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: --Previous Message--
: 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?
:
: 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.
:
: 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?
:
: 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.
:
:
: 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?
:
: 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
: 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?
:
: 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
: collapse but is only reduced? Would it be better to ground the input or
: reverse the polarity of the input?
:
: 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).
:
:
: 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?
:
: Thanks for the kind words. I'm a retired electrical engineer and high
: voltage hobbyist. See: http://205.243.100.155/frames/about.html
:
: No claims to fame, however... :^)
:
:
: 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?
:
: 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:
: 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.
:
:
: Good luck and best wishes,
:
: Bert

Again thank you Bert.

: You mentioned that a mulitlayer coil would be better suited and easier to wind than flat pancaked ones. I'm not quite following what the difference would be. The coil that I had planned to use was of course 300 turns of 23awg with a 2" aircore and then pancake 10-15 other layers on top with each connected in series. How is the mulitlayer coil you're talking about built? Lastly as I'm using about a maximum of 300vdc into the coils would it be better to use more turns of a narrower gauge wire or stick with the gauge I have?

Jerry
: