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Solid States Devices => solid state devices => Topic started by: tinman on November 23, 2015, 03:51:27 PM

Title: 47000 Watt Magnetizer
Post by: tinman on November 23, 2015, 03:51:27 PM
This is my attempt at building a magnetizer,so as i can make my own magnets.
It is needed for an up and coming project ,where as i have to magnetize an odd shape rotor-->a sample rotor is in the video. Most of you will know who's design the rotor is,and what machine it belongs to. But i will be going about the supplied magnetic field in a different way.

https://www.youtube.com/watch?v=a3wxqERrSbM


Brad
Title: Re: 47000 Watt Magnetizer
Post by: DreamThinkBuild on November 23, 2015, 11:10:27 PM
Hi Tinman,

Interesting project, is your design going to divert the flux through a C core on either side?

I've tried a precessed magnet(45 degrees) but used individual stator coils. When aligned to the center of the coils it generates a really nice multi-phase AC output. This design still has cogging as the plane of the magnet crosses the stator cores but it was pretty fun to build and learn from.

Looking forward to your build.
Title: Re: 47000 Watt Magnetizer
Post by: tinman on November 24, 2015, 10:19:59 AM
Hi Tinman,

Interesting project, is your design going to divert the flux through a C core on either side?

I've tried a precessed magnet(45 degrees) but used individual stator coils. When aligned to the center of the coils it generates a really nice multi-phase AC output. This design still has cogging as the plane of the magnet crosses the stator cores but it was pretty fun to build and learn from.

Looking forward to your build.

Nice build DTB.
I wonder if the coging was due to the fact that your magnet was not shaped so as the outer perimeter was always level with the core of the coil's like mine will be?.

Also,did it load the prime mover down when current was drawn from the coils?.

Brad
Title: Re: 47000 Watt Magnetizer
Post by: MileHigh on November 24, 2015, 12:53:48 PM
If you are doing a variation on a Jim Murray "wobbling rotor flux redirector" and deciding that you will make the wobbling rotor into the magnet, then don't hold out much hope.

Ask yourself this:  Is there any difference between a wobbling rotating magnet and a regular rotating magnet as far as it goes from the point of view of some pick-up coils surrounding the rotor?

The answer is no.  The pick-up coils are "blind" and they could not care less if the changing flux came from a wobbling rotor, a nice spinning axially magnetized cylinder, or from a Aborigine witch doctor frantically waving magnets around in front of the coils.

Jim Murray is quackery, but I know that a lot of the fun for you is building stuff.  Just don't expect anything unusual on the power generation side of things.

I looked at your clip.  If you engaged those big batteries to energize the coil with a big relay and the relay got stuck you could have a risk of a thermonuclear meltdown if you did not have a secondary switch for an emergency shutoff.  If you have a big knife switch lying around it would be useful as an emergency shutoff.

What about capacitors?  Do you have any big capacitors of sufficient voltage?  If yes, then a few big industrial power diodes in parallel for the capacitor and some in parallel for shorting out the big BEMF current pulse from the coil itself and a big knife switch and you might have a viable capacitor-based magnetizer.  It sounds safer to me.
Title: Re: 47000 Watt Magnetizer
Post by: tinman on November 24, 2015, 02:14:51 PM
If you are doing a variation on a Jim Murray "wobbling rotor flux redirector" and deciding that you will make the wobbling rotor into the magnet, then don't hold out much hope.

Ask yourself this:  Is there any difference between a wobbling rotating magnet and a regular rotating magnet as far as it goes from the point of view of some pick-up coils surrounding the rotor?

The answer is no.  The pick-up coils are "blind" and they could not care less if the changing flux came from a wobbling rotor, a nice spinning axially magnetized cylinder, or from a Aborigine witch doctor frantically waving magnets around in front of the coils.

Jim Murray is quackery, but I know that a lot of the fun for you is building stuff.  Just don't expect anything unusual on the power generation side of things.

I looked at your clip.  If you engaged those big batteries to energize the coil with a big relay and the relay got stuck you could have a risk of a thermonuclear meltdown if you did not have a secondary switch for an emergency shutoff.  If you have a big knife switch lying around it would be useful as an emergency shutoff.



I see a very big difference MH,but i dont think you do,or maybe you dont understand as to how i am going to go about it,or how the magnetic field is orientated on the !!wobbling rotor!!. It will not be anything like a normal rotor,or the Aborigine witch doctors waving magnets.

Quote
I looked at your clip.  If you engaged those big batteries to energize the coil with a big relay and the relay got stuck you could have a risk of a thermonuclear meltdown if you did not have a secondary switch for an emergency shutoff.  If you have a big knife switch lying around it would be useful as an emergency shutoff.

Way ahead of you there MH--i have the knife gate ;)

Quote
What about capacitors?  Do you have any big capacitors of sufficient voltage?  If yes, then a few big industrial power diodes in parallel for the capacitor and some in parallel for shorting out the big BEMF current pulse from the coil itself and a big knife switch and you might have a viable capacitor-based magnetizer.  It sounds safer to me.

I dont have any capacitors large enough to do the job. What i do have is some very large diodes,and they will be used across the coils to form the current loop upon switch off. I will be fireing the relays by using series capacitors. This way,by adjusting the value of the capacitors,i can adjust the time the relay is on,and i will just put a high value bleed down resistor across the capacitors,so as we have an auto reset on the caps.

I posted a comment on Aarons video about Jim Murrys generator,but he removed it within 15 minutes lol. Some just dont like the truth. Below is a screen shot i took right after i posted it .
Title: Re: 47000 Watt Magnetizer
Post by: MileHigh on November 24, 2015, 02:29:16 PM
Quote
I dont have any capacitors large enough to do the job. What i do have is some very large diodes,and they will be used across the coils to form the current loop upon switch off. I will be fireing the relays by using series capacitors. This way,by adjusting the value of the capacitors,i can adjust the time the relay is on,and i will just put a high value bleed down resistor across the capacitors,so as we have an auto reset on the caps.

Sounds great.  Don't wear a watch, you might get sucked in!

Quote
I posted a comment on Aarons video about Jim Murrys generator,but he removed it within 15 minutes lol. Some just dont like the truth. Below is a screen shot i took right after i posted it.

Thought control.  It's a giant false flag.  Those guys nuked the whales in the late 1970s.

https://www.youtube.com/watch?v=4IUxK_0WLbg
Title: Re: 47000 Watt Magnetizer
Post by: tinman on November 24, 2015, 03:14:47 PM
 author=MileHigh link=topic=16209.msg466628#msg466628 date=1448366028];



Quote
Ask yourself this:  Is there any difference between a wobbling rotating magnet and a regular rotating magnet as far as it goes from the point of view of some pick-up coils surrounding the rotor?

Take a look at the diagram below MH,and see if you can understand as to the operation and the forces involved. Although the rotor magnet is spinning,the coils see only a magnetic field shifting from side to side of the core. As the odd shaped rotor magnet spins,the center of the magnet moves away from the center of the core,and one field of that magnet begins to build in that core as the other field moves away from the core. The counter force from the core pushes down on the rotating magnet,at right angles to its rotating direction. Also note the angle the magnet will be on as to that of the shaft carrying the magnet,and the downward counter force from the coil-the back torque.

Well this is the way i see it anyway,and the only way to find out is to build it. But first i have to get the magnetizer up and working-which i hope to have finished by this saterday. Then we start some test,and see if we can actually make a decent magnet with it. If not,i feel a big rail gun coming up :D
Title: Re: 47000 Watt Magnetizer
Post by: MileHigh on November 24, 2015, 09:18:48 PM
It sounds like you are trying to "cheat Mother Nature" and avoid any Lenz Law back-torque from the pick-up coils.  I don't see that happening.

I can see that you want to magnetize the rotor axially and it looks like the coils will see very limited changing flux like that.  I thought you were going to magnetize the rotor radially.
Title: Re: 47000 Watt Magnetizer
Post by: tinman on November 25, 2015, 12:14:47 AM
It sounds like you are trying to "cheat Mother Nature" and avoid any Lenz Law back-torque from the pick-up coils.  I don't see that happening.

I can see that you want to magnetize the rotor axially and it looks like the coils will see very limited changing flux like that.  I thought you were going to magnetize the rotor radially.

Yes,the magnet will be magentized axially(through the thickness)
Why do you think the coil will see a very limited changing flux?
At 0*,the field in the core will be neutral.
At 90*,the field in the core will carry only one pole.
At 180* the field will once again be neutral.
At 270*,the field will carry the other pole.

Anyway,like i said-only one way to find out.


Brad
Title: Re: 47000 Watt Magnetizer
Post by: MileHigh on November 25, 2015, 10:23:52 AM
Yes,the magnet will be magentized axially(through the thickness)
Why do you think the coil will see a very limited changing flux?

Brad

Well, axially magnetized means relative to your diagrams the main flux through the thickness of the rotor will be horizontal.  Likewise, the return flux above and below the rotor will be horizontal.  Obviously this is a big simplification.  That means that the horizontal flux lines will be cutting across your pickup coils at about 90 degrees - the pickup coils are on a vertical axis in your diagram.  If you have changing flux that is purely horizontal and the pickup coils are vertical then the coils will pickup nothing.  Therefore your pickup coils will pick up relatively little changing flux and thus generate relatively little EMF and have a limited available output power.
Title: Re: 47000 Watt Magnetizer
Post by: tinman on November 25, 2015, 02:45:56 PM
Well, axially magnetized means relative to your diagrams the main flux through the thickness of the rotor will be horizontal.  Likewise, the return flux above and below the rotor will be horizontal.  Obviously this is a big simplification.  That means that the horizontal flux lines will be cutting across your pickup coils at about 90 degrees - the pickup coils are on a vertical axis in your diagram.  If you have changing flux that is purely horizontal and the pickup coils are vertical then the coils will pickup nothing.  Therefore your pickup coils will pick up relatively little changing flux and thus generate relatively little EMF and have a limited available output power.

I see no reason why the pickup coils will not see a changing magnetic flux,and a good one at that.
In fact,i will put together a quick demo tomorrow night,and we will see if sliding a magnet across an inductors core(with an air gap of course)back and forth produces a good EMF in that inductor.
I have not tried it yet,but my guess is that the core will carry the field that is under it just as good as it would with a magnet passing by it-as in a normal generator setup.
Title: Re: 47000 Watt Magnetizer
Post by: picowatt on November 25, 2015, 08:18:48 PM
I see no reason why the pickup coils will not see a changing magnetic flux,and a good one at that.
In fact,i will put together a quick demo tomorrow night,and we will see if sliding a magnet across an inductors core(with an air gap of course)back and forth produces a good EMF in that inductor.
I have not tried it yet,but my guess is that the core will carry the field that is under it just as good as it would with a magnet passing by it-as in a normal generator setup.

Tinman,

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?.

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.

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.   

PW   
Title: Re: 47000 Watt Magnetizer
Post by: MileHigh on November 25, 2015, 08:37:39 PM
I see no reason why the pickup coils will not see a changing magnetic flux,and a good one at that.

Really?  Look at my chicken scratchings.  What do you think about my marked up drawing?
Title: Re: 47000 Watt Magnetizer
Post by: DreamThinkBuild on November 25, 2015, 11:22:11 PM
Hi Tinman,

Quote
I wonder if the coging was due to the fact that your magnet was not shaped so as the outer perimeter was always level with the core of the coil's like mine will be?.

Yes, the design crossed the plane so that the magnets pole was angled toward the stator. This also introduced Lenz when loaded, it was not efficient.

Your design stays within the edge boundary of the magnet which would be interesting to see the difference.
Title: Re: 47000 Watt Magnetizer
Post by: citfta on November 25, 2015, 11:23:53 PM
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
Title: Re: 47000 Watt Magnetizer
Post by: DreamThinkBuild 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.
Title: Re: 47000 Watt Magnetizer
Post by: tinman 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

Title: Re: 47000 Watt Magnetizer
Post by: tinman 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.
Title: Re: 47000 Watt Magnetizer
Post by: tinman 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)
Title: Re: 47000 Watt Magnetizer
Post by: citfta 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
Title: Re: 47000 Watt Magnetizer
Post by: citfta 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
Title: Re: 47000 Watt Magnetizer
Post by: picowatt 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
Title: Re: 47000 Watt Magnetizer
Post by: tinman 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.
Title: Re: 47000 Watt Magnetizer
Post by: DreamThinkBuild 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.
Title: Re: 47000 Watt Magnetizer
Post by: citfta 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 (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.

Title: Re: 47000 Watt Magnetizer
Post by: MileHigh 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.
Title: Re: 47000 Watt Magnetizer
Post by: DreamThinkBuild 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.
Title: Re: 47000 Watt Magnetizer
Post by: tinman 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
Title: Re: 47000 Watt Magnetizer
Post by: tinman 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
Title: Re: 47000 Watt Magnetizer
Post by: gyulasun 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
Title: Re: 47000 Watt Magnetizer
Post by: citfta on November 29, 2015, 01:28:19 PM
Hi Brad,

Your wire is too small.  According to the ampacity charts that size wire is only good for a maximum of 302 amps.  If I understand your system you are trying to get 1000 amps through that wire.  You are going to have to parallel some of those wires together to reduce the voltage drop.

I don't have time right now to do the research but I think 35 ms is too short of an on time to magnetize something.  Just roughly I remember our magnetizers at work taking at least a second to magnetize something and several seconds to demagnetize an object.  I'll try to look up some info on that later in the day unless someone else gets it first.

Carroll
Title: Re: 47000 Watt Magnetizer
Post by: tinman on November 29, 2015, 01:40:58 PM
Hi Brad,

Your wire is too small.  According to the ampacity charts that size wire is only good for a maximum of 302 amps.  If I understand your system you are trying to get 1000 amps through that wire.  You are going to have to parallel some of those wires together to reduce the voltage drop.

I don't have time right now to do the research but I think 35 ms is too short of an on time to magnetize something.  Just roughly I remember our magnetizers at work taking at least a second to magnetize something and several seconds to demagnetize an object.  I'll try to look up some info on that later in the day unless someone else gets it first.

Carroll

Hi Carroll

No,the wire is not to small,as it is 12mm in diameter,not 12mm square area.The cable i am using is from the machine that had this battery bank in it,and as we heard from PW not so long ago,it dosnt take to much to gain instantaneous current,which is a lot different to that of continuous current.


Brad
Title: Re: 47000 Watt Magnetizer
Post by: tinman on November 29, 2015, 01:53:49 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

Hi Gyula

Yes-i believe the relay is letting me down here,and that clearly looks like arcing at the start of the power pulse. Voltage up to the relay remains at 49 volts when the relay switches on,but at the coil you can see a clear drop. The resistance of the coil i cant measure,as it only go's to the second decimal. So it seems that the relay is the cause of the current drop. The resistance across these batteries would be extremely low as they have a very large plate area. But how to switch a current load this large cleanly if not with a relay ?

I can magnetize metal objects,but only weakly. The field is very strong in the pot,as i placed a speaker magnet in there,and hit the button while holding it with my hand. It blew my hand out of the pot no problem at all--and i was holding it with a fair bit of force. I think the unclean switching is why i cannot get a good permanent magnet to form.


Brad
Title: Re: 47000 Watt Magnetizer
Post by: picowatt on November 29, 2015, 01:59:16 PM
Hi Carroll

No,the wire is not to small,as it is 12mm in diameter,not 12mm square area.The cable i am using is from the machine that had this battery bank in it,and as we heard from PW not so long ago,it dosnt take to much to gain instantaneous current,which is a lot different to that of continuous current.


Brad


What???

I have no idea what this comment is in regards to.

PW
Title: Re: 47000 Watt Magnetizer
Post by: tinman on November 29, 2015, 02:12:27 PM

What???

I have no idea what this comment is in regards to.

PW

In regards to a small wattage valued resistor being able to deliver a large amount of instantaneous current to a load in a pulsed situation. Of course in this case we are talking about 350 amp cables being able to handle say a quick 1000 amp pulse,due to the fact that the amp rating for cables is continuous.
Title: Re: 47000 Watt Magnetizer
Post by: picowatt on November 29, 2015, 02:36:51 PM
In regards to a small wattage valued resistor being able to deliver a large amount of instantaneous current to a load in a pulsed situation. Of course in this case we are talking about 350 amp cables being able to handle say a quick 1000 amp pulse,due to the fact that the amp rating for cables is continuous.

Tinman,

That was only with regards to dissipation.  It has nothing to do with somehow being "easier" to produce instantaneous versus continuous current.

A lower wattage resistor can handle a VI product for a short period of time that would otherwise cook that resistor if applied continuously.  That discussion was with regard to duty cycle, CVR wattage ratings, and primarily your 85 watts comment in that other thread.  This has little to do with what you are attempting to do and nothing to do with somehow being "easier" to produce instantaneous currents.

Possibly the linked document may be of interest to you:

http://www.oersted.com/magnetizing.PDF

PW
Title: Re: 47000 Watt Magnetizer
Post by: picowatt on November 29, 2015, 03:24:55 PM
Tinman,

Do you have any idea what kind of current you are pulling?

If the bulk of that 25 or so volt drop is across your relay contacts and at a large current, I'd be very concerned about the relay contacts welding together.  Be careful.

Have a plan for disconnecting the batteries (or you will find out which part of the circuit is dissipating too much, overheats,  and "fuses" open first).  At the least make sure that all your wiring, relay, and fixture is positioned away from flammable materials so that in the event of something catching fire it won't propagate quickly.  You should also have a fire extinguisher close by.

PW