Re: [TCML] Advice on MMC

[David Dean <deano@xxxxxxxxxxxxxxxx>]

Hi Andrew

I guess I did not read your post carefully enough.
Until Chip Ford ask:
He states that he will be using 4 x MOT. In that case, is a terry filter 
needed???
In answer to *that* question, my guess would be that a Terry filter is probably 
not needed, but a properly optimized Terry filter with the right number of MOVs 
for the voltage and possibly increased wattage rating for the resistors to 
handle the extra current would certainly not hurt anything.

Will try to address some of your original questions, comments interspersed:

On Monday 28 December 2009 04:48:41 pm andrew wrote:
> Hi
> I have been using Javatc to help me design my coil. I am currently trying
>  to decide on the correct capacitance value for the tank cap but am a
>  little confused about all the different capacitor values mentioned.
> 
> They are:-
> Primary Capacitor uF  ; I am asuming this is the actual tank cap used.
> 
Yes
> Resonant Cap Size, I think this is the capacitance value that resonates
>  with the transformer at 50 hz.
> 
Yes, if you have 50Hz in New Zealand
> Power factor cap size,  To correct the PF.
> 
Yes, but that is the mains resonant value for the primary of the transformer 
with the secondary shorted. Informational purposes, actual value required for 
any given setup may vary considerably. 1st place a TC is a non-linear load, 2nd 
tank cap adjusts power factor during charging part of cycle. Best to not use 
power factor correction unless you really need it, then start with small value 
and add incrementally till best result found.
 
> Static gap LTR cap size,   Is this the same as the Tank Cap?
> 
> srsg LTR cap size.       ditto but for a Sync gap.
> 
Yes, these are suggested values for use with a NST to maximize power throughput 
while protecting the NST from overvoltage.
> I was planning to use an asynchronous spark gap but from what I have read
> this is not recommended for coils designed with Java TC,
Asynchronous rotary spark gap is not recommended for coils powered by NST
Java TC is designed for NST coils
Probably why you read that
> so for simplicity I will go with a multi pipe static gap. My transformer is
> 4x MOT.  I am building a Terry filter for it.
> 
Fine
Question:
I assume when you say "My transformer is  4x MOT." you mean a stack of 4 MOTs in 
series to output approximately 9kV open circuit?
Another Question:
Are you using, or planning to use, any external ballasting for the MOTs?
And yet Another Question:
Are you using, or planning to use, a Variac, or other variable autotransformer 
to adjust the input voltage to the MOT stack?

> My question is, what is the best way to use Java TC to estimate the optimum
> Tank Capacitor size.
That is the $64.000 question.

What you need to know:
Open circuit voltage (measured is best)
Short circuit current (measured is best)
If using external ballast measurements are made with ballast in place
Input that data into the boxes marked "Rated V out" and "Rated mA"
in the transformer design section of JavaTC

Know that the MOT is not linear, and the impedance will change depending on the 
applied voltage, so the result you get will only be valid for the conditions you 
have used for inputs. If you are not planning to use a Variac, it should be 
close enough. If you *are* going to vary the input voltage you might want to 
measure your open circuit voltage and short circuit current at different input 
levels and recalculate to see if there are any gross anomalies that might change 
the value you choose for a MMC capacitor.
> When I know that, I can order my caps for the MMC.
Yep
> 
> Many thanks
> Andrew Buxton
> Newbie Kiwi Coiler
> 
> 
later
deano
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