Panasonic MINAS-BL GV Series Manual page 45

Description on the items related to motor selection
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.)
General inertia calculation method
Shape
Disk
J =
W : Weight [ kg ]
D
D : Outer diameter [ m ]
Prism
J =
W : Weight [ kg ]
c
a, b, c : Side length [ m ]
a b
Straight rod
J =
W : Weight [ kg ]
L
L : Length [ m ]
Reduction gear
Inertia on shaft "a"
J = J
a
J
n
1 1
n : A rotational speed of a shaft [ r/min]
n 1
J
2
2
b
n : A rotational speed of b shaft [ r/min]
2
Conveyor
J =
W : Workpiece weight on conveyor [ kg ]
W
D : Drum diameter [ m ]
D
* Excluding drum J
If weight (W [kg]) is unknown, calculate it with the following formula:
Weight W [kg
Density of each material
Iron = 7.9 × 103 [kg/m
Brass = 8.5 × 103 [kg/m
J calculation formula
1
2
W D
2
[kg∙m ]
8
1
2 2
W (a + b )
2
[kg∙m ]
12
1
W L 2
[kg∙m 2 ]
3
n
2
2
+ ( ) J
2
1 2 [kg∙m
n
1
1
W D 2
2
[k g m ]
4
3
kg/m ] × Volume V [m
3 ] Aluminum
3
]
Shape
Hollow cylinder
d
D
Uniform rod
D
L/2
L/2
Separated rod
S
D
]
Ball screw
F
W
P
3
]
= 2.8 × 103 [kg/m 3 ]
J calculation formula
1
J = W (D 2 + d 2 )
[kg∙m
8
W : Weight [kg ]
D : Outer diameter [ m ]
d : Inner diameter [ m ]
1
2 2
J = W (3D + 4L )
[kg∙m
48
W : Weight [kg]
D : Outer diameter [ m ]
L : Length [ m ]
1
J = W D 2 + W S 2
[kg∙m
8
W : Weight [kg]
D : Outer diameter [ m ]
S : Distance [ m ]
W P 2
J = J +
B [kg∙m 2
4 2
W : Weight [kg]
P : Lead [ m]
J : J of ball screw
B
2
]
2 ]
2 ]
]