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Author Topic: Transformer Induction  (Read 41577 times)
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Re: Transformer Induction « Reply #250 on: 2026-07-05, 19:51:33 »

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Quote from: partzman on 2026-07-05, 15:29:13
This is the data with the first column being the degrees, the second being the average voltage ...
The average of a sine waveform over 360° is zero.
The average of a square waveform over 360° is ½VP-P.

Average peak-to-peak voltage or average amplitude would have been better.

Quote from: partzman on 2026-07-05, 15:29:13
...measured across the 10K during the positive pulse application to the primary, and the third being the average voltage measured during the negative pulse application to the primary.

0, -5.20mv, +4.42mv
45, -3.70mv, +3.32mv
90, +57uv, +560uv
135, +2.87mv, -1.62mv
180, +5.20mv, -4.27mv
225, +2.09mv, -960uv
270, +380uv, +160uv
315, -991uv, +2.37mv

Could be a cos and -cos:
   
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Re: Transformer Induction « Reply #251 on: 2026-07-05, 20:24:03 »
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Quote from: Verpies on 2026-07-05, 19:51:33
The average of a sine waveform over 360° is zero.
The average of a square waveform over 360° is ½VP-P.

Average peak-to-peak voltage or average amplitude would have been better.

Could be a cos and -cos:

I'm sorry I wasn't clear on the probe measurements and calling it the "average" was incorrect.  The first voltage measurements were the peaks of the waveforms taken with the "A" cursor and the second voltage measurements were also the peaks taken with the "B" cursor.

Pm
   
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Re: Transformer Induction « Reply #252 on: 2026-07-05, 20:41:14 »
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Here is another test of a piece of wire inserted into the hole of the toroid where it's charge separated voltage produces a current in a separate voltage supply.

The first pix is of the test circuit showing the wire, diode, ground, and the CH3(pnk) probe connection.  The current probe is just to the right out of the pix, but attached to the red lead coming from the power supply.  Now one could argue that the top and bottom surfaces are contributing to the over all E-Field but this will be addressed in a following post.

The second pix shows the schematic of the circuit.  We see a Schottky diode connecting the wire to a 3.40v stabilized and bypassed power supply.  The idea being that when the charge separated voltage across the wire was greater than one Schottky diode drop above 3.40v, we should see a current flow from the wire to the power supply.

The third pix show the scope results of this test.  We see an average current flow of ~43ma in CH4(grn) when the wire CS voltage reaches 3.844v average as seen on CH3.  This means the Schottky diode has a conduction voltage of ~.444v which is within reason.

Pm
   
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Re: Transformer Induction « Reply #253 on: 2026-07-05, 21:29:03 »
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Here is yet another test showing no E-Field along the upper, lower, and outer surfaces using a resonance circuit made up of a formed shorting wire and an 8uf capacitor.

The first pix if a photo of the test setup.

The second pix is the circuit schematic showing how the loop is formed around the outside perimeter of the toroid with the cap positioned in the near center of the outside leg.  The other vertical leg of the wire is placed close to the primary 12T winding for maximum H-Field induction.  The leakage current on the outside of the toroid should be less than that on the inside of the core, but we see resonant current near equal to that of the inside LC test.  However, some of this is attributable to the lower resonance frequency.   

The third pix is the scope shot showing the measurement results.  With the bottom of the cap grounded and the top connected to Ch3(pnk). we see little to no overall average E-Field present.  What we do see is the charging and  discharging of the cap due to the resonant current flowing thru the loop.  The resonant frequency here is 138kHz which is  lower than the 164kHz with the internal LC because of the longer length of the shorting wire.

Pm
   
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Re: Transformer Induction « Reply #254 on: 2026-07-06, 07:45:55 »

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Quote from: partzman on 2026-07-05, 16:46:01
Smudge,

I lost my detailed response to your last post so here is my overall response showing one proof IMO of my position.

Here is a test where the scope probe is charge separated in the toroid core window and appears to indicate that the ~V/T to the primary exists only in the core window.

First pix is the actual test set, second pix is the circuit schematic, and the third is the scope results.

What is seen here is a wire that covers the outsides of the toroid with a scope probe CH3(pnk) placed in the core window and attached to one end.  The other end is connected to circuit ground with the scope probe ground wire also connected to this same circuit ground.  So, we have zero volts at the probe tip due to the grounded outer wire on the toroid and zero volts at the coax shield of the probe cable. 

We now see that there is a voltage across the probe as indicated on the scope pix that is the opposite polarity from the applied voltage on the primary.  This is due to the fact that the internal 10M resistor and remaining wire within the probe tip are charge separated by an amount very close to the V/T of the primary.  Notice this occurs within the upper and lower surfaces if you will of the toroid's core window.  Little to no voltage appears across the open circuited outer wire on the toroid.

It is clear to me that this configuration measures the full volts per turn and doesn't measure just the volts across the core window.  My first image below shows inducement into the entire probe connection circuit.  The next image shows that entire connection circuit rotated through succesive 90 degrees and in each case it measures the full volts per turn. 

Smudge
   
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Re: Transformer Induction « Reply #255 on: 2026-07-06, 08:36:46 »

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Quote from: partzman on 2026-07-05, 21:29:03
Here is yet another test showing no E-Field along the upper, lower, and outer surfaces using a resonance circuit made up of a formed shorting wire and an 8uf capacitor.

The first pix if a photo of the test setup.

The second pix is the circuit schematic showing how the loop is formed around the outside perimeter of the toroid with the cap positioned in the near center of the outside leg.  The other vertical leg of the wire is placed close to the primary 12T winding for maximum H-Field induction.
You accept that your H field induction is leakage flux so what you measure in this circuit is divorced from flux in the core.  You can make this outside circuit any shape you like as long as it encloses some leakage flux.  The induced voltage from your wire close to the core is completely cancelled by the induced voltage around the rest of your circuit, so has no effect.  The A field from the core is everywhere in your circuit and induces voltage all round it that integrates to zero as the circuit does not enclose the core flux.

Quote
The leakage current on the outside of the toroid should be less than that on the inside of the core, but we see resonant current near equal to that of the inside LC test.
Because that inside circuit also did not enclose core flux so it is the same situation.  What you have done here is clarify why that circuit get its high resonant current, it is all due to leakage flux (not leakage current which I am sure you did not mean).

Quote
However, some of this is attributable to the lower resonance frequency.   
The third pix is the scope shot showing the measurement results.  With the bottom of the cap grounded and the top connected to Ch3(pnk). we see little to no overall average E-Field present.  What we do see is the charging and  discharging of the cap due to the resonant current flowing thru the loop.  The resonant frequency here is 138kHz which is  lower than the 164kHz with the internal LC because of the longer length of the shorting wire.
Ignoring the HF bursts we do see Ch3 voltage rising and falling on alternate 4uS periods by an amount that agrees with the 8uF carrying the measured current.  It would not show the inducing E field from the core flux for reasons already stated.

Smudge
   
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Re: Transformer Induction « Reply #256 on: 2026-07-06, 16:53:55 »
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Quote from: Smudge on 2026-07-06, 07:45:55
It is clear to me that this configuration measures the full volts per turn and doesn't measure just the volts across the core window.  My first image below shows inducement into the entire probe connection circuit.  The next image shows that entire connection circuit rotated through succesive 90 degrees and in each case it measures the full volts per turn. 

Smudge

You are correct that the configuration is measuring the full volts per turn.  Where we differ is in the location of exactly where this V/T resides.  IMO based on all my tests, is there is little to no voltage in the loop around the upper, outer, and lower sides of the toroid!  If this is correct, this places the very tip of the probe at zero volts.  We already know the coax of the probe cable is at zero volts so this means the inner conductor/resistor of the probe is charge separated.  The polarity of the charge separation would force the tip positive but it can't go positive due to the fact (IMO) that the tip is at virtual ground.  So, the inner wire feeding the input amplifier to the scope is forced negatively.  This is exactly what we see in the scope pix when a positive voltage is applied to the primary.

If your interpretation was correct, the tip again will be charge separated in the positive direction and it's value would be displayed by a positive voltage on the scope.  However, this is not what we see!

Pm
   
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Re: Transformer Induction « Reply #257 on: 2026-07-06, 17:07:43 »
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Quote from: Smudge on 2026-07-06, 08:36:46
You accept that your H field induction is leakage flux so what you measure in this circuit is divorced from flux in the core.  You can make this outside circuit any shape you like as long as it encloses some leakage flux.  The induced voltage from your wire close to the core is completely cancelled by the induced voltage around the rest of your circuit, so has no effect.  The A field from the core is everywhere in your circuit and induces voltage all round it that integrates to zero as the circuit does not enclose the core flux.  Because that inside circuit also did not enclose core flux so it is the same situation.  What you have done here is clarify why that circuit get its high resonant current, it is all due to leakage flux (not leakage current which I am sure you did not mean).Ignoring the HF bursts we do see Ch3 voltage rising and falling on alternate 4uS periods by an amount that agrees with the 8uF carrying the measured current.  It would not show the inducing E field from the core flux for reasons already stated.

Smudge

Let me state my position on the H-Field.  The primary wire that is on the inside (or outside) of the core has two H-Fields.  One is on the 'inside' of the wire closest to the core and one on the 'outside' of the wire.  The 'inside' H-Field creates the flux in the core as well as the leakage flux.

The 'outside' is what creates the resonant current via induction.  I respectively disagree on the rest of your comments above for reasons I will show in a later post.

Pm
   
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Re: Transformer Induction « Reply #258 on: 2026-07-06, 17:16:33 »
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Smudge,

This is a test of the outside loop placed on the core but now open circuited.  The first pix is the test setup and the second pix is the schematic.

The third pix is the scope measurements of this loop.  No appreciable voltage is seen using the A and B cursors on CH3(pnk).  The scope probe and ground lead form a loop that is basically in parallel with the open loop so if there were any voltage present in either produced by the E-Field or the A_Field, it would be displayed as such on the screen.

Pm
   
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Re: Transformer Induction « Reply #259 on: 2026-07-08, 03:46:15 »

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hey pm

what if the open wire on just the outside of the core were on the other end of the core. just saying not right on the primary.   if its not any trouble.

mags
   
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Re: Transformer Induction « Reply #260 on: 2026-07-08, 15:33:30 »
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Quote from: Magluvin on 2026-07-08, 03:46:15
hey pm

what if the open wire on just the outside of the core were on the other end of the core. just saying not right on the primary.   if its not any trouble.

mags

Mags,

The voltage readings will be the same.

Pm
   
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Re: Transformer Induction « Reply #261 on: 2026-07-08, 21:35:56 »

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im just thinking....

mags
   
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Re: Transformer Induction « Reply #262 on: 2026-07-08, 22:00:26 »
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I would like to point out the following which I thot I had already posted but couldn't find it on the forum so if I did, here it is again.

The observation with this experiment is that the total voltage drops across each primary turn in the hole of a closed flux core (in this case our same toroid) sum to nearly the total V/T applied to the primary.  IOW, there is little to no voltage across the wire on the outside of the core.  IMO, any voltage drop in the outside wire is due to product of the current in the primary times the resistance of that portion of the primary winding.

The attached pix shows the test setup with a four turn primary that has little loops formed at the ends of each primary wire in the center or hole of the toroid.  Two probes are then used to take differential measurements of the average voltages present at the ends of each turn of the primary.  Measurements are taken when the primary has a positive voltage applied and also when the 3/4 bridge collapses with the voltage to the primary will then be negative.  With the intrinsic nature of a 3/4 bridge, the collapse or negative application to the primary will always be slightly higher than the positive application due to a diode in the flyback or collapse path back to the power supply.

This is a table of the voltage measurements.  The first voltage differential listed is taken during the application of a positive voltage to the primary and the second differential is taken during the primary collapse and is therefore negative.

#1 = 3.608v,   -4.080v
#2 = 3.640v,   -4.202v
#3 = 3.704v,   -4.241v
#4 = 3.600v,   -4.131v
__________________
Tot =14.552v, -16.654v

Vap=14.56,    -16.670v

VaP is the differential voltage measured across the leads attached to the primary for an accurate V/T for both polarities.  The results seem to indicate that nearly all the voltage drop across the excited primary exists in the wire in the hole of the toroid between the upper and lower surfaces,

Regards,
Pm
   
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Re: Transformer Induction « Reply #263 on: 2026-07-08, 22:01:49 »
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Quote from: Magluvin on 2026-07-08, 21:35:56
im just thinking....

mags

Could you maybe explain what you're thinking?

Pm
   
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Re: Transformer Induction « Reply #264 on: 2026-07-09, 03:17:10 »

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Quote from: partzman on 2026-07-08, 22:01:49
Could you maybe explain what you're thinking?

Pm

was thinking, if you see the pic of the toroid with the winding on the left, it shows that there can be some flux outside the toroid where the winding is, but none on the outside of the toriod on the right.  unless ofcourse there is over saturation of the core from driving the primary.

but, if you have tried my earlier suggestion and found it will be the same having the test wire outside the core where the primary is and on the other side of the toroid where the primary isnt, then it is what it is.

mags
   
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Re: Transformer Induction « Reply #265 on: 2026-07-09, 16:39:57 »
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Quote from: Magluvin on 2026-07-09, 03:17:10
was thinking, if you see the pic of the toroid with the winding on the left, it shows that there can be some flux outside the toroid where the winding is, but none on the outside of the toriod on the right.  unless ofcourse there is over saturation of the core from driving the primary.

but, if you have tried my earlier suggestion and found it will be the same having the test wire outside the core where the primary is and on the other side of the toroid where the primary isnt, then it is what it is.

mags

Yes, with an open loop, the voltage remains at or near 0v anywhere around the perimeter of the core.  If you meant measuring the resonant current in the L/C loop on the outside of the core, then as you move away from the influence of the H-Field of the primary. the current drops off considerably but there is some still measurable due to the small amount of leakage flux outside the core and it varies.

Pm
   
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Re: Transformer Induction « Reply #266 on: 2026-07-10, 10:20:36 »

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I have been busy setting myself up to do my own measurements on things I find interesting.  I expected my Rigol scope to be of a size to fit a standard 19 inch rack, and that tells you how long ago I last did any experiments.  But I digress, back to the topic in hand.

Quote from: partzman on 2026-07-06, 17:16:33
Smudge,

This is a test of the outside loop placed on the core but now open circuited.  The first pix is the test setup and the second pix is the schematic.

The third pix is the scope measurements of this loop.  No appreciable voltage is seen using the A and B cursors on CH3(pnk).  The scope probe and ground lead form a loop that is basically in parallel with the open loop so if there were any voltage present in either produced by the E-Field or the A_Field, it would be displayed as such on the screen.
Please do that test again with the scope probe connection as shown in the attached image, and not the alignment you used. This allows the leakage H field from the primary coil to pass through the area I have shaded green.  The scope should record the voltage induced around the periphery of that area. 

Smudge
   
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Re: Transformer Induction « Reply #267 on: 2026-07-10, 14:53:05 »

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Quote from: Smudge on 2026-07-10, 10:20:36
I expected my Rigol scope to be of a size to fit a standard 19 inch rack, and that tells you how long ago I last did any experiments. 
You bought yourself a Rogol scope !?  What vertical resolution ?  Which model ?
   
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Re: Transformer Induction « Reply #268 on: 2026-07-10, 15:25:16 »
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Quote from: Smudge on 2026-07-10, 10:20:36
I have been busy setting myself up to do my own measurements on things I find interesting.  I expected my Rigol scope to be of a size to fit a standard 19 inch rack, and that tells you how long ago I last did any experiments.  But I digress, back to the topic in hand.
Please do that test again with the scope probe connection as shown in the attached image, and not the alignment you used. This allows the leakage H field from the primary coil to pass through the area I have shaded green.  The scope should record the voltage induced around the periphery of that area. 

Smudge

OK this is the test you requested with the first scope pix below showing the differential of the peaks between the positive and negative pulses using the A and B cursors on CH3(pnk).  This does show that the H-Field of the primary is inducing this loop.

However, when using my differential test where the grounds are the scope probe lead's outer coax, the loop is much larger and not affected that greatly by the H-Field induction.  IMO, this would result in a more accurate measurement of any voltage developed across this loop by the E or A field only.

Although you didn't ask for it, the second scope pix shows your test with the loop rotated 90 degrees on the core.

Regards,
Pm



Although
   
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Re: Transformer Induction « Reply #269 on: 2026-07-10, 17:21:51 »

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Quote from: Verpies on 2026-07-10, 14:53:05
You bought yourself a Rogol scope !?  What vertical resolution ?  Which model ?
It is Rigol DS 1102 that has an 8 bit resolution.  That is enough for the initial work I have in mind where my theory tells me the effect I am looking for is quite significant.
   
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Re: Transformer Induction « Reply #270 on: 2026-07-10, 19:49:04 »

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Quote from: Smudge on 2026-07-10, 17:21:51
It is Rigol DS 1102 that has an 8 bit resolution. 
That model has not been manufactured in years.  I hope you paid only a few pounds for it.
   
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Re: Transformer Induction « Reply #271 on: 2026-07-11, 09:03:52 »

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Quote from: Verpies on 2026-07-10, 19:49:04
That model has not been manufactured in years.  I hope you paid only a few pounds for it.
£224 via Amazon UK.
   
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Re: Transformer Induction « Reply #272 on: 2026-07-11, 10:48:34 »

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Quote from: partzman on 2026-07-10, 15:25:16
OK this is the test you requested with the first scope pix below showing the differential of the peaks between the positive and negative pulses using the A and B cursors on CH3(pnk).  This does show that the H-Field of the primary is inducing this loop.

The leakage H field from the primary, being in in air is producing B=u0H tesla, which integrated over the area of the loop produces flux Phi whose rate of change gives the votages you measure.  Ignoring the HF ringing, the square wave voltage you measure and the time period tells you that rate of change, so you could establish the magnitude of that loop leakage flux.  And it will tell you that it is responsible for the current you observed in your closed loop LC circuit in post #253; that has a smaller area loop but since the leakage field is greatest near the primary coil will intercept almost the same value of flux.  There is of course the other non-leakage flux within the ring core that does not pass through this loop and therefore has no effect on the measurement.

Quote
However, when using my differential test where the grounds are the scope probe lead's outer coax, the loop is much larger and not affected that greatly by the H-Field induction.  IMO, this would result in a more accurate measurement of any voltage developed across this loop by the E or A field only.

Without a view of your differential measurement set up to see how the leakage flux passes through the loops of the probe connections I can't comment on what you are actually measuring.  But I must emphasize that your judgement concerning the E field from the non-leakage flux in the core is wrong and you have not persuaded me otherwise.  Your attempt to obtain evidence that the U shaped piece of wire placed close to the outer surfaces of the ring core is in a zero E=-dA/dt electric field ignores the effect of that field further away from that surface on the remainder of the external closed loop where its effect is completely nulled.  Perhaps the image below showing the E field from the core flux is present all around the external loop will help convince you. At any point in that external loop the induced current is zero, and zero current into the scope's internal impedance is zero voltage measured.

Regards
Smudge     
   
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Re: Transformer Induction « Reply #273 on: 2026-07-11, 21:13:19 »
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Smudge,

Here is the schematic of the differential test performed on the open loop outside the core.  The ground connection for each probe is made at the scope and transferred thru each probe's outer shield.  The CH1(yel) probe has a probe ground wire connected to the circuit supply ground and therefore is the overall ground for the CH2 and CH3 probes.

The probes appear to be able to be positioned at any location without any appreciable differential voltage being measured.

Pm
   
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Re: Transformer Induction « Reply #274 on: 2026-07-12, 10:35:07 »

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Quote from: partzman on 2026-07-11, 21:13:19
Smudge,

Here is the schematic of the differential test performed on the open loop outside the core.  The ground connection for each probe is made at the scope and transferred thru each probe's outer shield.  The CH1(yel) probe has a probe ground wire connected to the circuit supply ground and therefore is the overall ground for the CH2 and CH3 probes.

The probes appear to be able to be positioned at any location without any appreciable differential voltage being measured.

Pm
There is an induced voltage that varies with position of the single probe as you described in your post #268.  There is a reasonable explanation for voltage being induced into the scope ground connection so it is different from the usual scope measurement.  A differential measurement of a voltage using two probes requires the common ground connection to be at an intermediate potential, usually half the value so that each one yields half the actual voltage.  How do you achieve that when the ground leads themselves have induced voltage?  For your differential measurement with two probes the system is much more complicated and your 2D schematic is not sufficient for an analysis.  Photos showing the layout in 3D would be better.  My inital reaction is that the potential of the common ground connection of the two probes is undetermined in relation to your post #268 results and will always result in a zero measurement.

Smudge 
   
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