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Re: [TCML] Magnifier topics
Finn, all
I will add to my dropio location tonight an equivalent electrical diagram
for
the L1primary, IDR/ECFC, L2 secondary. One could argue the IDR is
two current source sheets in phase and parallel to one another, or you
are inducing a 2X voltage in ring via both phased primaries which leads to
double current through the bulk resistivity of the same. Doesn't matter, net
results are the same.
To Finn's earlier point, if one assumes a coupling coefficient of 1
(impossible
but makes math a little easier), current in IDR is a function of Itank X
active
turns ratio. So if we have 1kA assumed peak current times 16 active primary
turns would suggest a maximum current approaching 16kA in drive ring ==8^O
So... Yea heat rise might be a big deal with the ring. Another concern is
aluminum doesn't show heat "color" very well, everything is fine until
suddenly
you have molten aluminum going everywhere starting fires. ==8^O
I have built several IH systems based on this geometry, and smaller lighter
targets will heat to 900C easily especially at the ECFC where it is coupling
to L2.
The good news is we are running a fairly small real duty cycle (<10%)
and the thermal mass of the ring will help limit heat rise (dT/dt).
Coupling will reduce IDR currents from above, however they will still be
easily
5-10X tank current. Coupling coefficient to driver ring and L2 with a
geometry
like this is a three dimension relatively linear response with a function
very
similar to Capacitance equation (proximity effect) that has the general
form:
K ~ k1 (AL1) / k2 (d)
where K is system coupling coefficient
AL1 is active area under active turns on primary
k1 is proportionally constant for area
d is mean distance between primary and IDR
k2 is proportionally constant for L1 / IDR separation distance
I will upload measurements on an earlier system built to these general
guide lines that had a 3D sheet coupling response. That's why pancake coils
were used so frequently is early radio.
Acronym / Abbreviation definition time:
IDR - Current Drive Ring
IH - Induction Heating
ECFC - Eddy current flux concentrator
Regards
On Tue, Feb 23, 2010 at 12:35 AM, David Sharpe <sparktron01@xxxxxxxxx>wrote:
> Finn, all
>
> A preliminary conceptual scaled layout of the IDR primary is at
> dropio/Sparktron01.
>
> Tesla Magnifier Primary shows a elevation /sectional of L2 jacking screw,
> and pivot pin/IDR support brackets & 3/8" jack screws
>
> Tesla Magnifier Primary-2 shows jack screw arrangement and separation
> of primary around centered IDR ring.
>
> Tesla Primary 3 shows a vertical plan view of primary assembly. Notice
> that
> primary plate is symmetric along vertical center-line, guaranteeing
> alignment
> of lower primary assembly. Ground point as show is a standard Home Depot
> Thomas & Betts dual hole AL/CU mechanical lug with lug portion cut off.
> 2 6-32" tapped holes allows rigid mounting to primary plate. A fixed brass
> stud is dual mounted to the IDR plate and vertical adjustment is allowed by
> loosening one lug screw on each side of lugs, the re-tightening with a
> standard
> allen wrench (std screw is replaced with a socket cap for ground
> connection).
> A flexible ribbon attaches to a AL plate at bottom of L2 to accommodate
> vertical motion. RF ground is attached to bottom ground stud.
>
> So at least at first pass, mechanically everything is a go. I will pull HV
> OD tubing
> back to horizontal support, and install two 5 fluted ceramic standoff
> insulators;
> thereby HV is separated 180 deg on assembly with one connection above,
> opposite
> below primary assembly (can't get any better HV separation then that. ;^D
> )
>
> Regards
>
>
> On Sun, Feb 21, 2010 at 7:03 PM, David Sharpe <sparktron01@xxxxxxxxx>wrote:
>
>> Hi Finn
>>
>> On Sun, Feb 21, 2010 at 4:23 AM, Finn Hammer <f-h@xxxx> wrote:
>>
>>> David Sharpe skrev:
>>>
>>> L2 has been designed in coordination with new flux concentration
>>>> primary design. Once I get details fleshed out,
>>>>
>>> David,
>>>
>>> What you mention here, the flux concentration design, is new to me, and
>>> sounds interesting.
>>>
>>> Since the thread is in a dormant state, these last couple of days, I
>>> wonder if you could enlighten me about the theory behind this scheme.
>>>
>>> Eddy current concentration (Flux concentration), has been used by the
>> induction heating industry for over 60 years.
>>
>> Several examples of the IDR driver / eddy current flux concentration
>> principle are listed below...
>>
>>
>> http://www.google.com/patents?id=XX9jAAAAEBAJ&pg=PA1955&dq=vacuum+tube+induction+heating+current+concentraor&source=gbs_selected_pages&cad=2#v=onepage&q=&f=false
>> Particularly Figure 1, in this case a solenoidal primary driving the
>> ECFC to heat small diameter conductive targets
>>
>>
>> http://www.google.com/patents?id=s9ZMAAAAEBAJ&pg=PA1&dq=vacuum+tube+induction+heating+current+concentraor&source=gbs_selected_pages&cad=2#v=onepage&q=&f=false
>>
>>
>> http://www.google.com/patents?id=2XdeAAAAEBAJ&pg=PA1&dq=2847651&source=gbs_selected_pages&cad=2#v=onepage&q=2847651&f=false
>>
>> 2847651 intrinsically validates concept is workable with pancake coils.
>> In my case there will be two pancake coils on either side of the ECFC
>> and there will be 1/4" aluminum busbar welded to the ID of current
>> concentrator slug. The ID of ECFC drives L2 (Tesla Coil/Driver secondary).
>>
>> Secret is current is induced in area of washer is reverse direction of
>> exciting current (Lenz's Law). However once this sheet current hits the
>> radial
>> slot, in flows radially inward to lowest resistance path which is the ID
>> of the ECFC. This concentrated current now flows in same direction (in
>> phase)
>> with pancake primary excitation current. At a barebones minimum most
>> pessimistic case, I am increasing the coupled amp-turns in to L2 coil. If
>> coupling was perfect, and no losses in IDR ring, boosted magnetic field
>> would be DOUBLED (magnetic mirror effect) with no net power increase
>> required.
>>
>> So what is the advantages? Well looking at thelater patent it is obvious
>> that:
>>
>> 1. Highest voltages are on OD of pancakes, where radius of curvature is
>> maximum. That will allow HV operation with minimal leakage or flash over
>> hazard,
>> especially if a shallow "bowl" primary is used (included angle 10 deg
>> < x < 30 deg)
>>
>> 2. ID of pancakes are connected in series, effectively paralleling
>> current sources to plate. Yes the IDR will get warm/hot. However by wiring
>> ID of primaries
>> near ID of current concentrator, diametrically opposite of radial
>> slot, will dramatically reduce the voltage between the L1 primary/IDR and
>> the L2
>> driver secondary. I can now run extremely close radial spacing
>> between L1/IDR and L2 with minimal risk of flashover, even if I am using
>> 30kV or
>> more in the tank circuit.
>>
>> 3. I can now adjust the vertical alignment on axial centerline of the
>> pancake primaries to the IDR ring which gives effective control of L1
>> inductance,
>> coupling to L2 and IDR, and thereby coupled current to L2. This
>> methodology also allows very precise, repeatable frequency tuning control
>> without effecting bang size.
>>
>> 4. Furthermore, I can adjust vertical height of L2 independently in
>> relation to L1. So it is a fully adjustable primary geometry.
>>
>> The key: It is a RF ground referenced CURRENT DRIVEN system, with a source
>> impedance < 0.1 ohm.
>>
>> The only possible fly in the ointment is I may OVERCOUPLE L2 and start
>> getting racing sparks. If that happens, I simply decouple the system
>> by raising L2 as required to stop the breakdowns.
>>
>> The reason I ask is, that my gut feeling says this aluminum slug is going
>>> to get mighty hot, due to eddy current losses.
>>>
>>
>> Understood, but it can be force air or even water cooled in high power
>> applications. Also understood that it will be an additional loss term that
>> will be tricky to characterize.
>>
>>>
>>> Cheers, Finn Hammer
>>>
>>>
>> --
>> Dave Sharpe, TCBOR/HEAS
>> Chesterfield, VA USA
>>
>> Sharpe's Axiom of Murphy's Law
>> "Physics trumps opinion!"
>>
>
>
>
> --
> Dave Sharpe, TCBOR/HEAS
> Chesterfield, VA USA
>
> Sharpe's Axiom of Murphy's Law
> "Physics trumps opinion!"
>
--
Dave Sharpe, TCBOR/HEAS
Chesterfield, VA USA
Sharpe's Axiom of Murphy's Law
"Physics trumps opinion!"
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