J
=
J
1
+ ( )
2
J
2
3. Inertia and inertia ratio
Inertia is like the force to retain the current moving condition.
Inertia ratio is calculated by dividing load inertia by rotor inertia.
Generally, for motors with 750 W or lower capacity, the inertia ratio should be “20” or less. For motors with 1000 W
or higher capacity, the inertia ratio should be “10” or less.
If you need quicker response, a lower inertia ratio is required.
(For example, when the motor takes several seconds in acceleration step, the inertia ratio can be further increased.)
J
=
8
1
W D
2
[kg
∙
m
2
]
J
=
12
1
W
(
a
2
+
b
2
)
[kg
∙
m
2
]
J
=
8
1
W
(
D
2
+
d
2
)
[kg
∙
m
2
]
n
2
n
1
J
=
4
1
W D
2
[k g
m
2
]
W
: Weight
[kg]
D
: Outer diameter
[ m ]
W
: Weight
[kg]
D
: Outer diameter
[ m ]
d
: Inner diameter
[ m ]
J
=
8
1
W D
2
+
W S
2
[kg
∙
m
2
]
W
: Weight
[kg]
D
: Outer diameter
[ m ]
S
: Distance
[ m ]
J
=
J
B
+
4
2
W
P
2
[kg
∙
m
2
]
W
: Weight
[kg]
P
: Lead
[m]
J
B
: J of ball screw
J
=
48
1
W
(
3D
2
+
4L
2
)
[kg
∙
m
2
]
W
: Weight
[kg]
D
: Outer diameter
[ m ]
L
: Length
[ m ]
Shape
General inertia calculation method
Disk
J calculation formula
Shape
J calculation formula
W
: Weight
[kg]
a, b, c
: Side length
[ m ]
n
1
: A rotational speed of a shaft
[ r/min]
n
2
: A rotational speed of b shaft
[ r/min]
J
=
3
1
W L
2
[kg
∙
m
2
]
[kg
∙
m
2
]
W
: Weight
[kg]
L
: Length
[ m ]
W
: Workpiece weight on conveyor
[ kg ]
D
: Drum diameter
[ m ]
Inertia on shaft "a"
* Excluding drum J
Prism
Straight rod
Reduction gear
Conveyor
Hollow cylinder
Uniform rod
Separated rod
Ball screw
If weight (W [
kg
]) is unknown, calculate it with the following formula:
Weight W [
kg
@ 'HQVLW\ѩ>
kg/m
3
] × Volume V [
m
3
]
Density of each material
Iron
ѩ
= 7.9 × 103 [
kg/m
3
] Aluminum
ѩ
= 2.8 × 103 [
kg/m
3
]
Brass
ѩ
= 8.5 × 103 [
kg/m
3
]
D
W
D
P
W
F
a
b
c
D
L/2
L/2
a
J
1
J
2
n
2
n
1
b
L
D
d
S
D
6HOHFWLQJPRWRUFDSDFLW\
Description on the items related to motor selection
Summary of Contents for MINAS-BL GV series
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