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Author Topic: MEI Revisitation  (Read 451 times)
Group: Moderator
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Posts: 1148
All,

Looking over some old MEI files I found a particular topology that appeared to have a valid OU signature so after some current analysis, this is what I came up with.

The schematic is seen bellow and basically the device is a reactive-to-real converter with apparent gain.  The main difference between this topology and most all of my previous designs is that the load is split symmetrically between L1 and L3.  L2 supplies the induction to L1 and L3 through distributed capacitance.  I somehow have the feeling that additional primary and secondary coils could be used as well.

The first scope pix shows the input and output of the device.  CH3(pnk) is the rms output across one of the 50 ohm load resistors with the weakest output so the pout = 1.416^2/25 = 80.2mw to be conservative.  With the pin shown, the apparent COP = 80.2/59.84 = 1.34.

The second scope pix shows the rms of the input current to be 51.62ma which we will use to check the pin using the phase angle between CH1(yel) input voltage and CH4(grn) input current.  This is .05162*5.215*cos(77.12) = 60mw which is in very close agreement with the Math channel calculation.

Now the question is, what causes the gain?  In looking at the last pix of the spectrum analysis, it is my opinion that the gain comes from the harmonic content in the output loads that is being generated or accumulated in the device itself.  Look at the shape of the output in CH3(pnk).  It obviously contains many harmonics as is evidenced in the spectrum analysis.  Note that all the harmonics are odd (start with the fundamental being 3.545MHz).  In testing a similar device with a different coil arrangement, the gain was lower along with lower harmonic levels. 

So, if this is true that additional power is coming from the generated harmonics, then the challenge would be to arrive at the optimum parameters that are creating this effect.  At this point, I do not know how these harmonics are being created!

Regards,
Pm     
   
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Hi Pm,

Would like to ask how did you consider the 170 pF interwinding capacitance of the coils in the simulation schematic?

One more question: you mention the load is split between L1 and L3, if you meant the two 50 Ohm resistors in series with these two coils, then why did you consider 25 Ohm only for calculating the output power?  Are the two 50 Ohm resistors really  connected in parallel? They are in parallel via the two coils that have reactances at 3.54 MHz, no?

I do not know whether the T1 has ferromagnetic core or only has air core? 

Interesting setup, nevertheless.  If there is a core for the coils, then its non-linear operation may produce the harmonics I think. 

Gyula
   
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Hi Pm,

Would like to ask how did you consider the 170 pF interwinding capacitance of the coils in the simulation schematic?

Hi Gyula,

I must apologize for using the schematic feature of LtSpice for my regular schematics as it could be confusing.  Anyway, that 170pf is the actual measured capacitance between the flat pancake windings.
 
Quote
One more question: you mention the load is split between L1 and L3, if you meant the two 50 Ohm resistors in series with these two coils, then why did you consider 25 Ohm only for calculating the output power?

Instead of calculating for one 50 ohm resistor and multiplying by 2, I simply took a shortcut and divided the voltage squared by 25 ohm.  The other 50 ohm voltage was slightly higher so the stated pout is slightly less that the actual. 

Quote
Are the two 50 Ohm resistors really  connected in parallel? They are in parallel via the two coils that have reactances at 3.54 MHz, no?

Although the two load resistors are connected at the near ground end, they are considered to be in series with the two outer pancake coils that are separated by the open ended primary.
 
Quote
I do not know whether the T1 has ferromagnetic core or only has air core? 

Interesting setup, nevertheless.  If there is a core for the coils, then its non-linear operation may produce the harmonics I think.

There is no ferromagnetic core material used, all air cored.  The pancaked coils are clamped together tightly with flat plexiglass pieces and a plastic bolt in the middle.  I'm considering that the source of the harmonics is in the fact that the open ended primary is basically an open ended transmission line with reflections back to the driven end.  Why these harmonics are all odd is a question now that remains unanswered.

Regards,
Pm
 
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Gyula
   
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