47000 Watt Magnetizer

[DreamThinkBuild]

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]

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]

Tinman,

   

PW

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.

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

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]

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]

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