Spinning magnets with radio waves.

[MileHigh]

TK:

You can hook your signal generator up to a big old beefy audio amplifier.  Knowing you I am sure you have one lying around.  Or a few visits to the Sally Ann and you might get lucky.  I once found a Harman Kardon late-1970s receiver that was about 110 watts per channel at a garage sale.  The thing weighed about 40 pounds and was a TANK.  It had a monstrous transformer and was high quality all around.

I think the basic dynamics are that the higher frequency you go the higher power you have to pump into the coil.  You have to overcome increasing air friction requiring more torque and more speed.  The coil is the stator for a motor, so it draws power. I am not sure if the increasing impedance of the coil itself comes into play, which we know increases as your drive frequency increases.  If that does come into play, that also requires a higher drive voltage.  Also, there must be increasing counter-EMF generated, so that also demands a higher excitation voltage.

Plotting say five points on a graph of maximum speed vs. excitation voltage would be interesting.

MileHigh

[synchro1]

Here's Alfacentauro's 300k r.p.m. video again. The reason I'm posting it is because on review, at 38 seconds into the video I noticed a screen posting that reports "5000 hz pure sine", so 5k hz pure sine wave spins at 300k r.p.m. That means the Sphere video posted by Pirate88179, is most likely sine wave driven too.

http://www.youtube.com/watch?v=V1oFzXOZnE8

[TinselKoala]

TK:

You can hook your signal generator up to a big old beefy audio amplifier.  Knowing you I am sure you have one lying around.  Or a few visits to the Sally Ann and you might get lucky.  I once found a Harman Kardon late-1970s receiver that was about 110 watts per channel at a garage sale.  The thing weighed about 40 pounds and was a TANK.  It had a monstrous transformer and was high quality all around.

I think the basic dynamics are that the higher frequency you go the higher power you have to pump into the coil.  You have to overcome increasing air friction requiring more torque and more speed.  The coil is the stator for a motor, so it draws power. I am not sure if the increasing impedance of the coil itself comes into play, which we know increases as your drive frequency increases.  If that does come into play, that also requires a higher drive voltage.  Also, there must be increasing counter-EMF generated, so that also demands a higher excitation voltage.

Plotting say five points on a graph of maximum speed vs. excitation voltage would be interesting.

MileHigh

Yes, you are right about needing higher power for higher speeds, in my setup. Still, there's the finding that stopping the magnet spinning, at whatever input power and frequency, causes the input power to go up. 
At the frequencies we are dealing with....even the 5 kHz of the crazy 300000 rpm sphere.... simply switching a power mosfet or an H-bridge with the FG output will provide plenty of power, no big audio amp is needed. Besides, matching impedances for the output of the audio amp would be problematic.

[TinselKoala]

Here's Alfacentauro's 300k r.p.m. video again. The reason I'm posting it is because on review, at 38 seconds into the video I noticed a screen posting that reports "5000 hz pure sine", so 5k hz spins at 300k r.p.m.

http://www.youtube.com/watch?v=V1oFzXOZnE8

Doesn't it look like the sphere is nutating or precessing as well as spinning? I think it would be very interesting to do some high-speed or stroboscopic photography of that setup.

[synchro1]

@TinselKoala,

       Your current setup looks nearly identical to Alfacentauros. I am of the opinion that a bearingless magnet rotor will increase speed more then increased power. Frequency is increasing the speed of your axel rotor up to your present record, not power. Why not just pass a plastic sleeve through the air core and toss an inexpensive miniature cylinder magnet inside like Alfacentauro's for a stroboscopic view? We can see the cylinder rotor levitating in the video.

       Twinbeard speculates that extremely high speed rotating magnets create a vortex in the ether that accounts for his unexplainable output at 40k hz, by Bedini circuit, with a tiny 1/8" neo sphere. That's a mere 2.4 million r.p.m. He's approaching the RF envelope. Perhaps out of range for a sine wave spinner. Evacuating the spin chamber may be necessary to reach the next higher speed range. Alfacentauro reports "Strong wind". It's a mistake to raise power to overcome friction. Be prepared for some extrodinary effects up towards that speed range if you succeed!.