Re: Condenser Products capacitor performance

In a message dated 96-02-06 14:15:12 EST, you write:

>Hello all,
>After reading the following excerpt from a recent post, I thought I would
>give a report on the 
>first firing of my new .025 uF, 20 KV RMS commercial pulse discharge
>capacitors.  The initial 
>tests were outstanding.
>> ........I just finished blowing 2 caps in my TC primary last
>> night. I'd found some surplus 0.015uF 6.5KV DC film caps for $.99 each. I
>> bought 10, wired 9 in series/parallel to get 0.015uF at 19.5KV. I was
>> running about 6KV into the primary of my TC so I figured that a 3:1
>> margin was ok. WRONG! Both times that I approached resonance, beautifull
>> little sparks started showing thru the case of the caps......
>> .....I'm still argueing with myself over wether to build a oil and
>> film cap or to order one from Condenser Products.
>> I can tell you though, don't was your time with doorknob caps and 14 gage
>> primaries! 4" sparks vs. 12" with dc rated caps and 1/4 copper tubeing
>> primary. I can't wait to see what length sparks I'll get with a real pulse
>> rated cap.
>Secondary - 6" diameter on acrylic form with 943 turns of 22 gauge wire 
>            for a winding length of 26.5", sealed with epoxy
>Primary - 13 turns of .25" copper tube on a 20 degree inverted conical
>Final Toroid - 28" diameter homemade with a 5" cross section
>Spark gaps - 6 series copper pipes 3" long with vacuum motor quenching,
>              gapped at .0045"
>Transformer power - Neons, 15,000 VAC with 90 mA total current (1.35 KVA)
>Setup -  It consisted of using a balance primary with the capacitors on
>opposite sides of the 
>secondary for a total capacitance of .0125 uF.  The spark gaps were across
>the capacitors.  I 
>took care to keep off-axis inductance to a minimum.  There is less than 2'
>from each side of the 
>primary back to the spark gaps, including the length of the capacitor.  A
>"standard" filter 
>arrangement was used, .0009 uF and 2.2 mH was used per leg of the
>in the filter.  A 
>safety gap was in place.  The RF grounding system consists of (5) 10' x 5.8"
>copper clad rods 
>spaced 9' apart.  They are connected to one another via 2.125" wide solid
>copper strap that has 
>been soldered to the tops of each rod and buried along with the rods.
>Another identical copper 
>strap is soldered to this and connects the base of the coil via a connecting
>plate on the 
>secondary, per RQ's design.
>After making several runs with smaller toroids and trying different coupling
>heights, I have 
>gotten as much as 4.5' discharges to a ground point.  The free-air streamers
>are about 4'.  I am 
>tuned all the way out to the end of the 13 turns of the primary.  I need to
>make a larger toroid 
>to see if this can be improved without the addition of more power.  Based on
>my previous 
>experiences and others observations, the efficiency seems very high.  It
>calculates out to 300 VA 
>per foot of spark.  I suspect I am at or very near the maximum discharge
>length for this level of 
>input power.  I was pleasantly surprized by the results of this preliminary
>set-up.  I would 
>guess that I am approaching the level of diminishing returns on this size
>coil.  I will add more 
>power at a later date, as I have to move some items in my garage to allow
>longer free air sparks.
>After going to a larger toroid, I will need to either add more turns on the
>primary, or drop out 
>one of the capacitors.  I will initially drop out a capacitor, as this is
>easier thing to do. 
> I will no doubt lose some efficiency by doing this.  I will post the
>of both adding 
>turns and increasing capacitance.  I will not be able to get to this
>experimentation for about a 
>week, as I have to leave on business.
>Scott Myers


Sounds like a good project.  Nice sparks.  Keep us posted.  I know about
diminishing returns.  I have a coil about the same size, using one .025
Condenser Products cap,  I think I got about 4.0 foot discharges with 1.5 kva
in.  Now with a pole pig and 6 to 8kva in, I only get 6.0 foot discharges.  I
think I have reached the physical limitations of this system.  Still fun

Ed Sonderman