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Undefined variable problem when calculating the Coil inductance using mf.LCoil_1

Posted 31.03.2021, 21:36 GMT-4 Low-Frequency Electromagnetics Version 5.6 1 Reply

Michelle
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Hello, I am new to COMSOL. Recently, I am trying to calculate the inductance of a pair of close-loop Coils. However, I have this "undefined variable" problem when calculating the inductance using mf.LCoil_1. While in this example (https://www.comsol.com/model/self-inductance-and-mutual-inductance-of-a-single-conductor-and-a-helical-coil-12679) I found on the COMSOL website it seems fine to assume that variable?

Thanks

1 Reply Last Post 01.04.2021, 07:04 GMT-4
Edgar J. Kaiser Certified Consultant
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Posted: 4 years ago 01.04.2021, 07:04 GMT-4

Michelle,

I added a frequency domain step (at 50 Hz) to your model and this makes the inductance variables available. I am a little surprised as well that this is required, because inductance can in principle also be determined in a DC case. But on the other hand induction is not actually 'happening' in a way that could be measured. Make sure you add a small conductivity (e.g. 1 S/m) to the air domain, otherwise the frequency solver may not converge. For more accurate results you may also want to add infinite element domains around the air domain.

Cheers Edgar

-------------------
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Michelle, I added a frequency domain step (at 50 Hz) to your model and this makes the inductance variables available. I am a little surprised as well that this is required, because inductance can in principle also be determined in a DC case. But on the other hand induction is not actually 'happening' in a way that could be measured. Make sure you add a small conductivity (e.g. 1 S/m) to the air domain, otherwise the frequency solver may not converge. For more accurate results you may also want to add infinite element domains around the air domain. Cheers Edgar

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