Rare Earth Magnets (The Effect Loading vs Degaussing)

Hello Brain Gain

That was the historic reason for permanent magnets to have a 'soft iron keeper' across their poles - to retain that magnet's strength.

Whilst rare earth magnets are far more powerful, they do, over time, 'lose magnetic strength', the reason being random atomic movements within all materials.

Magnetic strength losses can be reduced by lowering the temperature of the magnet, thus reducing random atomic movement.

Your item (2) reasoning is correct - to a point, but the magnet can never recover to the same strength as it was when new, because that would require an injection of energy from outside the magnet.

No matter what is done, every permanent magnet is going to lose its strength over time, as the random atomic movement does generate a very small amount of internal heat, which is radiated and conducted away.

Energy lost to a system by heat loss, can only be replaced by a greater amount of energy either as heat or energy of a higher order than heat: Pressure/electricity/mechanical etc.

The loss of magnetism which occurs with permanent magnets is the main reason that very old hydro power stations have to increase excitation of the main alternator to obtain the same output - the small master DC Generator (Pilot Generator) atop the turbine shaft, has lost magnet field strength.

The small Master Generator (Pilot Generator) is immediately below the item marked '2' in the picture at left.

Below the Master Generator is the exciter generator (which uses electromagnets) and also has a DC output, that DC output excites the Rotor of the Main Alternator.

Some power stations over 100 years old have had to remove the Pilot Generator magnets, and send them for re-magnetising at a facility which does this.

Permanent magnet re-magnetisation is generally done using the same method as making a permanent magnet from new: By placing the magnet inside a shaped coil, and then a large bank of charged capacitors are discharged simultaneously into that coil.

Kind Regards....

Thank You for your information!

I hope you will stay with me awhile and not get put out because I am knot an engineer but an extremely creative technical minded person, so some of my terms may not be as exact as a professors but when I get Ideas they are based on the available information I can find, so finding some one that can fill in the blanks and will work with me to build my knowledge in what ever I am investigating no matter how stupid it may appear to be is very helpful. I find in general the reason so many Ideas fail is because they are so simple that they get labeled as ether stupid, or the classic "if it was that simple it would have already be done"!

Now first thing I am not sure if you meant it the way it sounds in your post but if you are implying that the magnet gets its strength from the energy that it takes to magnetize it that much I am fairly sure would be wrong, a magnet gets it strength from the alignment of the atoms, the magnetic field in a magnet was always there but until the atoms are aligned they randomly apposed to each other so the fields are canceled out, as I understand it it the powerful electro magnetic field that the energy creates dose the magnetizing (IE pull the atoms into alignment in a particular polar alignment) not the energy that it took to create that field, again my understanding is that there is no energy in stored in a magnet so no energy can be lost or consumed, the field is part of the atoms them selves, so my Idea is that any magnetic field or maybe even a material such as iron put in proper orientation to a magnet that was already magnetized would induce an alignment effect on the atoms of the affected magnet helping to reduce or even repair an intermittent degaussing effect of being pulsed by another magnet in opposition? Is this not similar to the Idea of the keeper was not its purpose to create a load on the magnet so that the fields of the atoms pulled in to alignment and the magnet would have a longer life span (sort of like the effect of pulling on both ends of a piled up chain until all the links were in a straight line)?

I hope you will give me you view. Thanks!

Hello Brain Gain

The material of what could be made into a permanent magnet, has the potential to be permanently magnetized.

But all those magnetic domains appear to be randomly pointed, and thus there is no "magnetic field" as such.

To snap or pull many domains into line or agreement, takes energy, generally with a high-current pulse from a capacitor bank discharge through a specially shaped coil for the particular shape/size of the intended permanent magnet.

It has not been possible to make a permanent magnet any other way, and if the atomic structure/physics of magnetic materials are studied, I do not think it would ever be possible to make permanent magnets any other way.

Lodestone or Magnetite from Asia Minor and other places, is a naturally occurring material which does have permanent magnet ability, caused by Earth's magnetic field over eons, or by a sudden lightning strike or several to the magnetite mass many years ago.

It is random atomic movement which destroys permanent magnets, and with heating (and faster random atomic movement) the loss of permanent magnetism is faster.

There is the critical temperature at which all permanent magnetism is lost, for each type of magnetic material, which is called the Curie Point, after the discoverer of the effect, and upon cooling below that point, the material regains the ability to be magnetized, but in the case of a permanent magnet heated above its Curie Point, the permanent magnet property is lost, although the material may be re-magnetized.

Part of the problem is that we do not really know what magnetism is, as for gravity, electricity, light etc, we can measure effects, try and deduce how the materials are designed, but we shall never know it all.

Kind Regards....

All of the above I have read before but is not the point of what I am posting to find out.

I am not looking to manufacture a magnet from scratch.....

although basic high school science experiments from when I was in school had you take a bar of iron rub a bar magnet across it about a hundred times and for several minutes you had a fair magnet and it was explained to us that the magnetic field of the magnet traveling along the surface of the iron aligned the poles of the atoms in the iron bar thus making it a magnet, but dew to the nature of iron it dose not hold the alignment for very long, but in this example no energy was transfered or infused into the iron from the magnet, so if a more appropriate metal was used instead of the iron bar then the magnet you made would last much longer, the use of very powerful energy hungry DC magnetic coils used for to manufacture magnets for sale is for speed of mass quantity production, if you used ordinary magnets to mass produce magnets you would have to hire hundreds of people and it would take each one weeks of stroking to make 1 magnet each for to sell.

What I am looking for a way to curb or compensate the degaussing effect that occurs when 2 magnets pass close to each other with like poles pushing against each other, according to one manufacturers website FAQs page when this happens modern rare earth magnets resists the degaussing effects but long term repeated exposure will cause a slow degrading of the magnetic field, this would mean after a while some of the the alignments within the magnet will become misaligned and that it was caused by the 2 like pole in close proximity pushing their own fields back into each other thus causing the misalignment. My contention is if the magnetic force of its own magnetic field pushing back onto itself can demagnetize itself over time then the reverse should work to correct the problem, by applying attraction during the time in between the pulses of repulsion you might be able to realign the little bit that was pushed out of alignment by the repulsion.

I am only trying to compensate for a slow external degradation effect of placing 2 magnets set to repel each other repeatedly at a rate of 1 time out of 3 time periods. And I am hoping that by applying the correction for a period twice as long as the duration in between the degrading pulses of the repulsion that you would equalise the 2 effects thus the magnet would remain unharmed.

Hello again Brain Gain

<"....but in this example no energy was transfered or infused into the iron from the magnet....">

True, but energy was required to align the magnetic domains.

That energy came from sunshine, which caused plants to grow, and you ate meat, fish, fruit, etc, burned fuel in muscles to produce movement, and thus the mechanical energy to stroke that steel bar.

If the reasoning from the iron keeper example is extended, then for longevity of rare earth magnets, the opposite pole to opposite pole of identically shaped and strength magnets would be the best means of magnetic field retention, because no force is required to maintain that position - the system is at the lowest possible energy level.

Is that what you are asking?

Kind Regards....

Thats a lot closer but not exact, what I have in mind will place the magnets in question moving in front of other magnets and they will be repelling each other as they pass across each other, so with out a method of correcting the damage to the alignment with in the magnets after each time this happens soon the magnets would be useless, what I am hoping is that by placing a load such as the idea of the iron keeper or what I would think would act as a far better keeper another magnet pulling on the 1st one located on the opposite side of the magnet that is being affected, hopefully keeping the magnet from failing do to degaussing from the magnets passing each other while repelling each other!

Hello again, Brain Gain

What is the purpose of your proposed mechanism?

Does it have some useful purpose?

If so, what useful purpose?

A diagram or picture would assist.

Kind Regards....

Do to the number of members and guests that at the mention of certain possibilities or projects transform into homicidal physicists, associates of an alien invasion force, or the president of a local prominent clown collage. For this reason I have avoided any detailed ideas for the purpose of what I want to doing with this information.

The most mainstream use that is somewhat accepted is the high speed levitating trains the use of natural magnetic materials wont work in the long run because of the degaussing effect cased by having the magnetic fields repelling, some of the designs the propulsion as well as the levitation is done with apposing magnetic fields, but with regular magnets out of the question electro magnets are all thats left and that makes them just to expensive to operate, so if I could find a solution to the magnet problem I could maybe afford to retire one day and waste the rest of my time and money on those other unnameable projects!

But if you cross your eyes and hope die laughing before you let anyone know about my planed Ideas I will if you wish I will send you a message with more of my impossible projects using the solutions that I seek!

Hello once again, Brain Gain

Send me a PM with your list of proposed projects.

I shall check out each one, and advise to the best of my ability.

Kind Regards....

Hi Brain Gain,

I have read your discussion with sparky on magnets. As I understand it, the magnetic field of a PM is what remains when the material is exposed to a much greater magnetic field ( magnetisation). Thus you must consider the PM to really be a combination of a weak permanent magnet plus a ramdom magnetic field. Any disruption to the magnetic field causes the magnetic grains in the PM to alter, this is a statistical thing and is very small compared to the whole. The purpose of the KEEPER is to preven any exposure of the PM magnetic field to any change. Thus it keeps the PM. It does not restore it. Any exposure of the PM field to a changing magnetic magnetic field will have a randomising effect and so this is why the MP slowly deteriates with use no matter what polarity is put on it. The only way to have a restoring effect is to expose it to the intense field that was used to make it in the first place. Consider also the HYSTERESIS curve.

Sorry I have not worked out how to post in CR4. Regards with your ideas and good luck. I have come to realise that one of the worst understood things is the second law of thermodynamics. So many people do not realise that they are atempting to contravene it somehow. It is actually one of the best established laws in the natural world and prevents many minds from getting that little edge to gain something from nothing. That said. If you don't understand why something does not work don't be put off by those who laugh at you but cannot do any better in explaining exactly why.

Hello again Brain Gain

<"....But if you cross your eyes and hope die laughing before you let anyone know about my planed Ideas I will if you wish I will send you a message with more of my impossible projects using the solutions that I seek!....">

I am still waiting for your message, which has yet to arrive in my mailbox.

Perhaps you did send it, and it got lost in cyberspace.

Could you please re-send the message as promised.

Kind Regards....

Hi BG,

to #1: high power magnets will not lose magnetisation if pulsed by other magnets of any type or shape or orientation. There will be some heat generated by eddy currents as both SmCo and FeNdB are electrically conducting and the rate of change of magnetic flux by moving or switching a magnetic field will induce a voltage that will cause a current and power loss. The energy will come from the moving magnet.

Losing magnetism with time (as in the example of old generators given by Sparkstation) happened with the FeCo-materials used from 1900 to 1950 but as soon as the Ferrites and later the rare earth magnet material was invented this was history.

There is some slight degradation with time and temperature ( a few %) if the magnet have not been stabilised by a thermal cycle up to 20°C above the highest temperature of use.

For de- and re-magnetisation of rare earth magnets you need minimum 4 Tesla, requiring big capacitor banks and copper coils that easily turn into pieces by the pulsed currents and magnetic forces.

Recovery of magnetic field is as soon as the eddy currents decay. A small amount at cooling down to original temperature. This temperature dependency can be avoided by adding some Gadolinium to the SmCo but this is used only in measurement where precision is required.

#2: as there is no demagnetising effect (or may be so slow that you cannot detect it), but have in mind that the orientation of atoms is very far from being perfect: only a small minority (0.1%) is oriented. It would be great to have this better!

#3: I never heard this but it is not likely to be true as this effect would prevent the use in high speed motors where high centrifugal forces exist - these motors are existing, bandages of carbon-fiber with epoxy are used to increase strength of bonding of the magnets to the rotor.

#4: nothing necessary as there is no decay of magnetic power with time

Try and measure your ideas.

Be cautious with uncoated (metallic!) rare-earth: any small amount of hydrogen will damage these permanently. This hydrogen will come from corrosion of iron or aluminum as the water involved will be turned chemically into hydroxide and this generates some hydrogen.

Have success

RHABE

Here are some things to read.

http://en.wikipedia.org/wiki/Remanence

http://en.wikipedia.org/wiki/Coercivity

http://en.wikipedia.org/wiki/Magnetization

We used to play with magnets with a capacitor bank we used for our laser experiments in the 1960's. These used ruby rods and a bank of flash tubes and a capacitor bank charged to 5,000 volts connected directly to the flash tubes with a gas filled spark gap acting as the switch. We then sent a spark to the glass of the spark gap and this would trigger it into a conductive state and the caps would discharge very quickly.(with a loud bang)

By replacing the flash tubes with a single turn of copper bus wire 1/2 inch wire, we could then magnetize anything we could fit into the single turn coil as the pulse was enough to magnetize whatever you liked.

It was always fun to give a grad student a small box of 250 or so small neodymium magnets as they came from the manufacturer (who would would pack these 2 cm x 2 cm x .5 cm pieces into the box prior to magnetization). We would watch as he opened the box (which was tied shut)... as soon as the lid was off they would all climb out of the box and there was no way he would ever put them back...as we insisted he do. hahaha.

I think you will find the strength of your magnets will degrade exponentially over time. After a number of pulses, the rate of degradation will diminish. The amount of energy required to remagnetize is much greater than the energy supplied by the magnet, making it inefficient to try to re-magnetize between pulses.

In my experience (decades old) good rare earth magnets would last for a long time, even when placed in opposition to the magnet next to them (N-N, S-S). That is the usual configuration of magnets to form magnetic lenses to focus an electron beam, as in TWTs. Granted, the magnets are stationary, relative to each other, and, while there are a lot of crazy E-M fields around them, they are somewhat shielded by iron pole pieces. The fact that we are still receiving data from decades old spacecraft is proof of the stability of the magnets.

Hi Esbuck and others,

you are absolutely right. The Pioneer space probes are now on their way for 30 years and can still rely on the Samarium-Cobalt magnets that are inside the SDG5 gyros built by Teledyne Systems.

Two uses: driving motor and two axis torquer.

The torquer is much more sensitive to degradation, nothing is known until now.

Much more demanding situation is in strap-down inertial navigation where the torquer is directly measuring the rate of turn of the airplane (3 axis: roll, pitch and yaw by 2 or more gyros, each gyro has two measurement axis perpendicular to spin axis).

These magnets are moving, they are subject to different and time-varying magnetic fields from the coils in immediate vicinity, they are subject to heat-inputs from these coils and nothing happens to these magnets!

So there is no problem with rare earth magnets regarding longterm stability.

RHABE

And I've just determined, (thankyou very much) why the gyrocompass isn't working! There is a differrence in polarity strength.

I hate to spoil all of the universes experts on physical laws but there is a hole in those laws you could toss a universe through! Everything in the universe is made up of atoms all atoms are made up of protons, neutrons, and electrons....

Our universe is said to be a closed system, so the number of these components in the universe at the first moment in existence is, and will be the same at the last moment!

Now heres the problem if you cant get something from nothing then ware did the universe that these laws absolutely explain, control, and exclude something from nothing, come from.

If it was not for this giant hole you would not be here in the first place to be bashing creative people over the head with these laws that are written with more hole than substance!

The fact that the universe exists means that it is possible for something to come from nothing, or do you think that everything here came from some ware else and if so how did it come to be there? And further more how did it get here? And so on and so on and........

Hello again, Brain Gain

I can see why you are worried, and you want to know where it all came from, and how all of it is still maintained.

I was once in that very same situation, and asked around, until I was advised to look in what that helpful person called: "The Manufacturer's Handbook".

So I'm going to advise you, to the very best of my ability.

If you have a Bible handy, turn to the first book, right at the start: Genesis.

The Name "Genesis" means "Beginnings".

So...Genesis Chapter 1 Verse 1 (Gen 1:1) "In the beginning God created the heaven and the earth."

The word translated as 'heavens" is the Greek word "cosmos", which means all things, not only in this galaxy, but everywhere.

Just so the reader of that first verse in the Bible could not misunderstand, the word "earth" means the "Planet Earth" the planet we live on.

Now I don't want to have a "Religious War" here at , as you may appreciate, but you did ask a valid question which does include Engineering and Scientific principles discussion, amongst other Principles.

Thus you are welcome to send me a Private Message (PM) to me at should you wish, and I shall endeavour to answer your questions to the best of my understanding.

Have a look at my Member Profile please, and know that I did not "come down in the last shower".

Kind Regards, as always, from far away....

Interesting, plausible, Ok now using that as the basses even a god must have had to follow procedures, after all first came the the space that he put everything and apparently that space came with laws that even he had to conform to...

Because next came light, that makes sense because light is not only the beginning of energy for all that came later but it would have been stars that would later be the core of the solar systems that way there was some ware to put the planets.

Next came the planets that make up the solar systems and they in turn make up the universe.

Next was life but with out everything in place it need to live and grow which was everything that came before it, it could not exist and would have perished.

Then in a flash was man and if he had came before any or all of the above then he would have perished at the moment of his creation.

So in this model of the law of creation which is as valid as any physicists model of creation it would show that once the space was created that would hold our existence then with it came the limitations it creates in order for everything to work with in it! Else there would have been no need to take the steps that is said to have happened in the bible, as all powerful as he is written to be he would have been able to have done it all in a single event.

But in this model and if indeed he was constrained by the power of the reality that was of his on construction then the ability to create something from nothing is with in the physics of our universe we just have not discovered it yet!

And those that say without absolute knowledge of everything that it can not be done you are no better that those in the dark ages that claimed that everything they could not understand was witch craft, or black magic, or voodoo, or even the devils doing, in several hundred more years our science my be seen as primitive as was there explanations are to us now! Who knows I sure don't but the next great set of fiscal laws set down to us may come from the next book that one day may be discovered by man that will create the next sequel to the greatest selling book in mans history the bible!

By the way, this wasn't to make any statement about the bible, or beliefs, I only did this to show that a model that explains the laws of the universe, no matter how likely they sound, or how well they fit what is known, or for how long the seam to fit it, dose not mean they are complete or correct! Anyone that with a little logical creativity can make almost anything into a model of what ever you are trying to explain and with the same long lasting fit!

Please nobody go all bible on me! Sorry if this bothered some one, it was only intended to show that nothing is absolute until you know everything! And once you know everything then you will know exactly what the point of all this was!

• First day: God creates light ("Let there be light!") - the first divine command. The light is divided from the darkness, and "day" and "night" are named.
• Second day: God creates a firmament ("Let a firmament be...!") - the second command - to divide the waters above from the waters below. The firmament is named "heavens".
• Third day: God commands the waters below to be gathered together in one place, and dry land to appear (the third command). "Earth" and "sea" are named. God commands the earth to bring forth grass, plants, and fruit-bearing trees (the fourth command).
• Fourth day: God creates lights in the firmament (the fifth command) to separate light from darkness and to mark days, seasons and years. Two great lights are made (most likely the Sun and Moon, but not named), and the stars.
• Fifth day: God commands the sea to "teem with living creatures", and birds to fly across the heavens (sixth command); He creates birds and sea creatures, and commands them to be fruitful and multiply.
• Sixth day: God commands the land to bring forth living creatures (seventh command); He makes wild beasts, livestock and reptiles. He then creates Man and Woman in His "image" and "likeness" (eighth command). They are told to "be fruitful, and multiply, and fill the earth, and subdue it." Humans and animals are given plants to eat. The totality of creation is described by God as "very good."
• Seventh day: God, having completed the heavens and the earth, rests from His work, and blesses and sanctifies the seventh day.

Taking into consideration when this was written it nevertheless is an amazing observation of cosmological, geological, botanical and biological progression. There is a scientific method at work here.

I thought I would just post something lighter in the way of physics.

This is something I read some ware along time ago that is both a mind expander and a tease....

Nothing from nothing is always nothing without exception!

Nothing contains just that, no length, no width, no hight, no volume it literately is nothing....

The space between two planets, stars extra is called a void, a void contains and is nothing....

And nothing as said before is nothing and cannot be measured in any way, or can it?

Do we not measure the distance between worlds stars and other objects across the nothingness of space?

So since we now can measure across nothing dose that mean nothing is really something? And that the void of space is also made up of something?

I would post a credit for this tidbit but frankly that information was lost long ago in the void of my mind!

Go along with the manufacturer suggestion!

I do not know basically anything about the rare earth magnets but, I do know however, that only small speakers used and may still use alnico magnets because most of them have been replaced with ceramic (Ferrite) type.

This very important that ceramic magnets are used in large speakers where, I guess, large sound pulses could soon degauss the permanent magnet had it been an alnico type.

The other example is the electric motor where the armature is excited from an external power source and could adversely affect the alnico permanent magnet. This is why the ceramic magnet is a the better option. (A motor in many cases acts as a generator for the speed-controller and it is very important to have a stable magnetic-field in a tape-player, for example, otherwise it would soon falter in sound reproduction had the magnet in the motor been an alnico type.)

In a generator of a small combustion engine, however, does not matter if the permanent magnets are alnico types because the coils are getting excited and not powered externally therefore, any EMF in the coils cannot exceed the strength of the permanent magnets which create them (it is impossible due to the laws of physics). When the engine stops the inductor-cores load the magnets so they do not loose their strength.

A lot of advances have been achived recently with permanent magnets as I noticed and I do not know anything about rear-earth magnets, but I'd say listen to the manufacturer only.

This blog is good to vent your thoughts but there were only two people, if you noticed, gave you a good input but, I think, you may need a little more help here since you know what you want to conjure in your workshop.

Ok Here is some ferromagnetic Magnets 101

This information comes word for word from "The Basics of Physics" by Rusty L Myers Pages 256-258

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An electric field surrounds any charged object.

The movement of charge creates a magnetic field.

For a magnet at rest the source of moving charge is not readily apparent.

The source of magnetism at rest is the movement of the charged electrons in the atoms making up the material.

Electrons in an atoms orbit (The term "orbit" is used loosely because the quantum mechanical model of the atom dos not contain electrons in well arranged orbits)the nucleus and spin on their axes.

The spin of electrons is more important in determining the magnetic properties of a material.

A minute magnetic field is produced from the movement of each electron in an atom.

Each electron in essence creates a sub-atomic-size magnet.

For most materials the electrons in its atoms are matched so that there are an equal number of electrons with sins in opposite directions.

When an equal number of electrons spin in opposite directions their magnetic fields cancel and there is no net magnetic field.

In some elements such as iron, nickel, and cobalt several valence electrons spin in the same direction producing a net magnetic field.

Materials in which atoms have an excess of electrons with the same spin are called ferromagnetic.

The magnetic field of each atom in ferromagnetic materials affects adjacent atoms.

The magnetic fields in many atoms become aligned in magnetic "neighborhoods" called magnetic domains.

Magnetic domains consist of billions of atoms having aligned magnetic fields.

Magnetic domains are about a millimeter in length.

In an ordinary piece of iron the domains are randomly oriented so that a piece of plain iron dose not act as a magnet.

How ever if a piece of iron is placed in a magnetic field the domains align with the magnetic field.

A weak magnetic field will cause the domains to align in the general direction of the field.

When the piece of iron is separated from the field the iron will lose its magnetic property quickly.

As the magnetic field strengthens the domains achieve greater alignment and the duration of the magnetism increases when the field is removed.

A permanent magnet results if the magnetic field is strong enough to cause the domains to remained aligned after the field is removed.

Permanent magnets can lose some or all of their magnetism when heated or disturbed for example by hammering.

The temperature at which a ferromagnet material loses its magnetism is called the curie point.

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With a great amount of luck maybe now you will believe that the power of the magnetic field in a rare earth magnet comes from the atoms that make up the magnets not the power from the capacitors used to generate the electro magnetic field that aligns the domains in the magnets. No power is transfered when a magnet is being magnetized. All of the power of a permanent magnet comes from the atoms that are aligned naturally into domains and then the external magnetic field that forces the domain to align.

You cannot stop the atoms from creating the magnetic fields only misalign them to ware the magnet dose not work.

In essence the magnet is atomic powered!

Hello Brain Gain

<"....With a great amount of luck maybe now you will believe that the power of the magnetic field in a rare earth magnet comes from the atoms that make up the magnets not the power from the capacitors used to generate the electro magnetic field that aligns the domains in the magnets. No power is transfered when a magnet is being magnetized. All of the power of a permanent magnet comes from the atoms that are aligned naturally into domains and then the external magnetic field that forces the domain to align.

You cannot stop the atoms from creating the magnetic fields only misalign them to ware the magnet dose not work.

In essence the magnet is atomic powered!....">

Please read some basic Science, and hopefully you will then understand.

There is no "holy grail" of "free energy" available from any magnet or collection/arrangements of magnets, anywhere.

There is no "Luck" involved at all.

A magnet in itself does have a magnetic field around it.

The permanent magnet in itself does not have any energy or power available.

A magnet in itself cannot do any useful work.

Work consists of effort or energy expended, which is always supplied by some external force through a medium of transfer: Lever/magnetic field/gravity/solar/heat/electricity/etc.

<"....No power is transferred when a magnet is being magnetised...."> - but the energy required to magnetise what will become a permanent magnet must always be supplied from an external source.

Energy from an outside source is required to demagnetise a permanent magnet.

<"....In essence the magnet is atomic powered!...."> - You have a complete misunderstanding if you use "atomic power" in the way used in your sentence.

Kind Regards....

You have to realise also that an artificial magnet during manufacture is shaped in a soft form and then it's annealed to achieve its permanent magnet properties prior to being magnetised.

Degaussing does not occur quickly. Just look at an engine fly-wheel magnet! It only happens when it's not loaded adequately after its removal when people fail to keep it adequately loaded. The heat from the engine can exceed well over 100C (due to poor air-cooling of the engine as opposed to a more stable one of a car engine) yet the magnets can still function for well over a decade even.

As long as the magnet is properly loaded even at operating temperatures will stay stable and cannot be adversely affected by EMF either.

Degaussing can only occur if the opposing field is substantially GREATER!

What's your opposing magnets' field like? Are they the same strength, barely different or the same?

That's why I said before go with the manufacturer suggestion.

The quotation you gave here is definitely confusing for many because it would quickly under mine the operation of many resonant circuits where there are many Ls and Cs working together side by side.

Some writers do not express their points clearly, only a few can, usually the ones who know what they're on about and definately not the copy-cat types, unless he's a hard to follow type due to being overly scientific.

So, if you overly concerned go with the manufacturer suggestion!

Hi

"You have to realise also that an artificial magnet during manufacture is shaped in a soft form and then it's annealed to achieve its permanent magnet properties prior to being magnetised."

That was long ago, today it is powder technology: grinding and mixing fine powders, then press and sinter, then magnetise!

Degaussing does not occur quickly.

This is limited only for some milliseconds by eddy-currents! And faster if Curie-temperature is reached.

Just look at an engine fly-wheel magnet! It only happens when it's not loaded adequately after its removal when people fail to keep it adequately loaded.

This effect is only existing in AlNiCo magnets and is an effect of the curvature of B/H-curve in the third quadrant. Any material that is operated on a significantly nonlinear part of its magnetisation curve will loose much of its field strength if the magnetic circuit is opened. To hold the magnetic circuit closed there are iron spacers needed.

The heat from the engine can exceed well over 100C (due to poor air-cooling of the engine as opposed to a more stable one of a car engine) yet the magnets can still function for well over a decade even.

Allowed operating temperature can be as high as 300°C.

You mix up drift of remanent flux density/ time if the magnet is not properly stabilised or operated at too high a temperature with demagnetisation by technical means.

As long as the magnet is properly loaded even at operating temperatures will stay stable and cannot be adversely affected by EMF either.

This is only depending on the magnetic hysteresis curve. If you generate m-fields of 4 to 7 Tesla then you can easily remagnetise (or demegnetise) also the strongest known permanent magnetic materials.

Degaussing can only occur if the opposing field is substantially GREATER! And this is possible by big EMF but will need ironless coils.

What's your opposing magnets' field like? Are they the same strength, barely different or the same?

The quotation you gave here is definitely confusing for many because it would quickly under mine the operation of many resonant circuits where there are many Ls and Cs working together side by side.

This is a totally different field, rethink your L's as being without cores, L-C oscillators will function as with soft-magnetic cores! You mix up magnetisation with charging a capacitor. If you really want to model this you have to add electrete characteristics to your capacitors.

It seems necessary to first get some textbook on magnetism, magnetic materials and use of permanent magnets. This may help to get rid of some erroneous assumptions.

RHABE

Hi,

Replying to your comment/s in bold.

That was long ago, today it is powder technology: grinding and mixing fine powders, then press and sinter, then magnetise!

Then it is still true that permanent magnets are shaped prior to magnetisation, is it not?

I did try to say that the ceramic magnets are better because they're less prone to loosing their strength over time as well as better against pulses in applications like large speakers, electric-motors and any other device which power is applied to (not generated by).

This effect is only existing in Alnico magnets and is an effect of the curvature of B/H-curve in the third quadrant. Any material that is operated on a significantly nonlinear part of its magnetisation curve will loose much of its field strength if the magnetic circuit is opened. To hold the magnetic circuit closed there are iron spacers needed.

The use of AlNiCo or whatever they maybe, in a combustion engine, can handle the type of physical stress that ceramic magnets could not, is it true? I do know that these type of magnets need to have their magnetic circuits closed. However, when a fly-wheel is removed, for any reason, then it should be placed on a jig that can keep the magnets loaded while the maintenance is carried out.

This is limited only for some milliseconds by eddy-currents! And faster if Curie-temperature is reached.

Allowed operating temperature can be as high as 300°C.

You mix up drift of remnant flux density/ time if the magnet is not properly stabilised or operated at too high a temperature with demagnetisation by technical means.

Talking about operating temperatures of the permanent magnets, you have basically just confirmed what I said that they can operate at elevated temperatures (in the excess of 100C). However, it would be foolish to design a machine to operate at the max limit of the material it's made from as it would not give room for tolerance.

This is only depending on the magnetic hysteresis curve. If you generate m-fields of 4 to 7 Tesla then you can easily remagnetise (or demegnetise) also the strongest known permanent magnetic materials.

I only tried to point out that any opposing force through a reaction, like EMF during generation, is not damaging to the magnet that causes it. Not in a short term and least of all if the magnet is a ceramic type!

This is a totally different field, rethink your L's as being without cores, L-C oscillators will function as with soft-magnetic cores! You mix up magnetisation with charging a capacitor. If you really want to model this you have to add electrete characteristics to your capacitors.

I only threw in the L-C concept, and I must admit I did not think about this topic when I read his quotation, because it is hardly relevant to his prime concern (The Effect Loading vs Degaussing).

It seems necessary to first get some textbook on magnetism, magnetic materials and use of permanent magnets. This may help to get rid of some erroneous assumptions.

I b...y will, don't you worry about it, since you started to become overly technical on this issue. I kind of realised it, at another discussion, that you probably more at home on this issue than most of us and it is undoubtedly a specialised area. I think, you can make a carrier out of it even.

However, I do not think, even your lash out at me on this topic, that I would have given our friend any misleading info considering the simple and humble nature of his original concern about Degaussing through pulsing.

Have a VG day!

Replying to your comment/s in bold. and italics. RHABE

That was long ago, today it is powder technology: grinding and mixing fine powders, then press and sinter, then magnetise!

Then it is still true that permanent magnets are shaped prior to magnetisation, is it not? Most are, but sometimes it is easier first to magnetise and then to cut or regrind or brake existing ones to desired shape. EDM is doing some damage by the spark pulses.

I did try to say that the ceramic magnets are better because they're less prone to loosing their strength over time as well as better against pulses in applications like large speakers, electric-motors and any other device which power is applied to (not generated by).Neither ceramic nor metallic are prone to loose strength over time except if treated wrong or overheated. Loosing strength over time was an effect existing with tungsten-steel, used between 1900 and 1940.

This effect is only existing in Alnico magnets and is an effect of the curvature of B/H-curve in the third quadrant. Any material that is operated on a significantly nonlinear part of its magnetisation curve will loose much of its field strength if the magnetic circuit is opened. To hold the magnetic circuit closed there are iron spacers needed.

The use of AlNiCo or whatever they maybe, in a combustion engine, can handle the type of physical stress that ceramic magnets could not, is it true? I do know that these type of magnets need to have their magnetic circuits closed. However, when a fly-wheel is removed, for any reason, then it should be placed on a jig that can keep the magnets loaded while the maintenance is carried out. I agree, else it will loose up to 90%.

This is limited only for some milliseconds by eddy-currents! And faster if Curie-temperature is reached.

Allowed operating temperature can be as high as 300°C.

You mix up drift of remnant flux density/ time if the magnet is not properly stabilised or operated at too high a temperature with demagnetisation by technical means.

Talking about operating temperatures of the permanent magnets, you have basically just confirmed what I said that they can operate at elevated temperatures (in the excess of 100C). However, it would be foolish to design a machine to operate at the max limit of the material it's made from as it would not give room for tolerance. You are right, never at the max limit.

This is only depending on the magnetic hysteresis curve. If you generate m-fields of 4 to 7 Tesla then you can easily remagnetise (or demagnetises) also the strongest known permanent magnetic materials.

I only tried to point out that any opposing force through a reaction, like EMF during generation, is not damaging to the magnet that causes it. Not in a short term and least of all if the magnet is a ceramic type! You are right once more, you cannot damage these magnets in ordinary motors. But if a specialised motor for ultrahighspeed is used with no iron in the windings and this motor is accidentally short circuited and thus operating as a short circuited generator, this will either burn the windings or demagnetise the magnets or blow up the power supply. We did blow up the transistors in TO3 housing (12 in 3 H-bridges), 3/8" holes in the metallic housings, metal caps vaporised: this was done only at too fast rundown. So it may be possible under extreme situations to demagnetise also these magnets.

This is a totally different field, rethink your L's as being without cores, L-C oscillators will function as with soft-magnetic cores! You mix up magnetisation with charging a capacitor. If you really want to model this you have to add electrete characteristics to your capacitors.

I only threw in the L-C concept, and I must admit I did not think about this topic when I read his quotation, because it is hardly relevant to his prime concern (The Effect Loading vs Degaussing).

It seems necessary to first get some textbook on magnetism, magnetic materials and use of permanent magnets. This may help to get rid of some erroneous assumptions.

I b...y will, don't you worry about it, since you started to become overly technical on this issue. I kind of realised it, at another discussion, that you probably more at home on this issue than most of us and it is undoubtedly a specialised area. I think, you can make a carrier out of it even. (It took a long time to accumulate the experience by a continues series of successes and failures.)

However, I do not think, even your lash out at me on this topic, that I would have given our friend any misleading info considering the simple and humble nature of his original concern about Degaussing through pulsing.

Have a VG day! Thank, same to you!

RHABE

Hi,

I have just only noticed your reply.

A quick question to your reply:

"...if a specialised motor for ultrahighspeed is used with no iron in the windings and this motor is accidentally short circuited and thus operating as a short circuited generator, this will either burn the windings or demagnetise the magnets or blow up the power supply."

Does that mean you are using the new type Ironless-Rotor-Motor?

Do youknow the type of magnet they have?

I had been offered a few types to buy but since the salesmen did not seem to know much about them I declined their offers.

bfn

"Does that mean you are using the new type Ironless-Rotor-Motor?

Do youknow the type of magnet they have?"

Yes indeed we do, any magnet type is used depending on needs.

I started with Sm-Co magnets (for a highly accurate instrument) as these are stable up to higher temperatures and have lower change of Bsat with temperature compared to any other material (if special grade with Gd content is used). These used in motor and torquer.

Then I switched to commercial motors with AlNiCo magnets (Infranor) for low distortion drive requirements. Then the same with ferrite-magnets (Heinzmann and Mattke) - these are cheaper.

Next would be FeNdB-magnets - these I have used only for non-motor application: magnetic field for sputtering equipment.

Some more details on my website.

RHABE

Just for curiosity with the Neodymium magnets to use in generators is it better if the coils are open air or the iron-core method is still better?

What you said before about the self destruction of the coil of the ironless-rotor with Ne-magnets makes me wonder if these magnets work better without iron-core even as generators? Is there a type of iron-core that can match these magnets in efficiency?

Stephen

Hi,

the iron-core is better in efficiency and use of magnet material but very complicated to design and complicated to operate as servo-motor as totally nonlinear.

Iron-less is simple to calculate, simple to build and simple to operate.

The magnetic circuit is not much changed by the current (magnetic field of the current). Giving flux density.

The current in the coils is giving force by vector product of flux-density x current to be multiplied by total length of effective wire.

The current is giving heat loss with resistance: R x I²

Inductivity is small so often neglected.

EMF/rotation-speed equals torque/current (friction neglected).

Battery-voltage minus EMF is giving effective Voltage,

effective Voltage/resistance is giving current.

Maximum current is fixed by thermal resistance of winding to environment and maximum allowable temperature.

What else?: Flux calculation, this I have to explain separately. I know, I should do a short tutorial on permanent-magnet motor and generator design.

RHABE

Hi,

I just wanted to hear if the air-core coil is a better option for Ne-magnets.

I always assumed that iron-core helps to collect/accumulate magnetic field better with respect to air-core, regardless the type of magnet.

However, is the type of iron-core used in motors and generators the same, due to the obvious?

These are the objectives for me to find out more especially for generation purpose and what sort of iron is the best?

Thanx for the run down info.

Stephen

Two answers regarding best magnetic steel:

If magnetic field is constant then pure iron is best in magnetic conductance.

If any alternating magnetic field is existing that is resulting in unwanted amounts of eddy-current losses then "transformer-steel" is best.

Transformer steel is iron-silicon (4...7% of Si).

Pure iron is easy to get as any steel with exceptional low carbon content. Those highly deformable steels used in deep drawing (automobile parts) is one of the best.

There are a lot of specialised alloys available but very expensive.

RHABE

You have partially answered my question I was hesitant to ask before namely, the "transformer-steel". Do generators and motors use this kind of steel?

There's a blog that sent me some info and it was mentioning the various level of silicon content. It appears Si can vary according to power. What about the frequency range? Where does the ferrite core application kick in?

Can soft-iron be used in pulsing method and

• up to what speed
• in solid-form or has to be laminated?

Do you source your work out or you have enough setup?

Steph

For pulsed applications, the hysterisis losses in an iron core will be excessive. The laminated silicon steel is good in those applications. Losses in these steels increase with frequency. That means you need thinner laminations as the frequency increases. Our pulse transformers require the highest Bsat. we can obtain. The best steels we have found for our application are made in Japan.

What form are they available in sheets, plates or any shape? I read that the cutting method of this material matters, does it?