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Author Topic: 47000 Watt Magnetizer  (Read 23032 times)

DreamThinkBuild

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Re: 47000 Watt Magnetizer
« Reply #15 on: November 26, 2015, 12:04:09 AM »
Hi Carroll,

Thanks for sharing.

In your design does the edge of the magnet stay within the core of the stator?

Mine crosses it which is the reason for the cogging I'm getting.

tinman

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Re: 47000 Watt Magnetizer
« Reply #16 on: November 26, 2015, 12:06:15 AM »
Hi Brad,

Some good news to support your idea for a wobble magnet generator.  I built a very crude version just to test the concept.  This is just a single ceramic ring magnet with north on one side and south on the other.   As you can see in the picture I am just swiping the magnet back and forth across the core of the coil.  Without the coil at all on the test stand the motor was drawing 1.8 amps after giving it some time to warm up the bearings and get loosened up a bit.  When I added the coil without any load the current only went up about .01 amps so the side to side motion of the magnet appears to be giving very little cogging effect.   The open voltage on the coil was only 6 volts but of course there is only one magnet and it was only turning about 1320 rpm according to the frequency as calculated by my scope.  When I loaded the coil with a 30 ohm load the current did not change going to the drive motor.  My voltage did drop to about 2.4 volts but I expected a pretty good drop because of the speed of the rotor and the fact I am only using a single ceramic magnet to excite the coil.  When I shorted the coil the current to the motor only went up .01 amps.  I expect this may be because of the slow speed of the rotor.  I have heard many times the higher speed on the rotor helps to overcome the lentz effect.  I am very interested to see how your larger build with good magnets will perform.  I would like to pursue that idea myself if I can get all the parts together to see what it will do.

Take care and keep up the good work and ideas.
Carroll

Hi Carroll.

Great job there. That really is pretty good for only 22Hz.
What was the voltage the motor was running on,so as we can do some quick power calculations.

Cheers

Brad


tinman

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Re: 47000 Watt Magnetizer
« Reply #17 on: November 26, 2015, 12:18:07 AM »
Tinman,

   

PW

Quote
Have you considered machining a pair of elliptical pole pieces angle mounted to your shaft with a neo ring magnet positioned between those pole pieces in lieu of making and magnetizing a custom shaped magnet?.

I did,but i dont think i would get a very good field/even field that way due to the round magnet and elliptical pole pieces.

Quote
As for your "47000 watt magnetizer", it all sounds a bit scary.  Welded contacts and melted aluminum aside, you must also ensure that the current thru the magnetizing coil and lead wires does not "ring down".  Polarity reversals during a ring down can partially demagnetize the previously achieved peak magnetization levels.

Yes,understood.
I am hoping that the large diode across the coil will stop any ringing,and the pulse will be as quick as i can get it with a relay. All contacts on the relays are brass,so there should be no welding taking place-->hopfully ;D

Quote
If you are bound and determined, consider charging a bank of capacitors via a current limiting resistor and then dumping that cap bank across your coil.  Even a few hundred milliseconds of activation is way more time than needed to flip domains.

I dont have enough caps to deliver the required energy to do the job,that is why i am going with the large battery bank.

tinman

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Re: 47000 Watt Magnetizer
« Reply #18 on: November 26, 2015, 12:20:12 AM »
Really?  Look at my chicken scratchings.  What do you think about my marked up drawing?

Yes,you have marked the field lines for the center position of the magnet in relation to the core of the coil-->but what about the field lines when only one pole of the magnet is under the core?(the center picture)

citfta

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Re: 47000 Watt Magnetizer
« Reply #19 on: November 26, 2015, 12:26:29 AM »
To first answer the question for DreamThinkBuild the magnet edge gets right to the edge of the core.  If it went further I think the voltage may have been higher.  But that may have started inducing some cogging also.  This is an area that needs to be explored.  How close to the core do you have to stay to not get excessive cogging and still get good output?

Brad I was using a scooter motor as my drive motor.  And it was being powered from a 12 volt battery that was showing about 12.5 volts.  I didn't go into much detail about that as this is a test setup for a much larger generator.  It has a crankshaft pulley from a Honda Civic on the main shaft as a flywheel for some other testing I was doing.  I just removed the large rotor and stuck that ring magnet on there to see what it would do.  Then mounted the coil next to it.  Nothing precise or very well thought out.  Just a quick test to try and verify if coils would put out power when the magnet is sweeping back and forth across the core.  I believe with a much larger and stronger magnet the output would be much better.  Obviously with something as small as the ring magnet I used you never get the full benefit of either the north or south pole because the other pole is always right nearby to influence part of the coil.  You design with the space between the poles should work much better.  At least that is what I think.  We will see when you get it built.

On another thought,  do you have any large machine shops near you?  They usually have large de-magnetizers which can also be used to magnetize objects.  They would probably do what you want for free or almost free and save you the trouble of having to build something to do it yourself.

Carroll

citfta

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Re: 47000 Watt Magnetizer
« Reply #20 on: November 26, 2015, 01:24:12 AM »
To add a little more info.  I boosted the voltage on the drive motor to 24 volts and as expected the voltage output doubled as well as the frequency.  So I am now getting 24 volts open circuit and 45 hz frequency.  The input current was only slightly higher but I did not have time to let things warm up first either.  I keep getting interrupted by family concerns so did not test under load.  However here is a screen shot from the scope.  You can see the output is not quite a normal sine wave but pretty close.  Again adjusting the angle to make the magnet move either more or less across the core will probably change that.

Carroll

picowatt

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Re: 47000 Watt Magnetizer
« Reply #21 on: November 26, 2015, 03:35:52 AM »
I did,but i dont think i would get a very good field/even field that way due to the round magnet and elliptical pole pieces.

Tinman,

You might consider elliptical pole pieces as mentioned but with a number of small neo cylinder magnets located as needed to provide the more homogeneous field you desire.

PW

tinman

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Re: 47000 Watt Magnetizer
« Reply #22 on: November 26, 2015, 05:53:57 AM »
Tinman,

You might consider elliptical pole pieces as mentioned but with a number of small neo cylinder magnets located as needed to provide the more homogeneous field you desire.

PW

Well I quite like the idea of making my own magnets, as they are expensive here in OZ. Im not sure how hard it is to magnetize a piece of soft iron, but half the fun is trying to do it-the other half is building the magnetizer.. speaking of the coil oscillating, wouldnt it do that with using a cap bank anyway, as you just have a tank circuit in reality when using caps.

DreamThinkBuild

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Re: 47000 Watt Magnetizer
« Reply #23 on: November 26, 2015, 02:45:53 PM »
Hi Carroll,

Quote
How close to the core do you have to stay to not get excessive cogging and still get good output?

The previous design is 5mm space between core and magnet. The magnet is 1-1/2" dia x1/2" thick N52

http://www.kjmagnetics.com/proddetail.asp?prod=DX88-N52

I did a quick test and I can move the coil out to about 2cm where the cogging diminishes and when the coil is shorted lenz is minimal but output drops. It still needs more testing with different angles to see how it goes.

citfta

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Re: 47000 Watt Magnetizer
« Reply #24 on: November 26, 2015, 03:46:41 PM »
Hi Carroll,

The previous design is 5mm space between core and magnet. The magnet is 1-1/2" dia x1/2" thick N52

http://www.kjmagnetics.com/proddetail.asp?prod=DX88-N52

I did a quick test and I can move the coil out to about 2cm where the cogging diminishes and when the coil is shorted lenz is minimal but output drops. It still needs more testing with different angles to see how it goes.

I was referring to the side to side movement of the magnet as it turns.  If you look at my picture if I increase the diameter of the magnet and move the coil out or increase the angle of the magnet it will move the edge of the magnet farther past the core of the coil.  I want to do some testing to see how that affects the cogging.  If I understand you correctly your magnet edges did move past the core and you got some cogging.  So I wonder where the sweet spot is?  Right now the inside edge of the magnet just does get to the outside edge of the core on my test setup.


MileHigh

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Re: 47000 Watt Magnetizer
« Reply #25 on: November 26, 2015, 04:26:12 PM »
Yes,you have marked the field lines for the center position of the magnet in relation to the core of the coil-->but what about the field lines when only one pole of the magnet is under the core?(the center picture)

Either orientation you will get EMF induced in the pickup coils but it looks pretty obvious that a radial magnetization pattern would induce more EMF in the piclup coils.  Either way, this whole Jim Murray business is peseudoscience junk.

DreamThinkBuild

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Re: 47000 Watt Magnetizer
« Reply #26 on: November 28, 2015, 04:56:11 PM »
Hi Carroll,

Sorry, I haven't tested which angle is best. I calculated the maximum angle for my current setup to be 30 degrees to keep it within the core right to the edge, 6 degrees to be completely in the core and 12.5 degrees to have the core cross the center line of the magnet.

My lab is ripped apart awaiting new desk/shelves so once things are setup again I can test between those angles to see which one has the best output.

I did a quick sim and it looks like keeping the highest angle right near the edge has the most flux through the core. Real testing usually reveals where the problem spots occur.

edit: Added zip file with animation, forgot gif won't work here.

tinman

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Re: 47000 Watt Magnetizer
« Reply #27 on: November 29, 2015, 01:54:30 AM »
A short update on the magnetizer.
1.4 kW's charge power ;)

https://www.youtube.com/watch?v=TPNLjxRf_GI

tinman

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Re: 47000 Watt Magnetizer
« Reply #28 on: November 29, 2015, 05:53:35 AM »
Well i got the pot magnetizer finished,but it will only magnetize steel/iron items very weakly.
Below is a scope shot of one single pulse,and i managed to get the pulse duration down to around 35mS. The start of the pulse is very erratic-->would this be due to the arcing across the solenoid contact's?. It also looks like the solenoid cannot handle the current,as i am supplying the unit with 48 volts,but it seems to drop off once the relay has closed properly. I know it's not the battery voltage dropping down,as that remains at 48 volts before the relay,and the cables are 12mm multi strand.


Brad

gyulasun

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Re: 47000 Watt Magnetizer
« Reply #29 on: November 29, 2015, 12:49:40 PM »
Hi Brad,

Yes, I also think the erratic start of the pulse can be caused by the arching across the solenoid contacts, looks like flyback pulses due to current interruptions.  You have surely checked and improved the contacts since then?
The voltage drop may still be caused by resistive loss as was the case initially for Luc's setup, when dealing with peak currents of several Ampers or some tens of Ampers , every milliOhm counts.

I think it would still be worth checking the voltage drop across the battery by your oscilloscope during the ON time, due to the 24 cells in series,  the inner resistances add up.
Just considering say 0.01 Ohm for a single cell,  24*0.01=0.24 Ohm and when you have a 10 Amper peak current at the switch-on moment, the drop is 2.4V. You seem to have a 23-24V drop from the start battery voltage...  as if you had a 100 Amper peak current at switch-on? (assuming the total 0.24 Ohm resistance in the circuit). I do not know the resitance of the solenoid.   
A quick test: connect a high uF capacitor across the battery bank and see whether the drop reduces.

Gyula