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Troubles of a new user

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Hello,

Although I have some experience with FEM, I am a new user of Comsol. I am trying to solve a simple problem in 3D: a square section solenoid with an iron core. After the definition of the materials and current at the winding block, I tried to compute the study, but I got the following message of errors:

" Attempt to evaluate negative power of zero.
- Function: ^
Failed to evaluate temporary symbolic derivative variable.
- Variable: mod1.mf.murzz@VDN$mod1.curlAz
- Defined as: (dmod1.mat2.def.MUR_dx1((sqrt(((mod1.mf.Bz^2)+((mod1.mf.By^2)+(mod1.mf.Bx^2))))/unit_T_cf))*((1/unit_T_cf)*((2*mod1.mf.Bz)*((((mod1.mf.Bz^2)+((mod1.mf.By^2)+(mod1.mf.Bx^2)))^-0.5)*0.5))))
Failed to evaluate temporary symbolic derivative variable.
- Variable: mod1.mf.murinvzz@VDN$mod1.curlAz
- Defined as: (((dmod1.mat2.def.MUR_dx1((sqrt(((mod1.mf.Bz^2)+((mod1.mf.By^2)+(mod1.mf.Bx^2))))/unit_T_cf))*((1/unit_T_cf)*((2*mod1.mf.Bz)*((((mod1.mf.Bz^2)+((mod1.mf.By^2)+(mod1.mf.Bx^2)))^-0.5)*0.5)))))*((-1)/(mod1.mf.murzz^2)))
Failed to evaluate temporary symbolic derivative variable.
- Variable: mod1.mf.Hz@VDN$mod1.curlAz
- Defined as: ((1/mu0_const)*(mod1.mf.murinvzz+(mod1.mf.Bz*((((dmod1.mat2.def.MUR_dx1((sqrt(((mod1.mf.Bz^2)+((mod1.mf.By^2)+(mod1.mf.Bx^2))))/unit_T_cf))*((1/unit_T_cf)*((2*mod1.mf.Bz)*((((mod1.mf.Bz^2)+((mod1.mf.By^2)+(mod1.mf.Bx^2)))^-0.5)*0.5)))))*((-1)/(mod1.mf.murzz^2)))))))
Failed to evaluate expression.
- Expression: d(d((-mod1.mf.Hx*test(mod1.curlAx)-mod1.mf.Hy*test(mod1.curlAy)-mod1.mf.Hz*test(mod1.curlAz)+mod1.mf.Jx*test(mod1.Ax)+mod1.mf.Jy*test(mod1.Ay)+mod1.mf.Jz*test(mod1.Az))*(dvol),{test@3}),mod1.curlAz)"

However, when I just modify the material of the core to another kind (air, for example), the study is computed without problems.


Could somebody help me in this problem?

Thanks in advance.



1 Reply Last Post 5 ott 2010, 02:11 GMT-4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 5 ott 2010, 02:11 GMT-4
Hi

are you shure that your material data you are usig is not designed to take into account the local temperature "T" or pressure "p", and that you have not defined these as Constants/parameters ?

If you are using the material database, many of these are non linear driven by environmental variables.

When you start define your material constants yourself, or use the "Buil-In" materials tzhat are normal all "constants"

--
Good luck
Ivar
Hi are you shure that your material data you are usig is not designed to take into account the local temperature "T" or pressure "p", and that you have not defined these as Constants/parameters ? If you are using the material database, many of these are non linear driven by environmental variables. When you start define your material constants yourself, or use the "Buil-In" materials tzhat are normal all "constants" -- Good luck Ivar

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