Back EMF vs Collapsed Spikes.....

[BEP]

@gyulason

A Schottky yes but even a Schottky isn't fast enough to recover all.
As far as what that circuit will do as a load of a cathode (emitter) follower - for every pulse you fire two will appear. The second will be incredibly short but possibly much higher amplitude. More pulses follow but they dampen quickly. I have seen flyback as much as 20 times the amplitude of the intended pulse. I've drawn a 1/2 inch arc from a 24VDC coil that had a bad snubber (It was a huge solenoid).

Lets say you have solved the CEMF problem and you are looking for flyback. Hit a coil with 1 watt of energy and open the switch (a very fast one) The field collapse potentially (pun intended) can produce almost 1 watt. If your first watt has already done its work then you have a free one comming back. I wish it was that simple!

BTW - there is a lot to consider on emitter followers. SS doesn't like that. You could wind up with oscillation and a popped tranny.

@Wattsup

Make sure you are looking at the video and not the coil diagram from me when trying to understand this. Using correct terms -  my circuit would not avoid CEMF unless it was open( no current flow when turned on ). Think of trying to compress a spring. Your push is the applied current. The spring pushing back is CEMF (not exactly but that is the idea - Newtonian magnetics).

The Cook style coils aren't interesting unless you have a sine signal source nearby overriding the -now- common 50/60 Hz noise. Mine always grew quiet if my fan was on. None of it made sense until I powered it with a battery or hit it with white noise.

Flipping your coil around will be the same handedness. Think about it for a moment.

[Nastrand2000]

so what I am understanding is that less resistance = more back EMF. BEMF being a counter force to the current flowing in said coil or wire. More resistance leads to a lower voltage collapse of the magnetic field stored in said coil or wire.
Jason

[BEP]

For the sake of clarity I'll correct your terminology (for any wanting to know - nothing against your wording).

Since we are talking about a coil of wire handling pulses or alternating current, -resistance is futile! - I just wanted to type that one

The correct term is inductive reactance - not resistance.

Take a look at http://www.tpub.com/neets/book2/4a.htm

Please note the value 2pi used in the formula. Unknown to many that is only valid when dealing with alternating current. That variable should be varied when dealing with pulses and must also consider duty cycle.

So, no. Less inductive reactance = less CEMF and also = less flyback voltage.

Flyback is the term I'm used to when talking about the reverse voltage generated by the collapsing field. I didn't run into the term BEMF until I dove into public free energy waters a few months ago. At best it is probably a 'mis-terminology' . I haven't researched this...

More inductive reactance could lead to less ?EMF if the reluctance is so high it prevents the field from building so it would have less to flyback -or collapse.

[gyulasun]

Bep, many thanks for your further comments.

In the video, I think there is an undefined situation (time 00:31- 00:48) when it shows you disconnect power, the field collapses and the (magnetic) poles reverse: for the poles to reverse should the created spike (the flyback pulse) see a closed circuit or not?  Do the magnetic poles change just because current is switched off in a coil?  Somehow this info if correct is new to me

There is another interesting practical circuit wrt bifilar coils to create high voltage with it as it were a high turn ratio transformer but in fact with low reciprocal property, unknown in usual step-up transformers,  see Naudin schematics on it here:
http://jnaudin.free.fr/html/tep4xfrm.htm
and the explanations here: http://jnaudin.free.fr/html/tep4xfrm.htm
and the low reciprocal effect here: http://jnaudin.free.fr/html/tep4nrcp.htm
I mention these because the circuit almost the same you kindly showed and also nicely fits to this topic as a practical example of utilizing collapsing field in bifilar coils.  (Naudin's Time Energy Pump concept is not important from our point of view now.)

I would have another question. What could happen with both the CEMF and the flyback pulse if I place a capacitor in parallel with the coil I excite with a pulse?  Say I deliberately create a resonant parallel circuit from an electromagnet's coil and choose the pulse frequency accordingly:  have you pondered on this situation?  One thing is sure: the incoming current would not see an inductive reactance hence the CEMF (Lenz) should be at a minimum and what about the flyback pulse's energy?  Will it swing inside the parallel circuit till losses consume it fully unless I do something to regain it?

Regards
Gyula

[BEP]

The poles reverse because the field is moving in the opposite direction ââ,¬â€œ collapsing instead of expanding.
Flyback is generated regardless of load or no load. If it is going into a high impedance load the voltage will remain high.

The referenced circuit is basically the same idea as mine except he will have some voltage increase. I wasnââ,¬â,,¢t looking for increase ââ,¬â€œ just some energy returned to the capacitor.

Adding a capacitor to an inductor only changes the times for field change. Actually you would have a tuned circuit or ââ,¬Ëœtank circuitââ,¬â,,¢. Nothing unusual about that.

Be aware of the action of current (Amps) when voltage is applied to an inductor or capacitor. Current leads voltage when power is applied to a capacitor by 90 degrees. Current lags voltage when power is applied to an inductor by 90 degrees.

What happens to CEMF and flyback?  CEMF is still there albeit slightly affected by the capacitorââ,¬â,,¢s charge time. Flyback is still there upon power removal but the capacitor holds a charge an lessens the effect greatly. When power is removed there will be some oscillation for a very short period as the energy equalizes across the tank circuit.