SuperMagnetMan - Fundamentals of Halbach Arrays

[Music] welcome back to another super magnet man video one of the topics that we get asked about all the time is haul back haul back arrays are very important part of magnet geometries and helping us better understand how to put fields together but interestingly enough it seems like everybody that hears the word haul back thinks this is some special magnet that is different and it's the answer to all problems because it makes the magnetic field stronger and it weakens one side and many times that's the right thing to do but not always so what I wanted to do is take a minute and help us better understand the real use of a haul back so I've got a whole bag made out of in 50 in 52 half inch cubes this is five magnets arrayed in the hall bag you can find this design on the Wikipedia which talks about this and I've got these five and we're going to take a look at the numbers on this in just a second to compare it I was wondering what would happen if I took the same half H cubes and arranged them all in the same direction so let's take a look at what the Gauss readings actually tell us to take a look at this we took our Gauss meter and we got us some readings above both sets of magnets so if you look at the surface of the magnet on this bottom one all the magnet should be essentially the same and when you put them together it's going to change a little bit and we see that the ends are fifty two hundred forty nine hundred and in the middle we get forty seven two forty nine hundred so it's just a tiny bit weaker in the middle overall this gives us an average of four thousand eight hundred and eighty Gauss and of course those readings are a little bit you could probably just say it's an average of 48 or 49 hundred either way now let's look at what we got on the surface of the haulback and this is where haulback really has its advantage this end magnet and this the end magnet are both about a hundred Gauss because you're measuring perpendicular to the flux the flux is actually going this way and it's going this way so you're not really measuring that is like measuring parallel to that so it's not getting anything to it you look at this one though and this magnet above it was seventy three hundred Gauss that's way higher than we get the single magnet magnetic field is about sixty two hundred Gauss but this one jumps at two seventy three hundred now there's a transition magnet again we're measuring perfect a parallel to the flow of magnetism so we don't really measure very much we're only getting five hundred and if you move back and forth a little bit you switch between north and south so we get seventy four hundred over this magnet just a little bit higher could be just depending on where you're measuring but sometimes magnets will do that it's just a little bit of difference and when we averaged this we get forty one hundred and sixty Gauss across the surface now if we take this magnet and go 1/2 inch above it this set of readings is one half inch above the surface of the magnet you see that we're down to eight hundred but then we're a solid 1,000 Gauss across the center and eight hundred on the end when we take the haulback and we are 1/2 inch above it we get two hundred one thousand twenty one thousand and three hundred what's happening with the haulback is since the North Pole is here and this is the South Pole we've got a little space in between it the magnetic field lines go like this so you're north and south are connecting if you look at this one this is being treated as if it's one large magnet and the magnetic flux lines would look like this so you're not seeing a big difference on the underside of this magnet it measures about three thousand Gauss but on the bottom of this one it would match exactly what we see above it would average about five thousand Gauss all across the bottom so if you're needing to move the magnetic field to the other side what you're really doing is taking the flux from three magnets and forcing it into two gives us a very strong field above these two but much weaker below the others now this has some specific applications when you look at this in the business world and we're out of commercial world and we're trying to design uses for this if you are working very close to the surface of the magnet like in a motor or an alternator design you can see that having these high values is very important that can get you a lot more power out of an electric motor or a lot more power out of an electric generator alternator type application and we're going to take a look at some magnets that are oriented this way as we look at this we have had a couple of magnets made that our haulback assemblies we've had the factory make these for us to give you an idea of what we have this one has two poles and it's about 5200 gauss on the center these are small magnets but each magnet is rolling the field around you can see that better with this how you can see that one half is one polarity and you see this sharp dividing line across the middle that lets us see where the poles are separating this one the high intensity field is here and here and you can see how each of these magnets because they're angle magnetized helps it bend the flux around we'll look at that in just a second as a drawing to show you how to do this but this this magnet is made of magnets that are about a half-inch thick their arcs segments all glued together with special magnetization to roll the field to these two high intensity points now we have another one that we made that is a little larger you can see it's much wider if we look at these two together you can see the width is twice the width and you can see that the magnets are twice as thick the outside diameter is a little bigger and so this is making us a very special magnet and we reach about 7,200 to 7500 Gauss on the poles here and you can see that with our viewing film once again seeing where the flux is going and how each of the magnets are rolling around the flux that's what these little lines are showing you is that flux just keeps turning because of the angle that they are magnetized at so these are two that we have as a standard product on our website we have another one that we made for research purposes years ago and this one is a it also uses two things number one while it is a haulback array and you can see the arrows showing you the angle that that's been magnetized we took advantage of another geometry modification what we did is used pyramid magnets so it's going from a to each pyramid to about a nine millimeter top and each magnet is two inches thick and each of these are angle magnetized what this does for us is gives us an incredibly powerful field on the inside we'll talk about that in a second again you can easily see the sharp dividing line showing us where the poles are that line that you see is perpendicular to the line of the maximum line of flux the flux line is here where we see the two poles so let's take a look on the board and see how this magnet is made to take a look at this Hall back in a little bit more detail I mentioned to you that we have angle magnetized but what does angle magnetization mean the reason that I say angle magnetization is your normal neodymium material is anisotropic and and isotropic means we can't change the magnetic domains after it has been magnetized so all of the domains are established at the very beginning it's in the very first step of making a magnet it has its domains established so how do we take something like this and magnetize at a 45 degree angle back to geometry what we do is cut the magnet we will take a magnet if we want 45 degree magnetization we will cut the magnet like this this will give us whatever angle that we want now what it also does is it creates wasted material here here and back here you can see we're losing some material but we need this particular design so that we can increase the flux in this path and you can notice that with this whole back I've got this written up here is 1.2 Tesla across that entire gap all the way across we average about 1.2 Tesla from one side to the other we can add some other magnets it reduces the gap in the middle but if we use some stacking magnets we can focus that field to about 1.6 Tesla which is an extremely powerful magnetic field certainly for a permanent magnet if we're making this magnet we're trying to do that we use again the same square block of material and but now with the flux going this way we will cut it like this and that gives us magnetic flux that's parallel to the base which are these end pieces here now one of the things about this material is while we cannot change the domain it could change the polarity we can take the same design and wear this might have North on the top and South on the bottom we can remag nough ties this so that it comes out with South on the top and north on the bottom that's not a problem it's a problem to change that angle or to go perpendicular to it or anything like that so this is a key part that helps us determine the cost factors in making a haulback first of all they're extremely powerful all pieces are repelling each other and they are going to you're gonna they're gonna try and bounce apart and to do so you have to make a special apparatus and many times you may use a hydraulic cylinder to force the pieces together to get them inside their fixture so that you can have this all of this adds to the cost and so this is one of the things to keep in mind when you're looking at using a haulback a super magnet man we like to help our customers determine is a haulback the right solution for your application sometimes all you may need is a standard magnet at other times if you really need the high-intensity fields we look at the haulback as an option to see how much field you really need if you need seven eight nine ten thousand gauss then a haulback may be the best option for you if you're making an electric motor or an alternator generator you might want to use the haulback because that is going to give you higher flux intensity then you're going to get with a standard magnet this is why many of the motors today that are coming out in the automotive industry are coming out as haulback motors because they know they can get more power out of the same weight motor so these are many considerations and a super magnet man we would love to talk with you about your application and help you develop the right solution using the right magnet geometry to solve your problem so whenever you have a problem give us a call and super magnet man will help you

Channel: SuperMagnetMan

Views: 537,054

Rating: 4.70785 out of 5

Keywords: Physics, engineering, halbach, halbach magnet, magnet, magnetism, science, education, Super magnets

Id: ep2PAMrzwEU

Length: 11min 33sec (693 seconds)

Published: Thu Sep 06 2018

Reddit Comments

[u/irve]

A nice layman video, bit on the simple side, TBH, but it's good to go over the basics every once in a while.

I started wondering if we could adapt the rolling flux idea of Halbach Array for the temporal cystals. So it would do this in the temporal domain to de-accelerate any ion flows we'd like to stabilize.