caps are:

14 caps, each with 4200 uF rated 400 V working voltage DC.

The equation from Cornell Dubilier (cap manufacturer) says:

R = (Vr - Vb/n) / (0.00075 C Vb)

with
Vr = rated working voltage for each cap
Vb = voltage over the series connected caps (= voltage over whole bank)
C = capacity of each cap
n = number of caps

This gives, with Vb = 3250V DC, a value of 16kΩ for each equalizing  
R. Not spectacular, so far - I thought. Now, I got curious as to what  
power rating these Rs should have. I came up with this:

P = U * U / R

U = 3250V / 14 =  abt 232 V
R = abt 16 kΩ

=> P = abt 3.5 W (taking 5 W Rs for safety reasons)

Selected Rs: 15 kΩ / 5 W MOF Resistors

Right ?

Thanks for comments.

73, Frank

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