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External currentdensity

N V S ANILBABU JAVVAJI

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hai. ihave been using 3D-AC/DC Module,Electric thermal interaction,Induction currents option for eddy current heating of a specimen.so in the sofware i have to give the external current desity in the subdomains.so can any one tell the formula that can be applied to a hollow circular coil(TORUS) shape.i want to calculate the current desity and how to give the x,y and z values in software

1 Reply Last Post Nov 13, 2010, 4:16 a.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago Nov 13, 2010, 4:16 a.m. EST
Hi

you can set up a cylindrical coordinate, or define your own coordinate, often this is simpler.
i.e. for a cylidrical loop in the x-y plane:

a) define a cylindrical coordinate system with axis along Z and centre at x0,y0 (default 0,0), and then define a current density J0[A/m^2] on phi hte cylindrical angle variable

b) remain in carthesian coordinates, type in Jex,y,z = (-J0*y/sqrt(x^2+y^2), J0*x/sqrt(x^2+y^2),0)

you might also define rxy=sqrt(x^2+y^2) as a variable to simplify the equation.

for a polloidal or thoric twisted current you should continue along these lines (avoiding the singularity on axis)

--
Good luck
Ivar
Hi you can set up a cylindrical coordinate, or define your own coordinate, often this is simpler. i.e. for a cylidrical loop in the x-y plane: a) define a cylindrical coordinate system with axis along Z and centre at x0,y0 (default 0,0), and then define a current density J0[A/m^2] on phi hte cylindrical angle variable b) remain in carthesian coordinates, type in Jex,y,z = (-J0*y/sqrt(x^2+y^2), J0*x/sqrt(x^2+y^2),0) you might also define rxy=sqrt(x^2+y^2) as a variable to simplify the equation. for a polloidal or thoric twisted current you should continue along these lines (avoiding the singularity on axis) -- Good luck Ivar

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