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# HFSS and me (problems with simulation time and convergence)

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#### Chourizo

##### Junior Member level 2
HFSS and me

Hello everybody!

I´m new at HFSS. I want to simulate the radiation of an inductor, but I have lots of problems:

1. The simulation should be quite simple, only an inductor with a diameter of 15mm and a lenght of 40mm, but it takes about three hours.

2. It needs more than three passes to converge, but it reports an "Out of memory error" after the third pass.

I am using the default configuration, deltaS=0.02, 20mm air around the coil, a Wave port and radiation boundary conditions.

Any idea? I´ve done the tutorials defined at the user guide and the simulation takes only a few seconds. Any help will be really useful!

How much memory does your PC have and how electrically large is your domain?

Re: HFSS and me (problems with simulation time and convergen

My PC is a dual core with 2GB of RAM, and the inductor consists on 16 turns with 2 mm pitch and a diameter of 1mm. The diameter of the coil is 16mm and the air is a cilinder with a radius of 20mm and 50mm height.

In other words, the volume is 3.14x(20)^2 mm^2 x 50 mm.

Is my model too big?

Electrical size is what matters, not physical size.

Re: HFSS and me (problems with simulation time and convergen

Then, the size is not the problem, right?

I´ve tried to modify the mesh, using surface approximation, healing the model... Do you have any idea?

What I'm getting at is what's your frequency of interest/solution frequency? If your domain/structure is many cubic wavelengths it will take a ton of memory and be slow.

Re: HFSS and me (problems with simulation time and convergen

Oh, ok, I understand. I don´t know, I´ve used the default values.

Here are the data of my Setup Analysis:

Passes 3 (It reports a memory error in the fourth pass)
Percent Refinement: 30
DestaS 0.02
Delta output 0.05
Max Refinement: 100000

Can I define a fixed frequency domain range? I am interested in the range [0.5 to 1.2]GHz

Re: HFSS and me (problems with simulation time and convergen

From the discussion the problem you are facing is not clear. kindly post your HFSS model, after running the model the problem you are facing can be solved.

^^^ This.

As a partial guess, you're sure you want the radiation of the inductor from 3/50 of a lambda away? Radiation boundaries should be lambda/4 away from your actual structure IIRC. Still, please post the model and which version you're using.

And with your question, yes, you can define a range to solve, but first you need a solution at one frequency. Then you can set a sweep of frequencies.

Re: HFSS and me (problems with simulation time and convergen

Then, if I solve for 1GHz:

lambda = 3E8/1E9 = 0.3m = 300 mm then lambda/4 is 75mm + coil external radius, right?

I´ll try this simulation and post my results.

I´m using HFSS 11.1.

Re: HFSS and me (problems with simulation time and convergen

I´ve done this simulation and the results are not good. The memory error cames at the third pass now, after three hours. The convergence of the solution was not possible at only two passes.

I´ve checked the mesh and it seems quite good, not too small.

Please, can anybody help me with that? Why can I simulate the tutorials in a few seconds and my project takes about three hours?

I think the key is the interaction between the loops of the inductor. The project is parametrized with variables, so I can change the number of the loops easily. I´ve set a 2 loops inductors, and the simlation runs in 5-10 minutes only and succesfully! Good!

Other issue: hoy to set the size of the wave port?

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