magnet moving over a conductive sheet?

[spudweiser]

hello everyone,

I am currently trying to model a permanent magnet moving over a conductive sheet of aluminium.

I am using the solid117 element for both the conductive sheet and the magnet. I am trying to determine the eddy currents generated within the conductive sheet.

So far i can get an output for the permanent magnet itself but i cannot get the conductive sheet to move relative to the magnet.

I have tried numerous methods such as defining a real constant velocity for the conductive sheet, to adding dof's and specifying a displacement, none of these have so far worked and i am at a loss as to how this movement can be generated with the solid117 element.

I have tried both transient and harmonic analysises.

Does anybody know how i can get the sheet to move and get the eddy currents on the sheet in the solid117 element? or does anybody know how to couple both a magnetic and structural field so as to solve this problem?

Thanks

Shane

 

[meshparts]

Hi, I hope that helps:

! set element key option for eddy domain:

et,1,solid117,1,1

! define velocities for alu

r,1,,,,,,,
rmore,,,velocx,velocy,velocz

! material properties of aluminium are typically:

mp, murx, 1, 5 ! magnetic permeability
mp, rsvx, 1, 45e-8 ! electrical resistivity

You can solve this problem statically, since the velocities are constant.

Regards,
Alex

 

[spudweiser]

Hi Alex,

When i use use the above i get back an error saying i cant use A+Volt DOF's of freedom in a magneto static analysis which is the dof i need for the eddy currents.

how would i get around this if i wanted to use static analysis?

When i tried transient it solves but again there is no output on the plate, do i need a defined air gap between the materials in the 3d model or is it ok to leave a gap between both the magnet and the conductive plate?

Thanks in advance,

Shane

 

[meshparts]

Hi Shane,

Of course not! It is not ok if you let a gap "of no elements" between the magnet and the aluminium plate! You must fill the gap whits air:

et,1,solid117! for magnets and air
keyopt,1,1,0 ! AZ degree of freedom: static/source domain
keyopt,1,2,0 ! no velocity effects

et,2,solid117 ! for aluminium plate
keyopt,2,1,1 ! AZ degree of freedom: static domain,
! induced eddy currentdomain
keyopt,2,2,1 ! velocity effects

! for Magnet
mp,murx,1,1000
MP,RSVX,1,9.579E-8
mp,MGXX,1,000

! for aluminium
mp,murx,2,1
mp,rsvx,2,8E-9
r,2
rmore,,,xveloc,yveloc,zveloc

! for air
mp,murx,3,1

The problem whith the static analysis is true. You could do a transient anaylis instead whith TIMINT,OFF,ALL.

Alex

 

[spudweiser]

hey Alex,

Thanks a million, i got it working in the end after i inputed the air elements and overlapped the volumes! I used the harmonic analysis at a very low frequency of 0.0001 to simulate a static analysis and i got the desired result.

Thanks again.

Shane