Re:Re: M.M.C.

[Terry Fritz <twftesla-at-uswest-dot-net>]

Hi Al,

        So your running two modified 15/60 transformers with shunts removed.
I'll just guess that is like a 15kV 180mA transformer.  The resonant
frequency is probably around 150kHz and your running a static gap.  

        If you run a resonant size cap of about 32nF at 194 BPS, you will
run around 22 amps RMS which would indicate a 10 row by 14 cap per string
MMC.  About 6 degrees C of heating.

        If you run a 120 BPS LTR size cap of 42nF at 120 BPS, you will still
run around 22 amps RMS so a 12 x 14 MMC is indicated.

        I am assuming Panasonic style caps here, but the key numbers are
22kV of voltage, 22 amps, and 30 to 40nF.  What ever caps you can find will
have to do this. 

        The small Seacor, Panasonic, and WIMA style caps are good to about 3
amps each string.  The big snubbers are like 12 amps but cost proportionally
more.  So it's time to look around and see what MMCs are available and go
from there.

        I am guessing a bit at all the numbers but it is probably close.

Cheers,

        Terry


At 06:55 PM 9/7/00 -0400, you wrote:
>Hi Terry.  I have never used any math to design any of my coils.  I just
>used trial and error and a common sense approach.  So I have no idea what
>frequency my coil operates at.  I just like to experiment, this is the
>fun part!  The spark gap I currently run is a R.Q. type.  It has 8 of the
>3/4" copper pipe couplings bolted into a 4" abs pipe coupling.  The gaps
>were spaced at .030 each with a automotive feeler gage.  That gives seven
>actual gaps, and they cover an area of roughly 2/3 of the interior of the
>abs coupling.  It is quenched by a 4" 120 volt muffin box fan epoxied to
>one end of the abs coupling farthest away from the working gap which is
>mounted flush with the other end of the coupling.  Now, as far as the
>value of the caps,  I really am not sure about that,  this is why I am
>enquiring about them,  I want something to do a sustained 60 minute run
>on my 8" coil without them melting down.  The coil is 18ga. iso
>fluorethane insulated or something like that prime solid motor wire,
>there is 7 and 1/2 pounds of this wire wound on the coil which is a
>cardboard concrete tube, cut down to a finished height of 25".  The wire
>covers the entire surface of the 25" form completely from end to end.  I
>just wound the wire until it ran out and then cut off the remainder of
>the tube, which started out as a 36" cutoff from the concrete form.  The
>tank uses two unpotted modified neons with two shunt plates removed from
>each tranny 1/2 section, they are allanson 60ma 15kv neons.  The tank is
>wired with 18ga. stranded silicon 40kv wire, it has two 3" ferrite donuts
>wound with 14ga. stranded thhn wire on the entry and exit of the spark
>gap.  The tranny outputs go through two 1" pvc tubes 12" long wound end
>to end with one layer of 23ga. scc solid wire for protection.  Both
>tranny outputs also go directly into a single beer bottle cap wired to
>each paralled high volt output and then to the dedicated Tesla ground to
>which the bottom of the secondary is also attached. That is my protection
>circuit for the tank. The primary is flat wound 14 turns with 3/8" refrig
>tube, spaced about 5/16 to 3/8 inch between each loop. So what type of
>indestructable mmc would you recommed for this coil?  I have no certain
>idea about the caps I want, since coilers seem to use a variety of them, 
>this is what I want to know.   I just want the best possible arrangement
>of caps/resistors to mount on my solid sheet of nomex board.  Which I
>will cut and drill to suit the caps/resistors I use.  Thank you.  Al.
>
>On Wed, 06 Sep 2000 13:28:58 -0600 "Tesla list" <tesla-at-pupman-dot-com>
>writes:
>> Original poster: Terry Fritz <twftesla-at-uswest-dot-net>
>> 
>> Hi Al,
>> 
>>      I need to know some details:
>> 
>> What frequency does you coil run at?  Poly caps heat more at higher
>> frequencies so they have to be sized to the frequency if one is 
>> trying to
>> be really careful.
>> 
>> What type of gap do you have.  The RMS current is directly 
>> propartional to
>> the firing rate.  I assume the firing voltage is about 21kV.
>> 
>> If you know the values of cap you want that helps ;-))
>> 
>> There is a simple BASIC DOS program below that can do the 
>> calculations for
>> you too:
>> 
>> http://users.better-dot-org/tfritz/site/programs/MMCCALC2.ZIP
>> 
>> The numbers change a bit depending on the exact type, value, and
>> manufacturer of cap you use.  I use ones from DigiKey which I know 
>> well,
>> but there are all kinds of great caps. 
>> 
>> Check the links in these posts out and let me know the data about 
>> your coil
>> and we can work the numbers.  If the voltage peak is within the DC 
>> rating
>> and the RMS current does not heat them more than 5C, they will last
>> thousands of hours...
>> 
>> At 11:40 AM 9/6/00 -0400, you wrote:
>> >Hi Terry and all.  Terry, what kind of polypropylene caps would you
>> >recommend for a coil using two paralleled 15kv-at-60ma modified neons 
>> that
>> >could sustain a minimum of a 60 minute run?  They draw 16 amps at 
>> full
>> >output but limited by 4500w 240v water tank elements.   At full 
>> blast
>> >with no resistive load they will pop a 20 amp breaker after about 
>> 10 to
>> >15 minutes, I guess from the heating effect on the 20a. line.  So I 
>> run
>> >them on a separate 30a. 10 ga. 120v. line to get sustained runs.    
>> 
>> >Thank you  Al.
>> >
>> 
>> 
>