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Re: [TCML] MMC Voltage consensus

Hi Ruben,
    Welcome to the wonderful world of opinions! "Safe"  is not a binary 
concept. it is a continuum of "greys". When MMCCalc says your  plan is very good, 
that is correct. When Javatc says 60kV is probably optimal,  that is also 
correct.  In MY opinion, you are OK with your design, which  has about a 50% safety 
margin. More would not be "safe", but would be  safER. Consider the following:
1) You are driving at 50 MPH and see a stopped car ahead. While  there are 
tables showing road/tire conditions and stopping distances, the real  question 
is "at what distance would YOU start braking"?
2) You are sky-diving. Tables notwithstanding, at  what altitude would YOU be 
comfortable opening your  'chute? 
Obviously, with a TC only a few caps will go "splat" if you're wrong, but  
the same principle applies. If knowing the odds gave you absolute answers,  
there would be no horse races.
Matt D.
In a message dated 1/3/08 5:18:41 A.M. Eastern Standard Time,  
ruben.peterstc@xxxxxxxxx writes:

Hello  all,

I'm just about to order capacitors for my  MMC

Arcotronics      RS-114-474    1500   0.047,   from
http://www.rsaustralia.com <http://www.rsaustralia.com/>  .

So far I'm planning 4 strings of 17 caps to give a rating of  11.06nf ,
25.5kv DC (running on a 12/30 NST, LTR with a static  gap).

Terry's MMCcalc, rates 25.5kv as very good, while Java TC  designer
recommends a peak voltage of 60kv.

I've read some places  that a voltage just over the peak transformer voltage
is sufficient; other  places that 1.8*peak is necessary; in addition to the
fact that dielectric  strength reduces with frequency (my coil will run at
about  429khz)

So I'm wondering if there is any consensus about the  recommended MMC voltage
rating, as well, Im after as any opinions and  recommendations. I'd Rather
the MMC cost $120 as opposed to $180++, but at  the same time I don't want to
blow caps (blowing cash I don't  have)

Many  thanks


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