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

[tinman]

 author=dieter link=topic=17611.msg517053#msg517053 date=1519386197]

And about the use of the term "Back-EMF", the reverse current of a collapsing field

No-that is not BEMF-->that is inductive kickback,or flyback as some call it,and the current flow is in the same direction as it was when connected to the source.

as well as the inductive impact of a secondary field like in a motor (Lenz Drag etc.) it's both the same thing, only the cause is a diffrent one.

No,they are not the same thing at all.

,

Back- electromotive  force simply means, a force that drives the current in the opposite direction,

Wrong again.
BEMF is the self induced EMF an electric motor produces.
The lower the BEMF value,the higher the value of current an electric motor will draw.
The higher the BEMF value,the lower the value of current the motor will draw.

And what makes this harder,is bullshit like this
https://ipfs.io/ipfs/QmXoypizjW3WknFiJnKLwHCnL72vedxjQkDDP1mXWo6uco/wiki/Counter-electromotive_force.html--> For example, the voltage drop across an inductor is due to the induced magnetic field inside the coil.[1][2] The voltage's polarity is at every moment the reverse of the input voltage.

What a crock of shit that is.
The CEMFs polarity is the same as the sources polarity--not bloody opposite/reverse.
If it were opposite,then we would have a huge current draw as soon as we attached the source voltage.Just take two 1.5 volt batteries,and connect them so as the negative of one is connected to the positive of the other,then connect the remaining two end to each other--so connect the two batteries in series-->then see what happens.

Only when the source EMF is disconnected,do we get a reverse voltage across the coil,as the field is now collapsing.

No wonder so many people have a hard time trying to work all this out,when you have idiots posting shit like that on websites all over the internet.

[dieter]

Au contraire, Brad.


Look: When a coil attracts a magnet and thebmagnet gets closer, it's increasing fieldstrength seen from the coil causes inductive coupling that is REPULSING the coil, as Lenz's law holds true. So, to oroduce attraction in a coil you need one polarity, to oroduce repulsion you need thr other polarity - in the same one coil. No matter whether the current is induced via Lenz Law or simply by wires attached.
Once these two current directions fight afaonst eachother in the coil, of course, this means increased RESISTANCE for the current that comes from the wire, and hence, as you stated, less current draw, WHILE THE MOTOR SLOWS DOWN and to maintain the RPM and torque, you will need to increase the Power from the supply to the coil.


This isn't so much about you being wrong, but much more about a somewhat pathetic attitude to jump in and call people idiots, "proofing" that every word they say is wrong while diverging from the thread subject.


If such a mood issue is something infective around here, then I am seriously concerned about this forum.

[citfta]

Dieter,

If you will read all the way through the following thread you will understand that the current does NOT reverse when the field collapses.  And the proper term is inductive kickback NOT back EMF.  There are many of us on this forum that have many many hours of research time on our benches.  As Brad has been trying to tell you your ideas are not supported by the test results.  This thread will help you get a better understanding of coil inductance and field collapse.

http://overunity.com/16203/inductive-kickback/#.WpBI2rNG3IU

Respectfully,
Carroll

[tomd]

This article explains clearly the effects of a collapsing magnetic field.
First you have the emf/current (in the direction of the original applied voltage source) induced from the collapsing magnetic field.
Second as a result of the current from the collapsing magnetic field there is a cemf against the direction of the induced emf and therefore against the original voltage source.

"Finally, the applied voltage is removed--made to equal Zero (Vapplied = 0 volts); the steady-state Magnetic Field now starts to collapse, which induces an E.M.F into the inductor thus causing a Current to flow (of the same polarity as that of the original applied voltage source). As in the applied case there is a Counter E.M.F. generated by the Current generated from the collapsing Magnetic Field, again impeding the collapse of said Magnetic Field."

http://www.williamson-labs.com/480_rlc-l.htm

[tinman]

This article explains clearly the effects of a collapsing magnetic field.
First you have the emf/current (in the direction of the original applied voltage source) induced from the collapsing magnetic field.
Second as a result of the current from the collapsing magnetic field there is a cemf against the direction of the induced emf and therefore against the original voltage source.

" As in the applied case there is a Counter E.M.F. generated by the Current generated from the collapsing Magnetic Field, again impeding the collapse of said Magnetic Field."

http://www.williamson-labs.com/480_rlc-l.htm

Finally, the applied voltage is removed--made to equal Zero (Vapplied = 0 volts); the steady-state Magnetic Field now starts to collapse, which induces an E.M.F into the inductor thus causing a Current to flow (of the same polarity as that of the original applied voltage source).

No
When the applied voltage is removed,the collapsing !magnetic ?! field induces a voltage across the coil that is of the opposite polarity to that of the source voltage.
The current will continue to flow in the same direction.