AC voltage from single magnetic pole

[citfta]

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

[nix85]

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.

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.

......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.

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.

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.

[citfta]

Video link:


https://vimeo.com/466592675




Carroll

[nix85]

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.

[citfta]

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