Page 42 - Electric Machinery Fundamentals

18 ELECTRIC MACHIN ERY FUNDAMENTALS

i
-...
N = 400
turns
B
j
1 0.05 em
1

Ie = 40 em

(
(a)

~. (Reluctance of core)
+
'iJ(=Ni)

CQ o (Reluclance of air gap)

(b)

FIGURE 1-8
(a) The ferromagnetic core of Example 1-2. (b) The magnelic circuit corresponding to (a).
2
2
The effective area of the air gap is 1.05 x 12 cm = 12.6 cm , so the reluctance of the air gap is
(1-32)

0.0005 m
(47T X 10 ')(0.00126 m')
= 316,000 A • turnslWb
Therefore, the total reluctance of the fl ux path is
~q = CR c + CQ{I
= 66,300 A • turnslWb + 316,000 A • turnslWb
= 382,300 A • tumslWb
Note that the air gap contributes most of the reluctance even though it is 800 times shorter
than the core.