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Author Topic: Simple to build isolation transformer that consumes less power than it gives out  (Read 361124 times)

Lynxsteam

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Can someone draw a diagram of how you think current flow is moving for one half of the sine wave?  I am unclear what the intended path is given all the various dots, wiring conventions, tags, etc....  I can see how the voltage could be amplified if the sine wave is in phase, but I don't see how amps wouldn't drop.  Also, in any cored transformer you lose some power due to eddy currents (heat).  And heat in the windings due to resistance.

wattsup

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The watt meter most likely shows measurement error. In best case you could find 100W+ 1 Ohm resistor and attach to "cold" wire from mains in series then put oscilloscope on resistor and see RMS amps.
You are mixing reactive power coming back from transformers with conventional power so funny things happen. :)

@T-1000

Well, the problem is with this set-up that the output transformer E-F-G-H was starting to give some slight smoke so I stopped the video. I will start again tonight and make a clear connection diagram and do some tests at lower voltage off the Variac. But again, my diagram is good for my transformers and may not apply to others.

The info on my transformers was supplied to me by the manufacturer. I asked them how many wire turns per coil and winding direction per coils but they did not provide that information. Just the info sheet as shown.

The point here is by using the same @JN diagram, if you start switching the wires around and re-do your tests, you may get to the same situation as I am at now.

What is incredible is that I am getting more voltage output then the applied input voltage while still being at the 120 volts connection mode so there is something happening with this method. If this was making a simple short circuit, that would explain the input amps/voltage/watts, but 2000 watts seems so high for such a reading, and then try to explain the increased output voltage.

Something is funny and it is not Red Skelton (although he is very funny).

wattsup

JouleSeeker

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@T-1000

Well, the problem is with this set-up that the output transformer E-F-G-H was starting to give some slight smoke so I stopped the video. I will start again tonight and make a clear connection diagram and do some tests at lower voltage off the Variac. ...
What is incredible is that I am getting more voltage output then the applied input voltage while still being at the 120 volts connection mode so there is something happening with this method. If this was making a simple short circuit, that would explain the input amps/voltage/watts, but 2000 watts seems so high for such a reading, and then try to explain the increased output voltage.

Something is funny and it is not Red Skelton (although he is very funny).

wattsup
Looking forward to seeing your connection diagram.  I'll try it.

Yes, the 2kW is indeed odd...  easiest thing to do would be to measure the input current using a clamp-on meter, as a check.  If things are starting to smoke, be quick  ;)

Hey, I remember Red Skelton -- very funny guy.

JouleSeeker

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  Having suggested a check using a clamp-on ammeter, I did it.. with interesting results.

See photo -- current shows as 0.12A, whereas the P3 kill-a-watt meter says about 0.2 A (and 19.5 W in). 
0.12A x 113.5V in = 13.6 W input.

The output P3 meter shows 64.5V and 15.8 W; but I'm beginning to suspect its accuracy here -- at least I need to check with different meters!  The clamp-on shows output current of 0.20 A (P3 meter shows 0.24A).
0.20A x 64.5V out = 12.9W output. 

At least we can compare with above, having used consistent tools:  12.9 out/13.6 in = 95%.
 Which is quite good, since as Lynx noted, there are losses in the two trafos.
Indeed, using one of these trafos, I found its eff ~ 84%, for just one trafo.

BUT I'm still trying to convince myself of the measurements... how we measure Pin and Pout.

The main conclusion is -- I don't trust using just the P3 Kill-a-watt power meter (hereafter, P3 meter) alone... even though it tested out well using light bulbs of known Lumens, straight from the mains -- there everything agreed and gave me some confidence in these meters.

Also -- I have another clamp-on ammeter, checked that, and the two clamp-ons agree with each other very well.  (And disagree with the P3, especially for the input current measurement.)


wattsup

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@JouleSeeker

Here is the diagram. Hope it is understandable.

I agree about the P3 as well as about mine. There is something not right with the reading. But what do you expect from a 20$ watt counting meter that is designed for 60Hz appliances that consume a steady and "non flybackable" (hichic) energy consumption. I think our regular measuring instruments have worked well till now. It is only when the amps are in the single decimal point range that we have to be careful and better to simply put a multimeter inline.

Anyways, the diagram shows exactly how I connected for the last video and I will do some more experimenting tonight. I will put two scope probes at various locations and see if there is any phase differences. I guess if the phasing is n ot the same, I should see two sine waves slightly offset.

Also, on the output, if this is AC output, then both output locations should show the same voltage level. Right or wrong? Well in my set-up, when you check the output on the scope on each of the load points, one is about many times higher then the other.  Don't know exactly how high yet. I will have to find some more scope probes because my last one just fizzed a few days ago. I'll have to dig around the office since i know I have two more somewhere. lol

Lastly, maybe @MH can see through this and come up with a half decent explanation but for now, I am at a loss to explain it.

wattsup

poynt99

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Steve,

Unless I am mistaken, it appears from your photo that the clamp meter has BOTH conductors of the line cord going through it. You must have only ONE conductor going through.

I suggest you move the meter over to where the wiring breaks out to the transformer leads, then you can clamp around ONE of the leads.

JouleSeeker

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Steve,

Unless I am mistaken, it appears from your photo that the clamp meter has BOTH conductors of the line cord going through it. You must have only ONE conductor going through.

I suggest you move the meter over to where the wiring breaks out to the transformer leads, then you can clamp around ONE of the leads.

You are mistaken in this case, Poynt -- there was only ONE conductor going through the clamp-on meter. 
The single conductor going through is a brown wire from the cord going to the P3 meter.
And when I used two clamp-on meters for comparison, each had ONE of the brown wires from this cord going through it.  Both clamp-on meters then agreed on the input current (and disagreed with the P3 meter).

Thanks for the diagram, Wattsup.

poynt99

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OK Steve, that's good. The point needed to be raised though. ;)

It's difficult to see that on the photo. It really does appear as though the whole cord goes through the clamp meter, surely you agree at least that it appears that way?

JouleSeeker

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Poynt: " It really does appear as though the whole cord goes through the clamp meter..."
   It may appear that way, but then the clamp meter would show zero amps.

Anyway, I've taken another photo showing two clamp meters -- each shows 0.14A (AC) while the P3 meter shows 0.25A (demonstrating the discrepancy and the reason I question things).

   Hopefully one can clearly see in this photo that one wire goes through each clamp meter.

I also looked at the power fact P.F. -- for the input, it shows as approx. 0.6  -- and it varies, 0.5 to about 0.7.  (The input power comes from a dimmer, which is connected to the mains.)
 Could this be why the P3 meter is having difficulty getting the AC amps (and the power)?  Also, are the clamp meters accurate when PF is NOT unity?  How does one measure the current accurately -- or better, the power -- when the PF is not 1.0?

JouleSeeker

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To further explore the question of how to measure Pinput when PF is not 1, I connected the input plug directly to the mains; see photo which now shows the clamp meters at 0.17 A while P3 shows 0.19A.  This is much better agreement than with the dimmer, where the PF was approx 0.6.  With the mains for this circuit, the input PF is shown on the P3 meter to be 0.99-1.0. 

   It thus appears that the P3 meter performs reasonably when the Power Factor is 1.0, but not reliable otherwise -- either the P3 or the clamp meters are not reliable when PF < 0.7 anyway. 

The question comes again -- how does one reliably measure the power (say, around 20 watts) when PF < 1?

poynt99

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I also looked at the power fact P.F. -- for the input, it shows as approx. 0.6  -- and it varies, 0.5 to about 0.7.  (The input power comes from a dimmer, which is connected to the mains.)
Ah, yeah. That's a definite no-no if you expect to be able to measure accurately with the meters you are using. Not even the clamp meters will measure accurately with a chopped up sine wave.

Quote
Could this be why the P3 meter is having difficulty getting the AC amps (and the power)?
Definitely!

Quote
How does one measure the current accurately -- or better, the power -- when the PF is not 1.0?
Buy a variac!

JouleSeeker

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  I have and have used a variac, with this very system Poynt, as I've discussed earlier on this thread.  But as Lynx noted, it may be that a spiked voltage is better for the response (better than simple sine-wave). 

  I may have to go back to the fancier DSO, and use P(t) = V(t) * I(t), getting the power moment-by-moment, thus getting the power waveform.  This can then be integrated to get the total energy; also the average power.  I was hoping the simpler meters would do the job, but evidently not for PF<1 and for non-sinusoidal waveforms.  It's an old problem. 


 For the output power, I still prefer calorimetry -- simply heating water with a resistance.  Power = Q(heat) / Time.

Or, if one could get Jack's circuit to work ou with sinusoidal waveforms and PF=1, then this should be easy to measure.
Any other ideas?


poynt99

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If you feel that a spiked voltage (not sure where or why) is better, then yes you will have to resort to using a DSO if you want to measure the power accurately.

What were your results when you used a variac?

T-1000

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@T-1000

Well, the problem is with this set-up that the output transformer E-F-G-H was starting to give some slight smoke so I stopped the video. I will start again tonight and make a clear connection diagram and do some tests at lower voltage off the Variac. But again, my diagram is good for my transformers and may not apply to others.


That looks like you are trying to use 2 primary coils on same transformer and they got connected in parallel but on such way they create max load to each other inside of transformer. Try to connect one of them in reverse order and see if you still get max amperage used without load. I strongly recommend to connect lightbulb in series for fuse element before Variac so in case of short circuit /max load on idle transformer your lightbulb will be lit brightly.

Cheers!

NerzhDishual

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Hi OU Dot Com Blokes,

AC Input vs AC Output power measurements... what a nuisance!  :(
These "kill a watt" cheap meters seem to cheat us.
Why not using at least DC input? With a DC bat and an inverter, for ex.
First "calibrate" = figure out the efficiency of this device and then take account  of it for
the COP calculations.

BTW: this could also be used for any Sonic Boiler... :P

--------------------
I played with:
1) A 1 to 1 small trafo (measured Henries: about 0.350 H primary and secondary).
2) A signal generator (see picture) (and also an home made 555  +  Mosfeet square wave gen).
3) And old hammeg HM207 scope.

I have noticed that, with *square* waves:
These square waves "morph" into nice sine waves when you approach the resonant freq of the
trafo (about 170 KHz in my case). A trafo as also some (small) capacitance. No?
When I reach this very freq the 'peak to peak' voltage is multiplied by more than ten.
Beware: no load here! No 'OU' claimed.

Anyway, I did not know that you can transform square waves into (more apparent 'voltageable')
sinus waves with a mere 1:1 trafo should you reach the right freq. Did you?
Of course, with a sine wave you can also observe a voltage multiplication at resonance.

Very Best from Brest,
Yann