inductance of a partially filled solenoid

[paujuan]

Hi,
I would like to know how to calculate the inductance of a solenoid once we put a ferrite rod inside it that only fills a small portion of its space. Let the magnetic field be considered constant (as the solenoid is long enough and the rod small enough): what is the flux increase due to the presence of the rod?
Thanks,

 

[chuckey]

You have to consider the reluctance of the mean magnetic path (total resistance of mag circuit) and how much of it is short circuited by your slug. I doubt if your calculations will be accurate as you will not know the magnetic path in the air outside the solenoid, and what percentage of the field is " captured" within the solenoid by your slug.
Frank

 

[paujuan]

Thanks for your reply. However, I consider that the reluctance cannot be directly calculated, as a geometrical approximation would be really far from the real results. Moreover, what if the rod is not placed axially with reference to the solenoid (e.g. with a 45º degree angle)??
Thanks,

 

[FvM]

Moreover, what if the rod is not placed axially with reference to the solenoid (e.g. with a 45º degree angle)??

Changes the problem to true 3D (axisymmetric could be still mapped to 2D), so welcome to the world of numeric field solvers!

 

[smijesh]

Axisymmetric model in FEMM will do the job.