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

[MileHigh]

Hi MileHigh,

I would like to understand what you mean by magnetic fields cancelling each other out when the coils have air between them?

I think that bucking or repelling magnetic fields try to push away each other, towards sideways. The closer to each other the repel poles get,
the more compressed (squeezed) the fields become and they come out from the gap towards sideways and then spread out again.

Long time ago I downloaded from a now defunct yahoo group some measured flux data (collected by a flux meter probe) on the surface of
ceramic magnets that included the repel mode between them too, see attached. (I cannot recall who uploaded it back then, unfortunately.)
In those measurements the magnets were fully pressed to touch each other surfaces when they were in repel mode. It is interesting that
the squeezed-out North fields have more than twice measured field values on the touching surfaces than the sum of the
two North field values of the individual magnets.

When there is a small air gap left between the facing surfaces, (still no entering slab of metal),  the flux from both magnets should be there
(albeit in a less squeezed form) and repel force would still be there of course between the facing cores as per the gap size would control it.

When the slab of metal approaches the two magnetically bucking cores, the bucking fields from both cores will attract the slab
(more or less equally if their fields are pretty close to each other in strength).

So how do you mean the magnetic fields cancelling each other out when the coils have air gap between them?

Thanks
Gyula

Gyula,

I think that you are just forgetting the basics for a momentary lapse.  The only thing that two separate magnetic fields do is vector addition.  So for those that may not understand that means the two magnetic fields act like the other field doesn't even exist, the two fields just pass right through each other.  You just add the two fields together to get the net magnetic field.

So, if you have a magnetic field going horizontally left to right, and another magnetic field going horizontally right to left, you just add them together.  Because of their respective directions, they cancel each other out.

Therefore, there is no squeezing or compressing going on like you are alluding to.  The people in the Yahoo group led themselves down the proverbial garden path.

Okay, in the next posting let me deconstruct the image you posted from the Yahoo group.

MileHigh

[MileHigh]

When you look at the measurements for the individual magnets, what is seriously missing is the orientation of the Hall sensor.  That is a major mistake but we can live with it.  We are going to assume that the Hall sensor is always placed parallel to the surface of the magnets.

Looking at the rectangular shape of the magnets, you can see increasing field strength going towards the corners of the magnets.  However, they fail to make any measurements at the corners themselves for the individual magnet fields, but effectively they do do corner measurements when making the combined magnet field measurements.  However, we can make some reasonable extrapolations with the data and arrive at a satisfactory conclusion.

For the individual magnet fields, we are pretty certain that the strength is the strongest at the corners, and we are pretty certain that the angle of the magnetic field emanating at the corners is roughly 45 degrees.  Let's assume for the sake of argument that a Hall sensor placed normal to the 45-degree-angle field at the corners will measure 1760 units of Gauss.  It seems perfectly reasonable because the measurements close to the corners are are between 1000 and 1100 Gauss and we can assume that the Hall sensor was placed parallel the surface of the magnet.  If the Hall sensor in that position was actually normal to the magnetic field you would measure a higher Gauss value, perhaps around 1400 units of Gauss.  So it is perfectly reasonable to assume about 1760 units of Gauss with the Hall sensor normal to the magnetic field.

So now let's look at the junction of the two magnets where the Hall sensor measures about 2500 units of Gauss.  Again, we will assume that the Hall sensor is parallel to that surface.

You have two magnets with 1760 units of Gauss at the corners at a roughly 45 degree angle.  Therefore you divide each measurement by the square root of two to get the individual components of the magnetic fields that are normal to the Hall sensor.  Therefore each magnet contributes about 1245 units of Gauss normal to the Hall sensor.  There are two magnets and therefore you get 2490 units of Gauss normal to the surface of the magnets.  This is also normal to the Hall sensor that is assumed to be parallel to the surface of the magnets at that position.  That is in line with the measured values of 2486 and 2680 units of Gauss in the Yahoo data.

So you can see it all works out.  By looking at the Yahoo data and making a few inferences and reasonable assumptions everything checks out as it should.

[MileHigh]

Hi MileHigh,

I would like to understand what you mean by magnetic fields cancelling each other out when the coils have air between them?

When there is a small air gap left between the facing surfaces, (still no entering slab of metal),  the flux from both magnets should be there
(albeit in a less squeezed form) and repel force would still be there of course between the facing cores as per the gap size would control it.

When the slab of metal approaches the two magnetically bucking cores, the bucking fields from both cores will attract the slab
(more or less equally if their fields are pretty close to each other in strength).

So how do you mean the magnetic fields cancelling each other out when the coils have air gap between them?

Thanks
Gyula

Let's do a thought experiment that anybody can replicate in real life.  You have two long and thin bar magnets, where one is slightly stronger than the other.

You set up the magnets like this:   [S============N]        [N=============S]

As the two magnets are brought together you feel increasing repulsion.  Then at a certain close distance from each other you feel nothing, no repulsion or attraction.  That is where the opposing north fields have cancelled each other out.  Then as you bring the two magnets closer together they are lightly attracted and the two north ends stick together.  This is where the stronger magnet has dominated over the weaker magnet and there is a small net magnetic field and a small attraction.

From the side view in Luc's setup, looking at a cross-section, you have two "E" cores facing each other.

If the metal slab is not between the cores, you have a wide air gap between the cores.  In this case much less flux produced by one core crosses the air gap and goes into the facing core.  Nonetheless, some flux will cross over into the facing core.  Whatever flux produced by the left core that goes into the right core will cause cancellation in the flux produced by the right core.  Likewise, whatever flux produced by the right core that goes into the right core will cause cancellation in the flux produced by the left core.

When the metal slab is in place, there is much less of a reluctance gap between the two "E" cores and therefore there will be correspondingly more flux going from the left core into the right core, and vice versa.  Hence, less overall inductance, less attraction for the slab, and more of the wire proportionally in the pair of coils that only functions like a resistor and not like an inductor.

If the two "E" cores produce additive magnetic fields, then one must assume that the attraction of the slab will be that much stronger and presumably balanced enough so that the slab does not scrape against one of the "E" cores.  In effect, for this setup, and for the bucking setup, the slab is dragged down into the bottom of a magnetic potential well, and then at TDC (or just before TDC) you stop energizing the coils to make the magnetic potential well disappear.  If the two coils are additive instead of bucking, one assumes that the slab will fall into a much deeper magnetic potential well and have much more kinetic energy as a result of the steeper fall into the well.

I asked Luc to try an additive instead of a bucking configuration but I don't think the question was acknowledged.  I would be very surprised if I missed something in my analysis.  From what I can see bucking coils in this configuration will work, but not be nearly as well as additive coils.  The wild card is that with the stronger magnetic forces, will the slab hit one of the "E" cores or not?

MileHigh

[gyulasun]

Dear MileHigh,

I have been busy for a while but will answer to you tonight or tomorrow morning, please bare with me till then.

Thanks,
Gyula

[wattsup]

@gyulasun

Thanks for your comments and I will answer them in bold.

Hi wattsup,

My "2 cents" answers  on your questions. I repeat here your questions:

"1) If you run an electric motor or transformer with AC, A) is there flyback, or, B) is flyback strictly present after a DC pulse only?
2) If #1 is A or B or both, why?"

Answers:
1) I do not think there is flyback with AC input so my answer is B

2) only the B because with a normal (50 or 60 Hz or whatever frequency) sinusoidal input voltage there is no interruption of the input current (zero crossing yes but it is not sudden).  Flyback pulse is strictly associated with a switch-off event under which no input current is drawn from the the input source which normally provides the input current during the ON times.  Again, the zero crossing event is not equivalent at all with a switch-off event by a dedicated switch.


Thank you very much for your answers which where exactly as one would hope to have in our present days.
My answer is written but is too long and I do not want to clutter @gotolucs' thread. haha
I will post in my own thread when it's time with your answers and my response.


Regarding your suggestion on using a 3rd primary MOT coil in series with the paralleled ones:  the use of this coil increases the overall impedance of the whole setup and as such you have to increase a little the input voltage to compensate for the reduced input current what this increased impedance causes. It is okay that you would receive flyback energy from the 3rd coil too, question is would this give more juice than what the increased input cost?  needs testing.

You wrote earlier that the 10 V or so input voltage level is rather low with respect to the mains 110-120 V these MOT primary coils were designed for originally. Here comes again that Luc drives these coils with pulsed DC and not AC, notice the pulsed DC involves already several Amper peak currents when the voltage level is at the 10 V area, while normal AC drive at 110-120 V input would result only in some hundred mA maximum or less input current levels (assuming no load condition).

One more thing: these "transformers" have open magnetic cores, rendering the original primary coil inductances much less than a closed core insures, and add to this the bucking magnetic coupling which further reduces the resulting inductance. The I core entering the gap between the two open cores increases this lowered coil inductance as we learnt from Luc inductance measurements, this is good.

Gyula


The added impedance is peanuts compared to what the added primary will do for the two working primaries on the wheel. As I had shown in my Half Coil Syndrome videos, by adding a second coil in series, the first coil displays a much higher action through the coil where the first coil will display a much larger single polarity. This single polarity would be more advantageous in @gotolucs case where his two primaries are on "open cores" as you so well defined. Right now the open core has a primary coil that has two polarities hitting it with no where to go and I suspect there is a good portion of the combined polarities that are simply cancelling each other out in relation to the passing plate. So by adding the third primary, this pushes one of the polarities out of the first two and into the third, thus this will lower cancellation potential in the working coils and increase the attraction of the passing plate.

Also, at pulse open, the side that is always connected (third coil) will rebias the first two primaries much more fully thus preparing the coil and core for the next complete change in polarity. I know you guys stand by the never proven, but always can I say "blindly" accepted, notion that the two primaries will produce a magnetic field and it is this field that will attract the passing plate, but in Spin Conveyance theory, this is not the case. It is the iron and copper atoms that do all the work. All that is required is to produce a change in the atomic alignments and the more change that is produced the more attraction it will produce simply mass to mass without any field requirement. I will explain this further soon because I do not want to use @gotolucs thread on anything off topic.

wattsup