Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>
At 09:52 PM 3/1/2007, Tesla list wrote:
Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>
Hi Skip,
Nope, can't back you up on this. Everyone that "learns" does so by
doing. You must "do" to "learn". Not realizing the difficulty
involved with winding a hv pole pig size transformer is not saying
that someone doesn't understand high voltages and associated
currents and the damage that can be done. It's simply an "area" of
high voltage in which they have yet to experience. For many, the
cost and difficulty is not an issue or a concern. The challenge
itself is often worthwhile.
Heck.. isn't that why we build tesla coils? Aside from the
satisfaction of making a big noise maker (always worthwhile),
there's the educational experience of learning about practical HV
design (hmm.. smooth edges good, raggedy edges bad, etc.) and things
just like transformer winding.
I could buy a pole pig once a year and never learn anything, or I
could try building one and learn all kinds of mechanical and
electrical tid bits.
Book knowledge only = ok, it should work.
Experience only = ok, it kinda works, but I don't know why.
Book and experience = It works better now that I applied experience
into the equation.
This parsing applies IF (and only if) you actually want to build
your own transformers.
Personally, I have no desire to learn the esoterica of HV
transformer winding.. I've wound my share of RF transformers,
designed and built a few lame PWM supplies and motor drives, and
used a lot of other people's work at lower frequencies, and over the
years I have learned (by reading and observation of colleagues'
pain) that I don't know enough about this, never will, and am happy
to let others fight that particular battle.
Sort of like doing masonry.. I've read the books so I know what the
process entails. I helped my wife build a small block garden wall (I
was mortar mixer and hod carrier). Watching someone who actually
does this for a living is amazing. They are fast, accurate, etc.,
and when it comes to doing stonework with random pieces, they do it
better than I can imagine. (because it's art, not engineering, I
suspect). I'm more than happy to do the heavy lifting of signing a
check rather than the heavy lifting of blocks and mortar. I suppose
it's the small experience that leads me to that. And, from some
small satisfaction that, if pressed when civilization craters, I can
probably build a wall if needed, although it won't be pretty or efficient.
I think doing the task of winding a pole pig transformer with all
it's dynamics is a monumental task, but nonetheless, one that must
be done to truly learn.
If that knowledge is worth possessing. It might be that the
knowledge worth having is that it's a pain in the rear to build your
own transformer and that buying someone else's toil is a "better deal".
(I concede that sometimes you have to try it once yourself to
recognize the truth in the previous statement...) But everyone
needs to decide where to spend their precious hours. Do you spend
it learning the esoterica of transformer design and winding? Do you
spend it learning how to make gorgeous spun toroids? Do you spend it
figuring out how to avoid destroying semiconductors? I'd venture
that nobody has enough time to do it all, even if they spent 24
hours a day, so at some point you have to do a bit of triage..
And that comes back to doing the things that interest you.. If
you're interested in winding your own transformer more power to you
(or for that matter, if you want to start with iron ore and
smelt,roll, and cut the steel to make the core, have at it...). I
know people who have made their own CRT phosphors and vacuum tubes, as a hobby.
Tony may not be ready to dive into a pole pig design (but it's good
that he's thinking). I certainly don't think he's shown any
evidence that he should stick to voltages under 12 volts. That's
just silly. You are correct that part of the design is
understanding the word LETHAL when dealing with high voltages, I
understand your concern there. We all have concerns with others
doing things we have done (when we realized the dangers by
"doing"), but they can't learn without doing, no matter how much you stress it.
Hmmm... There's a qualitative aspect here though. There was an
article about "improving" a 700VDC power supply in QST a year or so
back that had so many HV no-no's both in design and in the
photographs that I got tired of listing them all. (radically
increased stored energy, no margin on component ratings, unsafe test
setups) The editors of QST forwarded my concerns to the author and
his response was along the lines of "I've designed umpty digital &
analog circuits and been published and they all worked, so what's
your problem" You can be a wizard at circuit design and
construction and just totally miss the boat on HV work. Many
experienced electronics experimenters have no real appreciation for
things like catastrophic breakdown and stored energy.
I've always thought that most people who work with high voltage/high
energy/other inherently dangerous activities really only appreciate
the danger after one of those "near death" experiences where you go
"Wow.. that was a close one". I only wish I could find a way to
contrive such an experience for new engineers that would be safe, but scary.
When I started fooling with HV, an elderly HV guy (elderly is a good
sign, if you think about it; and elderly to me back in my early 20s
might not seem so today in my 40s....<grin>) said that everyone
should start with a decent sized Van deGraaff generator. High
enough voltage so that corona is omnipresent and you get a feel for
design issues and that the practical effect of a HV field can extend
quite a ways. Low enough energy so that the inevitable mistake hurts
but doesn't kill you. A low powered tesla coil is probably in the
same category. You can make some small mistakes and all that
happens is something catches fire, the insulation burns off, etc.
After you've done some small amount of doing, then it's time to make
that honest self assessment.. Is this something I really should be
doing? But heck, people do dangerous things with no experience all
the time. Most people survive through life.. partly by luck, partly
by self knowledge, and HV experimenting is no different. If you are
excessively bold, you wind up being a Darwin award holder.
Where it gets a bit stickier (and is a totally different subject) is
when other people's safety starts to enter the picture (public
shows, your kids wandering around your gear) or where there's
significant consequential risk if you "have a bad day" (gosh, sorry
we inadvertently burned down the school). That's where I think I'd
start to draw the line and require experience and a second set of
eyes. (And, I confess that I've become substantially more
conservative as I've gotten older...maybe it's those near death
experiences? maybe it's just experience and knowledge.. maybe
that's the difference between knowledge and wisdom?)
Jim