Back-EMF Manifesto - A Key, hidden in plain Sight.

[dieter]

Oh, and also important: the voltage height of the back-EMF highly depends on coil design, and therefor, the current will only flow backwards if it reaches a voltage higher than that of the supply. If it doesn't then, by means of logic, you are right. But it usually is higher. Often a multiple of the supply voltage.
Also important is a clean cutoff of the forward pulse.

[tinman]

Oh, and also important: the voltage height of the back-EMF highly depends on coil design, and therefor, the current will only flow backwards if it reaches a voltage higher than that of the supply. If it doesn't then, by means of logic, you are right. But it usually is higher. Often a multiple of the supply voltage.
Also important is a clean cutoff of the forward pulse.

First of all,your mixing up BEMF with inductive kickback.

Second---> 

the voltage height of the back-EMF highly depends on coil design, and therefor, the current will only flow backwards if it reaches a voltage higher than that of the supply.

Where can i get one of these overunity coils?.

To clear things up

BEMF is normally used when talking about the generating effect of electric motors.

CEMF is normally what we use when talking about inductors and coils.
The CEMF is of the same polarity as the current source that created it,but is always a lower value.
If it were the same value as the source EMF,then no current would flow.

Inductive kickback refers to the self induced EMF across any inductor/coil,when the source of the current to the coil is broken/interrupted/disconnected.
This self induced EMF from the inductive kickback,is of the opposite polarity to that of the current source that created it.


Brad

[PiCéd]

~2.64 watts?
https://www.youtube.com/watch?v=Gh6SBmwDsfk

[Magluvin]

author=Magluvin link=topic=17611.msg516966#msg516966 date=1519270261]


What is the reverse influence Mags?

Are you sure it's a magnetic field?

If we take a toroid core inductor for example-->is not the magnetic field contained within the core?
If so,then what field is collapsing inward around the wire ?

EMF is measured in volts--has nothing to do with current.

Brad

"What is the reverse influence Mags?"

Well after 'reverse influence' I have a comma and then I write CEMF, Counter 'Electro' Motive force' .  Not sure what is so hard to understand about that.


"Are you sure it's a magnetic field?"

Are you 'sure' it is something else? If so then please explain and or provide proofs otherwise.


"If we take a toroid core inductor for example-->is not the magnetic field contained within the core?
If so,then what field is collapsing inward around the wire ?"

For one, I dont believe that the magnetic field is only contained in the core of a toroid transformer/inductor.  My view of it is that the mag fields of the windings engage the core cutting across the hole in the middle of the core, thus cutting any other windings that also go through that hole..  And my view is that most all of the interactions between the windings happen in the hole of the toroid core. Ive said it before many times as to what i think on this stuff and nobody has presented any evidence to get me to think otherwise other than 'conjecture'. So maybe you have some proofs that can 'prove' me wrong as you are that one stating that the field only exists in the core.


"EMF is measured in volts--has nothing to do with current."

I get what you are trying to convey with that statement. What you are trying to say is that a changing magnetic field on a wire produces voltage in the wire and not causing moving currents in the wire of which could influence the voltages that we can read across that wire. E fields, right?  Show me proof.

Mags

[Magluvin]

Oh, and also important: the voltage height of the back-EMF highly depends on coil design, and therefor, the current will only flow backwards if it reaches a voltage higher than that of the supply. If it doesn't then, by means of logic, you are right. But it usually is higher. Often a multiple of the supply voltage.
Also important is a clean cutoff of the forward pulse.

"Also important is a clean cutoff of the forward pulse."

That statement is key to getting the reversal you speak of. Im glad you stated it.

I have gone over this before.  And I can agree that you have to have an absolutely clean cutoff in order to enable the possibility of an actual reverse current after cutoff.

Imaging this....  We apply input to the coil. Then we have a not so clean cutoff where a spark happens across the switch opening. That spark is part of the continued forward current I speak of.  So with an absolutely clean cutoff, the field collapse still generates a forward current, at first, but with the clean cutoff the self capacitance of the coil takes on the high voltage produced by the field collapse. Once it is peaked, it does a reversal like an LC resonator. Now when we had that clean cutoff, there was 'nowhere' for that voltage produced by the collapse to dissipate to other than the coil. So if you have an absolutely clean cutoff, and provide a path for the reverse currents to exit the coil after the forward current has peaked, then yes, you will have what you claim and I am in complete agreement with you that it can be had.

It would be a much easier conversation if you could show what you are doing to get the results you claim, as I can agree that it is possible you are getting reverse currents back to the source using a clean cutoff, but as to getting more back than you have put in, I cannot agree with that yet until you show it.

Ive been through this subject a lot over the years.  Im not here to claim that you are wrong, yet, because I dont know for sure what you are doing to get your results you claim.  Your statement of the 'clean cutoff' is where I have to agree with you 100%. But it is my contention that there is first a forward current in the coil before there is a reversal as you claim and it is not just only a reversal after the cutoff.  You can demonstrate this to yourself on any simulator as in a simulator a switch can give you that clean cutoff as you describe provided that in the sim your switch parameters can be set for infinite ohms when open. Then put the sim scope across the coil and you will see a forward spike and then the reverse spike..  And you can set up the circuit with a diode that can capture the forward spike and you wont see the reverse spike at all, demonstrating that the forward currents do happen firstly. 

Can you show us what you have going on so we can understand it better? It would be easier on everyone. 

Thanks

Mags