Lecture 3 Magnetic Circuits

Similar to Kirchhoff’s voltage law, we may write, for any closed path in a magnetic
circuit,
Around a closed path in a magnetic circuit the algebraic sum of ampere-turns is equal
to the algebraic sum of the products of the reluctances and fluxes.
Again, similar to Kirchhoff’s current law for a junction, for any closed path in a
magnetic circuit,
Which states that the algebraic sum of all the magnetic fluxes flowing out of a
junction in a magnetic circuit is zero.
Problems
D4.1 The magnetic circuit shown in Fig. below has an air gap cut in the right leg of
the core. The air gap is 0.1mm long. The coil is connected to a voltage source, and the
current drawn is adjusted so that the magnetic flux density in the air gap is 1.5T.
Assume that flux fringing in the air gap is negligible. The magnetic circuit has the
following dimensions: A c =16cm 2 , l c =40cm, and N=350 turns. The relative
permeability of the core is µ r =50,000.
(i)
(ii)
(iii)
Find the value of the current.
Calculate the magnetic flux
Determine the flux linkage of the coil
Dr. Ahsan Page 6