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Re: Passive Ballasting for DRSSTC - My thoughts before Ed Wingates Teslathon

Original poster: Terry Fritz <vardin@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Dan,

At 01:12 PM 8/25/2005, you wrote: 
Apparently, there has been an offlist discussion (without me of course)
regarding my ideas of a "passive ballast" for use in a DRSSTC.  Also, i
received word that Steve Ward was planning on basically debunking this
theory to fellow list members at the upcoming Teslathon this weekend,
again without me being present to provide my feedback on the subject.
Anyways, i thought I would add my thoughts on this practice ahead of
time so you can hear my side of the story.


Not even "I" had heard of this!!  Your spies are better than mine :o)))


Firstly, regarding the passive ballasting action of the DRSSTC, it
works.  Perhaps not in the way i think it works, but it does in fact
work.  Now, i'm much more of a practical engineer, than one that dives
into the hard core theory behind everything, so i'll be the first to
tell you that my theory could be incorrect.  But again, regardless, it
does work.


I hope it works since I am thinking of using it too!!!  My fabulous protectors:

http://drsstc.com/~terrell/notes/DRSSTCprotec.pdf

http://drsstc.com/~terrell/pictures/ArcFilter-01.JPG

Still sometimes allow the IGBTs to get damaged. The protectors catch 95% of the trouble, but that last darn 5%....

So I was thinking of adding some pure resistance too...


Here are several of my arguments so you can get my side of the story
before you hear someone elses ideas.

1.  The first argument Steve and Jimmy provided was that the ON time in
both of my experimental data was different.  Okay, this is a valid
argument.  I checked the data and in fact the ON time *is* different.
However, i was sure my drive pulsewidth was constant.  To verify this, i
had my technician re-check this data.  Again, the data was identical.
Even when the drive pulsewidth was identical, the ON time (primary
current) differed in each one.  Perhaps, this is more of a clue to why
the ballasting effect occurs.

Sounds like too subtle of a thing to account for so much difference... You guys will have to work out if this is significant...


2.  The second argument is that somehow the length of the wire affected
tuning or coupling.  Again, a good point, however i no longer use longer
wires when ballasting.  I use same length as original 4 AWG cabling, but
just use 8 AWG instead.  Steve also made a comment that perhaps I do not
retune when switching the wire sizes.  I personally can't see how
changing an identical wire length to a smaller gauge would affect
tuning.  Again, his point his valid, and this is something i can explore
further.

My protectors change reactances about 5 orders of magnitude beyond what another few inches of wire would. Again, I think that is just too tiny of a thing to make much difference.


3. The third argument proposed to me was that this was a fluke.

If something were just on the "hair trigger" edge, then a tiny change might make a giant difference. But you have gone through lots of IGBTs and such with constant results...

However, I have built (well, my technician working for me) has built
five identical DRSSTC II coils in the past year.  Three of which are
used for demonstrations i do during the year, and two which were sold.
In every case, this ballasting effect occurred and is measurable.

Cool!! You have "numbers" on your side... Someone to make coils for you!! SWEET!!! :-)))


4.  The fourth argument is that this passive ballasting is inefficient
and lossy.  This again is not true at all.  Power input to my coils
barely change at all when switching from the 4AWG to 8AWG primary wire.
Spark length also remains unchanged and in fact, the ballasting effect
only appears to work during ground strikes when currents peak to their
highest.

"Inefficient and lossy" has a far different meaning for DRSSTCs than conventional coils. Since DRSSTCs are continuous power input machines, they can sneak by with losses that would kill a conventional energy fixed coil. I can't imagine the losses from wire gauge in this case would be very noticeable at all...


Again, i don't claim to be an expert on theory and i'll be the first to
tell you that i am not. My theory behind why this actually occurs may be
incorrect, but the so called passive ballasting does work.  You can
argue with me and debate this as much as you want, but my experience and
measured data shows it to exist.

It is very hard to argue with "experience and measured data". It has a highly obnoxious habit of being totally true.. :-))) Like those Greyhound busses, just relax, and leave the theory to us :o)))


Now there are two ways to answer this post.  One is to be close minded,
act with attitude, and tell me that passive ballasting is impossible,
wastes energy, and does NOT work - as has been the typical response.
The second would be to try to discuss this in a positive manner and
perhaps provide insight to why i am getting these results.  Perhaps the
action isn't purely resistive or inductive as in a typical ballast - as
i originally thought.  But you guys tell me.  What are your thoughts.
I'm open ears.

I don't think we have all become polarized in to warring superstitious factions heck bent on destroying each other just yet :o)))) We usually save that for early spring >:D


Also, keep to the subject.  We all know active current limiting is the
ideal way to go (albeit at the expense of being a bit more complex) so
please don't turn this into an Active Limiting vs. Passive Limiting
thread.

Active limiting is needed with the IGBTs are too small to take a significant over current event. In the beginning, very large IGBTs were used that could handle say a 500% over current spike. But many are toying with very small IGBTs that "run" happily, but need to be "stopped" if thing go wrong. Like "me" :-)

http://drsstc.com/~terrell/pictures/H-Bridge-Finished.jpg

But I am thinking of pulling you passive ballasting into the active limiting world also to "help out"... So it is not a matter of "Active Limiting vs. Passive Limiting" but rather Active Limiting "AND" Passive Limiting to achieve the final goal of a DRSSTC that just can't be blown up :-))

Cheers,

        Terry


Dan