Re: [TCML] aspect ratio

[David Dean <deano@xxxxxxxxxxxxxxxx>]

Hi

I don't know anything about oil filed snubbers.  .02 mfd sounds good though. 
If they are mylar, as Dr. R suggests, it will be lossy.  Mylar will work O.K. 
at low power levels is spite of the losses, however at higher power they will 
not last long.  Keeping run times short and allowing plenty of time between 
runs to allow the caps to cool will of course prolong their lifetime 
somewhat.

You don't say if you have bleeders across each individual capacitor in the 
string, it is a very good idea to do so. My first MMC (actually an EMMC, 
pushing the voltage rating beyond the limits) I failed to order bleeder 
resistors with the caps. I had soldered a string of 11 caps together, charged 
it, discharged it, and was impressed by the bang. I decided to wait until I 
got bleeder resistors in to finish construction and left the string of caps 
on the bench with a jumper wire clipped across the ends. A week later when 
the resistors came in I picked the string up off of the bench and got a 
shock. I dropped the string, grabbed a meter and checked the charge across 
each cap.   They had varying amounts of charge and polarity on each cap.  The 
sum of the voltages from end to end was zero of course due to the jumper, but 
the caps showed substantial charge on some of them. 

Another thing to look out for in the case the oil filled snubbers are mylar or 
even if they are not, is how they fail when they fail. They may fail 
violently by exploding or by flaming out. It can make a mess if they blow up 
and throw hot oil all over the place, or cause a fire. It would be a good 
idea to shield the cap bank in a plastic container of some kind to prevent 
the mess in case of explosion, and keep a suitable fire extinguisher handy in 
case of fire.  And of course keep the power plug in reach so as to be able to 
remove power in a hurry in case of any type of catastrophe.

Good luck with your project

deano

On Thursday 22 November 2007 08:20:35 pm mark olson wrote:
> David,
>
> The cap bank is comprised of 24  .5 mfd 1500pv 1070va oil filled "snubbers"
> in series for a value of .02 mfd.
>
> Thanks,
> Marko
>
> >On Wednesday 21 November 2007 11:29:14 pm mark olson wrote:
> > > my coil (first attempt) suffers from some design errors.  with the wire
> > > size i used on the resonator along with the form diameter i used,
> > > 17ga on 8.375 pvc, aspect ratio is about 4:1.  30" primary. 1800 w
> > > xfmr. oil filled cap bank.
> > > will this coil work?
> >
> >The aspect ratio is fine, more details on the cap bank would be helpfull.
> >
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