STEORN DEMO LIVE & STREAM in Dublin, December 15th, 10 AM

[Airstriker]

Why wouldn't you want the magnets to completely saturate the core? Think about it a bit. When the magnets saturate the core, the core becomes a magnet and its external B field is oriented for maximum attraction to the magnets, thus providing maximum torque.

Wrong. Saturated core doesn't become a magnet. Saturated core has very little permeability. And permeability is a factor that tells you whether something is magnetically atractive or not. Low permeability means not a magnet at all ;]
And as for why I woudn't want the magnets to completely saturate the core... I simply don't believe that you can make the core fully saturated by magnets alone just right at the TDC and not at any point earlier. If you did it earlier than at TDC, you would simply loose torque. What's more... I don't think that you can flip (or rotate as you call it) all the domains of the core (meaning full saturation) by only using magnets and no matter how strong these magnets are. If I'm wrong I would like to see that happening on some video, FEMM simulation or something ;] I was not able to do it in FEMM.

There is no need to fully saturate the core when there is a large gap between the magnets and toroid.  This is just wasted energy.

That is also wrong. If you don't fully saturate the core you will not have any significant permeability change (drop). So the core will remain fully atractive and the rotor will brake.

The conclusion should be: You have to saturate the core to have the rotor going. The question is: Is it possible (and needed) to use the remanence of the core ?

In my opinion the difference: (Bsat - Br) for most materials is too little to use it. I mean use it in a way that the core doesn't saturate by magnets alone and still have a good amount of torque.
Notice one thing. Wouldn't it be much easier (and better), if you went through the whole hysteresis loop and use such magnets, that can saturate the core to the point, where B = something like Br ? This way you would end up with the same effect as if you would be using only the Br to Bsat part of hysteresis loop (use remanence as suggested by 0c).

Pitty Paul has left the forum (to be honest a bit childish and irresponsible move it has been); I just wanted to ask him for some simulation files cosidering toroid coil and magnets interactions. Would be nice to do some 3D simulations as only in this way we could trully see what's going on. Maybe somebody here has some 3D FEMM software ? (And knows how to use it hehe )

[0c]

My Response:  The reason why it appears to have very little remanence is because the core material is returned to its virginal state.

ie. very little remanence.

On the linear portions of the curve, "B" and "H" are proportional to the voltage and current by a constant.  This means the voltage and the current remains constant and doesn't require additional energy the deeper into the linear portions you go.

There is no direct relationship between voltage (electrical pressure) and any part of the BH curve. Current (the flow of electrons) is the only factor. Additional voltage (pressure) can be applied at the beginning of the pulse to help get the current flowing. Once flowing, there is indeed a constant relationship.

This is the easy axis.

Most BH graphs are designed to show the best characteristics of the materials being tested. That invariably means the material will be magnetized in the easy axis. There are some studies out there that show the difference when the material is magnetized in other directions.

The 4th and 5th paragraphs below the second image of the page, http://www.beigebag.com/case_xfrmer_4.htm , you will find how "B" is related to the voltage by a constant and "H" is proportional to the current when you're on the linear portions of the curve.  The flat portions representing the saturation area is not linear or related by a constant but is related by an integral.

From the page you referenced, 4th paragraph:
"In the B-H curve, B is proportional to voltage, and H is proportional to current."

You can imply some relationship to voltage if you like. Sorry, I don't see it that way. Current is the only factor I see.

The author of this page is claiming to be an expert on Cores and Transformers.

This is not a transformer. It is an electromagnet.

My Response:  There is no need to fully saturate the core when there is a large gap between the A and toroid.  This is just wasted energy.

How is it wasted? The saturation is acquired as a side effect of the magnet approaching the core and producing torque at the same time. No external energy is required to achieve this. It happens automagically. The external power is only required to "reduce" the attraction on the way out and only depends on the difficulty of rotating the domains approximately 90 degrees, so the field is reoriented in a circumferential direction and mostly constrained within the toroidal material.

Just knowing that it is related by an integral should tell you that it's going to require more energy the deeper you go into full saturation.  On the linear portions, the energy requirements don't increase the deeper you go into the linear regions, which will lead right up to the "knee" or transitional area.

I will agree the higher the level of saturation, the more power is required to saturate further. And "complete" saturation is not required to acieve our goals. For purposes of maximizing the return from the inductive spike, what's important is the "difference" in effective permeability when the magnet is at TDC and when it is farthest from the core.

WRT reducing the undesired attraction to the magnet as it departs, rotating the core's magnetic field so it is mostly contained inside the toroid is probably the most important concern. The saturation level is also a significant consideration. It's a tradoff and I'm not sure where the best balance is.

The fastest current rise will happen with minimum induction (maximum saturation). Easiest domain rotation will occur above the knee. Maximum reduction of magnetic attraction will occur at full saturation.

At this position, the magnets won't be attracted to the toroid because full saturation isn't needed due to the gap between the toroid and magnets.

The attractive force will decrease significantly with distance. But remember, that's what gives us our torque as well. Maximum torque is up close. It's another tradeoff.

It's going to be hard to find the optimum balance.

[0c]

Wrong. Saturated core doesn't become a magnet. Saturated core has very little permeability.

The B field represents the external magnetic field. Where is the B the greatest? At saturation. This is where the maximum external magnetic field is available.

Wrap some wire around a nail and see where it becomes strongest.

And permeability is a factor that tells you whether something is magnetically atractive or not. Low permeability means not a magnet at all ;]

Nope. Low permeability means it has less ability to become more magnetized than it currently is. Take a Neo magnet, for example. The permeability is almost minimum, just a bit higher than air. It will be very difficult to magnetize it more than it already is. In remanence, it has a very high magnetization, not very far from saturation.

And as for why I woudn't want the magnets to completely saturate the core... I simply don't believe that you can make the core fully saturated by magnets alone just right at the TDC and not at any point earlier.

Depends on the material, the A and strength of the magnets, and the distance. In the supplemental Steorn demo, the core was almost completely saturated when in contact with the magnet. Some materials saturate easily, Metglas saturates at a much lower B than Finemet.

If you did it earlier than at TDC, you would simply loose torque.

No argument.

What's more... I don't think that you can flip (or rotate as you call it) all the domains of the core (meaning full saturation) by only using magnets and no matter how strong these magnets are.

Flipping the domains is getting them to all align so like poles are facing in the same direction, all N poles pointing the same way.

Rotation is changing the direction all those poles are pointing.

Flipping is a lot of work. Rotation is considerably easier.

If I'm wrong I would like to see that happening on some video, FEMM simulation or something ;] I was not able to do it in FEMM.

I offered a little experiment a few posts back, so you can do it and see what I mean.

That is also wrong. If you don't fully saturate the core you will not have any significant permeability change (drop). So the core will remain fully atractive and the rotor will brake.

Do you have a steel washer handy (a simple ferromagnetic toroid)? Stick a neo magnet to the edge. The washer becomes a magnet and the far edge will act just like the magnetic pole that it is. Remove the magnet and wrap a few turns of wire in a toroidal fashion and briefly touch the ends of the wires to the terminals of a battery. The washer will again become magnetized but it won't seem to attract other iron or steel objects. Why not? Because the field is contained entirely within the donut itself.

That's what is required to release the rotor magnet. The toroid's magnetic field A to be completely contained and the affinity of the core to external magnetic fields (permeability) needs to be reduced as much as possible.

The conclusion should be: You have to saturate the core to have the rotor going.

Not completely, but the more saturated it is, the less resistance there will be to the rotor.

The question is: Is it possible (and needed) to use the remanence of the core ?

That's one of the questions I have been asking. I don't think we know the complete answer yet. It is possible, but does it actually do any good? The images in my head indicate that it should reduce the input energy required for the coil to saturate the core. They also indicate that the rotor magnet will experience greater torque.

In my opinion the difference: (Bsat - Br) for most materials is too little to use it.

You're missing the point. The Br means the core is already partially saturated. Bsat - Br represents the amount of work required to fully saturate, and believe me it's a lot less work than would be required to go from B=0 to Bsat.

[freeorbo]

Wow OC nice post! You're making a lot of sense here.

I agree also with what you're saying about the coil's function - it's to totally occupy the magnetic potential of the core. orbo is the exact opposite of an electromagnet. You're using current to keep magnetic fields from interacting.

I really don't think there is one secret ingredient to an Orbo interaction. It's a combination of factors. The Orbo that they are showing at Waterways is NOT the only way to demonstrate the phenomenon. It's a configuration that they figured out, working backward from their original discovery, and that's important to remember.

There's a way to do this all without toroidal coils.

Steorn themselves never say it's about the coils. They say

"Orbo is based upon time variant magnetic interactions, i.e. magnetic interactions whose efficiency varies as a function of transaction timeframes."

So my interpretation of that phrase is that during this 1/200th of a second interaction as the magnet passes the coil, the magnetic potential between the magnet and the core goes from basically zero to full.

It doesn't just appear at full; it builds. And that building of the field is what is causing your energy gain.

You're building the field and using it's magnetic potential to do work without having to have an equal amount of work to remove the field again.

Imagine a spring that takes a pound of force to compress and then lifts a 2lb weight.

I really feel that the core is a bit of a red herring here. It's just  the mechanism in this particular configuration.

The "magic" of Orbo seems to be that you can suppress the field (compress the spring) when the interaction between the magnet and core are distant and therefore less potential energy is between them.

And then as the field springs back open, the rotor has moved to where you have the greatest magnetic potential, and it springs open fully. I'd wager that the power of an Orbo interaction is repultraction, but assymetrical and heavier on the repulsion.

The attraction magnet sneaks it into position, and then at just past TDC, as the coil effect is wearing off, the repulsion kicks in and blasts the rotor on to the next interaction. 70% of the action is happening with no current from the reservoir at all.


You gain just a bit on each rotation but it adds up and up and you see acceleration until you are going so fast that the fields don't have a chance to fully establish on each interaction. You end up not getting the full potential energy from the magnets because the fields aren't "peaking" or "blooming" or however you'd like to put it.

I wouldn't put any money on seeing an Orbo go much more than 2000 RPM, and only then it would take a specific combination of materials with very high speed "field establishment"

By the way, are any materials rated by the speed of their hysteresis curves, not just the strength? That's probably more important.

[gravityblock]

@OC and ALL:

Does the uncurled A potential of the curled B field have anything to do with this.  I talked about this earlier and have forgotten about it until now.  The curled B field is located inside the core material, but the "B" in the B-H Loop is referring to the external magnetic field, so wouldn't this actually mean the "B" for the B-H Loop is referring to the uncurled A potential that is outside the core instead of the B field which is located inside the core material?

Either way, the uncurled A potential located outside of the core needs to be taken into consideration.

I'm really starting to get confused here.  I haven't had much time to go through and study the last few posts.  I think by having a few questions answered it will help me.  It's nice to have you join the discussion, freeorbo.

Thanks,

GB