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When powered from a DC voltage source, the current through the coil will max out at I = V/R where V is the applied voltage and R is the combined resistance in the coil(s). For a given configuration of air core coils, doubling the voltage will double the current, and double the resulting magnetic field. Either approach can work, but you'll encounter other "engineering" problems (switching transistor voltage capability, coil winding insulation strength) when running much above 1,000 volts. You can also run a number of identical coils in parallel to achieve similar results at lower voltage (but higher current). High current, moderate voltage transistors are inexpensive. High current, high voltage transistors can become very expensive, particularly above 1700 volts. : Tesla was trying to minimize the effects of winding capacitance since this application was intended for radio frequencies. Individual turns within a coil winding form small capacitors to other turns since they are in close proximity to nearby turns and there is a voltage differential between the turns. In a capacitor, the energy stored in the electric field is proportional to the capacitance times the voltage differential squared. In the case of a coil, the voltage Tesla mentions is really from a given winding turn to nearby turns. In a multilayer coil, the voltage difference (between a given turn in one winding layer to the turns in winding layers above and below) will be considerably higher than the voltage difference between adjacent turns in a flat spiral. Since the energy stored in these little capacitor goes up as the square of the voltage, the energy impact of the winding capacitance will be much greater in a multilayer coil thatn for a simple Archimedes spiral coil. However, the bottom line is this particular patent has absolutely NO bearing on what you are trying to do in your motor design since you will be using relatively slow, switched DC coils, and not high frequency AC. At low frequencies or with DC, inter-turn capacitance effects are negligible and can be ignored. : To me it seems as though something happens to the energy travelling No. For your application, you are more likely interested in maximizing the number of ampere turns within a given winding volume in order to get the maximum magnetic field. A simple multilayer coil is probably better suited for your application than using stacks of single layer pancake windings, and multilayer coils are considerably easier to fabricate. : So when power is stopped to the flat coil the magnetic field doesn't When you remove power, the magnetic field collapses at the same rate that the current falls to zero. When the winding current reaches zero amperes, the magnetic field is also zero. The magnetic field will not reverse unless the direction of the current flowing through the coil also reverses. If you are driving the coil from a DC source through a simple transistor switch, the field will rise to a maximum of Vin/Rcoil, and then fall back to zero when the transistor turns off with no current reversal. The actual rate that the current falls to zero in your application will be a function of the specific protection circuit that's used across the coil (to prevent overvolting the transistor) and the inducance and resistance of the coil(s). Thanks for the kind words. I'm a retired electrical engineer and high voltage hobbyist. See: No claims to fame, however... :^) : It really depends on the desired efficiency and the nature of your load. You can use a dropping resistor (simple, but no regulation and very inefficient), a series pass transistor/voltage regulator, or (for greatest efficiency) a DC-DC converter. Unfortunately, the operation of switching regulators and converters can become quite technical. You can find much more information by Googling on terms such as "series pass regulator", "switching regulator", and "DC-DC converter". Here are some examples: : Good luck and best wishes, Bert
: Bert, great info, thank you very much.
:
: You mentioned that to increase the magnetic field one could add series
: coils so long as the current remained constant. How does voltage affect
: the coil?
: With the ultimate goal of increasing the magnetic field of the coil would
: it be best to A: increase the number of turns? , or B: increase the
: voltage let's say from 300vdc to 3000vdc, or pancake more series coils and
: maintain current?
: I've been trying to understand this patent better but am having
: difficulty. Tesla mentions that if the coil is wound with parallel
: windings where the output of one is fed to the input of the other then
: "the potential difference between any two adjacent points in A and B
: will be 50volts and as the capacity effect is proportionate to the square
: of this difference, the energy stored in the coil as a whole will be two
: hundred and fifty thousand as great". What is he actually saying
: here?
: through the coil when the windings are in parallel that magnifies the same
: effect in a regular wound flat coil. I guess what I'm asking here is
: whether or not winding the coil in parallel will give me a greater
: magnetic field with the same input as opposed to a regular single wound
: coil?
: collapse but is only reduced? Would it be better to ground the input or
: reverse the polarity of the input?
:
: Your knowledge base is quite extensive and impressive and I certainly
: appreciate you taking the time to share what you have. If you don't mind
: my asking what is your background and your claim to fame so to speak?
http://205.243.100.155/frames/about.html
: Oh, before I forget how can I reduce the voltage of a 12volt system down
: to about 2 volts or less and maintain a decent current level? Have you
: ever done any testing with H2 generation by electrolysis? What are your
: thoughts?
http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/audio/part5/page4.html
http://www.powerdesigners.com/InfoWeb/design_center/articles/DC-DC/converter.shtm
http://www.maxim-ic.com/appnotes.cfm/appnote_number/2031
: Thanks again.
:
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