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Author Topic: AC voltage from single magnetic pole  (Read 39116 times)

partzman

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Re: AC voltage from single magnetic pole
« Reply #120 on: October 10, 2020, 01:39:16 AM »
Sorry to read that. Is it an ischemic stroke ?


This thread will be fine without your input for a while. There are other experimenters that join in.

Actually we just got the news that he didn't have a stroke a all according to the MRI but since he has epilepsy, they think he had a seizure either during or after the procedure which was a TFNA or TFN-ADVANCED™ Proximal Femoral Nailing System to fix his hip.  If true, then he is exhibiting Todd's Paralysis which mimics a stroke but are only temporary 'normally'.  He had all the classic stroke symptoms like left leg and arm weakness, slurred speech, drooping face, and difficulty swallowing, so we'll know more in the next 24-48 hours or so. 

Regards,
Pm


nix85

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Re: AC voltage from single magnetic pole
« Reply #121 on: October 10, 2020, 01:41:07 AM »
I'd like sc expert's opinion, if you got him bring him...

But for now address the last post.

verpies

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Re: AC voltage from single magnetic pole
« Reply #122 on: October 10, 2020, 01:49:57 AM »
Now that we are clear that your claim is for resistive coils too...

An external varying field perfectly includes varying field from an electromagnet, there is no sense to limit it to moving magnet.
Yes

And what then, if you insist on aircores, what is the difference between what you claim and a transformer in which core is removed from the secondary.
Primary produces time varying flux just like moving PM does, and we got an aircore secondary.
There is not much difference. The only one I would be worrying about is capacitive coupling at high frequencies between the primary and secondary, such as when one is wound over the other.

So you are claiming current in this secondary will not lag voltage even when inductance and frequency are high?

That question is ambiguous so I will have to add more details to it, like this:


Quote from: Amended Question
So you are claiming current induced in this secondary will not lag the voltage induced in this secondary even when inductance and frequency are high and secondary's self-capacitance is relatively low (or zero) and the only coupling between the primary and secondary is magnetic?
If you ask it like above then my answer is "yes"

Notice, that in such experiment the primary is only a source of varying magnetic flux and there is not access to electric signals in the primary. 
This means that you are not allowed to have any knowledge of electric signals in the primary, e.g. you are not allowed to place any electric probes in the primary circuit.

That would be completely wrong.
Why?

nix85

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Re: AC voltage from single magnetic pole
« Reply #123 on: October 10, 2020, 01:59:31 AM »
Why?

For simple reason that current cannot instantly start through any inductor, this is known as

τ = L/R inductor time constant, after ~5τ (transient time) current reaches 99.5%

Therefore inductor with big inductance and low resistance especially at higher frequencies will have significant IV phase shift no matter how you induce it.

verpies

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Re: AC voltage from single magnetic pole
« Reply #124 on: October 10, 2020, 02:03:19 AM »
For simple reason that current cannot instantly start through any inductor, this is known as
τ = L/R inductor time constant, after ~5τ (transient time) current reaches 99.5%
Therefore inductor with big inductance and low resistance especially at higher frequencies will have significant IV phase shift.

This is correct but only when that current is a consequence of applying an external voltage to that inductor.
We are not talking about that scenario.

nix85

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Re: AC voltage from single magnetic pole
« Reply #125 on: October 10, 2020, 02:05:55 AM »
Quote
This means that you are not allowed to have any knowledge of electric signals in the primary, e.g. you are not allowed to place any electric probes in the primary circuit.

How so, you are feeding the primary AC, you know the signal you feed it.

verpies

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Re: AC voltage from single magnetic pole
« Reply #126 on: October 10, 2020, 02:09:27 AM »
How so, you are feeding the primary AC, you know the signal you feed it.
If you acquire the knowledge inadvertently, then you musn't use it in your calculations or conceptual analysis.

nix85

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Re: AC voltage from single magnetic pole
« Reply #127 on: October 10, 2020, 02:11:51 AM »
This is correct but only when that current is a consequence of applying an external voltage to that inductor.
We are not talking about that scenario.

What you claim sounds unrealistic, so i'll be happy to find out what is the truth.

nix85

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Re: AC voltage from single magnetic pole
« Reply #128 on: October 10, 2020, 02:13:46 AM »
If you acquire the knowledge inadvertently, then you musn't use it in your calculations or conceptual analysis.

What. If you are feeding AC to the primary you know exactly what you are feeding it.


verpies

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Re: AC voltage from single magnetic pole
« Reply #129 on: October 10, 2020, 02:18:35 AM »
What. If you are feeding AC to the primary you know exactly what you are feeding it.

It is called an abstraction.  In this case an abstraction of the primary winding as a varying flux source only.


This means, that if you inadvertently acquire the knowledge of the AC voltage or amplitude or frequency or phase in the primary circuit then you mustn't use it in your calculations or conceptual analysis.  ...or use a secretive lab assistant that will set random amplitude, frequency and phase of the signal generator which supplies the primary winding with electric energy  ;) .

However, you can probe and use the knowledge about all electric signals occurring in the secondary circuit.

nix85

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Re: AC voltage from single magnetic pole
« Reply #130 on: October 10, 2020, 02:21:47 AM »
It is called an abstraction.  In this case an abstraction of the primary as a varying flux source only.


This means, that if you inadvertently acquire the knowledge of the AC voltage or amplitude or frequency or phase in the primary circuit then you mustn't use it in your calculations or conceptual analysis.  ...or use a secretive lab assistant that will set random amplitude, frequency and phase of the signal generator which supplies the primary winding with electric energy  ;) .
However, you can probe and use the knowledge about electric signals occurring in the secondary circuit.

Why would you deny yourself knowledge of the signal you feed into primary.
Is that some religious significance to you or.
No comment on emoji.

verpies

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Re: AC voltage from single magnetic pole
« Reply #131 on: October 10, 2020, 02:36:38 AM »
Why would you deny yourself knowledge of the signal you feed into primary.
Because that knowledge cannot matter in this experiment.


I remind you that we are trying to determine whether the induced voltage leads the induced current in one inductor which is subjected to a varying external magnetic flux.
How this flux variation is generated is immaterial for this determination.

The varying flux can be generated by a moving magnet or by another inductor or magnetoacoustic effect or Villari effect or precessing nuclei.
How the varying flux is generated does not matter because if it did, then you would be dealing with a different question.


nix85

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Re: AC voltage from single magnetic pole
« Reply #132 on: October 10, 2020, 02:41:12 AM »
That's different from not knowing what you feed it but ok.

partzman

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Re: AC voltage from single magnetic pole
« Reply #133 on: October 10, 2020, 04:30:02 AM »
This is a test that I will let the reader judge. 

Basically, there are three air coils with identical turns and DCRs that are placed in line horizontally as shown on a flat surface.  In this layout, the left coil is the current sensing coil, the right side coil is the voltage sensing coil and the center coil is driven with a 10kHz sine wave from a power amplifier. 

The start of each winding is positioned at the top so polarities may be observed from the connections.  IOW, the electromagnetic source coil in the center has the finish as the common or ground, the current coil is shown with conventional flow from finish to start and the voltage winding has the ground on the start.  These are opposite from the dot connections expected if the coils were stacked on top of each other so please consider this.

The resultant scope pix has CH1(yel) as the input voltage source to the center coil, CH3(pnk) as the output voltage of the voltage sensing coil. and CH4(grn) is the current flow in the current sensing coil.

Regards,
Pm

 

citfta

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Re: AC voltage from single magnetic pole
« Reply #134 on: October 10, 2020, 02:03:53 PM »
Good morning PM.


Nice clear test.  I do have one question.  What is your load?  If the left coil is the current sensing coil then what is the load it is connected to?


Thanks,
Carroll