Omron EasySpeed 3G3JE, User Manual, Page: 123 / 133

Chapter 7
7-5
Appendix
Motor Axis Inertia Conversion Example
J
L
: Motor axis inertia (kg·m
2
)
Jw: Load inertia (load side gear axis, kg·m
2
)
J1: Motor side gear inertia (kg·m
2
)
J2: Load side gear inertia (kg·m
2
)
Z1: Number of motor-side gear teeth
Z2: Number of load-side gear teeth
G: Gear ratio (reduction ratio) = Z1/Z2
● Calculating the Motor Axis Torque and Effective Torque
The torque required for acceleration is calculated from the load inertia at the motor axis, the motor's
rotor inertia, and the acceleration rate. In addition, the load torque is calculated from external forces
applied to the load (gravity and tension) and friction. These results are combined to calculate the
required torque from the motor.
Calculating the Acceleration Torque (TA)
T
A
: Acceleration torque (N·m)
J
L
: Motor axis load inertia (kg·m
2
)
J
M
: Motor rotor inertia (kg·m
2
)
η
: Efficiency of transmission mechanism (
η ≤
1)
t
A
: Acceleration time (s)
N: Motor revolutions (r/min)
J
L
Load Jw
Load side gear J2
Motor side gear J1
Motor
J
L
(kg·m 2 )
= J1 + G
2
(J2 + Jw
)
J
L
J
M
N
t
A
Time
Speed (rotational)
η
Motor
J
L
η
T
A
(N·m) = J
M
+
2
π
·N
60·t
A