Three-phase magnetic cube - Page 1
Forum section: electronics / projects

author: Circlotron
author_rank: Super Contributor
timestamp: October 31, 2014, 12:02:29 pm
content: Suppose we have a cube of magnetic material and we wind some wire around it. Apply a sine wave to the winding and the magnetic field points back and forth along the axis of the winding.Then we add a second winding at right angles to the first and supply this second winding with a sine wave 90 degrees phase shifted from the first winding. The vector sum of the two resulting magnetic fields would now point back and forth between the axes of the two windings.Now suppose we add a third winding on our cube at right angles to both previous windings, and we now supply our three windings with three sine waves each shifted 120 degrees as per a normal 3-phase AC power supply.What path would the resultant magnetic field now follow?Would this device be of any practical use?

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: October 31, 2014, 12:06:16 pm
content: Quote from: Circlotron on October 31, 2014, 12:02:29 pmMRI machine for four dimensional beings?

author: Jeroen3
author_rank: Super Contributor
timestamp: October 31, 2014, 01:35:50 pm
content: A circular motion inside a quarter orb?I don't know, what a philosophical question.

author: Cyberdragon
author_rank: Super Contributor
timestamp: October 31, 2014, 06:46:48 pm
content: Make the cube hollow and put some sort of metal gyroscope thing in it. Connect a 3-phase transformer and you have a nice desk toy. That is if the magnetic field will make it spin and rotate on the other axis.

author: German_EE
author_rank: Super Contributor
timestamp: October 31, 2014, 06:55:02 pm
content: Make the cube hollow then fill it with a mixture of mineral oil and iron filings. My bet is that there will be a small sphere of filings in the middle after a few minutes.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: October 31, 2014, 07:04:18 pm
content: Quote from: German_EE on October 31, 2014, 06:55:02 pmSure and when the Goa'uld come flying out, what then?

author: Cyberdragon
author_rank: Super Contributor
timestamp: October 31, 2014, 07:27:36 pm
content: Apparently they use these for "magnetic tracking". They also come with magnetic cores, but the picture of that took up the whole page.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: October 31, 2014, 07:40:54 pm
content: Quote from: Cyberdragon on October 31, 2014, 07:27:36 pmYears ago there was a university that had something like that. They built a big cage with three room size coils and the pick up looked like that cube. It was to track movements in 3D.Don't know what happened to that but I'd guess that's all obsolete with the Kinect and stuff like that.Or...http://en.wikipedia.org/wiki/Magnetometer#Fluxgate_magnetometer

author: T3sl4co1l
author_rank: Super Contributor
timestamp: October 31, 2014, 11:48:34 pm
content: The field vector at the center should trace out a circle, in the  plane I think.Why not figure it out for yourself? That's what they created math for...Tim

author: Circlotron
author_rank: Super Contributor
timestamp: November 01, 2014, 01:19:21 am
content: I thought it would trace out a circle with only the X and Y coils energised with 90 deg phase shift, same as sine and cosine on an oscilloscope. Lateral thinking is 1D, this is 3D.

author: ludzinc
author_rank: Unknown
timestamp: November 01, 2014, 02:36:07 am
content: Quote from: Cyberdragon on October 31, 2014, 07:27:36 pmCyberdragon,Who supplies those coils? I'm interested in these for active RF tags...Thanks!

author: German_EE
author_rank: Super Contributor
timestamp: November 01, 2014, 08:54:53 am
content: "Sure and when the Goa'uld come flying out, what then?"They drown in the mineral oil. Of course, if Sam Carter was around to supervise the experiment I would substitute baby oil, but I digress

author: calexanian
author_rank: Super Contributor
timestamp: November 02, 2014, 05:37:16 am
content: I think the turtles start right underneath the cube, And it goes turtles, all the way down...

author: Circlotron
author_rank: Super Contributor
timestamp: November 02, 2014, 07:19:22 am
content: Quote from: T3sl4co1l on October 31, 2014, 11:48:34 pmThinking about it some more, I suspect you are right. It would appear as a circle when looking from one particular corner of the cube down to the opposite corner.Does anyone know of some graphing software or preferably Open Office Calc add-on that would allow three axis graphing of a series of single points?

author: German_EE
author_rank: Super Contributor
timestamp: November 02, 2014, 11:13:04 am
content: My money is still on a sphere but I will settle for a cube with rounded edges. Think about it, a single coil will squeeze the magnetic field into a cylinder so a coil on all three axis will compress the fields into a single point at the center.

author: Richard Crowley
author_rank: Super Contributor
timestamp: November 02, 2014, 01:04:18 pm
content: Curiously reminiscent of the bubble memory design where orthogonal coils (along with permanent magnets) are used to move the magnetic bubbles around the garnet chip.http://youtu.be/0rqPmjmQOxwAnd coincidentally discussed in Dave's latest Mailbag videohttp://www.eevblog.com/2014/10/28/eevblog-677-mailbag/

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 02, 2014, 07:53:22 pm
content: Quote from: Circlotron on November 02, 2014, 07:19:22 amhttp://www.wolframalpha.com/input/?i=x%3Dsin+t%2C+y+%3D+sin%28t%2B2*pi%2F3%29%2C+z%3Dsin%28t%2B4*pi%2F3%29+graph

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: November 03, 2014, 01:24:57 am
content: Quote from: Richard Crowley on November 02, 2014, 01:04:18 pmNoooooooooooo!!!! I still have an Intel Bubble Memory reference design kit somewhere.

author: Richard Head
author_rank: Frequent Contributor
timestamp: November 03, 2014, 05:49:24 am
content: Seriously, how can the resulting magnetic field be one dimensional when the exciting source is symetrical in all 3-dimensions?It will have to be a sphere, no maths involved.

author: Circlotron
author_rank: Super Contributor
timestamp: November 03, 2014, 05:53:42 am
content: Quote from: Richard Crowley on November 02, 2014, 01:04:18 pmI first though of this 3-coil configuration about 10 years ago. Seeing the bubble memory stuff jogged *my* memory so I decided to see what other people thought.

author: Circlotron
author_rank: Super Contributor
timestamp: November 03, 2014, 05:59:03 am
content: Quote from: Richard Head on November 03, 2014, 05:49:24 amIf for example a circle leans forward off the page it will have an X,Y and Z component.And the excitation sources are not symmetrical. e.g. when X and Y are equal but opposite, Z will be zero.Perhaps "symmetrical" is not the right word.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: November 03, 2014, 02:38:08 pm
content: Quote from: Richard Head on November 03, 2014, 05:49:24 amWhat if it's on the surface of a magnetar? What then?

author: Richard Head
author_rank: Frequent Contributor
timestamp: November 03, 2014, 07:07:14 pm
content: Dunno, never been on a magnetar.

author: SeanB
author_rank: Super Contributor
timestamp: November 03, 2014, 07:17:20 pm
content: If you are on a magnetar then looking will probably not be high on the list of things, as you will be stripped of the iron in your blood at incredible speed, and the assorted particles you are made of will be sorted by paramagnetic value, irrespective of what they originally were atoms of. It literally will be happening faster than the impulses can travel to your brain and be decoded into an image and comprehended by the brain.Being at the epicentre of a nuclear blast ( as in right next to the outer casing) would happen slower.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: November 03, 2014, 08:37:28 pm
content: Quote from: SeanB on November 03, 2014, 07:17:20 pmWhat if I'm wearing a really good spacesuit?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 04, 2014, 12:10:25 am
content: What would you make the space suit out of? Neutronium?Which is what the magnetar is made of .Which begs the question.....Tim

author: T3sl4co1l
author_rank: Super Contributor
timestamp: November 04, 2014, 12:24:15 am
content: Quote from: Richard Head on November 03, 2014, 05:49:24 amHow could it be anything but a line curve? There is only one degree of freedom, time. The locus of a sphere either requires infinite time to describe, or exactly two (independent) dimensions.Which is a little interesting, because;The only way that would be possible (infinite time, single dimension) is if the LCM of frequencies applied to the axes is infinite.Any other relationship (i.e., a finite rational ratio) will eventually repeat, having described a spherical Lissajous figure with gaps in it. Which, in turn, means you could only do that if at least one axis has a rational coefficient and at least one other axis has an irrational (possibly transcendental is required?) coefficient.That is, for the set of points {x = sin(A * t), y = cos(B * t), z = sin(C * t)} for all real t, at least one of A, B or C has to be irrational, so that no harmonics of the sine waves overlap (thus creating a grid of holes in the sphere).Even then, I'm sure real analysis or topology would have something to say about the "texture" of this curve: even though it's ultimately describing a smooth surface (a perfect sphere), it's still a single line curve, and thus has infinite gaps between segments, even if those gaps have a total area of zero. The mathematical equivalent of running your finger along a stereolithography-printed object and feeling the ridges between individual curves, except instead of touching with a (finite) finger, you're analyzing the curvature of the shape with infinite precision.Whereas, a simple two dimensional description (e.g., z = sqrt(1 - x^2 - y^2)) provides perfectly bulletproof smoothness for "all but finite" points, or something like that (it still has ugly behavior at the equator, where x^2 + y^2 = 1, because the derivative blows up there; using the form x^2 + y^2 + z^2 = 1 avoids that).Or something like that.Anyway...We now return you to your regularly scheduled thread...Tim

author: Circlotron
author_rank: Super Contributor
timestamp: November 04, 2014, 01:28:56 am
content: A sine repeats every 360 degrees and the three coils have identical sine waves applied (phase shifted 120 and 240 degrees). Therefore, whatever vector is traced out, it will repeat in only 360 degrees. That would rule out a sphere which would require many rotation cycles to produce.

author: PointyOintment
author_rank: Frequent Contributor
timestamp: November 09, 2014, 10:11:55 am
content: Furthermore, if you all mean what I think you do by "spherical magnetic field", such a field cannot exist under any circumstances, due to thehairy ball theorem.