Confirming the Delayed Lenz Effect

[TinselKoala]

Yep.
The MoI of the rotor can usually be calculated quite accurately from the geometry and the material densities involved, and then the power dissipation required to turn the rotor at any given RPM can be determined by timing unpowered rundowns. A chart recorder (or a modern DSO that has a long-duration "chart recorder" mode)  is a definite asset for this kind of work.
http://www.youtube.com/watch?v=PJavCZX_-PI

Alternatively, a known load like a model airplane propeller can be used to determine the power dissipation.
http://www.youtube.com/watch?v=2koW-oC5hJs

[MileHigh]

If somebody wants to be really adventurous there is an interesting observation they could try making on their scope.

You pulse a coil and you can observe the exponential rise in current through the coil.  Nothing new there.

But can you see something different happening when you pulse a coil to keep a rotor turning?  The answer is yes, you should see that the current rises more slowly than expected - possibly??? - or possibly something else happens.  Note that the instantaneous voltage across the coil times the instantaneous current though the coil is the instantaneous power being pumped into the coil.  And the instantaneous power over the time that you are pulsing the coil represents the total energy you put into the coil.  That's the energy that you see when you get the back-EMF spike.  Or is it?

You know intuitively that when the drive coil is making the rotor turn, that means that the coil is exporting energy and transferring that energy into the spinning rotor.  Therefore, you have to expect that when you pulse the coil and pump power into it, and the coil is driving the rotor, that _some_ of the instantaneous power must be going into the rotor, somehow.  Can you observe this phenomenon with your scope?

So since you know that the coil is exporting energy to the rotor, that means that something must be different in the current waveform for the coil when it is driving the rotor.  You know this because the voltage waveform is a constant, so the current has to change.  Again, can you observe that on your scope?  Is there a way for you to develop a test that definitively shows that the the waveforms that you are observing for the coil clearly show that the coil is driving the rotor.  It's almost like there should be some observable "phantom" energy that you put into the coil, but you can't get it back in the back-EMF spike because some coil energy made the conversion over to rotational mechanical energy in the rotor.

Just some ideas in case anybody wants to open up some new territory.

MileHigh

[Farmhand]

If somebody wants to be really adventurous there is an interesting observation they could try making on their scope.

You pulse a coil and you can observe the exponential rise in current through the coil.  Nothing new there.

But can you see something different happening when you pulse a coil to keep a rotor turning?  The answer is yes, you should see that the current rises more slowly than expected - possibly??? - or possibly something else happens.  Note that the instantaneous voltage across the coil times the instantaneous current though the coil is the instantaneous power being pumped into the coil.  And the instantaneous power over the time that you are pulsing the coil represents the total energy you put into the coil.  That's the energy that you see when you get the back-EMF spike.  Or is it?

You know intuitively that when the drive coil is making the rotor turn, that means that the coil is exporting energy and transferring that energy into the spinning rotor.  Therefore, you have to expect that when you pulse the coil and pump power into it, and the coil is driving the rotor, that _some_ of the instantaneous power must be going into the rotor, somehow.  Can you observe this phenomenon with your scope?

So since you know that the coil is exporting energy to the rotor, that means that something must be different in the current waveform for the coil when it is driving the rotor.  You know this because the voltage waveform is a constant, so the current has to change.  Again, can you observe that on your scope?  Is there a way for you to develop a test that definitively shows that the the waveforms that you are observing for the coil clearly show that the coil is driving the rotor.  It's almost like there should be some observable "phantom" energy that you put into the coil, but you can't get it back in the back-EMF spike because some coil energy made the conversion over to rotational mechanical energy in the rotor.

Just some ideas in case anybody wants to open up some new territory.

MileHigh

I agree MileHigh and thanks for the info Tinsel, I have done a rough test to show less energy recovered when a rotor is loaded more, more load on the rotor less energy recovered. The coil does give energy to the rotor, the rotor does not get spun with no expenditure of energy after recovery even considering losses in other areas like diodes and resistance.

I can show on my scope with this motor that when I put the charging coil in place the voltage it produced into the cap for the drive coil is less, just a bit but it is clear. I'll find the video and note the time of it. I did show it I think. People don't see it though. The recovered energy is less because the coil gives energy to the rotor.

Cheers

[MileHigh]

Farmhand:

The person you quoted:

But I was told that there is a delay because of the inductance, I was told that for a small period as the magnetic field is building there is no current leaving the coil but there is current entering the coil.

That's a metaphysically wrong statement.  Current entering one side of the coil is equal to the current leaving the other side of the coil.

I will mention this and you might get the analogy (I have said it a million times before).   A coil stores energy.  A flywheel also stores energy.  So imagine the current through the coil is going around in circles through the coil.  That's just to help you remember the analogy:  The current flow through a coil is analogous to the the rotational speed of a flywheel.  Then part two of the analogy is that the voltage across the coil is like the torque on the flywheel.

Then for dramatic effect:  The analogy is absolutely real, they are essentially identical.

So, any circuit that you can dream up with a coil I can explain to you how a flywheel can fit into that circuit.  (We are excluding transformer coupling between coils here, but everything else is fair game.)

What this really means is that an inductor is juts an electrical version of a flywheel, and by the same token, a flywheel is just a mechanical version of an inductor.

This takes the "magic" out of coils and brings them into the real world.  Anything a coil can do a flywheel can do, period.

If you are lost and you can't make the connection or envision a thought experiment, then let me give you a starting point.  What about the infamous back-EMF spike.  How the hell does that relate to a flywheel?

Please think about it for a few days.

MileHigh

[Farmhand]

OK found it, from 7:20 in the linked video, first we see the cap voltage at 23.6 volts, then I move the charging coil away from driving the rotor and the cap voltage increases
to 26 volts at 8:06, the pulse width remains constant, but the rotor slows when the charging coil is moved away and the cap voltage rises. When the charging coil helps to drive the rotor energy is transferred to the rotor by the from coil/core/field.

http://www.youtube.com/watch?v=w1_KlgJ09Bs&list=UUBXqDE_ub_PAQRA9LfStmtA&index=4

Cheers

P.S. This is the waveform from my current setup at low speed with double pulses. I have changed the circuit a bit so that the charge battery is in series with the charging coil after the diode. It discharges into two levels looks like. Just looking at one event waveform. Can you see what is happening ?