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Author Topic: AC voltage from single magnetic pole  (Read 39477 times)

citfta

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Re: AC voltage from single magnetic pole
« Reply #60 on: October 09, 2020, 04:58:40 PM »
The problem with some of the people on these type of forums is they get some knowledge from YouTube or elsewhere and think they know more than those of us that have worked in electronics for years.  Let's look at one example of their misunderstanding.


Most anyone that has studied electronics for even a little while has heard the expression "Eli the Iceman".  And they have been taught that means that voltage leads current in an inductor and current leads voltage in a capacitor.  That adage of course is true if we are talking about CHARGING a coil or capacitor.  But that adage is wrong when we are talking about DISCHARGING a coil or capacitor.  A capacitor can only discharge if it has a voltage high enough to overcome whatever resistance is in the circuit.  So voltage leads current when discharging a capacitor.  And when voltage is removed from a coil the current in the coil tries to maintain itself so it will build a voltage high enough to overcome the resistance in the circuit and thus discharge the current in the coil.  So current LEADS voltage when a coil is discharging.


So what happens when a magnet is moving past a coil?  The coil will have a voltage induced into it whether there is a load connected to the coil or not.  This can easily be seen by just connecting a scope to the open leads of a coil and seeing the voltage on the scope just like the video Nix posted.  When a load is connected to a coil and the magnet passes the coil the coil is being both charged and discharged at the same time because the voltage is being induced into the coil from an external source and not being applied directly to the coil.  That is the difference.  When this happens the voltage and any current being used are in phase.  Again this can be proven by connecting a scope across the leads of the coil and across the load.  The scope leads across the load will be measuring the voltage drop across the load and hence the current through the load.  If the load is a resistive load then the voltage and current will be in phase just as Verpies has said.  i am in the process of uploading a video that shows this.  I will post a link when it finishes uploading.


Carroll
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nix85

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Re: AC voltage from single magnetic pole
« Reply #61 on: October 09, 2020, 05:28:24 PM »
Quote
The problem with some of the people on these type of forums is they get some knowledge from YouTube or elsewhere and think they know more than those of us that have worked in electronics for years.

The problem with these people who think just because they been in electronics for years they got real understanding of it.

Quote
Most anyone that has studied electronics for even a little while has heard the expression "Eli the Iceman".  And they have been taught that means that voltage leads current in an inductor and current leads voltage in a capacitor.  That adage of course is true if we are talking about CHARGING a coil or capacitor.  But that adage is wrong when we are talking about DISCHARGING a coil or capacitor.  A capacitor can only discharge if it has a voltage high enough to overcome whatever resistance is in the circuit.  So voltage leads current when discharging a capacitor.  And when voltage is removed from a coil the current in the coil tries to maintain itself so it will build a voltage high enough to overcome the resistance in the circuit and thus discharge the current in the coil.  So current LEADS voltage when a coil is discharging.

I agree that lag changes on discharge but his claim is that they are in-phase.


Quote
......When a load is connected to a coil and the magnet passes the coil the coil is being both charged and discharged at the same time because the voltage is being induced into the coil from an external source and not being applied directly to the coil.

Not applied directly to coil?? Is he kidding? Coil is part of the circuit, it has copper losses etc.

Quote
That is the difference.  When this happens the voltage and any current being used are in phase.

It depends on the load, just like in transformer plugged into wall 24/7, reactive power passes through it all the time, if we connect a small load to it, v-i phase shift will fall from 89° to say 85°, but with bigger load it may get to 0 and coil becomes purely resistive.

Quote
Again this can be proven by connecting a scope across the leads of the coil and across the load.  The scope leads across the load will be measuring the voltage drop across the load and hence the current through the load.  If the load is a resistive load then the voltage and current will be in phase just as Verpies has said.  i am in the process of uploading a video that shows this.  I will post a link when it finishes uploading.

LOL, that's what i been saying for 4 pages already. Resistance brings i-v into phase, but he claims they can be in phase in purely inductive circuit WITHOUT resistance.
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citfta

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Re: AC voltage from single magnetic pole
« Reply #62 on: October 09, 2020, 05:40:51 PM »
Video link:


https://vimeo.com/466592675




Carroll
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nix85

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Re: AC voltage from single magnetic pole
« Reply #63 on: October 09, 2020, 05:43:27 PM »
Ha, that video, current through a resistor + resistance of the coil itself. What a mockery.

Once again.. he claims they can be in phase in purely inductive circuit WITHOUT resistance.

To at least approach these conditions with resistive wire, one has to use the method i gave above.

1. Separate coil to measure voltage.

2. Measure current with clamp probe.

3. AT LEAST 50 turns of thick wire.
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citfta

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Re: AC voltage from single magnetic pole
« Reply #64 on: October 09, 2020, 05:44:43 PM »
Quote from: nix85 on October 09, 2020, 05:28:24 PM


It depends on the load, just like in transformer plugged into wall 24/7, reactive power passes through it all the time, if we connect a small load to it, v-i phase shift will fall from 89° to say 85°, but with bigger load it may get to 0 and coil becomes purely resistive.




That is just not true.  I tried the same set up with several different loads and the current and voltage were always in phase.  Now YOU show us something that proves us wrong.


Carroll
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nix85

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Re: AC voltage from single magnetic pole
« Reply #65 on: October 09, 2020, 05:54:39 PM »
Quote from: citfta on October 09, 2020, 05:44:43 PM

That is just not true.  I tried the same set up with several different loads and the current and voltage were always in phase.  Now YOU show us something that proves us wrong.


Carroll

Which means you got too much resistance and capacitance in the circuit and you have proved nothing. Also you used way too low speed, inductive reactance is XL= 2πfL.

Let's bring in someone whom you deem an authority as proposed, let's hear his opinion if current lags voltage in purely inductive circuit when induction is done by moving magnet.

How bout Thane Heins, is he a member here?
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NdaClouDzzz

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Re: AC voltage from single magnetic pole
« Reply #66 on: October 09, 2020, 06:01:47 PM »
Quote from: citfta on October 09, 2020, 04:58:40 PM
So what happens when a magnet is moving past a coil?  The coil will have a voltage induced into it whether there is a load connected to the coil or not. This can easily be seen by just connecting a scope to the open leads of a coil and seeing the voltage on the scope...

Question: Does the scope not represent at least a little bit of load on the coil, and wouldn't using a separate sensing coil similar to that used in the following video be a more accurate test? https://youtu.be/hw2bBYYHp34?t=89
Thank you.
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citfta

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Re: AC voltage from single magnetic pole
« Reply #67 on: October 09, 2020, 06:11:43 PM »
Hi NDZ,


That is a valid question.  But the input impendence of a modern scope is typically several megohms.  And I was using the 10x position on the probe.  So any loading of the coil by the scope is so small as to be almost unmeasurable.


Carroll
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NdaClouDzzz

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Re: AC voltage from single magnetic pole
« Reply #68 on: October 09, 2020, 06:12:45 PM »
Quote from: citfta on October 09, 2020, 06:11:43 PM
Hi NDZ,


That is a valid question.  But the input impendence of a modern scope is typically several megohms.  And I was using the 10x position on the probe.  So any loading of the coil by the scope is so small as to be almost unmeasurable.


Carroll

Thank you.
Regards
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citfta

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Re: AC voltage from single magnetic pole
« Reply #69 on: October 09, 2020, 06:14:40 PM »
Quote from: nix85 on October 09, 2020, 05:54:39 PM
Which means you got too much resistance and capacitance in the circuit and you have proved nothing. Also you used way too low speed, inductive reactance is XL= 2πfL.

Let's bring in someone whom you deem an authority as proposed, let's hear his opinion if current lags voltage in purely inductive circuit when induction is done by moving magnet.

How bout Thane Heins, is he a member here?


You are the one making the claim.  I asked you to back up your claim and now you want someone else to bail you out.  Show us the proof you are correct!



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ramset

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Re: AC voltage from single magnetic pole
« Reply #70 on: October 09, 2020, 06:19:54 PM »
NX
We can always bother Thane


However this seems more mainstream ?


Would be good to get moderators from EE or Physics Forum


However there are some builds to discuss here?


Perhaps a quicker route


I am absolutely going to be connecting with
EE and Physics Moderators


Good to have such on standby


May take until next week
Open Source community has many such
Members
However I have never participated in the venues
“ they “ frequent


Asking for help to get this done!


Could be A regular feature perhaps to bounce weird observations off?



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nix85

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Re: AC voltage from single magnetic pole
« Reply #71 on: October 09, 2020, 06:22:58 PM »
Quote from: citfta on October 09, 2020, 06:14:40 PM

You are the one making the claim.  I asked you to back up your claim and now you want someone else to bail you out.  Show us the proof you are correct!

No, your friend is making a claim which deviates from common understanding, proof is on him/you.

In the midtime, observe the phase shift without and with load in ordinary and bi transformer

By Heins

youtube.com/watch?v=4_zgR5fyF30
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partzman

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Re: AC voltage from single magnetic pole
« Reply #72 on: October 09, 2020, 06:23:37 PM »
Nix,

This test was done using an air core coil arrangement that has L1 ~100 turn for the voltage sense coil with L2 ~20 turns wound directly on top of L1 resulting in a rather tight coupling of k~.95 or so.  A ceramic PM was moved by hand past the coil assembly with the resulting traces sampled on a Tek MDO using a Tek TCP0020 current probe for the current sense.

Ch1(yel) shows the voltage across L1 and CH4(grn) shows the current through L2 shorted.  It is obvious that the voltage and current are in-phase.

I would attach a pix of the test coil but my camera at the moment is dead but will supply a pix later if needed.

If you would like any changes made to this simple test, let me know as I can wind any configuration you would request apart from an SC coil.

Regards,
Pm
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ramset

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Re: AC voltage from single magnetic pole
« Reply #73 on: October 09, 2020, 06:24:34 PM »
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citfta

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Re: AC voltage from single magnetic pole
« Reply #74 on: October 09, 2020, 06:36:31 PM »
Quote from: nix85 on October 09, 2020, 06:22:58 PM
No, your friend is making a claim which deviates from common understanding, proof is on him/you.

In the midtime, observe the phase shift without and with load in ordinary and bi transformer

By Heins

youtube.com/watch?v=4_zgR5fyF30


Your link is not working.  But it appears you are trying to change the subject again.  We are NOT talking about transformers.  We ARE talking about a magnet inducing voltage and current in a coil.  And the picture just posted by partzman also confirms the voltage and current are in phase in a generating coil.



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