Re: Higher current same capacitor question

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Esondrmn-at-aol-dot-com>

In a message dated 2/24/01 4:15:34 PM Pacific Standard Time, tesla-at-pupman-dot-com 
writes:

<< 
 Hi All,
 
 I have a question to do with capacitor sizes, current capability of the
 transformer,
 cap wear and tear etc.
 
 I have a Tesla Coil that is designed for a 15kV rms 120mA NST farm using a
 40nF
 MMC capacitor. I have recently aquired a 11kV rms 5kVA power distribution
 transformer, and I am wondering if I can take advantage of the increased
 current capabiltiy of the power transformer.
 
 My power supply is 230 V, 50Hz, 20 Amps max, which corresponds to
 418mA on the secondary of the power transformer.
 
 My 40 nF capacitor is way under resonant size for this transformer,
 which is 121 nF  !!
 
 Question 1: I have a static spark gap, so could I set the gap to fire at
 10-11kV
 and let the system run at an insanely high bps without damage to the MMC?
 Would the RMS current on the capacitor be way over their rating?
 Can I use the full current capability of this transformer with risking
 damage to the MMC?
 
 Question 2: I have two oil-filled plate caps that are not currently being
 used. However, I suspect that I CAN'T use the plate caps and the MMC
 together at all because of the differing dv/dt's of the capacitors - the MMC
 will discharge very fast and then the plate caps will expend energy
 re-charging the MMC. Is this correct ?The plate capacitors are 15kV DC 11 nF
 and        30 kV DC 5nF .
 
 Comments ? Suggestions ?
 Being a student, I can't buy any more MMC caps for a long while, and I can't
 afford to break the MMC I have.
 
 Thank you very much,
 Alan Williams.
  >>
Alan,

I believe you will need to go to a rotary gap with this much input current.  
My experience is that most static gaps will not provide adequate quenching 
(i.e. will fire and stay power arced) above about 2kva.  Some on this list 
have forced air quenched static gaps running at high power levels, but most 
switch to a rotary gap when using distributition transformers for power.

Your .04 ufd cap should work just fine.  You might look at Terry's mmc 
calculator to check the AC current rating.  Add more capacitance as you have 
money - and retune the system of course.  Increasing primary capacitance will 
produce longer sparks.  If you do go to a rotary gap, you should put a safety 
gap across it to save the caps from any problems.

Ed Sonderman