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problem with capacitor having conductive media
Posted 6 août 2015, 12:05 UTC−4 Low-Frequency Electromagnetics Version 5.0 3 Replies
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I am using this one as example:
www.comsol.com/model/frequency-domain-modeling-of-a-capacitor-12693
in the example, it use glass as media and conductivity is 0;
if I change the media to pbs buffer, which has conductivity 1.5 and permittivity 78, I get following result:
Frequency Capacitance(f)
0.0010000 250.00
0.010000 25.000
0.10000 2.5000
1.0000 0.25000
10.000 0.025000
100.00 0.0025000
1000.0 2.5000E-4
10000 2.5000E-5+7.2774E-10i
I found frequency*capacitance is a constant number. This is not going to happen in real world because when I input very very small frequency the result will go to infinity. In real case it should become a constant when frequency approaches to zero.
Can anybody help me with this? Is it possible to use comsol to simulate conductive media?
www.comsol.com/model/frequency-domain-modeling-of-a-capacitor-12693
in the example, it use glass as media and conductivity is 0;
if I change the media to pbs buffer, which has conductivity 1.5 and permittivity 78, I get following result:
Frequency Capacitance(f)
0.0010000 250.00
0.010000 25.000
0.10000 2.5000
1.0000 0.25000
10.000 0.025000
100.00 0.0025000
1000.0 2.5000E-4
10000 2.5000E-5+7.2774E-10i
I found frequency*capacitance is a constant number. This is not going to happen in real world because when I input very very small frequency the result will go to infinity. In real case it should become a constant when frequency approaches to zero.
Can anybody help me with this? Is it possible to use comsol to simulate conductive media?
3 Replies Last Post 7 août 2015, 07:05 UTC−4
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Posted:
9 years ago
Jiantao,
in a nonconductive medium the capacitor's impedance is purely reactive (imaginary) and can be described by a capacitance. In a conductive medium the impedance gets complex. A real resistive component and the imaginary capacitive component. Looking at the complex impedance is much more appropriate in this situation.
You can also interpret it as a parallel circuit of resistor and capacitor.
Cheers
Edgar
--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
in a nonconductive medium the capacitor's impedance is purely reactive (imaginary) and can be described by a capacitance. In a conductive medium the impedance gets complex. A real resistive component and the imaginary capacitive component. Looking at the complex impedance is much more appropriate in this situation.
You can also interpret it as a parallel circuit of resistor and capacitor.
Cheers
Edgar
--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Please login with a confirmed email address before reporting spam
Posted:
9 years ago
Thanks for your reply. After I change to conductive media(pbs buffer conductivity=1.5), the impedance is independent with frequency. Does it look like right? On a paper, I found in experiment, pbs buffer impedance is dependent on freq.
Jiantao,
in a nonconductive medium the capacitor's impedance is purely reactive (imaginary) and can be described by a capacitance. In a conductive medium the impedance gets complex. A real resistive component and the imaginary capacitive component. Looking at the complex impedance is much more appropriate in this situation.
You can also interpret it as a parallel circuit of resistor and capacitor.
Cheers
Edgar
--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Please login with a confirmed email address before reporting spam
Posted:
9 years ago
The reactive (imaginary) component has to be frequency dependent, whatever medium you are using:
Xc = 1/(omega*C).
--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com
Xc = 1/(omega*C).
--
Edgar J. Kaiser
emPhys Physical Technology
www.emphys.com