Okay, the video clips of the second presentation are now on Steorn's official YouTube page.
Starting off with the second Steorn official clip:
http://www.youtube.com/user/SteornOfficial#p/u/1/bSftoc9Pm1UAt 7:07 Sean says that "we have a very significant change in the inductance of the core material" to explain the change in rise-time for the current waveform. For starters, the core material does not possess the property of inductance. I am splitting hairs here and being picky because Sean has to explain what Steorn is doing without any ambiguity. Right now I can't explain why the slope of the current waveform changes so abruptly.
I just backed up and at 6:10 Sean says, "we have a very rapid permeability change of the material." So assuming Sean is implying that the core is fully saturated and that explains the abrupt change in the slope of the current waveform - that means that they are over-saturating the core with about 100 times more current than they need. Why would they do this, it represents so much wasted energy for nothing?
So let's talk about the biggie, the inductance increase when the rotor magnets move away from the toroidal coils. For starters, we are not sure how the inductance meter works. I am going to assume that it sends a sinusoidal signal through the coil and looks at the resulting current and phase angle. Does it do this at different frequencies? I don't know. Does it make "large signal" inductance measurements that may start to "clip" the core so that part of the large-signal excitation pushes the core into saturation? Does it make "small signal" inductance measurements with a low amplitude waveform which you assume will never push the core material into saturation? Is it all user-programmable, or does the device run an algorithm that runs a suite of large-signal/small-signal/different-frequency measurements and then crunches all of the disparate inductance measurements and generates some sort of average? I don't know the answer to these questions. Sean and company should have made it crystal clear how this inductance meter was working because it is crucial information.
Let's look at the case where you assume that the excitation from the inductance meter was a "large signal" excitation. In this case, when the magnet is close to the toroidal core, it affects the core material itself and keeps a small part of it saturated or near-saturated. This will make the large-signal inductance measurement go down, simply because the presence of the magnet makes the core appear to be smaller because a part of it is saturated or near-saturated. So the large-signal inductance measurement goes down the closer the magnet is to the core, and goes up the further the magnet is away from the core, which is exactly what Steorn demonstrated.
Now let's examine this in the context of the Steorn setup:
Here is a basic fact: If you have current flowing through a coil with no power source, just current recirculating all by itself through the coil, then if you dynamically increase that inductance with respect to time, the current in the coil will automatically DECREASE. The current HAS to decrease because you assume that you changed the geometry of the coil while the current was flowing through it to increase the inductance. Now the magnetic field is spread throughout a larger volume and the current has to go down because energy has to be conserved.
So in the case of the Steorn demo we know that the current does not decrease, even through it is "supposed" to decrease. I put "supposed" in brackets because in the Steorn case we have a power supply supplying energy and making the current flow through the toroidal coil. It's the POWER SUPPLY that supplies the EXTRA ENERGY to keep the current at a constant value. As the inductance increases with respect to time, the power supply is right there maintaining a constant current, which effectively results in an increase in energy being stored in the larger inductance.
Sean and Steorn are trying to pull a "fast one." The "extra energy" due to the increasing inductance actually COMES FROM THE POWER SUPPLY. Just by virtue of the fact that the current stays constant and the inductance increases slightly is telling you that the extra energy comes from the power supply.
To get a bit more technical, we know the charging time constant for an RL circuit is L/R. In the case for this demo, L is dynamic with respect to time and R is fixed. Therefore there is a "dynamic charging time constant" of delta-L(t)/R. delta-L for all values of delta-t is minuscule. Therefore the dynamic time constant is minuscule and for all practical intents and purposes you see no change in the current flowing through the toroidal inductor as the inductance increases a total of about 2.4% from the top-dead-center position to the further away position. In other words the power supply can keep up easily with the very slight increase in inductance over time such that the current does not appear to change at all.
To repeat, the "extra energy" is NOT FREE, and Steorn is trying to pull the wool over your eyes. Just the fact that the current stays constant for an increasing inductance with respect to time is telling you that the power supply is "filling in the gaps" resulting in the increased energy being stored in the larger inductor.
Also, don't forget at the same time the power supply is supplying a lot of energy that is being poured down the drain as dissipated heat. No matter what Sean tries to tell you, in the real world electrical power in a motor that gets dissipated as heat is LOST ENERGY BEING POURED DOWN THE DRAIN.
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Topic: Steorns December 2009 Demo (Read 98115 times)
