Sharing ideas on how to make a more efficent motor using Flyback (MODERATED)

[woopy]

Hi Synchro

Very nice explication
Have you some links on the subject for my info

Thank's

Laurent

[gotoluc]

I accept that challenge.
But i can tell you now with some certainty that a low impedance secondary coil will perform better due to lower resistive losses

Glad you accept!

And I would not argue with you that low impedance coils are more efficient since they have next to no resistance but the tradeoff is they have next to no inductance.
I'm suggesting we use the ideal qualities of each (tuned) at the appropriate time to achieve a longer flux holding time to switch a PM flux gate with less input power then just a low or mid impedance coil.

So no need to build a motor, just a flux gate will do. As we know a flux gate will make a motor work and what we need is one that can work with less power input so we get the magnets to do most of the work.

This is what I'm ideally proposing and thought I would make it clear before you start your build.

Thanks for your participation and looking forward to your results

Luc

[gyulasun]

....
My beginner's knowledge indicates that, during the pulse, the main (low voltage ) motor coil, get a certain amount of electric energy (voltage and current) from the power station. This energy is dissipated for a small part in  heat due to the impedance of the coil and for the main part in building a magnetic field . During the building of the magnetic field its magnetic strength increases with the increasing current in the inductor and propels the rotor magnet which get kinetic energy.
So it seems to me, that at the end of the pulse, all the electrical input energy should have been transformed in some heat and the kinetic energy of the rotor, yes or not? And  the magnetic field seems to stay there at its max strength until the end of the pulse. yes or not?
Than it seems commonly admitted that at the end of the pulse, the magnetic field brutally collapses and creates the flybackspike.
But if the input energy is totally dissipated at the end of the pulse, how does the collapsing magnetic field create this powerfull flybackspike ? What is the process ?
....

Hi Laurent,

During the time a magnetic field is building up in your coil (input current is ON) and starts to propel your rotor, the field is not fully used up at all in the process (some small part of the field strays away, this depends also on the mechanical construction), just like the field of a permanent magnet is not used up in a normal magnetic interaction.
Of course, normally the action-reaction force rules between the rotor and the magnetic field created from the input energy: if you try to brake the movement of the rotor, input energy consumption increases during the ON time of the input current (Lenz law). 

It is known that an inductance tries to resist to any current change. (A capacitor tries to resist to any voltage change across it). 

In this link I think the "why" i.e. why a coil resists to any current change) is correctly explained:

http://www.allaboutcircuits.com/textbook/direct-current/chpt-15/magnetic-fields-and-inductance/

Quote from the text:

"Because inductors store the kinetic energy of moving electrons in the form of a magnetic field, they behave quite differently than resistors (which simply dissipate energy in the form of heat) in a circuit. Energy storage in an inductor is a function of the amount of current through it. An inductor's ability to store energy as a function of current results in a tendency to try to maintain current at a constant level. In other words, inductors tend to resist changes in current. When current through an inductor is increased or decreased, the inductor "resists" the change by producing a voltage between its leads in opposing polarity to the change."

Perhaps these can explain better what may happen and helps you.

Gyula

[MileHigh]

With and without the capacitor. It's much the same as to why a vehicle going a set speed can be stopped quicker if you dont lock up the brakes and skid the wheels. Voltage leads current in an inductor,and if the applied voltage pulse is to quick and short,then there will be very little current that follows. However,if that spike is sent to a capacitor where the current leads the voltage,then you can be assured that the inductor will receive all of the !now stored! energy from that inductive kickback that was stored within the cap.

Yes, but you still have the mystery of where the pulse of energy from the drive coil goes and why at least when Luc holds the metal slab in his hands the magnetic attraction is imperceptible.  It doesn't mean it's not there, but at least to his hands it's imperceptible.  When you do a preliminary analysis in your head you would have an expectation that he might feel something.

Voltage leads current in an inductor,and if the applied voltage pulse is to quick and short,then there will be very little current that follows.

Let's try to be a bit more precise with your explanation.  You have to remember, it's not a voltage pulse, it's a current pulse.

For starters, what happens when coil A discharges into coil B, where the initial conditions are there is some current is flowing in coil A, let's say it's one amp,  and zero current flowing in coil B.  Let's say both coils are one Henry of inductance.  That analogous to what the situation is like in Luc's setup when there is no capacitor.  Anybody want to try to answer that?

[MileHigh]

My beginner's knowledge indicates that, during the pulse, the main (low voltage ) motor coil, get a certain amount of electric energy (voltage and current) from the power station. This energy is dissipated for a small part in  heat due to the impedance of the coil and for the main part in building a magnetic field . During the building of the magnetic field its magnetic strength increases with the increasing current in the inductor and propels the rotor magnet which get kinetic energy.
So it seems to me, that at the end of the pulse, all the electrical input energy should have been transformed in some heat and the kinetic energy of the rotor, yes or not? And  the magnetic field seems to stay there at its max strength until the end of the pulse. yes or not?
Than it seems commonly admitted that at the end of the pulse, the magnetic field brutally collapses and creates the flybackspike.
But if the input energy is totally dissipated at the end of the pulse, how does the collapsing magnetic field create this powerfull flybackspike ? What is the process ?

Laurent,

Your analysis is basically correct and I will "fill in some of the blanks" for you.   For starters, this statement, "This energy is dissipated for a small part in  heat due to the impedance of the coil and for the main part in building a magnetic field." should read as, "This energy is dissipated for a small part in heat due to the resistance of the coil and for the main part in building a magnetic field."

The impedance of the coil is associated with its inductance and stores energy, it does not dissipate energy and turn it into heat like a resistance.  So "impedance" and "resistance," although somewhat related because they are both associated with the blocking of the flow of current, in fact they are separate and distinct terms that should not be interchanged with each other.

So it seems to me, that at the end of the pulse, all the electrical input energy should have been transformed in some heat and the kinetic energy of the rotor, yes or not? And  the magnetic field seems to stay there at its max strength until the end of the pulse. yes or not?

You are essentially correct.  The electrical input energy goes to three places:  1) heat energy, 2) kinetic energy of the rotor, and 3) the BEMF pulse energy.

The magnetic field is not at it's max strength at the end of the pulse.  If the drive coil gives a big kinetic energy push to the rotor, then at the end of the constant-voltage energizing pulse from the reed switch there will be less current flowing through the coil.   In other words, without the rotor in place, then there will be more current flowing through the drive coil at the end of the constant-voltage energizing pulse from the reed switch.

You actually see this effect in your own clip, and I made reference to it in the form of a question but nobody responded.  Please review your clip and see if you can find any evidence for this effect.

But if the input energy is totally dissipated at the end of the pulse, how does the collapsing magnetic field create this powerfull flybackspike ? What is the process ?

As indicated above, the input energy is not totally dissipated at the end of the constant-voltage energizing pulse from the reed switch.  Some of the input energy remains at the end of the pulse on the rotor and it becomes the flyback pulse.

It goes full circle to what I said before:  How much energy is in the main drive pulse on the rotor from the drive coil?  How much energy is in the flyback pulse?  How do I measure and compare the two?