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



Original poster: Jimmy Hynes <jphynes@xxxxxxxxx>

I'm gonna try sending this again, since it didn't work the first time. Sorry if it comes through twice

Hey,

On 8/25/05, Tesla list <<mailto:tesla@xxxxxxxxxx>tesla@xxxxxxxxxx> wrote:
Original poster: "Mccauley, Daniel H" <<mailto:daniel.h.mccauley@xxxxxxxx> daniel.h.mccauley@xxxxxxxx >


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.



Hmmm? I talk to Steve all the time on AIM, and am not aware of any 'plans' to talk about stuff behind your back. I'm sure if it comes up, he would share his opinion, but I doubt he's scheming against you so he can attack when you are defensless :P


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'm sorry if i wasn't very clear on this before, but I wasn't arguing that it didn't work for you. I was basically arguing that its not doing what you think, and doesn't necessarily always work.




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.


First of all, I don't see how the drive pulsewidth can be different than the ON time, especially if you are not using a JK flip flop to ensure a soft turn off. Even given a constant ON time, there was a noticable effect. I wasn't claiming that the effect was purely different ON time, but that if you are gonna try to compare them, you should at least compare them honestly and not try to cheat a few cycles.



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.


Do you still notice the effect when you don't change wire length? I'd find that hard to believe. The only other change is the resistance, which is a simple ohms law calculation.



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


Not really a 'fluke', just that it works with your coil, with your tuning. Of course identical set ups will perform identically. It depends on how you tune the coil in the first place (running a slightly lower tuning effectively cancels out your 'ballast' inductance). In other designs, it may not be effective, and in the case of primary current feedback, it will do nothing, since it will simply drive it a bit slower, and keep building up current.



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.


First of all, any increase in resistance will increase loss. If you arent going for a resistive ballast, then you dont want unnecessary loss. If the effect were to be purely resistive, the loss would be enourmous. The effect you are seeing is NOT resistive, and therefore you do not see the loss.



Again, i don't claim to me 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 show it to exist.


Ok, I'll try to dive into some theory here...

First of all, we have to look at the possible effects of adding some small wire to the setup. The effects can be inductive, or resistive, or a combination thereof.

The extra inductance both changes the primary resonant frequency (as does changing the tap point), and reduces the coupling (as does raising the secondary). Therefore, you shouldn't add thin wire for the inductive effect, since you can simply retune (and raise the secondary, although it's probably more about the tuning), and thinner means more loss.

Resistive limiting is not practical. Either the loss is small and the regulation is horrible (as in your case), or the regulation is decent, but the loss is horrendous, or you can have the worst of both worlds :P

<http://www.hot-streamer.com/chunkyboy86/resistiveballasting.jpg>www.hot-streamer.com/chunkyboy86/resistiveballasting.jpg

The "minimum loss" box is where you're running with a few extra milliohms from "only" 8 gauge wire. You don't lose much, but the short circuit current is many many times the nominal current. The "max power" box still loses 50% of the power input, and has a short circuit current of 2x the nominal current. The "max regulation" box limits the short circuit current to a little over the nominal current, but the power lost is way more than power out. Since you are running in the first box, you do not see the huge loss, but resistance is not doing anything to limit the peak current either. A few milliohms has a short circuit current of thousands of amps!

Since there is a noticable effect, it has to be inductive, and can also be tuned out. Since you are using secondary feedback, if the primary frequency is off, it will not build up as much, and may not have a drastic (although it is noticeable in your pictures) effect under normal circumstances. How did you go about tuning the coil in the first place?


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'm trying to explain the theory and provide some insight on why you're getting your results, so hopefully you'll see this as the second type!



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 is better :P


Dan