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