Fuji Electric Frenic-Mini - Page 151

7.1 Selecting Motors and Inverters
7-9
Chap. 7 SELECTING OPTIMAL INVERTER CAPACITIES
Table 7.1 Moment of Inertia of Various Rotating Bodies
Mass: W (kg) Mass: W (kg)
Shape
Moment of inertia:
J (kg·m
2
)
Shape
Moment of inertia:
J (kg·m
2
)
ρ−
π
= ••• L)DD(
4
W
2
2
2
1
ρ= ••• LBAW
Hollow cylinder
)DD(W
8
1
J
2
2
2
1
+= ••
ρ
π
= ••
3
D
6
W
Sphere
2
DW
10
1
J ••=
)AL(W
12
1
J
22
a
+= ••
)A
4
1
L(W
12
1
J
22
b
•••
+=
)L
3
1
LLL(WJ
2
0
2
0c
•••
++≈
ρ
π
= ••• LD
12
W
2
ρ
π
= ••• LD
4
W
2
Cone
2
DW
40
3
J ••=
ρ= ••• LBAW
Rectangular prism
)BA(W
12
1
J
22
+= ••
)D
4
3
L(W
12
1
J
22
a
•••
+=
)D
16
3
L(W
3
1
J
22
b
•••
+=
)L
3
1
LLL(WJ
2
0
2
0c
•••
++≈
ρ= •••• LBA
3
1
W ρ= •••• LBA
3
1
W
Square cone (Pyramid,
rectangular base)
)BA(W
20
1
J
22
+= ••
ρ= ••• LA
4
3
W
2
)A
4
1
L(W
10
1
J
22
b
•••
+=
)L
5
3
LL
2
3
L(WJ
2
0
2
0c
••••
++≈
Triangular prism
2
AW
3
1
J ••= ρ
π
= ••• LD
12
W
2
ρ= ••• LA
12
3
W
2
Tetrahedron with an
equilateral triangular
base
2
AW
5
1
J ••=
)D
8
3
L(W
10
1
J
22
b
•••
+=
)L
5
3
LL
2
3
L(WJ
2
0
2
0c
••••
++≈
Main metal density (at 20°C (68°F)) ρ(kg/m
3
) Iron: 7860, Copper: 8940, Aluminum: 2700