How to Simulate Electric Motor Temperature Using Ansys Motor-CAD and Icepak

How to Simulate Electric Motor Temperature Using Ansys Motor-CAD and Icepak Hello everyone, this is Batuhan from Ozen Engineering. In this video, I will show you how you can perform your electromagnetic thermal coupled simulations for your electric motor.

The first product is Ansys Motor-CAD and the second one is Icepak. First, I want to show you how you can do it in Motor-CAD. I will be using the default motor provided by Motor-CAD. This motor has 18 slot numbers and 4 pole numbers.

If we go to winding, we can see that it uses 100 conductors per slot and it has 50 turns per winding layers. For the materials, it is using M350-50A for stator and rotor and copper for armature winding and N30-UH for the magnet.

For the settings, we will be using the default numbers provided by the Motor-CAD; all we have to do is change the phase advance from 0 to 8 and the temperatures for armature and winding to 40. These values are not affecting your thermal temperatures; they are just being used to calculate the thermal electromagnetic performance of your electric motor.

To couple the Motor-CAD electromagnetic losses to thermal model, all you have to do is check the setting to transfer the losses to thermal model. And then you can simply run your simulation by clicking Solve Electromagnetic Model.

After running your model, you can go to output data and see the losses that you can observe. Here, our armature DC losses are 127.9 watts and our iron losses are 7.7 watts for stator and rotor. To simulate the thermal performance of these losses, we can click Model and select Thermal.

Here, by the default settings, this electric motor has a housing with the fins. If you go to 3D views, you can see the housing is mounted on the electric motor. For the losses that we transfer from electromagnetic model, we can click Input Data and select Losses.

Here, as you see, the same numbers that we achieved from the electric model are transferred to the thermal model. For the cooling, we will be using natural convection and we will not be using any cooling systems as the current density of the electric motor is relatively small.

All we have to do is change the interfaces of stator lamination and housing from average surface contact to good surface contact to simulate the press fit or shrink fit in real-life cases. This will be reducing the thermal resistance between the two surfaces and increase the simulation accuracy.

Here, we can use the same settings as provided by the default settings. When we go to the Calculation tab, we can see the shaft speed is automatically assigned 3000 RPM, and we will be using the steady-state calculation type.

All we have to do is just run the Solve Thermal Model button to see the temperatures of each of the components. The Motor-CAD model is using a thermal circuit to solve the temperatures of each of the components.

If we go to Radial, we can see the magnets are reaching 116.6°C and the maximum winding that we can see from the left side of the window is 126.6°C.

You can also observe the same temperatures and the other side of the electric motors by using the axle section here, and you can observe the rest of the electric motor.

Now, I will be showing you how you can transfer this electric motor to Ansys Discovery, Maxwell, and Icepak to simulate the CFD version of this thermal simulation. To do that, we have two tools in Ansys Motor Kit.

The first one is Ansys Electronics Desktop, which is transferring your electromagnetic boundary conditions to Ansys Maxwell with the electric motor components, but it's not including the housing.

The second one is Ansys Discovery, which includes the housing, but this one is just for designing and drawing purposes. Let's start with the Ansys Electronics Desktop.

Before clicking the button, let's go back to the Electromagnetic Model and change the input data, settings, and the calculation; the model size should be full machine.

Normally, the symmetric model can be analyzed in Ansys Maxwell or Ansys Icepak, but to make the simulation more clear and understandable for the full size of the motor, I will be using the full machine for the motor kit.

Then, you can go to Ansys Electronic Desktop and choose the Ansys Electronic Desktop 3D, not solved, and choose the file that you want to export the script at. After choosing the file, then you can simply click Export, and the Motor-CAD will be exported to your script within seconds.

After exporting your script, all you have to do is just to double-click the script, and it will open the Ansys Maxwell 3D and start creating the full mesh, full model of your electric motor.

The script is finished; now, we can go and double-click the Motor-CAD script button here to see the 3D model of the electric motor. As you see, the script is only using half of the electric motor.

In order to simulate the full machine of it, we can scroll down in the properties of the project and find the half-excel parameter and change it to 0. When we change it back to 0, it will be showing the full model of the electric motor. Now, we have the full model of the electric motor.

The next step is to change the solution type from transient to eddy current solution. The reason is that for the coupling, we don't need to have the torque and the speed variables of the electric motor. Instead, all we have to do is calculate the losses of the electric motor.

To do that, we have to change it to transient to Ansys magnetic eddy current. Once you change it, most of the features will be disappeared, but still, we will have the required settings from the Ansys Maxwell transient. Here, we need to change this excitation current to 5A.

The added current uses the peak current of your electric motor. So, as you remember from the motor kit, the peak current of the electric motor was 5A. The next step is assigning the core loss and the added effects to this electric motor to include these losses into our model.

First, let's go to set core losses. Here, as you see, the only two components are defined in their materials, stator and rotor. You have to check these variables and click OK. And the next one is including the add effects into our simulation.

First, uncheck all the settings here, and only keep the stator, rotor, and the magnets. The reason that we are not including the winding is we didn't include each of the turns of the windings, and the following is the method of adding Ansys solutions to our Ansys model.

Instead, we model them as a block, so we cannot estimate the AC losses or the AD effect on these windings. After including the losses again, we need to add a solution setup. Here, you can right-click the analysis and create an analysis setup.

After you are adding the solution setup, you can go and change the percent to percent error from 1 to 0.1 to increase the accuracy of your model.

For the convergence, change its values to 3. And for the solver, adaptive frequency should be 100, since we are rotating our electric motor at 3000 RPM, and this model has 4 number of poles, so the calculation makes the adaptive frequency 100 Hz. You can keep the rest of the settings as they are.

Now, we are done with the settings of the electromagnetic. Before running this simulation, let's go back to Motor-CAD and click Tools and create the script to design the housing, stator, and rotor of the electric motor in Discovery.

After you have the Discovery, first choose your file that you want to export the script. After you are choosing your file, you can click Export. Once you have the Discovery export or the file that you name, you will have the Python code on your file.

Go to Discovery or SpaceClaim that you would like to have, and from the interface, choose Script Editor on the right side. And open the file that you exported from Motor-CAD. The Python code will appear on your script editor.

To run the simulation, click the Play button, and this will take 5 to 10 minutes based on the complexity and the geometry of your model. As you see, the drawing is finished under 5 minutes by using this script in Ansys Discovery. Now, we have to save this geometry as a STEP file.

To do that, go and click Save As from the left top button, and change the file type into STEP file. And go click Browse, and choose the file that you want to export the model at.

Once you exported the model, you can close Ansys Discovery; you can save the model or the project in Ansys Discovery, but since we already have the model, I don't see any requirement to save it. The next thing that you need to do is going back to Electronics Desktop and click iSpec Model here.

Once you have the iSpec model, you need to import the file that we just exported from Ansys Discovery to Ansys iSpec. To do that, click Modular and go to Import, and select the model that you exported. I already exported two files, so these are the same.

Once you export the model, you will have the STEP file in your iSpec simulation. To make the simulation faster and reduce the complexity of the model, we have to unite some part of the electric motor into the same model. For example, we have different parts of the housing in different components.

Instead, we can click all of them by using the Control button and choose Unite button to merge them into one component. Now, we have the housing into one piece. And as we see, the armature winding are separated by different components.

In order to unite all of them, we can basically click all of them by using the Shift command and choose Unite. Now, we reduce the complexity of the model. As you see, the region is automatically assigned by the iSpec. Here, we need to assign the materials of these components one by one.

For the armature, we have to right-click and choose Assign Material and search copper. For the stator weight, we can use plastic, of course.

For stator and rotor lamination, we need to use M350, but you can use any available lamination materials since the thermal characteristics of the laminated steels are relatively similar to each other.

For the magnets, you can go and assign material and you can choose any magnets; negative magnets, actually, for this purpose, since almost all of the magnet materials for thermal conductivity and the specific heats are the same. So, let's choose N30UH to make the same as Motor-CAD.

For this shaft, we can also merge these components into one piece and assign material as cast iron, as most of the cases. For the bearing, we can also assign them as steel or aluminum or any material you want. This will not affect the overall performance of the thermal of your electric motor.

And lastly, for the housing, we need to go back to Motor-CAD since this is affecting the thermal performance and check which material we used in Ansys Motor-CAD. Go to Input Data and click the Materials, and it uses Aluminum alloy 195 cast. Go to Assign Material and search Aluminum.

We can use the similar material that we have in our library. The values that we need to be careful about are actually the thermal conductivity and the specific heat.

The thermal conductivity should be 168, and the specific heat should be 833. So, we can scroll down and find a similar one, and we can go and edit the materials. The specific heat should be 833, and the thermal conductivity should be 168. And click OK. And yeah.

So, as you see, we assigned the materials for all of the components. Make sure that you assign all the materials for each of the components; otherwise, you will have errors in your iSpec simulation. The next step is assigning the surface material between the surfaces.

Normally, you can assign different materials for each of the components, but here, to make the video shorter and reduce the complexity of the electric motor, I will simply choose all the materials and choose as steel oxidized surface.

There are multiple materials that you can choose as surface material that you can go and check and apply for your requirements. Now, it's time to couple the iSpec model to Maxwell. To do that, we have to select the heat source components in our thermal simulation.

These are magnets, since they have the magnet losses, even though they are relatively small. Of course, the armature or the phase windings, stator, and rotor. After selecting these components, right-click and go to Assign Thermal and choose EM loss.

Here, we have to check Use this project, so it will recognize the Ansys Maxwell in the same project. As you see, it automatically assigns the Motor-CAD script Maxwell project, which are Maxwell 3D project over here.

Check these two settings and go to Variable Mapping and click Map Variable by Name, and then OK. Here, we don't need to change any variables. We have a loss multiplier here that, in further iterations, you might need to change this multiplier to make the simulations closer to your experimental data.

Now, the last thing that we need to assign is the outlet for our CFD simulation. As you know, this fluid region is full of air, and there should be an outlet to complete the simulation flow.

To do that, go to a region and right-click and select all faces, and right-click to one of these faces and assign Thermal and Opening and Free. You can keep the same settings as they are. Now, let's add a solution setup. Here, you can right-click Analysis and add Solution Setup.

The maximum iteration per sol can vary based on your electric motor simulation and complexity of your model. Here, I can keep it as 200, and you need to change the radiation model to Discrete Ordinate to simulate the radiation in our model, and we need to include the gravity.

In the convergence, you don't need to change anything, but you can reduce the convergence of your flow to make your simulation more stable. Here, in the Solver settings, we have to add a very small z velocity into our simulation to provide a small percent of air into our fluid domain.

And for the radiation, you can change these values as 3 to make the accuracy and redundancy of the model better. And then you can click OK. Now, you can right-click the iSpec design and choose Design Settings, and these are the operational settings of your environment.

I want to operate the electric motor air at 40 degrees, as we did in Motor-CAD. The last thing that we need to assign into our simulation is mesh settings. If you go to Simulation, you will see the Global Mesh Settings over here.

You can increase the mesh settings all the way to find to make your simulation faster and more accurate. But to keep the video shorter, I will make it as far, and I will enable the Mesh Region, and I will keep the Facet Level as same. And I will click OK.

Now, let's generate the mesh to see the quality of our meshes. If it is not enough, we can increase the initial mesh settings in the Global Mesh. The mesh is generated, and the pop-up window shows the mesh settings, actually the visualization of our model.

Here, if you click the Geometry Boundary Selection and choose the housing, you can see the meshes on the housing. You can right-click the mesh, the housing actually, and hide the selection and choose; we can actually hide the region to see the winding meshes.

As you see, the meshes appear on the winding. These meshes are sufficient for our initial simulation for this tutorial. Now, you can close the pop-up window. Let's validate the simulation to see if everything is fine.

As you see, all the simulation settings are assigned and coupled, so we can simply run the simulation. Before running the simulation, I would like to show the optional settings that you would like to monitor during the simulation.

If you want to monitor the temperature of any of the components of your electric motor, you have to simply choose the magnet or any components. Here, I will choose these magnets and right-click and go to Assign Monitor, and we have two options here.

The point is assigning the material center point as the monitoring point, and you can simply choose this one to monitor the temperature of the magnet in the center.

Or if you want to monitor the one face of your model, you can go and change the Select Model into Face, or you can simply click F on your keyboard. And you can choose any faces on the electric motor to see the temperature of the component.

Here, let's choose this part and Assign Monitor and click Face and choose the Temperature. We can also choose the housing faces to monitor the thermal. Let's hide this one. Let's see; we want to monitor this part of the housing for the temperature. Now, all the settings are completed.

You can right-click the Setup one and run your Analysis. Here, the iSpec will first run the Motor-CAD or the Maxwell model that we created in the current simulation and collect the data to transfer the iSpec to simulate the thermal. Here, this simulation may take a couple of minutes.

As you see, the simulation is complete. Here, we can see the green line shows the coil temperature, the red line shows the magnet, and the blue one shows the housing. Here, we can add a marker to see the temperature of each of these components.

The winding reaches 92.5°C, magnet reaches 89°C, and housing outer surface that we assigned to monitor is achieving 88.4°C. And we can also observe the residuals here. Now, as a last step, let's plot the contour map of the temperature for this electric motor.

To do that, we have to choose all of the components of this electric motor and right-click, Plot. Here, we have to check Plot on Surface Only. As you see, we are able to see the contour map of the electric motor.

Here, the back side is cooler than the front side, since we assigned very small air inlet from the Z axis. And as you see, the middle section of the housing is more hot than the rest of the electric motor housing. The reason is that the winding is located on this part.

To see that, let's hide the housing and choose all the components of the electric motor without housing and plot the temperature again. Plot Surface Only. And as you see, we are able to see the final temperature of the electric motor for the temperature analysis.

Here, we can also go and add a marker from the Plot Field section, and without clicking any button, we can observe from the left-hand side; the winding reaches 92.4°C, and the housing is around 90°C. So, this is everything about this video.

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