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Author Topic: LaFonte Group can turn off permanent magnet without work  (Read 87696 times)

mscoffman

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Re: LaFonte Group can turn off permanent magnet without work
« Reply #120 on: April 11, 2010, 08:10:05 PM »
@butch;

My view is that the particle domains of ferrites are to magnetic fields,
sort of like antennas are to emf. The smaller the domain the less amenable
they become to having lenz induced eddy currents. In my view the adhesive
binding agent plays an important role by creating resistivity between
metal particle domains. The more you compress them the higher the
ferrite density, but also the higher the leakage conductivity can become.
You can use the old stamped iron "layers" if the frequency is low and
the magnetic field always comes in from the same angle because of
the right hand rule. But when frequencies become RF and magnetic fields
can come in from different angles that is when the domain isolated
ferrites are required. While ferrite's all probably reduce eddy currents
the ferrite magnetic parameters of inductance, historysis, and remnance
probably vary all over the place in various metallic compositions. Don't
forget that many applications of ferrites have RF frequency ranges in
the megahertz or gigahertz regions and I don't think this application is
in those frequency ranges yet. For the frequencies you are dealing with
standard stamped armature iron probably has near optimal characteristics
but would be difficult to make for an experimental version. There is the
open question of what happens in the "mixer" ring as the rotational
frequency increases. It could be that reaction forces act inside this
ring material.

:S:MarkSCoffman

Low-Q

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Re: Something I was told and resistance readings of different powders
« Reply #121 on: April 11, 2010, 09:49:30 PM »
Quote from: Butch LaFonte link=topic=8852.msg237222#msg237222 A=1271003438
I did some research on the web and called one guy who sold iron powder and he told me that any powder had high resistance even copper powder if it is just in a lose pile. He said to think of it as large copper spheres in a pile and only the area where the spheres touch each other is the place where current could flow. But he also said that the more you compress the powder toward resembling a solid the electrical resistance drops. What do you guys think about his comments? It seems to me that the ideal material is soft ferrite in powder form, but I have not been able to find it yet. The Switcher needs as close to zero eddy current in the stator as possible. I would really appreciate it if you guys that are making the different powder based stators could take some resistance readings after the resin has cured and is in solid form. I'm very concerned that builders are going to get rotor drag from eddy currents in the stator and get discouraged because they think it is the Lenz effect doing it when it reality it is eddy current drag.
Thanks guys,
Butch
It is true what you have been told regarding compressed DRY powder. However, if you put resin in there, there will allways be a given space between each metal sphere, so they dont touch. Because it is litterally impossible to make a resin-powder mixtrure that has a mixdure ratio that make each metal particle collide and make a conductive path all the way through. Yes, some of the particles will make small chains of conductivity, but it will be litterally impossible to make the piece of compressed powder-resin mixdure to be conductive all the way.

Vidar

LarryC

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Re: LaFonte Group can turn off permanent magnet without work
« Reply #122 on: April 12, 2010, 01:06:10 AM »
@Bruce, thanks for the build info.
@All,
Lots of interesting posting. But, I liked Mark's comment 'For the frequencies you are dealing with standard stamped armature iron probably has near optimal characteristics but would be difficult to make for an experimental version'. That is what I am currently using but it is limited to certain configuration where the lamination's can be edge to edge.

The other day when I was testing a request from Gyula, I noticed a rotor speed up in switching from the 10 ohm load to unloaded. I was using a different magnet configuration from my original and had to go back to the original to get rid of the speed up. I retried the new configuration test today, which has four 1" diameter magnets instead of the two that I showed in my last pictures.  So 2 N poles and 2 S poles and because of the predrilled holes they are 3/8" apart. Not the best setup as this causes more peaks in the waveform and got the following results:

                    AC input
Ohm              Watts          RMS     
100               37              17.4
50                 35              11.3
10                 28                2.78
unloaded        24               31.9

I use a variac to adjust the input voltage to the AC induction motor, so that a speed of ~2950 rpm is maintained, so that is why the Watts varies.
@Gyula, LC meter is in and the primary coil is 172 MH.

Not sure what is causing this speed difference, but I am ordering 2" X 1" X 1/2" magnets to eliminate the 3/8" gap. Those results should be more conclusive, if there is a problem.

Regards, Larry   
« Last Edit: April 12, 2010, 01:58:35 AM by LarryC »

Bruce_TPU

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Re: Something I was told and resistance readings of different powders
« Reply #123 on: April 12, 2010, 01:07:01 AM »
It is true what you have been told regarding compressed DRY powder. However, if you put resin in there, there will allways be a given space between each metal sphere, so they dont touch. Because it is litterally impossible to make a resin-powder mixtrure that has a mixdure ratio that make each metal particle collide and make a conductive path all the way through. Yes, some of the particles will make small chains of conductivity, but it will be litterally impossible to make the piece of compressed powder-resin mixdure to be conductive all the way.

Vidar

That is correct!  There is zero conductive path through these homemade black Iron powder bars.

Butch LaFonte

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Eddy current test fixture for real world machines
« Reply #124 on: April 12, 2010, 06:02:34 PM »
[A author=Bruce_TPU link=topic=8852.msg237266#msg237266 date=1271027221]
That is correct!  There is zero conductive path through these homemade black Iron powder bars.
[/quote]
I can not emphasize enough the importance of eliminating all eddy current drag in the switcher stator.
Does anyone have an idea for a simple test fixture that a sample of a material could be placed in and the sample be free floating and rotate a field across the sample and try to find a material that would not move due to eddy current drag. The problem here is the fixture design would need to be designed so the pull of the magnet did not move the sample, but at the same time the filed lines would be cutting through the sample.
Any ideas? Mark could build it I believe and we could test everyones samples. Mark has a motor that rotates at 20,000 RPM. We could come up with a standard size and shape for the samples. Just think, we could find a truly eddy current free, cheap to make, home made magnetic material not in theory, but practice.
Thanks,
Butch

Low-Q

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Re: Something I was told and resistance readings of different powders
« Reply #125 on: April 12, 2010, 06:16:26 PM »
That is correct!  There is zero conductive path through these homemade black Iron powder bars.
Not only for black iron powder, but also for metal powder as well - when mixed with resin.
I have btw. made black iron powder myself by using clean water and 50V applied to two iron plates in it. It bubbles from one plate and make black powder from the other. I picked up all the powder with a neodym magnet untill the water was again clear and pure. These iron powder particles I believe is quite small - nano particles?

Vidar

gyulasun

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Re: Eddy current test fixture for real world machines
« Reply #126 on: April 12, 2010, 11:32:21 PM »
Quote
author=Bruce_TPU link=topic=8852.msg237266#msg237266 date=1271027221]
That is correct!  There is zero conductive path through these homemade black Iron powder bars.

I can not emphasize enough the importance of eliminating all eddy current drag in the switcher stator.
Does anyone have an idea for a simple test fixture that a sample of a material could be placed in and the sample be free floating and rotate a field across the sample and try to find a material that would not move due to eddy current drag. The problem here is the fixture design would need to be designed so the pull of the magnet did not move the sample, but at the same time the filed lines would be cutting through the sample.
Any ideas? Mark could build it I believe and we could test everyones samples. Mark has a motor that rotates at 20,000 RPM. We could come up with a standard size and shape for the samples. Just think, we could find a truly eddy current free, cheap to make, home made magnetic material not in theory, but practice.
Thanks,
Butch

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.  I know ferrite is very hard to grind though.

@Larry

Thanks for the measurements. Well, if you could connect a 61uF capacitor in series with the 172mH output coil, then your "generator" output would be a real, non inductive 10 Ohm impedance and would match perfectly to a 10 Ohm resistor load at the 49.16Hz output frequency (i.e. at 2950RPM).
It maybe is not easy to find a 61uF non electrolytic cap, motor run capacitors could be an option.

Thanks to you all,

Gyula

Bruce_TPU

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Re: Eddy current test fixture for real world machines
« Reply #127 on: April 13, 2010, 03:19:54 AM »
I can not emphasize enough the importance of eliminating all eddy current drag in the switcher stator.
Does anyone have an idea for a simple test fixture that a sample of a material could be placed in and the sample be free floating and rotate a field across the sample and try to find a material that would not move due to eddy current drag. The problem here is the fixture design would need to be designed so the pull of the magnet did not move the sample, but at the same time the filed lines would be cutting through the sample.
Any ideas? Mark could build it I believe and we could test everyones samples. Mark has a motor that rotates at 20,000 RPM. We could come up with a standard size and shape for the samples. Just think, we could find a truly eddy current free, cheap to make, home made magnetic material not in theory, but practice.
Thanks,
Butch


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.  I know ferrite is very hard to grind though.

@Larry

Thanks for the measurements. Well, if you could connect a 61uF capacitor in series with the 172mH output coil, then your "generator" output would be a real, non inductive 10 Ohm impedance and would match perfectly to a 10 Ohm resistor load at the 49.16Hz output frequency (i.e. at 2950RPM).
It maybe is not easy to find a 61uF non electrolytic cap, motor run capacitors could be an option.

Thanks to you all,

Gyula

Brilliant, Gyula!!  Great Idea for Butch to test the black iron oxide powder or another mixture....

Cheers,

Bruce

Paul-R

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Re: Something I was told and resistance readings of different powders
« Reply #128 on: April 13, 2010, 10:23:52 AM »
Not only for black iron powder, but also for metal powder as well - when mixed with resin.
I have btw. made black iron powder myself...
Are we talking about iron powder (i.e. iron filings) or iron oxide
like this UK link:
http://cgi.ebay.co.uk/BLACK-IRON-OXIDE-High-grade-material-500g_W0QQitemZ370364347806QQcmdZViewItemQQptZUK_BOI_Medical_Lab_Equipment_Lab_Supplies_ET?hash=item563b6f759e

Are both equally good?

LarryC

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Re: Eddy current test fixture for real world machines
« Reply #129 on: April 13, 2010, 05:35:21 PM »
@Larry
Thanks for the measurements. Well, if you could connect a 61uF capacitor in series with the 172mH output coil, then your "generator" output would be a real, non inductive 10 Ohm impedance and would match perfectly to a 10 Ohm resistor load at the 49.16Hz output frequency (i.e. at 2950RPM).
It maybe is not easy to find a 61uF non electrolytic cap, motor run capacitors could be an option.
Gyula

The closes I could come to 61uF was 72uF using two 142uF in series.

                Ac Input
Ohms         Watts       Vrms
10                28         2.78      No Cap
10                48         5.40      With Cap
 
Double the output, but at an increase in input torque.

Tried running it at 45Hz, which would be a match for the 72uF, but the torque curve on the AC induction motor won't allow the rotor to stay in that range.

Regards, Larry

               

gyulasun

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Re: LaFonte Group can turn off permanent magnet without work
« Reply #130 on: April 13, 2010, 06:26:30 PM »
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

Butch LaFonte

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Re: Eddy current test fixture for real world machines
« Reply #131 on: April 13, 2010, 07:46:32 PM »
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
[/quote]
Great idea Gyula, thanks so much.
Butch

Butch LaFonte

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Two Switcher update video's uploaded to Youtube, and drag comment
« Reply #132 on: April 13, 2010, 09:17:08 PM »
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

LarryC

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Re: LaFonte Group can turn off permanent magnet without work
« Reply #133 on: April 14, 2010, 12:22:56 AM »
[/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

 

gyulasun

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Re: LaFonte Group can turn off permanent magnet without work
« Reply #134 on: April 14, 2010, 12:42:34 AM »
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