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[PaulLowrance]

http://en.wikipedia.org/wiki/Counter-electromotive_force

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The counter-electromotive force (abbreviated counter emf, or CEMF ) [1] is the voltage, or electromotive force, that pushes against the current which induces it. CEMF is caused by a changing electromagnetic field. It is represented by Lenz's Law of electromagnetism. Back electromotive force is a voltage that occurs in electric motors where there is relative motion between the armature of the motor and the external magnetic field. One practical application is to use this phenomenon to indirectly measure motor speed and position [2]. Counter emf is a voltage developed in an inductor network by a pulsating current or an alternating current [1]. The voltage's polarity is at every moment the reverse of the input voltage [1][3].

In a motor using a rotating armature and, in the presence of a magnetic flux, the conductors cut the magnetic field lines as they rotate. The changing field strength produces a voltage in the coil; the motor is acting like a generator.. (Faraday's law of induction.) This voltage opposes the original applied voltage; therefore, it is called "counter-electromotive force". (by Lenz's law.) With a lower overall voltage across the armature, the current flowing into the motor coils is reduced. [4]
[edit] Efficiency

If it is assumed that a motor is 100% efficient with no friction or windage losses, the speed of the armature will increase until the back electromotive force is equal to the applied electromotive force, i.e. there will be no net electromotive force, no current flow and hence, no net force. The armature will spin at a constant rate, of its own accord.
[edit] References

   1. ^ a b c Graf, "counterelectromotive force", Dictionary of Electronics
   2. ^ Back-EMF
       
   3. ^ Naval Electrical Engineering Training Series, Module 02 - Introduction to Alternating Current and transformers", Inductance, self-inductance
       
   4. ^ "Nuclear Power Fundamentals Training Manuals". DC Generators, Counter-Electromotive Force
       
      (CEMF), DC Equipment Terminology, Electrical Science Volume 2.

[Jimboot]

   
This is important. Lumen, that MP1906P4AF is not a Metglas MAGAMP core. You can tell by the last letter, which is "F", which means it's a flat loop, not square loop. That has a permeability of 80000, not 1000000!

Although the other core is a MAGAMP core, part number MP1005L4AS, but that's a very small core, 10.92mm (0.43") OD.

So for those who want the Metglas core with 1 million permeability, the part number must start with MP and the last letter must be 4AS. If it ends with an "F", then it's the flat loop (transversely annealed).

bugger. I ordered those as I couldn't work out how to buy on Elna

[dradak1]

This is not my Theory AirStriker and it is supported by quite a few people.  Steorn has his setup the way he does trying to patent the device and to try to get around what is already open-sourced or patented.

GB

I salute them for there findings but I completely agree with you and that is why they are trying to sell licenses since patent can't be obtained.

Dragan

[interestedinou]

Anybody see this on the Steorn public forum? It's a post from Sean McCarthy.

"The magnetic arrangement on the rotor is the same in both cases, an N pole above an S pole (or the other way around). The coils in the pulse motor (like the coils on the Orbo motor) are both facing up."

[ken_nyus]

I'm curious what Sean means when he mentions that the use of a torroid is irrelevant in http://www.steorn.com/forum/comments.php?DiscussionID=62319&page=1#Item_14. Anyone have an explanation?

Cheers,
Adrian

I also read over at Steorn, Sean saying that there are many types of Orbo that share the same principle, he mentioned mOrbo, eOrbo, and ssOrbo.

I take these to mean mechanical orbo, the electromagnetic Orbo, and I guess he means the solid state Orbo.

So in that greater sense the toroid is not as important.