LaFonte Group can turn off permanent magnet without work

[Low-Q]

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]

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]

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]

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]

@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