
6-6 Power Electronics and Motor Drives
6.2.1 Magnetic Device with PM
Figure 6.8a shows a magnetic device including an iron core, a PM, and an air gap. e Ampere law
around the dashed line is
H t H g
m m g
+ = 0
(6.2)
where
H
m
and H
g
are the magnetic eld strengths of the PM and air gap, respectively
t
m
and g are the PM and the air gap thickness, respectively
TABLE 6.1 Main Properties of Hard Magnetic Material
B
rem
(T) H
c
(kA/m) Curie T (°C)
Operating
T
max
(°C)
Density
(kg/m
3
) {B
m
H
m
}
max
(kJ/m
3
)
Ferrite 0.38 250 450 300 4800
30
A
lnico 1.20
50 860 540 7300 45
S
mCo 0.85 570 775 250 8300 140
NdFeB 1.15 880 310 180 7450 260
1.4
1.2
1.0
0.8
0.6
0.4
H
m
field strength ...