Fuji Electric ALPHA7, User Manual

Page: 651 / 662

CHAPTER 16 APPENDIXES
24
Capacity Selection Calculation
16
(1) Calculating the load inertia (J
L
)
Calculate the inertia (J
L
) of the load of the mechanical system converted to the motor axis.
Calculate the inertia of the parts rotating (moving) along with motor rotation, and obtain the sum of
all.
(2) Calculating the load torque (T
L
)
Calculate the load torque converted to the motor axis.
(3) Temporarily select the motor capacity
Select the motor capacity satisfying the following two conditions.

Allowable load inertia
J
L
≤ J
M
× 100 (30) ···················· In case of slow travel under speed control
J
L
≤ J
M
× 30 (10) ······················ In case of positioning under position control
J
L
≤ J
M
× 10 (-) ························ In case of frequent positioning
(Approximate measure: Starting and stopping at every 0.5 seconds or more frequently)
Values in parentheses indicate operation with the GYG motor.
 Load torque
T
L
≤ T
R
× 0.9 ··························· 0.9 indicates a typical margin of safety.
(4) Calculating the shortest acceleration/deceleration time (calculating the accelerating/decelerating
torque)
Check the shortest acceleration/deceleration under consideration of load conditions. If the
acceleration/deceleration time is designated, calculate the acceleration/deceleration torque.

Shortest acceleration/Deceleration time

Acceleration/Deceleration torque
t
AC
: Acceleration/Deceleration time [s]
J
M
: Inertia of servomotor [kgm
2
]
J
L
: Inertia of load converted to motor shaft [kgm
2
]
T
L
: Load torque converted to motor shaft [Nm]
T
AC
: Acceleration/Deceleration torque [Nm]
N
1
: Rotation speed after speed change [r/min]
N
0
: Rotation speed before speed change [r/min]
（Ｊ
Ｍ
＋Ｊ
Ｌ
）×２π×（Ｎ
１
－Ｎ
０
）
６０（Ｔ
ＡＣ
－Ｔ
Ｌ
）
ｔ
ＡＣ
＝
（Ｊ
Ｍ
＋Ｊ
Ｌ
）×２π×（Ｎ
１
－Ｎ
０
）
６０（ ｔ
ＡＣ
）
＋Ｔ
Ｌ
Ｔ
ＡＣ
＝