6.9. Relative Effective PermeabilityΒΆ

A simple model of the relative effective permeability of the ferrite core \(\mu_{cer}\) is related to the relative permeability of the unbounded ferrite material \(\mu_r = \mu / \mu_0\) by [8]. This was explained as a step-up in flux and hence of emf due to the core by Burgess in 1946 [11].

  • \(D_F\): Demagnetization factor of ferrite core
  • \(\mu_r\) Relative permeability of the unbounded ferrite material

For most ferrite material, \(\mu_r\) is very large ( \(\mu_r \gg 1\) ) so that \(\mu_{cer}\) is approximately inversely proportional to the demagnetization factor:

\[\mu_{cer} \cong D_F^{-1}\]

Devore and Bohley mentioned that a improved model of relative effective permeability in the equation of radiation resistance [16].

  • \(D_w\) is demagnetization factor of winding
  • \(l_F\) is length of ferrite core
  • \(l_w\) is length of winding
  • \(A_F\) is cross section area of ferrite core
  • \(A_w\) is cross section area of winding