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Re: MMC size: (Was: Re: Success with PP Multi-Mini Cap)



Reinhard & MMC fans,


<SNIP>
My final
> xformer setup will be 5.5kVA worth of modified neons and the
> primary cap will be 120nF. I will use 15 caps in a row and 29
> strings in parallel. I will be using 5Mohm equalizing/discharge
> resistors across each cap (will be tried on my testbed setup,
> first, to see if it makes a difference in TC spark length) and
> heavy buss bars on the end connections. I havenīt decided yet
> if I will cross link the parallel strings. 

<SNIP>

To crosslink or not to crosslink, that is the question.  Seems like it
would be better to NOT crosslink them, for survivability reasons.  If in
one string some caps short, then the voltage across the remainder of the
string will increase, leading to premature failure of them as well.  But
only one string would get affected.  On the other hand, if the strings are
crosslinked, then shorted caps in one string will increase the voltage
across the remaining caps in ALL the strings, which could result in many
caps in many strings getting blown out.

The only advantage that I can think of for crosslinking caps is that you
would need only N equilizing resistors, where N is the number of caps in
series in any one string.  Not crosslinking will require as many resistors
as there are capacitors, = more expense and work.  But I think the
survivability of capacitors outweighs the hassle and expense of more
resistors.  (Don't forget that the el cheapo 1/4 or 1/2 watt resistors are
only rated for 250-350 volts across each, so you will need to series a few
across each cap.)   

Any other opinions?

--Steve Young