Transient Thermal Analysis Of Power Electronics

Chapter 45: Transient Thermal Analysis of Power Electronics

45

Transient Thermal Analysis of Power Electronics 

Summary



Introduction



Modeling Details



Solution Highlights



Results



Modeling Tips



Pre- and Postprocess with SimXpert



Input File(s)



Video

856 857 857 857

860

919

864

919

865

856 MD Demonstration Problems CHAPTER 45

Summary Title

Chapter 45: Transient Thermal Analysis of Power Electronics

Features

Transient thermal analysis using CHEXA elements

Geometry Units: mm, g, sec, C Copper Aluminum

10 X 10 X 8 1.295 X 1.295 X 0.2

Y

Flux 1.4907 W/mm (0 to 10 seconds)

Material properties

2

k Cu = 0.386W   mm – K  Cp Cu = 0.383J   g – K 

Z

X

k Al = 0.204W   mm – K  Cp Al = 0.896J   g – K 

Analysis characteristics

Nonlinear transient thermal analysis

Boundary conditions

All material is initially at 25oC then a heat flux is applied on top surface of the copper chip for 10 seconds.

Element type

8-node CHEXA

FE results

Temperature contours at t = 10 seconds.

CHAPTER 45 857 Transient Thermal Analysis of Power Electronics

Introduction This problem demonstrates the transient thermal capability of SOL 400 in solving a short duration heating on a chip through a copper tab attached to an aluminum backing.

Modeling Details Units: mm, g, sec, C Copper Aluminum

10 X 10 X 8 1.295 X 1.295 X 0.2

Y

Flux 1.4907 W/mm (0 to 10 seconds)

Figure 45-1

2 Z

X

Chip Analysis (Nastran Test File: chip1.dat)

In many applications, the power dissipation inside integrated circuits is transient in nature. The device maybe turned on for 10 seconds or less. The above model (Figure 45-1) consists of D2pak copper tab mounted on the aluminum heat sink. Due to the symmetry, only a quarter of the model is meshed.

Solution Highlights The following are highlights of the Nastran input file necessary to model this problem: $! NASTRAN Control Section NASTRAN SYSTEM(316)=19 $! File Management Section $! Executive Control Section SOL 400 CEND ECHO = SORT $! Case Control Section IC = 13 SUBCASE 1 $! Subcase name : NewLoadcase $LBCSET SUBCASE1 DefaultLbcSet THERMAL(SORT1,PRINT)=ALL FLUX(PRINT)=ALL ANALYSIS = HTRAN SPC = 15

858 MD Demonstration Problems CHAPTER 45

DLOAD = 16 NLSTEP = 1 BEGIN BULK $! Bulk Data Pre Section PARAM* SIGMA 1.7140E-9 PARAM POST 1 $! Bulk Data Model Section PARAM PRGPST NO MAT4 1 0.386 0.383 0.00895 MAT4 2 0.204 0.896 0.00271 PSOLID 1 1 PSOLID 2 2 $ CHBDYG Surface Elements CHEXA 126 1 17 18 1 + 147 183 CHEXA 127 1 179 181 147 + 148 184 CHEXA 128 1 18 20 2 + 149 147 CHEXA 129 1 181 185 149 + 150 148 $ Loads for Load Case : tran TABLED1 1 LINEAR LINEAR + 0.0 1. 10. 1. 10.1 + ENDT $! TLOAD1 1 2 1 QBDY3 2 1.5 0 2176 CHBDYG 2176 AREA4 148 150 158 156 $ Dynamic Load Table : flux_time TABLED1 1 0. 1. 10. 1. 10.2 0. 100. 0. ENDT $ Default Initial Temperature TEMPD 13 25. DLOAD 16 1. 1. 1 NLSTEP 1 12. + GENERAL -10 0 5 + FIXED 600 5 + HEAT UPW 0.01 0.01 0.01ITER + 10 2 0.2

Cu Al PSOLID_1 PSOLID_2 19

179

181+

183

180

182+

1

181

185+

147

182

186+

0.0

100.

+ 0.0+

20.

2

0.

+ + + +

The transient thermal analysis is indicated by ANALY=HTRAN. The IC option in the case control section points to the initial temperature of the model. In this case, The IC=1 points to the TEMPD in the bulk data section, and the initial temperature is set at 25 oC. The DLOAD bulk data in the case control either points to the DLOAD in the bulk data with same ID. Furthermore, the DLOAD in the bulk data section can then point to the multiple load set ID that refers to either TLOAD1, which called a time dependent table TABLED1 or TLOAD2 which has built in function such as unit step, sine, or cosine functions.

CHAPTER 45 859 Transient Thermal Analysis of Power Electronics

TABLED1 + + TLOAD1 QBDY3 CHBDYG

1 LINEAR LINEAR 0.0 1. 10. ENDT 1 2 2 1.5 0 2176 AREA4 148 150 158 16 1. 1.

DLOAD

1.

10.1

0.0

100.

+ 0.0+

1 2176 156 1

Field 3 on the TLOAD1 record has an integer value of 2 which points to a transient heat load of QBDY3 with this same set ID. In the field 6 of the TLAOD1 is the ID of time-dependent table of this heat flux. We see that the heat load is 1.0 from time equals to 0 to 10 seconds and, at 10.2 seconds, we shut this heat load back to zero.

Solution Procedure The nonlinear procedure used is defined through the NLSTEP entry: NLSTEP + + + +

1 GENERAL -10 FIXED 600 HEAT UPW 10

12. 0 5

5 0.01

2

0.01 0.2

0.01ITER

2

+ + + +

We are running a total 600 time steps with equal steps of 0.02 seconds and output the temperature at every 5th step. This means that the temperature will then be output at 0.1, 0.2, and 0.3 seconds, respectively. Also we can use the Method called FIXED and the convergence is set on the error on temperature (U) with 0.01 as the error tolerance. Grid point 195 is the fastest responding in the copper tab; it is also used in subsequent graphs to illustrate how fast the chip heats up and cools down.

Figure 45-2

Early Temperature History of Grid Point 195

860 MD Demonstration Problems CHAPTER 45

Results

Figure 45-3

Temperature Contours at 5 Seconds

Figure 45-4

Temperature History Past 10 Seconds

Suppose that the user decided to add a fan to increase the cooling on top. To simulate this, we will apply convection boundary condition on the top surface where the convection coefficient is a function of time and the ambient temperature is also at 25oC. We can then compare this run against the previous run that has no convection. Convection is applied as a heat transfer coefficient of H = 0.02W   mm 2 – C  . The temperature contours at 5 seconds are shown in Figure 45-5.

CHAPTER 45 861 Transient Thermal Analysis of Power Electronics

Figure 45-5

Temperature Contours at 5 Seconds

Another comparison between the two models is shown in Figure 45-6, where the influence of the cooling is very obvious with the entire model returning to the initial conditions after about 20 seconds.

Figure 45-6

Temperature Histories With and Without Cooling

By applying the convection on the top surface, the temperature of the chip is now cooled from 40.3 to 33.2oC. In this run we have a total of three time dependent boundary conditions. The DLOAD in the bulk data section (Nastran test file Chip_spcd1.dat) points to multiple TLOAD1 options as shown in the table below.

TLOAD1 ID

SPCD/DAREA

Grid (enforced temperature as a function of time)

H(time)

2

5

2556

Heat flux(time)

1

3

Tambient(time)

6

8

Boundary Conditions

TABLED1 (ID) 2 1

2555

3

862 MD Demonstration Problems CHAPTER 45

The SPCD is used only on enforced temperature as a function of time. TLOAD1 TLOAD1 TLOAD1 TABLED1 + + TABLED1 + + TABLED1 + $! PCONV MAT4 SPOINT SPCD SPC1 TEMP $! SPOINT SPCD SPC1 TEMP QBDY3 CHBDYG TEMPD SPCADD DLOAD NLSTEP + + + +

1 2 6

3 5 8

1 LINEAR LINEAR 0.0 1. 10. ENDT 2 LINEAR LINEAR -10. 0.02 0.0 20. 0.02 ENDT 3 LINEAR LINEAR 0.0 1. 100. 4 3 2555 5 4 21 2556 8 7 21 3 2176 148 21 23 24 1 GENERAL -10 FIXED 600 HEAT UPW 10

1 3 2

1 1

3

0

1.

10.1

1.

100.

+ 1.+

0.02

5.

0.02

10.

+ 0.02+ +

1.

ENDT

0.0 1.

2555

25. 2555 25.

2555 2556

1.0 2556 0.02 0 AREA4 158

2556 1.5 150 25. 4 1. 12. 0 5

7 1.

156

1

1.

2

0.01ITER

2

5 0.01

2

2176

0.01 0.2

1.

6 + + + +

SPOINT 2555 indicates the ambient temperature for the convection, while SPOINT 2556 represents the variation of convection coefficient with time.

CHAPTER 45 863 Transient Thermal Analysis of Power Electronics

CONV

Heat Boundary Element Free Convection Entry

Specifies a free convection boundary condition for heat transfer analysis through connection to a surface element (CHBDYi entry). Format: 1

2

3

4

5

6

7

8

9

CONV

EID

PCONID

FLMND

CNTRLND

TA1

TA2

TA3

TA4

TA5

TA6

TA7

TA8

1

2

3

4

5

6

7

8

9

CONV

2

101

3

201

301

10

Example:

Field EID PCONID

Contents

10

Type

Default

CHBDYG, CHBDYE, or CHBDYP surface element I > 0 identification number. I>0

Convection property identification number of a PCONV entry.

FLMND

Point for film convection fluid property temperature.

I>0

0

CNTRLND

Control point for free convection boundary condition.

I>0

0

TAi

Ambient points used for convection.

TA1 for TA2 I > 0 for TA1 I > 0 for TA2 through TA8 through TA8

$ Convection to Ambient of Load Set : htime PCONV 4 3 0 0.0 MAT4 3 SPOINT 2555 SPCD 5 2555 25. SPC1 4 2555 TEMP 21 2555 25. SPOINT SPCD SPC1 TEMP

2556 8 7 21

CONV CHBDYG

2201 2201 17

2556 2556

1.0 2556 0.02

4 18

1.

2556 AREA4 37

73

2555

864 MD Demonstration Problems CHAPTER 45

The SPOINT 2556 is on the field 5 (CNTRLND) on the CONV, and the SPOINT 2555 is on the field 6 (TA1). The field 6 on the MAT4 option is the convection coefficient times the tabeld1 ID 2 where this a function of time. At time equal to zero, the value is equal to 0.02, and time equal to 10 seconds, the value is 0.03. For SPOINT 2556, we used SPCD and SPC1 to specify enforced temperature as a function of time. The value of 1.0 that specified on the field 5 on the SPCD bulk data entry actually is a scale multiplier to the TABLED1 ID 2 that it refers to. The ambient temperature is constant at 25oC, but we could make it time dependent as well. It is important that for any enforced temperature as a function of time or any use of a control node in RADBC or CONV bulk data entries, that a value of 1 is specified on field 5 on the TLOAD1 or TLOAD2 entry to indicate that this refers to the SPCD.

Modeling Tips The transient thermal analysis involved a lot more data compared to a steady state thermal analysis since every time step requires a temperature distribution. It is sensible to monitor those nodes that handle the time-dependent boundary conditions. In this case, the convection coefficient as a function of time is applied to SPOINT 2556 which, when plotted as a graph in SimX, should behave as described by the input. The other point of interest is where the heat load is applied. Adaptive time stepping facilitates capturing transient thermal behavior more precisely than uniform stepping, because the length of each time step changes based upon changes in temperature. To invoke adaptive time stepping requires the nonlinear procedure defined through the NLSTEP entry: NLSTEP,6,12.0 ,GENERAL,10,1,10 ,ADAPT,0.001,1.0E-5,0.5 ,HEAT,U,1.0E-6,1.0E-6,1.0E-6,AUTO and a backward Euler thermal operator with the NDAMP parameter: PARAM,NDAMP,0.5 This will run for a total time period of 12 seconds with an initial time step of 12/1000. The minimum time step is 12*1e-5; the convergence is set to U and is at 1e-6. The allowable range of the NDAMP parameter is -2.414 to 0.414, and any NDAMP value that violates this range is reset to the closest allowable value. Here it triggers the backward Euler operator. (NDAMP = 0 would be the Crank-Nicholson operator). The adaptive time stepping would avoid the small oscillation seen in Figure 45-4 since the backward Euler operator is both stable and immune to oscillations. The input files nug_45c.dat and nug_45d.dat use this operator.

CHAPTER 45 865 Transient Thermal Analysis of Power Electronics

Pre- and Postprocess with SimXpert Run SimXpert with Structures Workspace a. For the Default Workspace, select Structures

a

866 MD Demonstration Problems CHAPTER 45

Specify the Model Units a. Tools: Options b. Observe the User Options Window c. Select Units Manager d. For Basic Units, specify the model units e. Length = mm; Mass = g; Time = s; Temperature = celsius, Force = N f. Click OK

a

b

d c

e

CHAPTER 45 867 Transient Thermal Analysis of Power Electronics

Create a Surface with a 45° Angle a. Create two straight curves b. Geometry tab: Curve/Curve c. For X,Y,Z Coordinate, enter 1.295, 0, 0; click OK d. For X, Y, X Coordinate enter 1.295, 1.295, 0; click OK e. Click Apply f. For X,Y,Z Coordinate, enter 10, 0, 0; click OK (not shown) g. For X,Y,Z Coordinate, enter 10, 10, 0; click OK (not shown) f. Click Apply

b

c

d

e

f

868 MD Demonstration Problems CHAPTER 45

Create a Surface with a 45° Angle (continued) a. Create two straight curves b. Geometry tab: Surface/Filler c. For Curves screen, select 2 curves d. Click OK

b

c d

c

CHAPTER 45 869 Transient Thermal Analysis of Power Electronics

Mesh the Surface a. Create mesh seeds on the four curves of the surface b. Meshing tab: Automesh/Seed c. For Curves screen, select the shortest curve and the opposite curve d. Select Number of Elements, enter 5; click OK e. Do this for the lower-right curve, using One Way Bias f. Select Number of Elements and L2/L1 g. For Number of Elements, enter 10 h. For L2/L1, enter 5; click OK i. Do this for the last curve, using One Way Bias (not shown) j. Select Number of Elements and L2/L1 (not shown) k. For Number of Elements, enter 10 l. For L2/L1, enter 0.2; click OK (1/5) (not shown)

b

c

d

e

i c f

g h

f

870 MD Demonstration Problems CHAPTER 45

Mesh the Surface (continued) a. Create mesh seeds on the four curves of the surface b. Meshing tab: Automesh/Surface c. For Surfaces to mesh screen, select the surface d. For Mesh type, select Quad Dominant e. For Mesh method, select Mapped f. Click OK

b

c

d e

c

f

CHAPTER 45 871 Transient Thermal Analysis of Power Electronics

Reflect the Part a. Reflect (mirror) the Part (surface and its mesh) b. Tools: Transform/Reflect c. To define a plane to reflect about, create a node at the origin (0,0,0) and one above it (0,0,10) d. Nodes/Elements tab: Create/Node e. For X,Y,Z Coordinate, enter 0,0,0; click OK f. For X,Y,Z Coordinate, enter 0,0,10; click OK (not shown) g. Click OK

d

e

g

872 MD Demonstration Problems CHAPTER 45

Reflect the Part (continued) a. Reflect (mirror) the Part (surface and its mesh) b. Tools: Transform/Reflect c. For Plane, select Any Plane d. Select Make Copy e. Select Nodes f. Select the node at the origin g. Select the node at the tip of the surface (interior angle is 45°) h. Select the node that is above the origin

g

b

c d e

h

f

CHAPTER 45 873 Transient Thermal Analysis of Power Electronics

Reflect the Part (continued) a. Reflect (mirror) the Part (surface and its mesh) b. From Reflect - Any Plane pick panel, select Parts c. Screen select the Part d. Click Done; then click Exit

c

b

d

874 MD Demonstration Problems CHAPTER 45

Create a Square Surface to be Congruent at Lower-left a. Create a square surface at the lower-left corner of the Part b. Geometry tab: Curve/Curve c. For Entities screen, select the node at the origin and the node to its right d. Click OK

b

c d

c

CHAPTER 45 875 Transient Thermal Analysis of Power Electronics

Create a Square Surface to be Congruent at Lower-left (continued) a. Create a square surface at the lower-left corner of the Part b. Geometry tab: Surface/Filler c. For Curves screen, select the curve just created and the curve just above it d. Click OK

b

c d

c

876 MD Demonstration Problems CHAPTER 45

Mesh the Square Surface at Lower-left a. Create a square surface at the lower-left corner of the Part b. Meshing tab: Automesh/Surface c. For Surfaces to mesh screen, select the square surface just created d. Click OK

b

c

d

c

CHAPTER 45 877 Transient Thermal Analysis of Power Electronics

Connect the Adjacent Elements (continued) a. Connect the adjacent elements using equivalence b. Nodes/Elements tab: Modify/Equivalence c. Set geometry to wireframe (not shown) d. Tools: Identify to display the node labels (not shown) e. For Entities screen, select all the nodes f. For Merging tolerance, enter 0.05 g. Click OK

b

e

f

g

e

878 MD Demonstration Problems CHAPTER 45

Connect the Adjacent Elements (continued) a. Connect the adjacent elements using equivalence b. Click OK c. View: Clear Labels (not shown) d. Tools: Identify (not shown) e. For Identify Entities pick panel, select Nodes (not shown) f. Click All (not shown) g. Click Exit (not shown) h. Observe only one node label i. View: Clear Labels (not shown)

b

h

CHAPTER 45 879 Transient Thermal Analysis of Power Electronics

Sweep 2-D Elements to Create 3-D Elements a. Create 3-D elements by sweeping the 2-D elements b. Meshing tab: FEM based/Normal c. For Shell Elements screen, select all the elements d. For Distances, enter -8 e. For Layers, enter 8 f. Click OK

b

c

d f

e

c

880 MD Demonstration Problems CHAPTER 45

Sweep 2-D Elements to Create 3-D Elements (continued) a. Create 3-D elements by sweeping the 2-D elements b. Model Views: Isometric View c. Observe the 3-D elements

b

c

CHAPTER 45 881 Transient Thermal Analysis of Power Electronics

Create 3-D Elements for Applying Heat Flux a. Create 2-D elements at the location where they are needed b. View > Entity Display Filter: Show/Hide 3D FE c. Tools: Transform/Translate (not shown) d. For Translate XYZ, enter 0, 0, 8 e. Select Make Copy f. Select Elements g. Model Views: Top h. Screen select the 2-D elements for the square surface i. Select Done j. Model Views: Isometric View

d

j g

e

f h

b

i

882 MD Demonstration Problems CHAPTER 45

Create 3-D Elements for Applying Heat Flux (continued) a. Create 3-D elements by sweeping the 2-D elements b. Observe the new 2-D mesh that is to be sued to create the 3-D elements for the application region for the heat flux c. Rotate model as needed

b

CHAPTER 45 883 Transient Thermal Analysis of Power Electronics

Create 3-D Elements for Applying Heat Flux (continued) a. Create 2-D elements at the location where they are needed b. Meshing tab: FEM based/Normal c. For the Shell Elements screen, select the 2-D elements that were just created d. For Distances, enter -0.2 e. For Layers, enter 2 f. Click OK g. Model Views: Isometric View (not shown) h. Render:FE Shades with Edges (not shown)

b

c d f

e

c

884 MD Demonstration Problems CHAPTER 45

Create 3-D Elements for Applying Heat Flux (continued) a. Create 3-D elements by sweeping the 2-D elements b. Observe the 3-D meshes

b

CHAPTER 45 885 Transient Thermal Analysis of Power Electronics

Delete All 2-D Elements a. Eliminate all 2-D Elements for the model b. Edit: Delete c. From the Delete pick panel, select Elements d. Select Advanced e. From the Extended Pick Dialog, select CQUAD4 f. Select the entire model g. Click Done h. In the Delete window, click Yes i. Click Exit

c b

e d g

i f

h

886 MD Demonstration Problems CHAPTER 45

Connect All 3-D Elements a. By using equivalence, all 3-D elements can be connected b. Modes/Elements: Modify/Equivalence c. For Entities screen, select the entire model d. For Merging tolerance, enter 0.5 e. Click OK f. Click OK

b

c

d

e

f

CHAPTER 45 887 Transient Thermal Analysis of Power Electronics

Material Properties a. Design material properties for Copper and Aluminum b. Materials and Properties tab: Material/Isotropic c. For Name, enter Copper d. For Young’s Modulus, enter 210 e. For Poisson’s Ratio, enter 0.28 f. For Thermal Conductivity, enter 0.386 g. For Specific Heat, enter 0.383 h. For Thermal Density, enter 0.00895 i. Click OK

b

c d e

f

g h

i

888 MD Demonstration Problems CHAPTER 45

Material Properties (continued) a. Design material properties for Copper and Aluminum b. Materials and Properties tab: Material/Isotropic c. For Name, enter Aluminum d. For Young’s Modulus, enter 210 e. For Poisson’s Ratio, enter 0.28 f. For Thermal Conductivity, enter 0.204 g. For Specific Heat, enter 0.896 h. For Thermal Density, enter 0.00271 i. Click OK

b

c d e

f

g h

i

CHAPTER 45 889 Transient Thermal Analysis of Power Electronics

Element Properties a. Define element properties for Copper and Aluminum parts of the model b. Materials and Properties tab: 3D Properties/Solid c. For Name, enter SOLID_Copper d. For Entities screen, select the solid elements that are to represent the Copper e. under Material on the Model Browser tree, select Copper f. Click OK

b

c

d

d

e

f

e

890 MD Demonstration Problems CHAPTER 45

Element Properties (continued) a. Define element properties for Copper and Aluminum parts of the model b. Materials and Properties tab: 3D Properties/Solid c. For Name, enter SOLID_Aluminum d. For Entities screen, select the solid elements that are to represent the Aluminum e. Under Material on the Model Browser tree, select Aluminum f. Click OK

b c

d

d

e

f

e

CHAPTER 45 891 Transient Thermal Analysis of Power Electronics

Define Time Dependent Heat Flux on Copper Chip a. To define the time dependent heat flux that is to be normal to the Copper chip, first define the time dependent function for the heat flux b. Fields/Tables tab: Tables/NastranBDF/Tabled1 c. For Name, enter TABLE_1 d. For X and Y values, enter the values shown below e. Click OK

b

c

d

e

892 MD Demonstration Problems CHAPTER 45

Define Time Dependent Heat Flux on Copper Chip (continued) a. Define the time dependent heat flux that is to be normal to the Copper chip b. LBCs tab: Heat Transfer/Normal Flux c. For Name, enter Normal_Flux_Copper_Chip d. For Entities screen, select the nodes at the top of the chip e. For Heat Flux, enter 1.4907 f. Under Flux vs Time scaling function on the Model Browser tree, select TABLE_1 g. Click OK

b

c d

d e f

g

CHAPTER 45 893 Transient Thermal Analysis of Power Electronics

Define Time Dependent Heat Flux on Copper Chip (continued) a. Define the time dependent heat flux that is to be normal to the Copper chip b. Observe the model with the applied heat flux

b

894 MD Demonstration Problems CHAPTER 45

Create a SimXpert Analysis File a. Create a SimXpert analysis file for performing an MD Nastran analysis b. Right click on FileSet, and select Create new Nastran job c. For Job Name, enter a title d. For Solution Type, select SOL400 e. For Solver Input File, select the path f. Unselect Create Default Layout g. Click OK

b

c

d

e f g

CHAPTER 45 895 Transient Thermal Analysis of Power Electronics

Create a SimXpert Analysis File (continued) a. Create a SimXpert analysis file for performing an MD Nastran analysis b. Right click on Load Cases and select Create Loadcase c. For Name (title), enter NewLoadcase d. For Analysis Type, select Nonlinear Transient Heat Trans e. Click OK

b

c

d e

896 MD Demonstration Problems CHAPTER 45

Create a SimXpert Analysis File (continued) a. Create a SimXpert analysis file for performing an MD Nastran analysis b. Right click on Loads/Boundaries and select Select Lbc Set c. For Selected Lbc Set, enter DefaultLbcSet; click OK d. Under LBC Set in the Model Browser, double click on DefaultLbcSet to observe the lbcs that are assigned e. Click Cancel

d

b e c

CHAPTER 45 897 Transient Thermal Analysis of Power Electronics

Create a SimXpert Analysis File (continued) a. Create a SimXpert analysis file for performing an MD Nastran analysis b. Under Simulations, transient analy power... in the Model Browser, double click on Solver Control c. Select Solution 400 Nonlinear Parameters d. For Default Init Temperature, enter 25; click Apply e. Select Output File Properties f. For Test Output, select Print g. Click Apply h. Click Close

c

d

f e

b

2009 MSC.Software Corporation

g h

898 MD Demonstration Problems CHAPTER 45

Create a SimXpert Analysis File (continued) a. Create a SimXpert analysis file for performing an MD Nastran analysis b. Under Simulations, transient_analy_power... NewLoadcase in the Model Browser, double click on Loadcase Control c. Select Subcase Transient Heat Transfer Parameters d. For Initial Time Step, enter 0.02 e. For Number of Time Steps, enter 600 f. Click on Temperature Error g. For Temperature Tol., select 0.01 h. Click Apply (not shown) i. Click Close (not shown)

. .

b d c

e

f

g

CHAPTER 45 899 Transient Thermal Analysis of Power Electronics

Create a SimXpert Analysis File (continued) a. Create a SimXpert analysis fole for performing an MD Nastran analysis b. Under Simulations, transient_analy_power...,Load Cases, NewLoadcase in the Model Browser, right click on Output Requests c. Select Nodal Output Requests d. Select Create Temperature Output Request e. Click on Suppress Print f. For Sorting., select By Frequency/Time g. Click OK

c

d

e f b

g

900 MD Demonstration Problems CHAPTER 45

Run a SimXpert Analysis a. Perform a SimXpert thermal analysis b. Under Simulations in the Model Browser, right click on transient analy power elect c. Select Run

b

c

CHAPTER 45 901 Transient Thermal Analysis of Power Electronics

Attach the SimXpert Analysis Results File a. Attach the SimXpert result file b. Click on Attach Results c. For File path, select the results file transient_analy_power_elect.xdb d. Click OK

c

b

d

902 MD Demonstration Problems CHAPTER 45

Display a Chart of Temperature Results a. Display the thermal results for all the times b. Results tab: Results/Chart c. For Results Cases., select the results for all the times d. For Results Type, select Temperatures e. For Target Type, select Nodes f. Pick Filters: Accumulate Mode

b

d

e

c

f

CHAPTER 45 903 Transient Thermal Analysis of Power Electronics

Display a Chart of Temperature Results (continued) a. Display the thermal results for all the times b. Select two nodes; e.g., Node 1522 and Node 67 c. For Independent axis., select Time d. Click Add Curves

d b c

b

b

904 MD Demonstration Problems CHAPTER 45

Display a Chart of Temperature Results a. Display the thermal results for all the times b. Observe the temperature results

b

CHAPTER 45 905 Transient Thermal Analysis of Power Electronics

Define Free Convection off Heat Storage Body a. Define free convection off top of model b. LBCs tab: Heat Transfer/Free Convection c. For Name, enter Free Convection_Al_Body d. For Ambient Temperature, enter 25 e. To make picking easier, hide the lbc Normal Flux_Copper_Chip (not shown) f. For Entities screen, select the nodes at the top of the Aluminum body. Make sure to select the node at the corner g. DO NOT CLICK OK

b

c

.

d f

f

f

906 MD Demonstration Problems CHAPTER 45

Define Free Convection off Heat Storage Body (continued) a. Define free convection off top of model b. Change the picking to Pick Filters: Accumulate Mode c. Change to different view using Model Views: Front (not shown) d. For Entities screen, select the remaining nodes at the top of the Aluminum body e. Click on Advanced f. For Convection coefficient, enter 0.02 g. Click OK

b

d e

f

g

d

CHAPTER 45 907 Transient Thermal Analysis of Power Electronics

Define Free Convection off Heat Storage Body (continued) a. Define free convection off top of model b. Observe the model with its free convection markers

b

908 MD Demonstration Problems CHAPTER 45

Create a SimXpert Analysis File a. Create a SimXpert analysis file for performing an MD Nastran analysis b. Under FileSet in the Model Browser, right click on Create new Nastran job c. For Job Name, enter a new title d. For Solution Type, select SOL400 e. For Solver Input File, select the path f. Unselect Create Default Layout g. Click OK

b

c

d

e f g

CHAPTER 45 909 Transient Thermal Analysis of Power Electronics

Create a SimXpert Analysis File (continued) a. Create a SimXpert analysis file for performing an MD Nastran analysis b. Right click on Load Cases, and select Create Loadcase c. For Name (Title), enter NewLoadcase d. For Analysis Type, select Nonlinear Transient Heat Trans e. Click OK

b

c

d e

910 MD Demonstration Problems CHAPTER 45

Create a SimXpert Analysis File (continued) a. Create a SimXpert analysis file for performing an MD Nastran analysis b. Right click on Loads/Boundaries, and select Select Lbc Set c. For Selected Lbc Set, enter DefaultLbcSet d. Double click on DefaultLbcSet to observe the lbcs that are assigned e. Click Cancel

.

e

b

c d

f

CHAPTER 45 911 Transient Thermal Analysis of Power Electronics

Create a SimXpert Analysis File (continued) a. Create a SimXpert analysis file for performing an MD Nastran analysis b. Double click on Solver Control c. Select Solution 400 Nonlinear Parameters d. For Default Init Temperature, enter 25;click Apply f. Select Output File Properties g. For Text Output, select Print; click Apply h. Click Close

c

d

b

g f

h

912 MD Demonstration Problems CHAPTER 45

Create a SimXpert Analysis File (continued) a. Create a SimXpert analysis file for performing an MD Nastran analysis b. Double click on Loadcase Control c. Select Subcase Transient Heat Transfer Parameters d. For Initial Time Step, enter 0.02 e. For Number of Time Steps, enter 600 f. Click on Temperature Error g. For Temperature Tol., enter 0.0.1; click Apply h. Click Close (not shown)

d c

e

f

g

b

CHAPTER 45 913 Transient Thermal Analysis of Power Electronics

Create a SimXpert Analysis File (continued) a. Create a SimXpert analysis file for performing an MD Nastran analysis b. Right click on Output Requests c. Select Nodal Output Requests d. Select Create Temperature Output Request e. Click on Suppress Print f. For Sorting, select By Frequency/Time g. Click OK

c

d

e f b

g

914 MD Demonstration Problems CHAPTER 45

Run a SimXpert Analysis a. Perform a SimXpert thermal analysis b. Right click on tran_analy_with_free_conv c. Select Run

b

c

CHAPTER 45 915 Transient Thermal Analysis of Power Electronics

Attach the SimXpert Analysis Results File a. Attach the SimXpert result file b. Click on Attach Results c. For File path, select results file tran_analy_with_free)conv.xdb d. Click OK

c

b

d

916 MD Demonstration Problems CHAPTER 45

Display a Chart of Temperature Results a. Display the thermal results for all the times b. Results tab: Results/Chart c. For Result Cases, Select the results for all the times d. For Result Type, select Temperatures e. For Target type, select Nodes f. Pick Filters: Accumulate Mode

b

d

e

c

f

CHAPTER 45 917 Transient Thermal Analysis of Power Electronics

Display a Chart of Temperature Results (continued) a. Display the thermal results for all the times b. Select two nodes; e.g., Node 1522 and Node 67 c. For Independent axis, select Time d. Click Add Curves

d b c

b

b

918 MD Demonstration Problems CHAPTER 45

Display a Chart of Temperature Results (continued) a. Display the thermal results for all the times b. Observe the temperature results

b

CHAPTER 45 919 Transient Thermal Analysis of Power Electronics

Input File(s) File

Description

nug_45a.dat

MD Nastran transient thermal input file - fixed step without cooling

nug_45b.dat

MD Nastran transient thermal input file - fixed step with cooling

Ch_45a.SimXpert

SimXpert data corresponding to nug_45a.bdf

nug_45c.dat

MD Nastran test deck using adaptive approach for heating only

nug_45d.dat

MD Nastran test deck using adaptive approach for heating with convection cooling

Video Click on the image or caption below to view a streaming video of this problem; it lasts approximately 30 minutes and explains how the steps are performed.

Figure 45-7

Video of the Above Steps