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Specogna Ruben – ANSYS TutorialLecture 3 – Magnetostatic Problems

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ANSYS 7.1 TUTORIALMagnetostatic problems

Ruben Specogna

A.A. 2005/06

Università di UdineDipartimento DIEGM

Gruppo di Elettrotecnica


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Magnetostatic problems

• Usually the formulation used is based on magnetic vector potential A:

• First example:– Infinite rectangular massive

conductor carrying uniformcurrent 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

JA

0

1


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Preprocessing task• File “Magnetostatica_2D_corr_imp_planare.txt”

/PREP7 !start the preprocessing

/TITLE,2D Planar Magnetostatic !defining title

et,1,plane53 !defining element type (ET)

et,2,plane53!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 ! Permeability of airmp,murx,2,1 ! Permeability of the conductor


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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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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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Solution & postprocessing

Finish

/SOLU

alls,all

antype,static !magnetostatic solution

solve

Finish

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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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.

EXAMPLE 2


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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

tc=.50

td=.75

wc=1

hc=2

gap=.25

space=.25

ws=wc+2*space hs=hc+.75 w=ta+ws+tc hb=tb+hsh=hb+gap+td acoil=wc*hc !coil area jdens=n*i/acoil !coil current density


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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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Materials

!default air mat = 1ASEL,S,AREA,,2 AATT,3 !coreASEL,S,AREA,,1 ASEL,A,AREA,,12,13,1AATT,4 !upper ironASEL,S,AREA,,3,5,1 ASEL,A,AREA,,7,8,1AATT,2 !lower iron

/PNUM,MAT,1 !(*) ALLSEL,ALLAPLOT

!(*) with aplot will plot every material with! different colors (like the figure)


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Mesh and force computation

SMRTSIZE,3 !setting the refinement of the mesh

AMESH,ALL !mesh all the areas

ESEL,S,MAT,,4 !select elements of material 4 CM,ARM,ELEM !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 !scaling lengths in meters

FINISH !finish the preprocessing


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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 !select automatically all boundary nodes

D,ALL,AZ,0 !impose A=0 on this nodes

ALLSEL,ALL

FINISH !finish the preprocessing

/SOLU

MAGSOLV !solve for magnetostatic

SAVE

FINISH


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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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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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Preprocessing task/prep7

/title,3D Actuator

n=500 !turns of the coil

i=6 !current per turn et,1,96 !element type solid96mp,murx,1,1 !assign mur=1 at air

!activate a table for non-linear materials

tb,bh,2,,40 !B-H tabletbpt,,355,.7 !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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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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Material and meshing

vsel,s,,,1 !setting up materials

vatt,3

vsel,s,,,3,5

vatt,2

allsel,all

smrt,8

mshape,1,3d !tetrahedral mesh

mshkey,0 !free mesh

vmesh,all !mesh all volumes

/pnum,mat,1 !plot different materials with different colors

/number,1 !no numbers

eplot !plot elements


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Source

esel,s,mat,,3 cm,arm,elem !create the component “arm”fmagbc,'arm‘ !will calculate force on “arm”allsel,allvlscale,all,,,.001,.001,.001,,0,1 !scaling in meters

local,12,0,0,0,75/1000 !change system of coordinateswpcsys,-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)eplotsave !save the databasefinish


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Bound. con.s & Solutiond,2,mag,0allsel,all

/solumagsolv,3,,,,,1finish

/post1fmagsum,'arm'finishsave

/solu*dim,cur,array,1cur(1)=ilmatrix,1,'coil','cur'finish

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