9.2 Electrostatic Simulations 3

9.2 Electrostatic Simulations

Problem: Given is an electrostatic system with edge as shown in figure 9.2. The aimof the simulation is to compute the potential distribution in the device, the electricfield and the maximal field strength as well.

Abb. 9.2. Two-electrode-system with edge.

Preprocessor:

Preprocessor↓ /PREP7

Element Type↓ Add↓↪→ Add↓ ↪→ Electrostatic↓ 2D Quad 121 ok↓ close↓

ET

Definition of material properties εr = 1.Material Props↓ Material Models↓

↪→ Electromagnetics↓↓ Relat.Permittivity↓↓ Constant↓↓↪→ define PERX = 1 ok↓ x ↓

MP

Definition of keypoints:Modeling↓ Create↓ Keypoints↓ In Active CS↓

↪→ define coordinates: (apply each with Apply↓ , at the end ok↓ )

K

N 1 2 3 4 5 6 7X 0 0.2 0.2 0 0 0.1 0Y 0 0 0.2 0.2 0.14 0.1 0.06

Definition of areas:Modeling↓ Areas↓ Arbitrary↓ Through KPs↓... ↪→ for A1 select keypoints 1, 2, 3, 4 Apply↓... ↪→ for A2 select keypoints 5, 6, 7 Apply↓ ok↓

A

Selection of keypoints via ⇑ or by specifying the command directly:A, 1,2,3,4 <return>

A, 5,6,7 <return>

4 9 Introduction on ANSYS

In order to distinguish between different areas:PlotCtrls ↓ Numbering ↪→

Line (from off to on )

Area (from off to on ) ok↓

APLOT

Subtraction: A1 - A2.Modeling↓ Operate↓ Booleans↓ Subtract↓ Areas↓

↪→ select area A1 Apply↓↪→ select area A2 Apply↓ ok↓

ASBA

Grid control: Overall 0.01 m; at keypoint number 6: 0.002 m.Meshing↓ Size Cntrls↓ ManualSize↓ Keypoints↓... All KPs↓ ↪→ 0.01 ok↓

KESIZE

... Picked KPs↓ ↪→ select keypoint 6 Apply↓ ↪→ define value 0.002 ok↓

MeshingMeshing↓ Mesh↓ Areas↓ Free↓ ↪→ select area nr 3 or specify 3 ok↓AMESH

Abb. 9.3. Grid for two-electrode-system.

Solution:

Solution↓/SOL

Define Loads↓ Apply↓ Electric↓ Boundary↓ Voltage↓ On Lines↓... ↪→ select lines 8, 6, 5, 9 (left) Apply↓... ↪→ VOLT = 10 Apply↓

DL

... ↪→ select line 2 (right) Apply↓

... ↪→ VOLT = 0 ok↓

9.2 Electrostatic Simulations 5

By default: lines without specification will be defined as symmetry lines. However, wedefine these symmetry lines explicitly with the DL command:DL, 1 , 3 , symm <return>

DL, 3 , 3 , symm <return>

Solve the problem:Solve↓ Current LS↓ SOLVE

Postprocessor: The results are shown in figure 9.4.General Postproc↓ /POST1

Plot Results↓ Contour Plot↓ Nodal Solu↓ ok↓... ↪→ DOF Solution↓ Electric potential↓ ok↓

PLNSOL

... ↪→ Electric Field↓ Electric field vector sum↓ ok↓

Plot Results↓ Vector Plot↓ Predefined↓... ↪→ Elec field EF↓ ok↓

PLVECT

(a) (b)

Abb. 9.4. ANSYS solution: (a) equipotential lines, (b) electric field.

The maximal electric field strength is 322 V/m in elements but 396 V/m on nodes.

Restart: New Input:

4! Important: Erase the last two lines (finish and exit) in the Logfile and save itwith a different name.File↓ Clear& Start new ...↓ >> Do not read file ok↓ ↪→ Yes↓ /CLEAR

File↓ Read Input from ...↓ (select file) ok↓ /INPUT