Reactive power - Reactive Generator research from GotoLuc - discussion thread

[penno64]

Was thinking exactly the same thing. Aussie gear.

Penno

[gotoluc]

Interesting Luc.

There are a number of things going on that are affecting the scope measurement. Also note that most of the power from the FG is being wasted inside the FG's 50 Ohm output resistor.

If you look at the wave forms when the circuit is connected, you will notice that the math trace indicates almost as much negative power as positive power. You judge this by estimating the area inside the trace. It comes down to comparing the area inside the positive triangular shape vs. the area inside the long/shallow negative shape. They seem pretty close, but I would guess judging by eye (not always a reliable method) that the positive area is larger. A good indicator if you are searching for OU.

Another way you can try to see what the net MEAN is, is to adjust the time (horizontal axis) so that precisely one cycle is displayed on the screen. You may have to go out of horizontal cal for this. Then see what the math mean indicates.

The "modulation" you are seeing can be due to one of two things, or even both; 1) Moire patterns and 2) undersampling in the scope. The fact that the mean varies so much as you change the time base settings is cause for concern. When those math peaks appear and disappear, or seem to jump up and down in amplitude, that is usually the result of undersampling. The longer you make the time base setting to display more cycles, the worse the problem becomes. If the scope has a relatively short or small memory depth then these problems can rear their ugly heads.

Thanks for the reply and information poynt
 
I was doing like you say (looking at the surface area of consumption and return) and why I started the video that way so you could see how close they are.

I'll try it with one cycle to see what the math comes up with but I think I did try that already and the math mean wasn't stable.
I think you're right,  there must be a sampling limit and that's why the data changes so much.

I was testing the toroid today with 12vdc pulses and collected the flyback to another 12vdc battery using my best Shottkey diode.
At 650Hz with 10% duty cycles I was able to collect back around 95% of the energy after dc rectification. I didn't bother calculating the LED power, which I don't think is much, as you know these LED's make a good show with short pulses in the 1khz with next to no power.

After spending the day doing tests I've concluded it's under unity but one of my better power return scores.

Thanks for your reply

Luc

[verpies]

I think one point that should not be overlooked is that when Itsu tuned it to full resonance the bulb in the primary glowed a bit, showing more input at full resonance than when just off a fraction.

That is because the system is not tuned precisely under load.
 
Itsu is using two identical caps and loosely coupled coils but the current flowing in the secondary winding under load, effectively DECREASES the inductance of the primary winding (due to Lenz law, reflected impedance, etc...)

If Itsu had searched for the precise primary LC resonance frequency (f_P) under load  - while the secondary winding was connected only to the output bulb (no cap), then he would find that f_P is higher with a loaded secondary winding than with an unloaded or open secondary winding.

Finally, if he tuned* the secondary LC tank's resonance frequency (f_S) to be equal to the primary resonance frequency (f_P) under load, according to the procedure just outlined above, then the whole system would behave more perfectly (like in the first video).


P.S.
* e.g.: by decreasing the series capacitance in the secondary LC tank.

[itsu]

By the way Itsu how did you get an Oscilloscope with "Australian Defence Force" written on it ? 

Cheers

Simple:

http://www.ebay.com/itm/Tektronix-TDS3054B-Digital-Phosphor-Oscilloscope-/321215388314?pt=AU_B_I_Electrical_Test_Equipment&hash=item4ac9edda9a


Regards itsu

[itsu]

That is because the system is not tuned precisely under load.
 
Itsu is using two identical caps and loosely coupled coils but the current flowing in the secondary winding under load, effectively DECREASES the inductance of the primary winding (due to Lenz law, reflected impedance, etc...)

If Itsu had searched for the precise primary LC resonance frequency (f_P) under load  - while the secondary winding was connected only to the output bulb (no cap), then he would find that f_P is higher with a loaded secondary winding than with an unloaded or open secondary winding.

Finally, if he tuned* the secondary LC tank's resonance frequency (f_S) to be equal to the primary resonance frequency (f_P) under load, according to the procedure just outlined above, then the whole system would behave more perfectly (like in the first video).


P.S.
* e.g.: by decreasing the series capacitance in the secondary LC tank.

Thanks verpies,

my idea was that i had created an overcoupled bandpass filter, but i can have a go at your suggestion/solution.

Regards Itsu

[Dave45]

Gentlemen its a pleasure watching you work, your teaching the rest of us with limited experience,
Thank you very much.

dave

You may consider this circuit by Mr Lindman, some of you have probably already seen it but thought I would bring it to your attention if you havent.

[Farmhand]

That is because the system is not tuned precisely under load.
 
Itsu is using two identical caps and loosely coupled coils but the current flowing in the secondary winding under load, effectively DECREASES the inductance of the primary winding (due to Lenz law, reflected impedance, etc...)

If Itsu had searched for the precise primary LC resonance frequency (f_P) under load  - while the secondary winding was connected only to the output bulb (no cap), then he would find that f_P is higher with a loaded secondary winding than with an unloaded or open secondary winding.

Finally, if he tuned* the secondary LC tank's resonance frequency (f_S) to be equal to the primary resonance frequency (f_P) under load, according to the procedure just outlined above, then the whole system would behave more perfectly (like in the first video).


P.S.
* e.g.: by decreasing the series capacitance in the secondary LC tank.

The fact still remains that all the current supplying the primary to power the load (via transformation) is delivered through the globe in the primary circuit, and if the load is using most power at full resonance in the secondary circuit the maximum current should flow through the bulb when maximum power is dissipated in the secondary load ( assuming an ideal supply ). Or to be more correct when the maximum power is dissipated in the secondary load the most power will be delivered by the supply via the primary. Not much else matters in the big scheme of things.

Cheers

The insinuation by some is that when the secondary load is dissipating the most power the supply is outputting the least power or the (primary is consuming the least power). Completely illogical.

..

[itsu]

Ok, i toke a quick shot at trying to get a flatline response on the parallel (left) bulb during resonance by manipulating the cores inside the coils.
This should also manipulate the inductance like decreasing the capacitance as mentioned by verpies, but its not working as expected.
I get a async resonance response when doing so and still the left bulb has some signal during resonance allthought i can bring the overall
resonance signal down meaning that the left bulb won't light anymore, but the cost is that also to right bulb is less intense.

So i leave it as it is.


I got more questions about the input and output power when in resonance.
The next 3 pictures show:

1 the output bulb (right) power at resonance            (2x 122mW  = 244mW), (Ch1 RMS x Ch4 RMS)
2 the input power of the whole system at resonance  (2x 147mW  = 294mW), (Ch3 RMS x Ch4 RMS)
3 the input bulb (left) power at resonance                (2x 13.5mW =  27mW). (Ch2 RMS x Ch4 RMS)

(i use 2x as my current probe is at the 2mA/mV setting).

So we have still 23mW unaccounted for, but that will be found in some thermal losses i guess.

Regards Itsu

[TinselKoala]

If you have a phase shift between voltage and current... which apparently you do... is it still legitimate simply to multiply RMS voltage by RMS current to get a power figure?

[gyulasun]

Ok, i toke a quick shot at trying to get a flatline response on the parallel (left) bulb during resonance by manipulating the cores inside the coils.
This should also manipulate the inductance like decreasing the capacitance as mentioned by verpies, but its not working as expected.
I get a async resonance response when doing so and still the left bulb has some signal during resonance allthought i can bring the overall
resonance signal down meaning that the left bulb won't light anymore, but the cost is that also to right bulb is less intense.

So i leave it as it is.

...

Hi Itsu,

You are surely familiar with the coupling coefficient, k, between coils in mutual induction, two coils can be under,  critical or over coupled, for those wishing to learn about these, here is a link:
http://www.crystal-radio.eu/enkoppelfactor.htm

When you tried to move (manipulate) the ferrite cores in your coils, both the coupling and the inductance of each coil changed at the same time,  a better method is to change the distance between the coils and fine tune the coils for a voltage peak each time. To do this in your case, no ferrite cores should overlap between your two coils and individual cores should be used for each coil to do the fine tuning which is needed because changing the distance detunes both coils and it is not enough to change the generator frequency for compensating this detuning: you would need to fine tune the coils by their cores at each new distance (ideally, in fact you would need a trimmer capacitor in parallel for each coil too because moving the cores can also change the coupling albeit the coils are just not moved).

Of course, such tuning can be a tedious process, the final goal would be to achive the critical coupling which would insure maximum power transfer with a single peak response (notice that you also get a single peak response when the coils are undercoupled). 

Regarding the flat line response of the left hand side bulb, you can achieve that by slightly reducing your generator output level...  and I say this because in your present setup the maximum current which is drawn and governed by the right hand side bulb at resonance is just able to make the left hand side bulb to slightly glow. (The voltage drop across this left hand side bulb increases at resonance because the resistance of the bulb increases as the small glow is starting (typical nonlinear resistance increase/response of the filament to heat.) 

I am not saying you should undertake a tedious fine tuning process to achieve the max power transfer with critical coupling, (that would involve separating the two coils) you have already done an excellent series of tests on this.

Greetings, Gyula

[itsu]

If you have a phase shift between voltage and current... which apparently you do... is it still legitimate simply to multiply RMS voltage by RMS current to get a power figure?

Hi Tinselkoala,

i guess its not, as when testing a simple 1.2uF MOV capacitor (with 10M Ohm bleeder) with a 1.3KHz sign wave signal,
it shows a phase shift of 76 degrees with 6.21V Rms at 62mA Rms current.

Doing the numbers by hand P= U * I * Cos Phi shows a power of 93mW, while my scopes math shows 84mW mean (remember, current and thus power times 2 because i use a probe terminator in 2mA/mV setting)
Its close but not spot on 

So allthough the above pictures of the in-/output show only a "slight" phase shift, we better forget the mentioned power figures.

Regards Itsu

   

[itsu]

Of course, such tuning can be a tedious process, the final goal would be to achive the critical coupling which would insure maximum power transfer with a single peak response (notice that you also get a single peak response when the coils are undercoupled). 

Hi Gyula,

yes tell me about it   

Whenever i moved a core, the whole setup had changed and i had to move the coil again etc.
Guess its best like you said to use a trimmer to fine tune this and leave the cores fixed.

Anyway, thanks for the link and info, allways good to have some information handy.
The over coupled picture in there i had in mind when i spoke earlier of my idea of an overcoupled bandpass filter

Regards Itsu

[gyulasun]

...
Whenever i moved a core, the whole setup had changed and i had to move the coil again etc.
Guess its best like you said to use a trimmer to fine tune this and leave the cores fixed.

...

Hi Itsu,

If you wish to tinker with this parallel-series LC circuit to get the maximum power transfer (i.e. to achieve critical coupling between the coils), first you would need to separate the two bobbins so that different distances could be set between the coils i.e. to be able to vary the coupling.
Then divide the tuning ring cores equally: I assume you have say 6 then 3 of them would be inserted for the left and the other 3 for the right hand side coil or if you have only 3 ring cores, then just use 1-1 and look for the new (increased) resonant frequency. I edited a snap shot from your video to show how I think the positioning of the ring cores inside the bobbins, this way the changing distance could influence the resonant frequency of the LC circuits in the least degree (the cores that give the permeability would be the furthest away from each other).

You could use an L meter for each separate coil to position the cores in each bobbin to their outer edge area as I tried to indicate in the photo by ring symbols, and adjust both coils separately for the same uH or mH value by fine positioning the cores and fix them, then attach the bulbs and the tuning caps and look for the new resonance at an initial distance of say 5cm.

Then try to decrease the distance by say 1cm and watch the brightness of the right hand side bulb whether it increases:  here I have assumed of course that the 5cm distance causes an undercoupled response. IF this turns out to be the case, then the brightness of the right hand side bulb will be increasing as you reduce the distance between the coils, till the brightness starts decreasing at certain closeness: it may indicate you have reached the overcoupled case where two voltage peaks start to appear below and above of the resonant frequency which so far has been kept more or less at the same value. (In the overcoupled case the response will have a dip at the original resonant frequency as you surely know.)  By positioning the cores towards the opposite edges of the bobbins, you may not have to use trimmer capacitors for fine tuning:  if you carefully retune the generator a little when you reduced the distance to say 3cm then you have compansated the detuning effect of the increasing mutual inductance (here I assume of course that at 3cm you still have not reached the overcoupled case and brightness would further increase when you go to a 2.5cm distance from the 3cm).  At the critically coupled state the single peak response widens with respect to the undercoupled case, meaning the bandwidth of the two LC circuits gets widened but still there is a single peak.

This is briefly the tuning process, if you have questions please ask.

Gyula

[verpies]

1 the output bulb (right) power at resonance            (2x 122mW  = 244mW), (Ch1 RMS x Ch4 RMS)
2 the input power of the whole system at resonance  (2x 147mW  = 294mW), (Ch3 RMS x Ch4 RMS)
3 the input bulb (left) power at resonance                (2x 13.5mW =  27mW). (Ch2 RMS x Ch4 RMS)

If you have a phase shift between voltage and current... which apparently you do... is it still legitimate simply to multiply RMS voltage by RMS current to get a power figure?

I think Itsu's scope is multiplying the instantaneous samples of current and voltage.  He should have simply written  (Ch1 * Ch4),  (Ch3 * Ch4),  (Ch2 * Ch4), etc...

I hope, his scope only displays the RMS averages for each channel but makes multiplications for each sample.
I'm not sure what type of average his math channel is displaying/applying to the results of these multiplications  ...I think it's an arithmetical mean - not RMS, because it displays the word "mean".

[itsu]

This is briefly the tuning process, if you have questions please ask.

Gyula

Thanks Gyula,

Its a clear process to follow, i will take a shot at it later this week.

Regards Itsu