[TCML] MMC design

[Mddeming at aol.com]

In a message dated 1/16/08 11:00:29 A.M. Eastern Standard Time,  
dunnsept at verizon.net writes:

I'm  going through some of the MMC calculators on the net trying to figure 
this  stuff out.
I have a 9kv NST and LTR capacitance is 12.5nF
output of the  NST is ~13kv p-p   (close enough)
so, assuming 0.1 2kv caps
1  string of 8 = 16kv and 13nf
2 strings of 16 = 32kv and 13nf

is 16kv  "high enough" above the NST?
is it just a waste to go with 2 strings of 16,  should I, in this scenario, 
stick with 1 string of 8 and call it  good?
if the caps were 0.047 and 2kv, then 2 strings of 8 = 16kv and  11.75nf
or 3 strings of 11 at 22kv and 12.82nF

which is more  important in designing the MMC?
is it more important to be as close as  possible to the LTR value or have 
enough voltage "padding" above the xmfr?  is there some other factor in here 
to use (like the discharge energy or  something?)
thanks

Paul (I didn't expect the Spanish Inquisition) in  Michigan...  

_______________________________________________


Hi Paul,
 
There is some flexibility around the LTR value; many folks consider  20% 
tolerance as OK. In general, longer strings = more voltage-spike protection,  more 
strings = more current handling capability. Dr. R's suggestion  will give you 
a virtually bullet-proof design from a voltage standpoint.  You didn't 
mention the current rating of your transformer. Too few strings, and  your caps will 
heat up on peak currents, too many and your cost goes way  up.
 
Matt D 
"NOBODY expects the Spanish Inquisition" Ximinez  ;-))  



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