Answer to Question 5

 

Back

The magnetic circuit above is made of a magnetic material of relative permeability 175.  It has a square cross section 2.5 cm 2.5 cm, and the average length is 25 cm.  There is a air gap cut into it that is 1.0 mm in length.  Calculate:

(a) the reluctance of the material;

(b) the reluctance of the air gap;

(c) the total reluctance.

(a) Formula:

A = (2.5 10-2 m)2 = 6.25 10-4 m2

 

S1  = 0.25 m (4p 10-7 H m-1 175 6.25 10-4 m2) = 1.82 106 H-1

 

(b) Formula:

S2  = 1.0 10-3 m (4p 10-7 H m-1 6.25 10-4 m2) = 1.27 106 H-1

 

(c) Formula:

Stot = 1.82 106 H-1 + 1.27 106 H-1 = 3.1 106 H-1 (2 s.f.)