Magnet coil cores, demagnetization power and Lenz delay.

[MarkE]

http://www.youtube.com/watch?v=90rMGmskqXQ

That is a great demonstration of how one can:

Add multiple fields together.
Vary physical position of magnetics to vary the torque / BEMF constants of a motor.  When the BEMF is small, so too is the torque constant.  Hence the very long spin-up time under no load of Steorn's silly WaterWays demonstrations.  BEMF is a factor in Steorn's motors and the Orbette's.  But the coupling is so weak that it can be hard to see.  Steorn misrepresented that the only place that the BEMF would be seen would be in the top of the current trace.  It can also be seen and is more pronounced as I recall in the timing of the coil current build-up prior to coil saturation.

[TinselKoala]

That is a great demonstration of how one can:

Add multiple fields together.
Vary physical position of magnetics to vary the torque / BEMF constants of a motor.  When the BEMF is small, so too is the torque constant.  Hence the very long spin-up time under no load of Steorn's silly WaterWays demonstrations.  BEMF is a factor in Steorn's motors and the Orbette's.  But the coupling is so weak that it can be hard to see.  Steorn misrepresented that the only place that the BEMF would be seen would be in the top of the current trace.  It can also be seen and is more pronounced as I recall in the timing of the coil current build-up prior to coil saturation.

I think you too may be missing the great difference between a core effect motor and the typical electromagnetic attraction or repulsion of an ordinary pulse or commutated or even a brushless synchronous motor. The generator effect is decoupled from the drive effect. The magnet passage may even contribute to the saturation of the core, lessening the current that needs to be applied to drive the core through the critical region of the B-H hysteresis loop.

There was much in the Steorn story that actually turned out to be true. Even though my Orbette 2.0 used mechanical bearings rather than the magnetic suspension of the Steorn motors, I was able to build in adjustability that they did not, and so I was able to achieve much better acceleration than they could, as well as getting better cancellation of the generator effect. The Orbette in the video outperforms the Steorn motor by a fair margin in terms of acceleration, and from what I could see from their scopeshots, also in electrical power vs. mechanical power. (I know the mechanical power dissipation of my rotor very precisely at any given rpm, thanks to a precise knowledge of the MoI and about a mile of chart-recorder paper and a great USDigital DAC system with a 4000 line rotary encoder monitoring rotor speed.)

I tried a dozen different toroid materials and many winding combinations, and I even went so far as to do quantitative measurements relating the applied current to the attractive force/distance characteristic of a probe magnet, using a digital force gauge and a micrometer-adjustable test fixture. All that data is still on a computer in Canada, probably, but I may be able to find some of the graphs if I look hard enough. The generator effect can be practically eliminated, as I showed for one coil in the video, but the attraction of the rotor magnets to the cores is not affected very much at all by the slight changes in vertical positioning needed. The coils are actually _off_ as the rotor magnets approach the nearest point, and since the coil's position is optimized there is very little induced voltage as the magnets approach. The cores feel the field but the windings don't. Then at the instant of closest approach the current is turned on to the coils. The external field of the magnets as they approach have already driven the core up near the "elbow" of the hysteresis loop and the slight application of current then pushes the core into full or nearly full saturation, at which point the attractive force is reduced, by enough of an amount that the "fleeing" magnets are not retarded nearly as much as they were pulled in during the approach. Normally of course these two forces would be approximately equal, if the cores were not energized, even with them in the optimum position for cancellation of the generator effect. The result is the "slow in, fast out" or rather pulled in hard and pulled back less hard, that drives the motor. It's weird to drive a motor by lessening the attraction on the way out, almost as if you change the core from "iron" to "wood" at the instant of the magnet's closest approach.

Of course the effect is not that radical, it only amounts to a few percentage points of difference in the forces, but this is enough to produce surprisingly strong accelerations, with the right "squareloop" materials for the core, and careful attention to winding and wire routing to  minimize leakage and fringing fields from the toroidal coils.

You may recall that Steorn's toroids in the "plinth" Orbos were mounted face-on to the rotor. I believe this was a mistake on their part; you can see that mine are mounted edge-on, which works better, because with the face-on mounting there is a virtual "hole in the donut" that causes a mechanical loss right at the point of closest approach. With the face on coils there are actually two "valleys" and a "hill" between them at the critical moment and this wastes some of the mechanical power. The edge on configuration that I used makes it easier to null the generator voltage, it eliminates the odd shape of the force-position curve caused by the donut hole, and provides a smoother "more pull in" and "less pull out" force profile from the rotor magnets acting on the core.

Core effect motors are a neglected area of research I think. They are really remarkable. I was also able to get fairly radical gains in performance, using ferrite "beads" that are actually cylinders, by winding them toroidally, mounting them "corner-on" to the rotor, and biasing the far end with little strong magnets to "presaturate" the cheap already low permeability of these beads. Just as synchro is trying to describe above but without really understanding. He seems to think that the magnets work by repelling or attracting the rotor to "help" the pulsed coils do their work. But in a core effect motor they work differently, by moving the saturation level of the cores so that it takes less current to fully saturate them.

[MarkE]

I think you too may be missing the great difference between a core effect motor and the typical electromagnetic attraction or repulsion of an ordinary pulse or commutated or even a brushless synchronous motor. The generator effect is decoupled from the drive effect. The magnet passage may even contribute to the saturation of the core, lessening the current that needs to be applied to drive the core through the critical region of the B-H hysteresis loop.

I am pretty sure that I understand the operation of these devices and the key role that saturating the core plays.  The saturation decouples by factors of 100's or even 1000's to 1 the motor K before the magnetics saturate.  That's why the voltage across and the current through the coils is so stable:  saturation drives the K to next to nothing.  But before the coils saturate, while current is building up and after the pulse ends and the current decays the inductors return to their linear regions and the BEMF effect of the moving magnets can be seen in the oscilloscope rising and falling current waveforms.

There was much in the Steorn story that actually turned out to be true. Even though my Orbette 2.0 used mechanical bearings rather than the magnetic suspension of the Steorn motors, I was able to build in adjustability that they did not, and so I was able to achieve much better acceleration than they could, as well as getting better cancellation of the generator effect. The Orbette in the video outperforms the Steorn motor by a fair margin in terms of acceleration, and from what I could see from their scopeshots, also in electrical power vs. mechanical power. (I know the mechanical power dissipation of my rotor very precisely at any given rpm, thanks to a precise knowledge of the MoI and about a mile of chart-recorder paper and a great USDigital DAC system with a 4000 line rotary encoder monitoring rotor speed.)

Your work was always vastly superior to Steorn's.

I tried a dozen different toroid materials and many winding combinations, and I even went so far as to do quantitative measurements relating the applied current to the attractive force/distance characteristic of a probe magnet, using a digital force gauge and a micrometer-adjustable test fixture. All that data is still on a computer in Canada, probably, but I may be able to find some of the graphs if I look hard enough. The generator effect can be practically eliminated, as I showed for one coil in the video, but the attraction of the rotor magnets to the cores is not affected very much at all by the slight changes in vertical positioning needed. The coils are actually _off_ as the rotor magnets approach the nearest point, and since the coil's position is optimized there is very little induced voltage as the magnets approach. The cores feel the field but the windings don't. Then at the instant of closest approach the current is turned on to the coils. The external field of the magnets as they approach have already driven the core up near the "elbow" of the hysteresis loop and the slight application of current then pushes the core into full or nearly full saturation, at which point the attractive force is reduced, by enough of an amount that the "fleeing" magnets are not retarded nearly as much as they were pulled in during the approach. Normally of course these two forces would be approximately equal, if the cores were not energized, even with them in the optimum position for cancellation of the generator effect. The result is the "slow in, fast out" or rather pulled in hard and pulled back less hard, that drives the motor. It's weird to drive a motor by lessening the attraction on the way out, almost as if you change the core from "iron" to "wood" at the instant of the magnet's closest approach.

It is out of the ordinary but all the ordinary physics still apply.  The coil orientation would in a perfect world yield zero modulation of the top of the waveform.  The energy transfer that is necessary to the operation of the device as a motor is all in those rising and falling edges.  Altering the core bias with the rotor magnets changes those edges.

Of course the effect is not that radical, it only amounts to a few percentage points of difference in the forces, but this is enough to produce surprisingly strong accelerations, with the right "squareloop" materials for the core, and careful attention to winding and wire routing to  minimize leakage and fringing fields from the toroidal coils.

The squarer, the better for these types of machines.

You may recall that Steorn's toroids in the "plinth" Orbos were mounted face-on to the rotor. I believe this was a mistake on their part; you can see that mine are mounted edge-on, which works better, because with the face-on mounting there is a virtual "hole in the donut" that causes a mechanical loss right at the point of closest approach. With the face on coils there are actually two "valleys" and a "hill" between them at the critical moment and this wastes some of the mechanical power. The edge on configuration that I used makes it easier to null the generator voltage, it eliminates the odd shape of the force-position curve caused by the donut hole, and provides a smoother "more pull in" and "less pull out" force profile from the rotor magnets acting on the core.

You found that because you possess orders of magnitude better understanding of physics than the saps at Steorn.

Core effect motors are a neglected area of research I think. They are really remarkable. I was also able to get fairly radical gains in performance, using ferrite "beads" that are actually cylinders, by winding them toroidally, mounting them "corner-on" to the rotor, and biasing the far end with little strong magnets to "presaturate" the cheap already low permeability of these beads. Just as synchro is trying to describe above but without really understanding. He seems to think that the magnets work by repelling or attracting the rotor to "help" the pulsed coils do their work. But in a core effect motor they work differently, by moving the saturation level of the cores so that it takes less current to fully saturate them.

What you've got is a mechanical version of a magnetic amplifier.  The non-linear region headed into saturation provides signal gain needed to make the approaching and departing transactions asymmetric with respect to force versus position.  That in turn allows the external power source to transfer energy that accelerates the rotor.  I think that small diameter hollow cylinders of very square magnetic material would be ideal.

[synchro1]

Here's a better example of the shorted generator coil positioning effect:


https://www.youtube.com/watch?v=EYUTFi8Zdt4

[synchro1]

The video demonstrates different configurations of two competing forces.

A "Lenz reversal" would require induced voltage to orient such that if current were to flow the current would reinforce the inducing field.  You have offered no evidence that such a thing occurs.

@MarkE,

The important point in this video is how the balance between attraction and repulsión is effected by distance positioning. Both Konzen and kEhYo orient their monopole rotor magnets facing North pole out; Both their coils have the backing magnets in opposition behind ferrite cores. The video demonstrates that magnet stacks in repulsión share attraction to a steel magnetic keeper when pushed toward each other at a distance just to the inside of a "Neutral Zone" of perhaps 1/16 of an inch in width. kEhYo's GAP power coil is in the "Repulsión Zone". Konzen's shorted coil sweet spot is closer to the rotor where attraction to the ferrite balances the repulsión to his backing magnets. The identical coil, disconnected from the input source, shorted and repositioned closer to the rotor now causes the rotor to speed up solely from forces inside the shorted generator coil alone! This "Neutral Zone" should appear as a bright ridge though a magna-viewer film, contrasted by dark areas on either side. A piezo positioning chip would offer another alternative for automatically locating the shorted coil in the acceleration zone demonstrated by Doug Konzen, who uses a risky hands on approach.