7/25/2019 Models.llse.Busbar Llse

1/12

Solved with COMSOL Multiphysics 5.0

1 | E L E C T R I C A L H E A T I N G I N A B U S B A R

E l e c t r i c a l H e a t i n g i n a Bu s b a r

Introduction

This model analyzes a busbar designed to conduct a direct current from a transformer

to an electrical device; see Figure 1. The current conducted in the busbar produces

heat due to the resistive losses, a phenomenon referred to as Joule heating. The Joule

heating effect is described by conservation laws for electric current and energy. Once

solved for, the two conservation laws give the temperature and electric field,respectively.

Figure 1: Photo of a busbar installation, and the geometry of the busbar used in this model.

The goal of your simulation is to precisely calculate how much the busbar heats up and

to study the influence of a design parameter, the width of the device, on thephenomenon.

Model Definition

The busbar is made of copper while the bolts are made of titanium. This choice of

materials is important since titanium has a lower electrical conductivity than copper

and is subjected to a higher current density.

All surfaces, except the bolt contact surfaces, are cooled by natural convection in the

air surrounding the busbar. You can assume that the bolt cross-section boundaries do

not contribute to cooling or heating of the device. The electric potential at the

7/25/2019 Models.llse.Busbar Llse

2/12

Solved with COMSOL Multiphysics 5.0

2 | E L E C T R I C A L H E A T I N G I N A B U S B A R

upper-right vertical bolt surface is 20 mV, and that the potential at the two horizontal

surfaces of the lower bolts is 0 V.

Copper

Titanium

GroundElectric potential: 20mV

All other boundaries: natural convection

Figure 2: Material and boundary settings in the model.

Results and Discussion

The plot shown in Figure 3displays the temperature in the busbar, which is

substantially higher than the ambient temperature 293 K. The temperature differencein the device is less than 10 K, due to the high thermal conductivity of copper and

titanium. The temperature variations are largest on the top bolt, which conducts

double the amount of current compared to the two lower ones.

Figure 3: Temperature distribution in the busbar.

7/25/2019 Models.llse.Busbar Llse

3/12

Solved with COMSOL Multiphysics 5.0

3 | E L E C T R I C A L H E A T I N G I N A B U S B A R

The color range of the plot in Figure 4better illustrates the low temperature variation

in the copper part of the device. The temperature distribution is symmetric with a

vertical mirror plane running between the two lower titanium bolts and running acrossthe middle of the upper bolt. In this case, the model does not require much computing

power and you can model the whole geometry. For more complex models, you should

consider using symmetries in order to reduce the size of the model.

Figure 4: Temperature distribution in the copper part of the busbar.

Increasing the width of the busbar while keeping the applied potential constant leads

to a lower temperature in the device, as shown in Figure 5. While the increased

cross-sectional area leads to more heat produced by resistive losses, there is an even

7/25/2019 Models.llse.Busbar Llse

4/12

Solved with COMSOL Multiphysics 5.0

4 | E L E C T R I C A L H E A T I N G I N A B U S B A R

larger increase in the cooling effect as the total surface area increases, resulting in the

lowering of the temperature.

Figure 5: Average temperature in the busbar plotted against its width.

Notes About the COMSOL Implementation

The busbar geometry you are using in this model comes from Solid Edge . The

LiveLink interface transfers the geometry from Solid Edge to COMSOL Multiphysics.

Using the interface you are also able to update the dimension of the busbar in the Solid

Edge file. In order for this to work you need to have both programs running during

modeling, and you need to make sure that the busbar assembly file is the active file in

Solid Edge.

Model Library path: LiveLink_for_Solid_Edge/Tutorial_Models/

busbar_llse

Modeling Instructions

1 In Solid Edge open the file busbar_assembly.asm, which you find if you browse

to the models Model Library folder.

7/25/2019 Models.llse.Busbar Llse

5/12

Solved with COMSOL Multiphysics 5.0

5 | E L E C T R I C A L H E A T I N G I N A B U S B A R

2 Switch to the COMSOL Desktop, then start a new model.

N E W1 In the Newwindow, click the Model Wizard.

M O D E L W I Z A R D

1 In the Model Wizardwindow, click the 3Dbutton.

2 In the Select physicstree, select Heat Transfer>Electromagnetic Heating>Joule Heating.

3 Click the Add.

4 Click the Study.

5 In the tree, select Preset Studies for Selected Physics Interfaces>Stationary.

6 Click the Done.

G E O M E T R Y 1

LiveLink for Solid Edge 1

1 In the Model Builderwindow, right-click Component 1>Geometry 1and chooseLiveLink Interfaces>LiveLink for Solid Edge.

2 In the Settingswindow forLiveLink for Solid Edge, locate the Synchronizesection.

7/25/2019 Models.llse.Busbar Llse

6/12

Solved with COMSOL Multiphysics 5.0

6 | E L E C T R I C A L H E A T I N G I N A B U S B A R

3 Click the Synchronize.

By this action you transfer the geometry of the busbar from Solid Edge to

COMSOL Multiphysics.

4 In the Settingswindow for LiveLink for Solid Edge, click to expand the Parameters

in CAD Packagesection.

The table contains a dimension, width.busbar.par, which is part of the Solid

Edge model. The dimension refers to the width of the busbar and it was selected to

be linked to COMSOL in Solid Edge and saved in the Solid Edge file. Such linked

dimensions are retrieved and will appear in the CAD namecolumn of the table, when

you click the Synchronizebutton. The corresponding entry in the COMSOL name

column, the parameter LL_width_busbar_par, is a global parameter that is

generated automatically in the COMSOL model. When it is created during

synchronization, LL_width_busbar_paris assigned the current value of the

corresponding Solid Edge dimension. This value, 70 mm is displayed in the COMSOL

valuecolumn.

Global parameters in a COMSOL model allow you to parameterize settings and can

be controlled by the parametric solver to perform parametric sweeps. Thus, by

linking Solid Edge dimensions to COMSOL global parameters, the parametric

solver can automatically update and synchronize the geometry for each new value

in a sweep.

7/25/2019 Models.llse.Busbar Llse

7/12

Solved with COMSOL Multiphysics 5.0

7 | E L E C T R I C A L H E A T I N G I N A B U S B A R

G L O B A L D E F I N I T I O N S

Parameters

1 In the Model Builderwindow, expand the Global Definitionsnode, then click

Parameters.

2 In the Settingswindow for Parameters, locate the Parameterssection.

The table already contains the automatically generated global parameter that is

linked to the Solid Edge dimension.

Continue with loading additional parameters for setting up the physics.

3 Click Load from File.

4 Browse to the models Model Library folder and double-click the file

busbar_parameters.txt.

You will set up a parametric sweep with the width parameter,

LL_width_busbar_par. A parametric sweep can be over multiple parameters, and,

although not detailed in this step-by-step instruction, you may also set up parameter

sweeps to study for example the influence of the applied potential, Vtot, or the

maximum mesh size parameter, mh.

M A T E R I A L S

Add Mater ial

1 In the Model Builderwindow, right-click Component 1>Materialsand choose Add

Material.

2 Go to the Add Materialwindow.3 In the Searchtext field, type copper.

4 Click the Search.

5 In the tree, select Built-In>Copper.

6 In the Add materialwindow, click Add to Component.

7 In the Searchtext field, type titanium.

8 Click the Search.

9 In the tree, select Built-In>Titanium beta-21S.

10 In the Add materialwindow, click Add to Component.

Titanium beta-21S

1 In the Model Builderwindow, expand the Component 1>Materialsnode, then click

Titanium beta-21S.

7/25/2019 Models.llse.Busbar Llse

8/12

Solved with COMSOL Multiphysics 5.0

8 | E L E C T R I C A L H E A T I N G I N A B U S B A R

2 Select Domains 24, highlighted in the figure below.

H E A T T R A N S F E R I N S O L I D S

Heat Flux 1

1 In the Model Builderwindow, right-click Component 1>Heat Transfer in Solidsand

choose the boundary condition Heat Flux.

2 In the Settingswindow for Heat Flux, locate the Boundary Selectionsection.

3 From the Selectionlist, select All boundaries.

4 Remove Boundaries 8,14, and 28, marked in the figure below, from the Selection

list.

5 Check that the Selectionlist contains all other boundaries, that is, Boundaries 17,

913, and 1527.

6 In the Settingswindow for Heat Flux, locate the Heat Fluxsection.

7 Click the Convective heat fluxbutton.

8 In the htext field, type htc.

E L E C T R I C C U R R E N T S

Ground 1

1 In the Model Builderwindow, right-click Component 1>Electric Currentsand choose

the boundary condition Ground.

7/25/2019 Models.llse.Busbar Llse

9/12

Solved with COMSOL Multiphysics 5.0

9 | E L E C T R I C A L H E A T I N G I N A B U S B A R

2 Select Boundaries 8 and 14, highlighted in the figure below.

Electric Potential 1

1 In the Model Builderwindow, right-click Component 1>Electric Currentsand choose

the boundary condition Electric Potential.

2 Select Boundary 28, highlighted in the figure below.

3 In the Settingswindow for Electric Potential, locate the Electric Potentialsection.

4 In the V0text field, type Vtot.

M E S H 1

Size

1 In the Model Builderwindow, under Component 1right-click Mesh 1and choose Edit

Physics-Induced Sequence.

2 In the Model Builderwindow, under Component 1>Mesh 1click Size.

3 In the Settingswindow for Size, locate the Element Sizesection.

4 Click the Custom.

5 Locate the Element Size Parameterssection. In the Minimum element sizetext field,

type mh-mh/3.

6 In the Curvature factortext field, type 0.2.

7/25/2019 Models.llse.Busbar Llse

10/12

Solved with COMSOL Multiphysics 5.0

10 | E L E C T R I C A L H E A T I N G I N A B U S B A R

7 Click the Build All.

S T U D Y 1

In the Model Builderwindow, right-click Study 1and choose Compute.

R E S U L T S

Temperature (ht)

1 In the Model Builderwindow, expand the Results>Temperature (ht)node, then clickSurface 1.

2 In the Settingswindow for Surface, click to expand the Rangesection.

3 Select the Manual color rangecheck box.

4 In the Maximumtext field, type 315.8.

You should see a plot similar to the plot in Figure 4.

D E F I N I T I O N S

1 In the Model Builderwindow, under Component 1right-click Definitionsand choose

Probes>Domain Probe.

2 In the Settingswindow for Domain Probe, locate the Expressionsection.

3 In the Expressiontext field, type T.

7/25/2019 Models.llse.Busbar Llse

11/12

Solved with COMSOL Multiphysics 5.0

11 | E L E C T R I C A L H E A T I N G I N A B U S B A R

4 On the Domain Probetoolbar, click the Update Results.

The average temperature is displayed in the Tableswindow.

S T U D Y 1

Parametric Sweep

1 In the Model Builderwindow, right-click Study 1and choose Parametric Sweep.

2 In the Settingswindow for Parametric Sweep, locate the Study Settingssection.

3 Click Add.

4 Click Range.

5 Go to the Rangedialog box.

6 In the Starttext field, type 40[mm].

7 In the Steptext field, type 10[mm].

8 In the Stoptext field, type 70[mm].

9 Click the Replace.

10 Right-click Study 1and choose Compute.

As the parametric sweep progresses you should see the Tableswindow updated with

the average temperature in the device for each parameter value.

R E S U L T S

Temperature (ht) 1

1 In the Model Builderwindow, click Results>Temperature (ht) 1.

2 In the Settingswindow for 3D Plot Group, locate the Datasection.

3 From the Parameter value (LL_width_busbar_par (m))list, choose 0.05.

4 On the 3D plot grouptoolbar, click the Plot.

5 In the Model Builderwindow, expand the Temperature (ht) 1node, then click Surface

1.

6 In the Settingswindow for Surface, locate the Rangesection.

7 Select the Manual color rangecheck box.

7/25/2019 Models.llse.Busbar Llse

12/12

Solved with COMSOL Multiphysics 5.0

12 | E L E C T R I C A L H E A T I N G I N A B U S B A R

8 In the Maximumtext field, type 323.5.

Probe 1D Plot Group 4

1 In the Model Builderwindow, click Results>Probe 1D Plot Group 4.

2 In the Settings window for 1D Plot Group, locate the Plot Settingssection.

3 Select the x-axis labelcheck box.

4 In the associated text field, type Busbar width (m).

5 Select the y-axis labelcheck box.

6 In the associated text field, typeAverage temperature (K).

You should see a plot similar to the plot in Figure 5.