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Re: [TCML] reply to herr zapp about mikes capacitor fail...



.22 uf 1600V sounds a lot like panasonic ECQ-E caps that I had a huge pile of and sold mostly to folks on this group 5 or more years ago - if it is those capacitors, that rating was an AC rating, as I recall, so the quantity you need in series to be safe is less.


----- Original Message ----- From: "Quarkster" <quarkster@xxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Saturday, October 03, 2009 7:41 PM
Subject: Re: [TCML] reply to herr zapp about mikes capacitor fail...


DC -

The "16 minimum" per string applies when the familiar .15uF, 2,000 C-D 942C capacitor is used. According to Mike, he is using a .22uF, 1600 volt capacitor, which means he needs 19 (or 20) caps to maintain a "2.5*Erms" margin.

Regards,
Herr Zapp

----- Original Message ----- From: "DC Cox" <resonance@xxxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Saturday, October 03, 2009 1:30 PM
Subject: Re: [TCML] reply to herr zapp about mikes capacitor fail...


A few more ideas:

Alway rate the MMc cap value for at least 2.5 x Erms of the nst.  If you
fail to do this step, and then a single cap fails, that shorts thus putting
a lot more stress on the remaining caps.  Best to "do it right" the first
time and then not have the heartache of testing your caps to find the bad
units.  Usually, by then, it's too late because the extra stress has done
internal damage to the remaining caps and they also start failing --- like a
domino effect.

Usually, with a 12 kV nst use 16 to 18 (16 min) in a single series. Also,
be sure to keep your total spark gap spacing to under 0.180".

Dr. Resonance




On Sat, Oct 3, 2009 at 12:15 PM, mike osipowicz <yosip1115@xxxxxxxxxxx>wrote:


hello, here are the questions, and answers.... What are the voltage and
current ratings of your NST?
2. Are you using a variac to run the NST at greater than nameplate input
voltage?

3. What are the specific details of your MMC:
a) Value and voltage ratings of the individual capacitors, and if all the
capacitors in your MMC are identical;
b) Number of series-connected capacitors per string;
c) Number of parallel strings used;
d) Peak current rating of capacitors.

4. What type of spark gap are you using, and what is the total gap spacing
you were using when the cap "blew up"?

5. What was the coil doing just prior to the capacitor failure?

6. How did the capacitor fail (what did you see)? Did smoke come out? Did
the case split open? Did you see internal arcing? Etc, etc.

All this information will help find out why your capacitor failed, and how to prevent repeat failures with remaining capacitors in your MMC, or with additional capacitors you may add to the system.1. the voltage of my NST is 12kv, the amps, 60 MA, two in parallel. 2. it is plugged directly into the
wall, with a switch, no variac used.3. the MMC, it was originally 18,
.22MFD, 1.6kv caps in series for 10 NF, and 28kv. they are all identical
accept for the two large ones I added on, is that the issue? I use the
original 18 caps a lot, with no problems, they are cornell dubliner brand,
the others were a different brand, and were two .02 MFD, 15kv rating,
polypropheline.4. the spark gap is just a simple static gap, set at about 1/6 inch? it was fine with the smaller cap bank, running 30 MA...5. the coil worked great for a few seconds! amazing! but... that quickly died off, it worked good for a second or two, then it died down quickly, I would unplug it, reset the spark gap closer, and try it again, same problem, until the side of one of the caps blew out, and caught on fire... fun.6. I saw some internal arcing, and some smoke came out when the total failure beganwell, the rest of my coil is this: dryer duct toroid, 4 inch secondary, 25 gauge, 1000 feet. 1/4 inch copper tubing primary, two 30 MA NST's, air compressor
que


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