1. 2010. 11. 25 Photonic Systems Laboratory School of EE, Seoul National University Photonic Systems Lab School of EECS, S.N.U. Electro-Magnetic Fields I Experiment #6 FEMM (Finite Element Method Magnetics)

2. Photonic Systems Lab School of EECS, S.N.U. FEMM ? Finite Element Method Magnetics Finite Element Method - Technique to solve partial differential equation 1. Divide the objects in finite element 2. Determine points of contact 3. Approximate differential eq. of the points to 1 st order differential eq., and solve it Not only electromagnetism problems, but also heat, and current flow problems

3. Photonic Systems Lab School of EECS, S.N.U. FEMM Window Modeling Solving Scaling Moving Grid on/off Dot on a grid (Recommend to use) Coordinate

4. Photonic Systems Lab School of EECS, S.N.U. FEMM Flow Sequence 1. Modeling 2. Select Material 3. Determine Boundary Condition, Current 4. Solve the equation 5. Analysis

5. Photonic Systems Lab School of EECS, S.N.U. 1. Modeling 1. Dot a point : Left click to dot on a screen, or enter Tab key and enter a coordinate. 2. Draw a line : Left click starting and ending point in order. 3. Draw an arc : Same as above method. Except a process to determine an angle. - If you want to select what you drew, then click proper menu and right click on the object. It is possible to select multiple element. - If you want to delete what you drew, then right click and enter delete key. 1 2 3

6. Photonic Systems Lab School of EECS, S.N.U. 2. Select Material(1) 1. Click material menu 2. Left click on the material 3. Right click a point, and enter space 4.You can’t select any material. So see next page! 1 23

7. Photonic Systems Lab School of EECS, S.N.U. 2. Select Material(2) 1. Select built-in material Properties -> Materials library Drag & Drop 2. Select new material Properties -> Materials -> Add property Load B-H curve.txt Ex) Air -> ( 공기 ) PM Materials\NdFeB Magnets\NdFeB 32MGOe -> ( 자석 ) Soft Magnetic Materials\Silicon Iron\M-19 -> ( 자석 ) Solid None-Magnetic Conductors\Copper -> ( 구리 )

8. Photonic Systems Lab School of EECS, S.N.U. 2. Select Material(3) 3. Set material in a proper range - Determine size of mesh to calculate. - It is usually checked, but you can uncheck it and change the mesh size. Display a direction of magnetization

9. Photonic Systems Lab School of EECS, S.N.U. 3. Determine Boundary Condition(1) 1. Properties -> Boundary -> Add Property 2. Select boundary and Enter space Generally, set 0 on the boundary of Air You can see that boundary property Zero has been made

10. Photonic Systems Lab School of EECS, S.N.U. 3. Determine Current(2) 1. Properties -> Circuits (1) Set current (2) Make a name and Save it - If you click Series, a direction of current is set orthogonal to the screen 2. Properties -> Materials -> Add property (1) Set current (2) Make a name and Save it 1. 2.

11. Photonic Systems Lab School of EECS, S.N.U. 3. Determine Current(3) 3. Material menu -> Select material (1)Click Material menu (2) Select material(right click) which you want to set current (3) Click In circuit menu, you can see what you saved at 1,2. - If you click Series, you can set Number of Turns

12. Photonic Systems Lab School of EECS, S.N.U. 4. Solve The Equation 1. Save 2. Click 1,2,3 3. See result 1 2 3 Divided finite element (determined by mesh size)

13. Photonic Systems Lab School of EECS, S.N.U. 5. Analysis(1) 1 2 3 1.Contour plot : show Flux line 2.Density plot : show Flux density (Check Show density plot) 3.Vector plot : show Vector field 2. 3. Click a point where you want to know a value 1.

14. Photonic Systems Lab School of EECS, S.N.U. 5. Analysis(2) 4. X-Y plot click Draw line menu -> select line to plot click Plot menu -> set plot type 4. 5. 5. Integrate : click Range select menu -> set range click Integrate menu -> set value to integrate D P EX) Magnetic field energy R I

15. Photonic Systems Lab School of EECS, S.N.U. Pre-report 1.Draw a Magnet Air M-19 steel NdFeB 32 MGOe (set proper direction) 2.Draw an Electromagnet Copper (same magnitude, opposite direction) ( Hint : set mesh size properly ) In pre-report, you have to include drawings which has mesh lines, and flux lines same as above. (Total 4 drawings)

16. Photonic Systems Lab School of EECS, S.N.U. Report (In Class Assignment) B(T) H(A/m)0 0.1500123.519 0.2009630.552 0.2481437.6 0.2981447.046 0.3500468.533 0.39817104.49 0.42934152.57 0.44729203.1 0.47283318.66 0.48707472.83 0.49566636.65 0.50142800.48 0.50434954.69 0.507261118.5 0.510191284.8 0.514061439 Data2 (PB40’s B-H value) Q1. Simulate a following figure with data by using FEMM. Show direction and magnitude of flux lines through PB40. I (current flow through copper) = 1A N (Number of Turns) = 100 times n( Number of Total mesh) = 5000~10000 nodes Data3 (PB40’s B-H curve) B(T) H(A/m) Data1

17. Photonic Systems Lab School of EECS, S.N.U. Report ( Home Assignment) Q2. For a problem 4-24 in page 196, Simulate following figure by using FEMM. a. Show equipotential line both inside and outside of cylinder. b. Plot a voltage distribution through y-axis. (where V 0 =10V, and inner radius b=10mm) V=V 0 V=−V 0 b V=0 ( Hint : set any outside field ) (0,0)

18. Photonic Systems Lab School of EECS, S.N.U. Ref. Electrostatics Problem(1) File -> New -> Electrostatics Problem To analyze electrostatics problem, The difference between Magnetics Problem and Electrostatics Problem (Magnetics Problem) (Electrostatics Problem) (Difference)

19. Photonic Systems Lab School of EECS, S.N.U. If you don’t set any BC, Neumann BC where is applied. Ref. Electrostatics Problem(2) Kind of boundary condition 1.Dirichlet BC : 2.Neumann BC : 3.Mixed BC : (Fixed Voltage)

20. Photonic Systems Lab School of EECS, S.N.U. Ref. Electrostatics Problem(3) Properties -> Conductors -> Add property 1. Set voltage or charge 2. Make a name 3. Select line which you want to give a property 4. Set property to the line