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Author Topic: Reactive power - Reactive Generator research from GotoLuc - discussion thread  (Read 362138 times)

gotoluc

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Hey Luc

The 2 coils have the same resistance, but they have way different inductance, and capacitance.

The toroid has more inductance and capacitance. That coil may not allow much current above 100 or even 200hz let alone 1khz as a coil alone, not in resonance.   Does your sig board do sweeps? I might think that there is a lower than 4mhz resonant freq for the toroid, by the looks of it anyways, especially if it is series bifi.

If it really is set as series bifi, and it really only conducts well at around 4mhz, then the other coil will be way above that before it rings.

Mags

Hi Mags,

yes, I'm aware the 2 coils have different Inductance and Capacitance. The prior posts were questioning the CSR (shunt) to be the possible source of causing the Negative mean. So, the idea of changing coils with a coil of the same DC resistance was to see if the CSR would still be the same.  If the mean was negative for both cases then we would know the CSR is the cause.

My SG doesn't do an auto sweep. However, I did a full manual one.  On the bifilar Toroid from 1hz to 200hz you can see current. From 200hz to 200khz there is nothing. From 200khz it starts to go negative means and peaks at 4.7Mhz.
I tried it with my old Wavetek 134 SG and it is exactly the same thing. The only thing with the Wavetek is I can only go to 2Mhz. However, the output is higher so at 2.23Mhz I can get -395 mean or 392 mean with ch 2 inverted.

See scope shots of using Wavetek at 2Mhz on Toroid.

Luc

MarkE

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Those are all good comments.  The other thing that can be done is to run the signal from a current sense resistor through a low pass filter that cancels the L/R pole of the CSR.   But there are other pitfalls to watch out for as well, including the fact that the frequency response of an oscilloscope probe using the probe hook and a 4" or 6" ground lead is anything but flat.  A great find are high frequency ground adapters available from Probe Master in San Diego, California:  4983HG.  These  look like little wound springs that fit snugly over the ground ring of a scope probe when the probe hook is removed.  It places the ground connection a quarter inch from the probe tip center.  Probing this way is almost as good as probing with a board level coaxial connector for the scope probe.  Probe Master sells those things for less than $3.00 each.  In my opinion they are a must have in any measurement kit.

Another useful trick is to go buy extra scope ground clips and insert a 50 Ohm resistor at the alligator clip between the clip and the lead.  A little 1/8 Watt resistor works great.  This damps out most of the overshoot that results from the stray inductance.  It's not a perfect solution, but it cleans things up quite a bit.

The bottom line is that one needs to be careful measuring current especially with signals that content in the MHz.

gotoluc

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Luc,

All three of the resistors in your video are wirewound.

The LVR series is specified as "low inductance", but the actual inductance is not given in the data sheet.

The RS series was available in a "non-inductive" wind, but they would have then had the "R" replaced with an "N" (i.e., "NS" series), so I would consider the RS inductive.

Be aware that a lot of manufacturers consider anything under 100nH as being low or non-inductive, which, for low value resistors used at higher operating frequencies, is way too much inductance.  The best I have been able to find are Caddock units specified as 4nH when measured .1" from the resistor body (which adds 0R1 at 4MHz).

A rough estimate to follow for a "normal" sized straight wire is ~20nH per inch, which is ~0R5 of reactance at 4MHz.  Therefore, a 0.2" length of wire is ~0R1 at 4MHz.  That's means that just 0.1" of wire at each end of a "non-inducive" 0R1 resistor will add another 0R1 of reactance to that resistor at 4MHz (effectively doubling its value).  A six inch cliplead has about 3R of reactance at 4MHz.

Don't you have some small wattage (1/4W or 1/2W) carbon or MF resistors that you can neatly parallel (very short leads) to make a low value CSR?  Putting resistors in parallel (with very short/neat leads) also places their inductance in parallel which reduces the total inductance. 

Using a larger value resistor for your CSR (=/>1R) will also reduce CSR measurement errors due to inductive reactance.  Roughly speaking, assuming zero inductance resistors, a 0R1 CSR with 0.1" leads is 0R2 at 4MHz (100% error), a 1R CSR with 0.1" leads is 1R1 at 4MHz (a 10% error), and a 10R CSR with 0.1" leads is 10R1 at 4MHz (a 1% error).

PW

Thanks for checking on those resistors PW

I don't have anything at 1 Ohm that's not wire wound. So I tried it with the Dale LVR 0.1 Ohm, see scope shot. I set my ch 2 menu at x10 so the mean is the final value.

Last week I ordered these resistors: http://www.ebay.com/itm/221065910130?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649  the idea is to group 5 together to have a 0.1 Ohm MF precision resistor capable of handling 10W. They come from China so it's going to take a while before I have them.

I do have a 10 ohm 5% MF Resistor but I think it eats up the negative mean. See 10 Ohm scope shot.

Thanks for your help

Luc

picowatt

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Those are all good comments.  The other thing that can be done is to run the signal from a current sense resistor through a low pass filter that cancels the L/R pole of the CSR.   But there are other pitfalls to watch out for as well, including the fact that the frequency response of an oscilloscope probe using the probe hook and a 4" or 6" ground lead is anything but flat.  A great find are high frequency ground adapters available from Probe Master in San Diego, California:  4983HG.  These  look like little wound springs that fit snugly over the ground ring of a scope probe when the probe hook is removed.  It places the ground connection a quarter inch from the probe tip center.  Probing this way is almost as good as probing with a board level coaxial connector for the scope probe.  Probe Master sells those things for less than $3.00 each.  In my opinion they are a must have in any measurement kit.

Another useful trick is to go buy extra scope ground clips and insert a 50 Ohm resistor at the alligator clip between the clip and the lead.  A little 1/8 Watt resistor works great.  This damps out most of the overshoot that results from the stray inductance.  It's not a perfect solution, but it cleans things up quite a bit.

The bottom line is that one needs to be careful measuring current especially with signals that content in the MHz.

MarkE,

Good comments Mark.  I have something similar to those Probe Master probe ground contacts.  A few are a bit distressed from bending and soldering...


Those attempting to make accurate measurements of non-sinusoidal waveforms, and in particular when square waves or pulses are involved, should appreciate the higher frequency harmonics present in their waveforms and the effects CSR/ stray inductance (and capacitance) has on those harmonics.  Even severely distorted or clipped sine waves contain very significant amounts of harmonic content.

One might consider a 10Kc square wave or rectangular pulse as a 1OKc signal because that is what a scope or frequency counter reads out.  But that is just the trigger or repetition rate of the signal.  The actual frequency content of that 10Kc waveform is dependent on its rise and fall times, with faster edges (and sharp, square corners) representing higher frequency harmonics.  Only when measuring a pure, undistorted sine wave does a frequency counter or scope readout tell the full story regarding frequency content.

Many people are now using a digital scope of some type and many of those scopes have an FFT mode for spectral analysis.  Using and familiarizing one's self with that mode would allow the experimenter to gain a better appreciation of the actual frequencies they are attempting to measure, and the required measurement bandwidth for which they must reduce or eliminate errors due to undesired stray L's and C's.

I would encourage anyone with a digital scope to connect an FG to their scope so that both the FG's wave shape (normal mode) and spectral display (FFT mode) are visible on the scope simultaneously and observe the frequency content as the FG wave shape, frequency, and duty cycle are modified.   

PW   


picowatt

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Thanks for checking on those resistors PW

I don't have anything at 1 Ohm that's not wire wound. So I tried it with the Dale LVR 0.1 Ohm, see scope shot. I set my ch 2 menu at x10 so the mean is the final value.

Last week I ordered these resistors: http://www.ebay.com/itm/221065910130?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649  the idea is to group 5 together to have a 0.1 Ohm MF precision resistor capable of handling 10W. They come from China so it's going to take a while before I have them.

I do have a 10 ohm 5% MF Resistor but I think it eats up the negative mean. See 10 Ohm scope shot.

Thanks for your help

Luc

Luc,

As I mentioned, using a CSR with a value of 0R1 is difficult to do.  Just 0.1" of wire at each end can cause a 100% error at 4MHz. 

Could that "eats up the negative mean" with the 10R MF actually indicate a less inductive/more accurate CSR reading?

Does your FG have a 50R output, and can you identify the 50R on its PCB (should be close to and connected to the FG output terminal)? 

What is the FG's maximum open circuit output amplitude at 4MHz and would you be concerned with shorting the FG output?

PW

verpies

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Hi Verpies,
My experience doesn't agree with this... Bulbs show any real power...
I've found I can run an incandescent bulb on the output of a car ignition coil (maybe 5000v, 1000Hz) at 40w, or an MOT (2000v ish), and it's exactly as bright as it is with 40w mains (at 240v AC, 50Hz). Just the same...
But that's different.  You are referring to measuring output power and I am referring to measuring input power.

When the bulb is the measuring device and the sole load at the same time (as it is on the output side), then it is an accurate indicator of power.
However, an incandescent bulb does not work well as an input power indicator because it is not the entire load on the input side.  Read about MPTT.

verpies

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The input circuit is of high voltage and low current (hence little to no illumination of the series input bulb), and the output circuit is low voltage and high current, hence the output bulb lights.
That's true.

Now all that's missing is an explanation why the input circuit of a 1:1 transformer operates at higher voltage than the output circuit.

P.S.
According to the video, the primary winding forms a parallel LC circuit and the secondary winding forms a series LC circuit.

DilJalaay

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That's true.

Now all that's missing is an explanation why the input circuit of a 1:1 transformer operates at higher voltage than the output circuit.

P.S.
According to the video, the primary winding forms a parallel LC circuit and the secondary winding forms a series LC circuit.


As at high frequencies, rules changed, now the 1:1 transformer will not behave same as at low frequencies.


Just my thoughts, looking for the experts opinion.

poynt99

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Re: Reactive power - Reactive Generator research from GotoLuc - discussion thread
« Reply #563 on: February 01, 2014, 01:54:08 AM »
That's true.

Now all that's missing is an explanation why the input circuit of a 1:1 transformer operates at higher voltage than the output circuit.

P.S.
According to the video, the primary winding forms a parallel LC circuit and the secondary winding forms a series LC circuit.

Because the circuit(s) are in resonance (Fo), and a parallel LC circuit (input) has a high impedance and high voltage at Fo, while a series LC circuit (output) has a low impedance and high current at Fo.

gotoluc

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Re: Reactive power - Reactive Generator research from GotoLuc - discussion thread
« Reply #564 on: February 01, 2014, 05:59:31 AM »
Hi PW, poynt99 and all,

I have a new video of the same Bifilar Troid under test but using a 1 Ohm 5% Metal Film Resistor as CSR.

The other change is I thought of the trick of using a magnet on the toroid core with a pickup coil to see if I could pickup power at a lower frequency then Mhz range.
Turns out I can light an LED at 625Hz with zero cost to the input power. However, we still have a problem as the mean is Positive with Ch 2 inverted or a Negative with it not inverted.

I'll leave it to you Pros to figure out. Anyone is welcome to join in if you feel up to the task.

Link to video: http://www.youtube.com/watch?v=cQe49jH_3lA&feature=youtu.be

Please note an error on my part in the video, I keep saying the time division is micro seconds when it's mostly all in milli seconds.

Luc

poynt99

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Re: Reactive power - Reactive Generator research from GotoLuc - discussion thread
« Reply #565 on: February 01, 2014, 04:51:56 PM »
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.

itsu

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Re: Reactive power - Reactive Generator research from GotoLuc - discussion thread
« Reply #566 on: February 01, 2014, 06:50:18 PM »
Because the circuit(s) are in resonance (Fo), and a parallel LC circuit (input) has a high impedance and high voltage at Fo, while a series LC circuit (output) has a low impedance and high current at Fo.

Intriguing stuff, as it LOOKS like we have 2 parallel LC circuits, but indeed, one (the output) is also (and here acts like) a series LC circuit.

I made a replication of this circuit and made some voltage and current measurements with the scope.
We do have some coupling between the both coils as, when at resonance, both bulps light up at the same time.
Also it seems to me that the both bulb voltages act as CSR's and can be used to indicate the current (leading / trailing the SG voltage at the input)

Video here: http://www.youtube.com/watch?v=_WU2SrKDNY4&feature=youtu.be

Regards Itsu

synchro1

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Re: Reactive power - Reactive Generator research from GotoLuc - discussion threa
« Reply #567 on: February 01, 2014, 07:35:46 PM »
Hi PW, poynt99 and all,

I have a new video of the same Bifilar Troid under test but using a 1 Ohm 5% Metal Film Resistor as CSR.

The other change is I thought of the trick of using a magnet on the toroid core with a pickup coil to see if I could pickup power at a lower frequency then Mhz range.
Turns out I can light an LED at 625Hz with zero cost to the input power. However, we still have a problem as the mean is Positive with Ch 2 inverted or a Negative with it not inverted.

I'll leave it to you Pros to figure out. Anyone is welcome to join in if you feel up to the task.

Link to video: http://www.youtube.com/watch?v=cQe49jH_3lA&feature=youtu.be

Please note an error on my part in the video, I keep saying the time division is micro seconds when it's mostly all in milli seconds.

Luc




625 hertz is divisible by the Shumman constant of 7.8, nearly exactly 80 times. Does this indicate the possible existence of an oscillating frequency of magnetisem harmonic?

MileHigh

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Re: Reactive power - Reactive Generator research from GotoLuc - discussion thread
« Reply #568 on: February 01, 2014, 11:14:21 PM »
Another awesome clip Itsu!

Farmhand

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Re: Reactive power - Reactive Generator research from GotoLuc - discussion thread
« Reply #569 on: February 02, 2014, 04:03:56 AM »
It depends on the globes used, power applied ect. and the current caused. If the globe in series with the primary requires more current to glow than is supplied to the transformer to light up the other globe then it won't even glow.

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. To me this says the current input at full resonance is just enough to light the bulb in the primary circuit.

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

Cheers