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Back-emf and flux linkage - Simple question!!!
Posted May 3, 2010, 11:31 a.m. EDT 1 Reply
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Greeting Everyone
In the model I am sending, I would like to know how can I measure the flux linkage of the coils! and the afterwards the back-emf!!
I will be very thankfull if somebody can help me!!
In the model I am sending, I would like to know how can I measure the flux linkage of the coils! and the afterwards the back-emf!!
I will be very thankfull if somebody can help me!!
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1 Reply Last Post May 4, 2010, 3:20 p.m. EDT
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Posted:
1 decade ago
Hi
Well for me the induced voltage is the integration of the electric field E_Phy around one loop, so I would use
Sudomain integration one one coil (i.e. 39 at time 0.1[s]) with the "compute volume integral checked"
Ephi_emqa/Area
which gives me some 4.11[mV], Area is defined as the integration of "1" over the coil area. The voltage is the electric field times the loop length = 2*pi*r
If I integrate the same subdomain to get the total current by integrating "Jiphi_emqa" I read -82.7[A] (this time witout the volume integration checked).
This should obey Ohms law R[Ohm] = rho[Ohm*m]*L[m]/(A[m^2]) = L[m]/(A[m^2])/(sigma[S/m])
and if I integrate over the same sundomain the value
1/Area^2/sigma_emqa
this time with the volume integration as I want the loop length included, I get some 50[uOhm] and I see that this corresponds to Ohms law. U=R*I
For me this is the best you can get to the back EMF or induced voltage from the magnetic field variation, and it is very similar to what is described in the generator examples in the acdcmodel.pdf document.
Do you agree ?, pls check carefully, ideally with a simpler example that you can check analytically
Have fun Comsoling
Ivar
Well for me the induced voltage is the integration of the electric field E_Phy around one loop, so I would use
Sudomain integration one one coil (i.e. 39 at time 0.1[s]) with the "compute volume integral checked"
Ephi_emqa/Area
which gives me some 4.11[mV], Area is defined as the integration of "1" over the coil area. The voltage is the electric field times the loop length = 2*pi*r
If I integrate the same subdomain to get the total current by integrating "Jiphi_emqa" I read -82.7[A] (this time witout the volume integration checked).
This should obey Ohms law R[Ohm] = rho[Ohm*m]*L[m]/(A[m^2]) = L[m]/(A[m^2])/(sigma[S/m])
and if I integrate over the same sundomain the value
1/Area^2/sigma_emqa
this time with the volume integration as I want the loop length included, I get some 50[uOhm] and I see that this corresponds to Ohms law. U=R*I
For me this is the best you can get to the back EMF or induced voltage from the magnetic field variation, and it is very similar to what is described in the generator examples in the acdcmodel.pdf document.
Do you agree ?, pls check carefully, ideally with a simpler example that you can check analytically
Have fun Comsoling
Ivar