
3.SELECTING A MOTOR SPECIFICATIONS FOR THE αiS/αi SERIES B-65262EN/03
- 50 -
Inertia of a heavy object moving along a straight line (table, workpiece, etc.)
SI unit
][
2
2
2
mkg
l
W
b
J ⋅×=
÷
ø
ö
ç
è
æ
π
W : Weight of the object moving along a straight line [kg]
l : Traveling distance along a straight line per revolution of the
motor [m]
Gravitational system of units
][
2980
2
2
scmkgf
lW
b
J ⋅⋅×=
÷
ø
ö
ç
è
æ
π
W : Weight of the object moving along a straight line [kgf]
l : Traveling distance along a straight line per revolution of the
motor [cm]
Example)
When W is 1200(kg) and l is 20(mm), J
w
of a table and
workpiece is calculated as follows:
J
w
=1200×(0.020÷2÷π)
2
=0.01216 [kg⋅m
2
] =0.1241[kgf⋅cm⋅s
2
]
Inertia of an object whose speed is increased above or decreased below the
speed of the motor shaft
The inertia applied to the motor shaft by inertia J
0
is calculated as
follows:
0
2
0
2
1
2
1
J
Z
orJ
Z
Z
J ××=
÷
ø
ö
ç
è
æ
÷
÷
ø
ö
ç
ç
è
æ
J
0
: Inertia before the speed is changed
Z
1
,Z
2
: Number of teeth when the gear connection
1/Z : Deceleration ratio