Hi Larry,

Thanks for the measurements.  Something would need to be mechanically reconsidered and redesigned I guess, there is too much interaction between the prime mover and the load.  I think you are aware of this.

Just out of curiosity, have you considered creating a parallel resonant output circuit by connecting the same resonating 72uF caps in parallel with the output coil? This time you would have to use a normal mains transformer like the ones in wall plugins, the primary could come in parallel with the parallel output tank and the secondary AC output would be terminated with the 10 Ohm load (here you may have to change the value of the load slightly up or down, depending on the turns ratio of the mains transformer just at hand).  Also you may have to change the RPM a little to get resonance.  If you have no any mains transformer (with any output between 6 to 24V secondaries) for this test, no problem of course, theoritically it should perform the same matching like in the series resonance case, where there is low impedance involved.

Have you found a more sinusoidal output waveform with the caps?

Thanks,  Gyula

Hi Butch,
I think if you could find an induction cooker near to you then just placing the sample ferrite material over the cooker surface you could test how much it warms up if any.  The shape could be as needed for the application. Most induction cookers work around 25-27kHz frequency, not at 60 or 50Hz.
If there is no any induction cooker in the neighbourhood, you may find one working on display at the kitchens department stores?
Another possibility is using an induction heater but it must be built unfortunately (see here one: http://www.richieburnett.co.uk/indheat.html )
It is also possible to rotate the sample ferrite in the air gap of two facing strong Neo magnets in attraction, at a given rpm. If the sample is conductive, will heat up.
For making a suitable ferrite based material, I think you could grind normal off the shelf ferrite cores of high permeability and then mix this ferrite powder with a binding material like Bruce showed in his video. There would be no problem if the grinding left some rough grained mixture because the ferrite already was manufactured earlier, just from fine grindings to minimize eddy current losses, you would just bring it into a new shape with the resin.
Gyula
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Great idea Gyula, thanks so much.
Butch

http://www.youtube.com/user/LaFonteGroup
Also I wanted to mention that we calculated that at 20,000 RPM the switcher rotor magnet poles are moving along the iron surface (.005" air gap) at 180 miles per hour. Now if there is eddy current drag in the stator just think of the drag on the rotor magnet. Think of holding the magnet in your hand out the window of a car and going 180 miles per hour with the magnet just .005" from an iron sheet.
Butch

[/quote author=gyulasun link=topic=8852.msg237450#msg237450 date=1271175990]
Thanks for the measurements.  Something would need to be mechanically reconsidered and redesigned I guess, there is too much interaction between the prime mover and the load.  I think you are aware of this.

Just out of curiosity, have you considered creating a parallel resonant output circuit by connecting the same resonating 72uF caps in parallel with the output coil? This time you would have to use a normal mains transformer like the ones in wall plugins, the primary could come in parallel with the parallel output tank and the secondary AC output would be terminated with the 10 Ohm load (here you may have to change the value of the load slightly up or down, depending on the turns ratio of the mains transformer just at hand).  Also you may have to change the RPM a little to get resonance.  If you have no any mains transformer (with any output between 6 to 24V secondaries) for this test, no problem of course, theoritically it should perform the same matching like in the series resonance case, where there is low impedance involved.

Have you found a more sinusoidal output waveform with the caps?

Thanks,  Gyula
[/quote]

Actually, for testing this type of generator I like a lot of interaction between the prime mover and the load. You can easily hear the rotor Rpm increase or decrease when the torque changes due to manually changing Ohm loads. I run it around 2950 Rpm, because that is close to the best torque/current point on a AC induction motor single phase. Most DC motors don't respond much speed wise to changes in load torque, except for series wound DC motors. Of course, in production a totally different prime mover would be needed.

No, I haven't previously considered your new test request. But, I would like to take a pass, unless you feel it is really necessary. If so, please explain why.

Yes, as would be expected, caps have a smoothing effect on the waveform.

Looking forward to testing with the new ordered magnets to eliminate the 3/8" gap between the 1" Dia magnets.

Regards, Larry

 

Hi Larry,

No I do not feel like the parallel resonance test is really neccessary.

On the interacion between the prime mover and the load I meant the cap tuning reflected back to the input power draw.

Thanks you very much your kindness and keep up the great work.

Respectfully
Gyula