Siemens Sinamics V90 Operating Instructions Manual page 426

Appendix
A.2 Motor selection
Inertia and inertia ratio
Inertia refers to the force required to keep a certain physical state. Inertia ratio indicates
dynamic response performance of motors. The smaller the inertia ratio is the better response
performance a motor has.
Typical load inertia equations
Mechanism
Axis of rotation on center
Axis of rotation off center
Conveyor
Object hung with pulley
424
Equation
W: Mass (kg)
a: Length (m)
b: Width (m)
W: Mass (kg)
a: Length (m)
b: Width (m)
R: Rotational diameter (m)
W: Mass (kg)
D: Pulley wheel diameter (m) Ball screw
W: Mass (kg)
D: Pulley wheel diameter (m)
J : Pulley inertia (kg·m )
2
p
Mechanism
Axis of rotation on center
Axis of rotation off center
Reducer
Operating Instructions, 04/2019, A5E36037884-007
Equation
W: Mass (kg)
D : External diameter (m)
1
D : Internal diameter (m)
2
W: Mass (kg)
D: Workpiece diameter (m)
R: Rotational diameter (m)
W: Mass (kg)
P: Lead (m)
J : Ball screw inertia (kg·m
b
W: Mass (kg)
n /n : Speed of each motor
1 2
(rpm)
J /J : Inertia of each motor
1 2
(kg·m )
2
SINAMICS V90, SIMOTICS S-1FL6
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2