This is the kind of information I like to find when it comes to trying to prove theories and ideas about thing people have in their heads, I start suspecting a third element involved when I noticed inconsistency or large ranges in peoples voltage guestimations. Your video certainly clarifies these uncertainties and inconstancies when it comes to me guessing rough voltages based on spark gap distances as I'll know from this video that I'll be wanting to use >=100mm spheres when it comes to more accurate readings. I get a funny feeling there will also be other variables that could lead to minor variations, for example, humidity, ambient temperature, air pressure etc. But this is something I honestly had no idea about until coming across this video. Keep this kind of stuff going, these kinds of videos I find to be very interesting!
Thanks for your comment. Yes indeed there are theoretical and empirical formulae which allow the precise effects of pressure, temperature, humidity etc to be predicted, however the 'rule of thumb' at STP (normal lab conditions, standard temperature and pressure) is still 3kV/mm field strength. You can find these in books such as 'High Voltage Engineering and Testing' ISBN: 978-1-84919-263-7 and 'Insulators for High Voltages' ISBN: 978-0-86341-116-8
ridefast0 Thanks again for even more references, I've added those books to my "to read" section in google books, so I should hopefully get round to reading some of those in my breaks and whatnot, they certainly look a lot more interesting than my Inspection and Testing books... less physics in those... x[
Awesome tutorial man, well worth it to make a video! Your right about the various spark lengths having a difference in output due to coronal loss, thanks for the cool video!
This is good work, well thought out and presented.....very sorry that I found it , by chance, much later than you published it and after I stoped playing with Tesla Coils. I woul be interested to know have the ultimate air breakdown voltage is defined and established I have always assumed it to be 1mm gap = 1kV which seems to be the popular rule of thumb but your work seems to dispute this commonly held belief Thanks again
Basically it is a two-stage process. First step is to calculate the maximum breakdown voltage for a given air gap between theoretical very large, smooth electrodes, which in room conditions is mainly a function of gap length. A useful simplification for this is E (kV) = 6.08*sqrt(d) + 24.22*d with d in cm. Second step is to calculate how the shape of the electrodes increases that e-field strength. The ~1kV/mm figure can work for pointed electrodes like needles (if you want to make longer sparks) but it can be ~3kV/mm if the electrodes are large and smooth, such as a short gap between two large spheres. Power companies prefer to avoid sparks and corona so they use long gaps and smooth surfaces where possible.
want to make a suitable hv circuit for my small plasma ball it's hv transformer went bad, tried with the ignition coil of my bike and a transistor oscillator, was getting hv shocks all ove the circuit, plasma ball was working.
Correct, for the symmetrical gaps where both electrodes are away from ground (allowing the e-field to be symmetric), the polarity of the voltage does not matter. The sphere-sphere gap is less sensitive to pulse shape and is best for all measurements including pulses. The needle-needle gap might be OK for DC or peak value of low frequency (50/60Hz) AC. The needle-sphere gap showed a strong polarity dependence as shown in the video. Thank you for your question.
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This is the kind of information I like to find when it comes to trying to prove theories and ideas about thing people have in their heads, I start suspecting a third element involved when I noticed inconsistency or large ranges in peoples voltage guestimations.
Your video certainly clarifies these uncertainties and inconstancies when it comes to me guessing rough voltages based on spark gap distances as I'll know from this
video that I'll be wanting to use >=100mm spheres when it comes to more accurate readings.
I get a funny feeling there will also be other variables that could lead to minor variations, for example, humidity, ambient temperature, air pressure etc.
But this is something I honestly had no idea about until coming across this video.
Keep this kind of stuff going, these kinds of videos I find to be very interesting!
Thanks for your comment. Yes indeed there are theoretical and empirical formulae which allow the precise effects of pressure, temperature, humidity etc to be predicted, however the 'rule of thumb' at STP (normal lab conditions, standard temperature and pressure) is still 3kV/mm field strength. You can find these in books such as 'High Voltage Engineering and Testing' ISBN: 978-1-84919-263-7 and 'Insulators for High Voltages' ISBN: 978-0-86341-116-8
ridefast0 Thanks again for even more references, I've added those books to my "to read" section in google books, so I should hopefully get round to reading some of those in my breaks and whatnot, they certainly look a lot more interesting than my Inspection and Testing books... less physics in those... x[
Awesome tutorial man, well worth it to make a video! Your right about the various spark lengths having a difference in output due to coronal loss, thanks for the cool video!
You are very welcome. I'm glad this was useful for you.
This is good work, well thought out and presented.....very sorry that I found it , by chance, much later than you published it and after I stoped playing with Tesla Coils.
I woul be interested to know have the ultimate air breakdown voltage is defined and established
I have always assumed it to be 1mm gap = 1kV which seems to be the popular rule of thumb but your work seems to dispute this commonly held belief
Thanks again
Basically it is a two-stage process. First step is to calculate the maximum breakdown voltage for a given air gap between theoretical very large, smooth electrodes, which in room conditions is mainly a function of gap length. A useful simplification for this is E (kV) = 6.08*sqrt(d) + 24.22*d with d in cm. Second step is to calculate how the shape of the electrodes increases that e-field strength. The ~1kV/mm figure can work for pointed electrodes like needles (if you want to make longer sparks) but it can be ~3kV/mm if the electrodes are large and smooth, such as a short gap between two large spheres. Power companies prefer to avoid sparks and corona so they use long gaps and smooth surfaces where possible.
Love the graph, would it be possible to get an EXCEL Spreadsheet showing this?
M Schumacher Hi there. Yes I can forward it if you can provide an e-mail address.
please: miguel.3088.ma@gmail.com
want to make a suitable hv circuit for my small plasma ball it's hv transformer went bad, tried with the ignition coil of my bike and a transistor oscillator, was getting hv shocks all ove the circuit, plasma ball was working.
Hi,
The needle points curve in the chart is for bipolar voltage stress of the needle gap?
Same question for sphere gaps.
Correct, for the symmetrical gaps where both electrodes are away from ground (allowing the e-field to be symmetric), the polarity of the voltage does not matter. The sphere-sphere gap is less sensitive to pulse shape and is best for all measurements including pulses. The needle-needle gap might be OK for DC or peak value of low frequency (50/60Hz) AC. The needle-sphere gap showed a strong polarity dependence as shown in the video.
Thank you for your question.
Cool, I'll probably be making one of these sometime in the future.
Good luck with your project.
THANK YOU!