ANSYS 7.1 TUTORIAL
Magnetostatic problems
Ruben Specogna
A.A. 2005/06
Università di Udine
Dipartimento DIEGM
Gruppo di Elettrotecnica
Specogna Ruben – ANSYS Tutorial
Lecture 3 – Magnetostatic Problems
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Magnetostatic problems
• Usually the formulation used is based on magnetic vector
potential A:


1
     A  0 J


• First example:
– Infinite rectangular massive
conductor carrying uniform
current density
– It has planar symmetry  2D
– b=h=10mm
– ET PLANE53 for second order element for 2D magnetostatic
(both planar and axialsymmetric problems), see PLANE13 for 1st
order element
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Lecture 3 – Magnetostatic Problems
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Preprocessing task
• File “Magnetostatica_2D_corr_imp_planare.txt”
/PREP7
!start the preprocessing
/TITLE,2D Planar Magnetostatic
!defining
et,1,plane53
!defining element type (ET)
et,2,plane53
title
!plane13 for first order. For axisymmetrical problem add:
!keyopt,1,3,1 and keyopt,2,3,1
!syntax: KEYOPT,material_constant,kp_number,kp_value
b=10e-3
!geometric parameter
h=10e-3
!geometric parameter
curr=1
!current
Jsz=curr/(b*h)
!corrensponding current density
mp,murx,1,1
mp,murx,2,1
! Permeability of air
! Permeability of the conductor
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Lecture 3 – Magnetostatic Problems
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Model & materials
wpave,10*b/2,0
!setting a new working plane
rectng,-b/2,b/2,-h/2,h/2
!conductor
rectng,10*(-b/2),10*(b/2),10*(-h/2),10*(h/2)
!air
asel,all
!selecting all areas
aovlap,all
!find intersections in the areas
numcmp,all
!number compression
aplot
!plotting areas
!material properties
!air
asel,all
aatt,1
!conductor
asel,s,,,1
aatt,2
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Lecture 3 – Magnetostatic Problems
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Mesh, source & b. cond.s
!mesh generation
alls,all
smrtsize,1
!specify the refinement of the mesh
mshape,1
!triangular mesh
mshkey,0
!free meshing (not mapped mesh)
amesh,all
!mesh all areas
!current source
esel,s,mat,,2
!selecting area 2 (massive conductor)
bfe,all,js,1,,,jsz !apply the source (body force element)
!Syntax: BFE, ELEM, Label, STLOC, VALx, VALy, VALz, VALphase
!boundary conditions
lsel,s,ext
!select all “external” lines automatically
dl,all,,AZ,0,1 !force Az=0 on the nodes upon external lines
!Defines DOF constraints on lines.
!Syntax: DL, LINE, AREA, Label, Value1, Value2
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Lecture 3 – Magnetostatic Problems
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Solution & postprocessing
Finish
/SOLU
alls,all
antype,static
solve
Finish
!magnetostatic solution
The results can be seen with the GUI at:
General Postprocessing  PlotResult  Contour Plot  2D Flux Lines
or:
General Postprocessing  PlotResult  Contour Plot  Element Solution
and then select the variable to display: for ex. BSUM, JTSUM
Then we can plot a vector field with:
General Postprocessing  PlotResult  Vector Plot  Predefined
and then choose for ex. B, H or JT (plf2d command)
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Lecture 3 – Magnetostatic Problems
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EXAMPLE 2
We’ll consider an actuator. All materials are linear.
We would like to calculate the force on the mobile armature.
Due to axialsymmetry we will solve a 2D axialsymmetric problem.
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Lecture 3 – Magnetostatic Problems
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Preprocessing Example 2
/PREP7
/TITLE,2D Axisimmetrical Actuator
ET,1,PLANE53
KEYOPT,1,3,1
!activating key option for axialsymmetry
MP,MURX,1,1
!air
MP,MURX,2,1000 !iron
MP,MURX,3,1
!core (copper)
MP,MURX,4,2000 !iron
n=650
!some useful constants: number of turns
i=1.0
!current
ta=.75
!follows some geomtric constants
tb=.75
ws=wc+2*space
tc=.50
hs=hc+.75
td=.75
w=ta+ws+tc
wc=1
hb=tb+hs
hc=2
h=hb+gap+td
acoil=wc*hc
!coil area
gap=.25
jdens=n*i/acoil
!coil current density
space=.25
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Lecture 3 – Magnetostatic Problems
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The geometry
/PNUM,AREA,1 !with aplot will plot every area with different colors
RECTNG,0,w,0,tb
RECTNG,0,w,tb,hb
RECTNG,ta,ta+ws,0,h
RECTNG,ta+space,ta+space+wc,tb+space,tb+space+hc
AOVLAP,ALL
RECTNG,0,w,0,hb+gap
RECTNG,0,w,0,h
AOVLAP,ALL
NUMCMP,AREA
APLOT
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Lecture 3 – Magnetostatic Problems
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Materials
!default air mat = 1
ASEL,S,AREA,,2
AATT,3 !core
ASEL,S,AREA,,1
ASEL,A,AREA,,12,13,1
AATT,4 !upper iron
ASEL,S,AREA,,3,5,1
ASEL,A,AREA,,7,8,1
AATT,2 !lower iron
/PNUM,MAT,1
ALLSEL,ALL
APLOT
!(*)
!(*) with aplot will plot every material with
!
different colors (like the figure)
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Lecture 3 – Magnetostatic Problems
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Mesh and force computation
SMRTSIZE,3
AMESH,ALL
!setting the refinement of the mesh
ESEL,S,MAT,,4
CM,ARM,ELEM
!select elements of material 4
!mesh all the areas
!with this collection of elements creates the
!component named “ARM”
FMAGBC,'ARM‘
!tells ANSYS that after solution I want to know
!the resulting force on the component ARM
ALLSEL,ALL
ARSCAL,ALL,,,.01,.01,1,,,1
FINISH
!scaling lengths in meters
!finish the preprocessing
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Lecture 3 – Magnetostatic Problems
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Bound. cond.s & solution
ESEL,S,MAT,,3
!selecting the coil material areas
BFE,ALL,JS,1,,,jdens/.01**2 !imposing the source
ESEL,ALL
NSEL,EXT
D,ALL,AZ,0
ALLSEL,ALL
FINISH
/SOLU
MAGSOLV
SAVE
FINISH
!select automatically all boundary nodes
!impose A=0 on this nodes
!finish the preprocessing
!solve for magnetostatic
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Lecture 3 – Magnetostatic Problems
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Postprocessing
!starting postoprocessing task
/POST1
!plot 2D flux lines
PLF2D
!calculate the force on the ARM
FMAGSUM
!plot vector field B
PLVECT,B,,,,VECT,ELEM,ON
!plot |B| as a scalar field
PLNSOL,B,SUM
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Lecture 3 – Magnetostatic Problems
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EXAMPLE 3
3D actuator problem.
Saturable materials: the solution is non-linear.
(3 materials: air, core (saturable), armature (saturable). The coil is not meshed)
Due to symmetry we model only ¼ of the domain.
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Lecture 3 – Magnetostatic Problems
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Preprocessing task
/prep7
/title,3D Actuator
n=500 !turns of the coil
i=6
!current per turn
et,1,96 !element type solid96
mp,murx,1,1 !assign mur=1 at air
!activate a table for non-linear materials
tb,bh,2,,40
tbpt,,355,.7
!B-H table
!define all the points
!of the B-H curve
,,405,.8
,,470,.9
,,555,1.0
,,673,1.1
…for all the points…
tbcopy,bh,2,3
!copies the table
!from material 2 to material 3
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Lecture 3 – Magnetostatic Problems
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Geometry
/pnum,volu !plot the volume’s numbers
block,0,63.5,0,25/2,0,25
/view,1,1,1,1 !change the angle of view (see syntax)
/replot
!replot
block,38.5,63.5,0,25/2,25,125
block,13.5,63.5,0,25/2,125,150
vglue,all
block,0,12.5,0,5,26.5,125
block,0,13,0,5.5,26,125.5
vovlap,1,2
numcmp,volu
cyl4,,,0,0,100,90,175
vovlap,all
numcmp,volu
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Lecture 3 – Magnetostatic Problems
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Material and meshing
vsel,s,,,1
vatt,3
vsel,s,,,3,5
vatt,2
allsel,all
smrt,8
mshape,1,3d
mshkey,0
vmesh,all
/pnum,mat,1
/number,1
eplot
!setting up materials
!tetrahedral mesh
!free mesh
!mesh all volumes
!plot different materials with different colors
!no numbers
!plot elements
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Lecture 3 – Magnetostatic Problems
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Source
esel,s,mat,,3
cm,arm,elem
!create the component “arm”
fmagbc,'arm‘
!will calculate force on “arm”
allsel,all
vlscale,all,,,.001,.001,.001,,0,1 !scaling in meters
local,12,0,0,0,75/1000 !change system of coordinates
wpcsys,-1
!define a wp based on the system of coord.
!define a racetrack coil
race,.0285,.0285,.014,n*i,.018,.0966,,,'coil1'
/eshape,1 !display the coil (it's NOT meshed)
eplot
save !save the database
finish
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Lecture 3 – Magnetostatic Problems
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Bound. con.s & Solution
d,2,mag,0
allsel,all
/solu
magsolv,3,,,,,1
finish
/post1
fmagsum,'arm'
finish
save
/solu
*dim,cur,array,1
cur(1)=i
lmatrix,1,'coil','cur'
finish
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Lecture 3 – Magnetostatic Problems
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