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Author Topic: Investigating "anomalies" in Bifilar coils  (Read 157116 times)
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As a seco d test TK

If you get your BPC to once again show 0 current input-what do you get across !what would be! R2 in my video?

Brad

Well, with the resistors in place I can't quite get down to "zero" input current because R2 represents a power dissipating load, but pretty close. At resonant frequency (which did not change due to the resistors) the input current read 1.8 mA rms and the "R2" current read 8.6 mA rms. This is with the FG set for 5 v p-p sine.
   

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Well, with the resistors in place I can't quite get down to "zero" input current because R2 represents a power dissipating load, but pretty close. At resonant frequency (which did not change due to the resistors) the input current read 1.8 mA rms and the "R2" current read 8.6 mA rms. This is with the FG set for 5 v p-p sine.

1-Using your current value(1.8mA),and then the voltage RMS value across the coil as a whole-what is your total P/in?

2-What are the values of your resistor's?,so as we can calculate the power dissipated by the two resistors.


Brad


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Ok,here is the video,and the test setup--easy for all to try.

This finding open's a can of worm's,and in the video's to come,i will show you why.

Is the value of current flowing through the center of the winding,the same as the value of current flowing into the coil ?
In this case,the answer is no,when we reach a certain frequency-and above.
It dose not have to be the resonant frequency to see this effect.

Even though we have a series circuit(resistor/coil/resistor/coil),where the two coils and two resistors are the same,R2 shows at least twice the current flowing through it,than that of R1.
TK has achieved a much higher differential between the two resistors-maybe he will post his results here. 

More to come--lets screw with ohms law

https://www.youtube.com/watch?v=MaZhCyKIAvg


Brad


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1-Using your current value(1.8mA),and then the voltage RMS value across the coil as a whole-what is your total P/in?

2-What are the values of your resistor's?,so as we can calculate the power dissipated by the two resistors.


Brad

I used 100 ohm resistors, same as you, measured the RMS voltage across the resistors one at a time on the same scope channel, and calculated the current by Ohm's Law I = V/R.

I've already taken mine apart so I can't give you the input power just now, but the result from a simple P = I2R calculation would probably be misleading anyway. I _think_ this is a Transmission Line phenomenon where you have standing waves in the coil which cause peaks and valleys in the measured voltage at various places in the coil.  Using the "helicap" model of a transmission line we made in another thread I shot a fast demo video of a similar thing happening in that system when supplied with a frequency sweep. You could even think of it as a  "tidal bore" kind of thing, where a forward-travelling wave meets another wave (its own reflection) travelling the other direction and reinforces itself making a hump.

I'd like to see what Partzman thinks about this, he's the expert in transmission line theory.

A suggestion for you to try would be this: Find the "middle" of your monofilar coil winding, cut it there and put in a 100R resistor. Then repeat your test and see if you can get the same kind of result using the monofilar coil and the right frequencies.

My transmission line demo video is up now:

http://www.youtube.com/watch?v=f4T5KKQjz0s

« Last Edit: 2017-04-27, 12:17:47 by TinselKoala »
   

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I can confirm using my current probe (so no resistors) that there is a difference in current while measuring the input current or the middle tap current of my TBP coil.
21.4mA rms at input, 25.28mA rms at the middle tap.  (yellow is voltage across the TBP coil,  green the currents)

See below screenshots, first is input at 1MHz (resonance is at 300KHz), second is the middle tap.

Itsu


   

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More dramatic when using the resonance frequency (300Khz)
input current (flatlining) 1.16mA rms, middle tap current (constant) 13.95mA rms

Measuring the voltage across the TBP coil shows we have 20Vpp at the input, and half (10Vpp) at the middle, so probably there lies the explaination.


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More dramatic when using the resonance frequency (300Khz)
input current (flatlining) 1.16mA rms, middle tap current (constant) 13.95mA rms

Measuring the voltage across the TBP coil shows we have 20Vpp at the input, and half (10Vpp) at the middle, so probably there lies the explaination.


Itsu
So you halve the voltage,but the current value is 1202% more  ???
I dont think the half voltage value is it at all.

So P/in is 7.07VRMS @ 1.16=8.2mW-->?
At mid point,power is 3.535VRMS @ 13.95mA=49.3mW-->?

Itsu

Below is a drawing of a test i just carried out,where i calculated power dissipated by each individual component.
Could you carry out the same test?

Cheers

Brad


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The only time that P=I*U with AC sine wave, is when we are in resonance, else you need to include the phase difference between U and I.
I measure around 81° phase shift when not in resonance.

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The only time that P=I*U with AC sine wave, is when we are in resonance, else you need to include the phase difference between U and I.
I measure around 81° phase shift when not in resonance.

Itsu

I agree about these measurements not conveying the whole story and am under the impression that this is simply a parallel LC resonator.

Unfortunately my lab is broken apart because I am moving so I can't test.  I would appreciate it if somebody could confirm or deny my suspicions that this is a distributed, parallel LC network, and could be the reason that the current flows are not the same.

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So you halve the voltage,but the current value is 1202% more  ???
I dont think the half voltage value is it at all.

So P/in is 7.07VRMS @ 1.16=8.2mW-->?
At mid point,power is 3.535VRMS @ 13.95mA=49.3mW-->?

Itsu

Below is a drawing of a test i just carried out,where i calculated power dissipated by each individual component.
Could you carry out the same test?

Cheers

Brad

Brad,

That's an interesting experiment you have devised!  In the power measurements you show the total output power across R1 and R2 to be 54.79mw while the input power is 74.24mw for a COP = 0.74.  The additional power across L1 and L2 is reactive so how can we tap that if we include it to achieve an overall COP = 2.058?

TK,

Thanks for your vote of confidence but I am far from an "expert" in transmission lines but I will agree with you that Brad's results are from tline characteristics of the TBP.  I've attached a sim plot of your TBP showing the maximum differential "rms" current which is at ~270kHz.  At this point, the resistive power output to the input power is ~97% as can be determined from the expanded plot view.

Ignore the extra stuff in the schematic as I use it for a scratchpad sometimes.

Regards,
PM 
   
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Quote
My transmission line demo video is up now:

http://www.youtube.com/watch?v=f4T5KKQjz0s

Very nice work TK, you beat me to it, now I don't have to do it, I was going to use NEON bulbs, but the LED's are probably smoother acting. KUDOS. Also since I don't post videos the best I would have offered is still photo's, thus not very dynamic.

To Itsu and Tinman

Also nice work, it will be good to see the pancake coil transmission line finally vetted one way or the other. Partzman is well down the road with this research.

Regards

p.s. down for a bit, I've got a blown head gasket on an 11 HP Briggs and Stratton that I need to replace, the grass is growing and I've gotta get to mowing 3+ acres. It's a wonder I have any time at all with some 26 tires on equipment around the homestead here that one or another is always going flat, not to mention engine repairs and maintenance. Add to that a greenhouse to plant. Keeps me going at 70+.


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So you halve the voltage,but the current value is 1202% more  ???
I dont think the half voltage value is it at all.

So P/in is 7.07VRMS @ 1.16=8.2mW-->?
At mid point,power is 3.535VRMS @ 13.95mA=49.3mW-->?

Itsu

Below is a drawing of a test i just carried out,where i calculated power dissipated by each individual component.
Could you carry out the same test?

Cheers

Brad

Tinman,

here a similar drawing as you presented with my measurments in it.
I have no resistors, but used my current probe and in the drawing i have shown where.

I did not made the calculations like you did as i doubt that can be done the way you did.

The screenshot is the total input measurment, we are at 1MHz , so NOT at resonance.


For what its worth:


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Here is another characteristic of the transmission line aspect of the TBP that is not intuitive.  Again using TK's TBP values and referring to the previous post "TBP Current Differential" pix, the attachment below shows an expanded view at the peak of the R1/ R2 currents.

The frequency is ~507kHz during this particular resonance point and the important thing to notice is the current in R1 is ~160 degrees or so out of phase with the current in R2.  An explanation is in order for those not familiar with LtSpice, every 2 port component placed on a schematic has a conventional current flow direction assigned to it which means current enters terminal #1 and exists exits terminal #2.  The dotted arrows show this current flow direction in R1, R2, and R3.

So, the current flow seen in the plot for R1 represents the conventional flow from the generator to the junction of L1/C1 of the TBP.  IOW, when the current is positive, it is in the direction of the dotted arrow for R1.  The same holds true for R2 that is, when the current is positive, it is in the direction of the dotted arrow for R2.  However, since the currents of R1 and R2 and nearly out of phase, this means that when positive current thru R1 enters at L1/C1, positive current thru R2 is entering L23/C13.  IOW, positive currents are entering opposite ends of the "odd" L winding nearly in phase with each other.  These currents are dispersing thru the C1-C13 displacement currents to the "even" L winding.  In like manner at the same point in time, positive currents are exiting each end of the "even" L winding again nearly in phase.

Regards,
PM

Edit: Changed "exists" to "exits".   
« Last Edit: 2017-04-27, 22:34:22 by partzman »
   

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Tinman,

here a similar drawing as you presented with my measurments in it.
I have no resistors, but used my current probe and in the drawing i have shown where.

I did not made the calculations like you did as i doubt that can be done the way you did.

The screenshot is the total input measurment, we are at 1MHz , so NOT at resonance.


For what its worth:


Regards Itsu

So your total P/in is 29mW

L1 is dissipating 16.5 mW,and L2 is dissipating 30mW

Ok,regarding power factor when we do our math.
When i made the calculation's,it was calculated at a power factor of 1 --all real power.
The more the power factor is below 1-getting closer to 0,the real power consumed become's less than the apparent power tells us. So if the power factor was less than one,then the real power is also less than that we calculated.
Also,we must remember that if the power factor at the input is less than one,then so is the power factor at the output-or the measured dissipated power points--so what you do for one,must also be done for the other.

I think you will find that the power factor measured from R2 and L2,is closer to 1 than that of the P/in  O0
So that would mean that the  P/in would be further away from the real power value,than that of the power measured from R2 L2.

Things to think about.


Brad




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Quote
Things to think about.


  :D You can say that again!


Something in my measurements must be amiss as the current in the total measurement and the one across L2 should be the same (same position current probe).
Unless my putting the voltage probe ground lead at the L2 - position influence this current,  have to look at that again.


Itsu
   

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OK,so i have made this very easy for some one well versed in calculating power factor into the below results.

You will see that i raised or lowered the voltage value by small increments of each channel,so as both wave forms are even-close to V/D line-making the job easier  O0

Each pic below shows the scope positions,and attached is the associated scope shot with the values of each channel.

So,who is well versed enough to calculate-->
1-Total P/in
2-Dissipated power of R1+L1
3-Dissipated power of R2+L2


Brad


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  :D You can say that again!


Something in my measurements must be amiss as the current in the total measurement and the one across L2 should be the same (same position current probe).
Unless my putting the voltage probe ground lead at the L2 - position influence this current,  have to look at that again.


Itsu

Itsu

They wont be the same  :o
Place a couple of 100 ohm resistors in there,and try the LED test--the LED wont lie  O0

See my post above as well.


Brad


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Meanwhile i set up a joulethief using one of my TBP coils, just to see if it works and to do some tests with it.

Well it does work (can't see one doing that with a monofilar pancake coil  ;) ).

Will try to raise the pulses to near resonance frequency (300KHz) to exite a similar second TBP coil.

Screenshot shows the collector pulses in purple and the input voltage of a depleted  AA battery.
Picture is the little setup.


Itsu
   

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Itsu

They wont be the same  :o
Place a couple of 100 ohm resistors in there,and try the LED test--the LED wont lie  O0

See my post above as well.


Brad

Right,  i will test that later today, just need to clip on my ground probe in the middle to see if anything changes.
Else its like TK mentioned already, this transmissionline effect what makes his leds turn off and on (standing waves) in his excelent video above.

Regards Itsu
   

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Right,  i will test that later today, just need to clip on my ground probe in the middle to see if anything changes.
Else its like TK mentioned already, this transmissionline effect what makes his leds turn off and on (standing waves) in his excelent video above.

Regards Itsu

Maybe.
But thing is,this works over a wide range of frequencies,and not one single frequency for one particular portion of the coil.

Im leaning toward displacement currents being additive to the input current.

Im hoping ION will join us here,and carry out some calculations on my posted pic and associated scope shot's,with the values for each test.


Brad


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Can you measure temperature of both resistors ?  C.C
   
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Just so you know... you don't need a pancake coil to show this effect. Here I have tested it with my Tesla Bifilar _solenoid_ coil at 580 kHz. First scopeshot below is current through 100 ohm R1 (input) and second scopeshot below is current through 100 ohm R2 (centertap). Shots were obtained by just moving the probe and its reference lead from one resistor to the other. (And I had to change the V/div setting for the R2 measurement!)  Function generator is isolated, and is set to make 10V p-p sine wave at 580 kHz (where the R1 current is minimized).


Now we need someone to test a monofilar coil with a resistor across its centerpoint to see if this same effect can happen there!


Note that I have "tricked" the scope to read the Current value correctly, by telling it I have a 0.1x probe. Using a 10x voltage probe across a 100R resistor gives equivalent values to a 0.1x current probe.  Say I measure 2.2 v p-p across a 100R resistor using a 10x probe set on the probe and on the channel menu. By Ohm's Law I=V/R this gives 0.022 A or 22 mA. But the scope reads 2.2 V! So I set a different probe attenuation value in the channel menu but leave the probe itself at 10x for all the benefits that has. Select 1x in the menu and the scope reads 0.220A, still too high. Select 0.1x and voila, the scope now reads 0.022A or 22 mA. The Rigol actually has _sixteen_ selectable probe attenuation values, in the usual 1-2-5 steps from 0.01x to 1000x. And the channel "units" label can be set to say A for amps instead of volts. And it's clever enough to know if I multiply this channel by a channel set to read Volts, it gives me the answer in W for watts!
   
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OK,so i have made this very easy for some one well versed in calculating power factor into the below results.

You will see that i raised or lowered the voltage value by small increments of each channel,so as both wave forms are even-close to V/D line-making the job easier  O0

Each pic below shows the scope positions,and attached is the associated scope shot with the values of each channel.

So,who is well versed enough to calculate-->
1-Total P/in
2-Dissipated power of R1+L1
3-Dissipated power of R2+L2


Brad

Brad, can your scope measure the Phase Shift between channels? Or can you post one shot with just a single full cycle of both channels horizontally so we can estimate it visually?


Anyhow... for the power calculations.... I'll take a shot at it.

 I think for the moment we can disregard the dissipation in the Coil portions and just look at the resistors themselves.

In your first shot, to get the input power, we are looking at the voltage across 200 ohms so this is shown by the CH2 measurement, which is 6.20 Vrms, giving a current of 0.031 Arms.
So the total power IN is P=I2R = 0.192 watts.

EDIT: Do we need to make any corrections for possible phase shift at this point?

For the second shot, looking at the Vdrop across R1, again we read CH2 at 1.36 Vrms, which gives a current value of 0.0136 Arms, and a power dissipation of P=I2R = 0.0185 watts.

For the third shot, looking at the Vdrop across R2, we read CH2 again, at 2.56 Vrms, for a current of 0.0256 Arms, and a power dissipation of 0.0655 watts.

So we have Pin = 0.192 W and total dissipation in the resistors of 0.0185 W + 0.0655 W = 0.084 W dissipated in the resistors, compared to 0.192 W input. 

HOWEVER... The picture changes if we take the R+coil readings on CH1 and do that math. I get a total "dissipation" value of 0.2371 W which would lead us to conclude that we have an OU COP of about 1.23.

Cheezburger Time !!!


But is this really correct? We know that the pure resistors are dissipative loads that give off power as heat, lost to the system. But what about the coils? Neglecting their DC resistance of course... is the inductive load actually dissipating power like the resistors do ... or is it _storing_ it?



I've been working on this for about an hour, and it's late and I am coffee-deprived, so PLEASE check my math and assumptions everybody!

« Last Edit: 2017-04-28, 12:50:04 by TinselKoala »
   

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Brad, can your scope measure the Phase Shift between channels? Or can you post one shot with just a single full cycle of both channels horizontally so we can estimate it visually?


Anyhow... for the power calculations.... I'll take a shot at it.

 I think for the moment we can disregard the dissipation in the Coil portions and just look at the resistors themselves.

In your first shot, to get the input power, we are looking at the voltage across 200 ohms so this is shown by the CH2 measurement, which is 6.20 Vrms, giving a current of 0.031 Arms.
So the total power IN is P=I2R = 0.192 watts.

EDIT: Do we need to make any corrections for possible phase shift at this point?

For the second shot, looking at the Vdrop across R1, again we read CH2 at 1.36 Vrms, which gives a current value of 0.0136 Arms, and a power dissipation of P=I2R = 0.0185 watts.

For the third shot, looking at the Vdrop across R2, we read CH2 again, at 2.56 Vrms, for a current of 0.0256 Arms, and a power dissipation of 0.0655 watts.

So we have Pin = 0.192 W and total dissipation in the resistors of 0.0185 W + 0.0655 W = 0.084 W dissipated in the resistors, compared to 0.192 W input. 

HOWEVER... The picture changes if we take the R+coil readings on CH1 and do that math. I get a total "dissipation" value of 0.2371 W which would lead us to conclude that we have an OU COP of about 1.23.

Cheezburger Time !!!


But is this really correct? We know that the pure resistors are dissipative loads that give off power as heat, lost to the system. But what about the coils? Neglecting their DC resistance of course... is the inductive load actually dissipating power like the resistors do ... or is it _storing_ it?



I've been working on this for about an hour, and it's late and I am coffee-deprived, so PLEASE check my math and assumptions everybody!

I think for far too long,we have only measured power into a coil/inductor,and paid no attention as to what is actually happening within the coil it self.

Regarding the single wound pancake coil.
I dug out half a turn,at the mid point (1/2 the length of wire),and pop'd in our 100 ohm resistor.
Yes,i can get the same effect,but no where near as strong-at any frequency.

I will do the wide screen shots tomorrow,as it's relax time now  O0

What i really need is an FG that pumps out watts of power,instead of only mW's  :D
This way,we could see if our coils were getting hot. If there getting hot,then the power is not being stored.

A scope with a bloody math function that actually calculates the value,instead of just showing the trace,would be on the shopping list as well.4 channel's,with isolated grounds  O0


Brad


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Your Atten can't do trace math? ISTR something about that. Well, I don't really trust the Rigol's trace math very much either, really, and I didn't include RMS values in those shots up above because the scope's values are a little smaller than they should be for pure sine waves... wait, maybe that's telling me they aren't really pure sine waves and the "p-p x 0.3535" calculation doesn't apply.

For the FG pumping out the power, it's not hard at all to cobble together a simple powered transistor amplifier that can be driven by the FG and put the same sinus signal at greater voltage into your coils.

As far as a 4ch scope with isolated channel references... that's a toughie. I've used some 2 channel scopes, portables, with isolated references like the Fluke 199 ScopeMeter and the Tek THS720P (has power quality analysis built in!) but I can't think of any quality 4ch units with isolated references. However... the cure for that is Differential Voltage Probes !! And real Current Probes !! They can be costly too though. I wish I had one of each myself.  But there are pitfalls.... we are dealing with a situation where inductance can have a great effect on measurements and that's not even including phase shift/power factor.

Remember this blast from the past?
http://www.youtube.com/watch?v=KWDfrzBIxoQ


   
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