Model Induction Motor with Fan

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Christo van Rensburg
Christo van Rensburg on 18 Nov 2021
Commented: Joel Van Sickel on 3 Dec 2021
Good day,
I'm looking to model an induction motor with an axial fan attached to its rotor side via a gearbox. At the moment I have the power source, motor and a fan model connected. For the gearbox I simply multiply the electrical torque with the GR to give to the fan model.
Below is how the model looks in Simulink at the moment. In the inertia block attached to the motor "R"-port, I have accounted for the motor, gearbox & fan inertias.
I'm not getting the correct steady-state load on the rotor side. Below is what I have so far.
On the left in the figure above, the speed and load is supposed to remain constat after 5 s.
If anyone has any experience in modelling a similar system or could help me identify why it is doing this it would be greatly appreciated.
  1 Comment
Pat Gipper
Pat Gipper on 29 Nov 2021
I wonder if it would work better if you modelled the fan in Simscape like the picture below?

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Answers (1)

Joel Van Sickel
Joel Van Sickel on 29 Nov 2021
2 things,
  1. please see the comment from Pat, it does make sense to keep the whole model in simscape. There are also fan examples and blocks you can look at (the fan blocks probably require additional licenses besides Simscape Electrical)
  2. When debugging your model, you want to start small, so just running the motor on a constant physical load. I would replace the fan with a simple inertia (which you already have) and a damper block. See if you can run the motor to a steady state load that makes sense with this simple load to make sure everything on the electrical side is working as you expect. If it is, then you know there is a bug in your fan model.
Joel Van Sickel
Joel Van Sickel on 3 Dec 2021
Hello Christo,
Have you tried part 2 of my advice in running with a constant physical load and isolating what the issue is? Something is wrong with your model and you need to debug to identify what the issue is. It might be that the fan is parameterized or modelled wrong, or the motor ins't being controlled correctly, but until you identify the issue, you can't move forward. An open loop control simulation would make it much easier to identify what the problem is. Also, you can attatch a controlled torque source to just your fan model to see how it works. Because you are combining an induction motor, it's drive (I don't know if it's just hooked up to line voltages or has an inverter on it), and a fan model, there are numerous parts that might not be set up correctly to simulate well. That is why I recommend putting a constant load (damper) on the motor and see how it behaves without the fan. This simplifies the model and allows you to verify if that part of the simulation is working. Similarly, get the fan model working with just a controlled torque source before you attatch it to the motor.

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