Fuji Electric ALPHA5 Smart - Page 613

CHAPTER 15 APPENDIXES
Capacity Selection Calculation 15-21
15
(1) Calculating the motor speed (N)
Calculate the motor shaft speed according to the configuration of the machine and the line speed.
(2) Calculating the load inertia (J
L)
Calculate the inertia (GD
2
) of the load of the mechanical system converted to the motor shaft.
Calculate the inertia of the parts rotating (moving) along with motor rotation, and obtain the sum of
all.
(3) Calculating the load torque (T
L)
Calculate the load torque converted to the motor shaft.
(4) 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.
(5) 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
(Mechanical efficiency (η)： assuming 100%).
 Shortest acceleration/Deceleration time
 Acceleration torque
 Deceleration torque
(J
M
+ J
L
) × 2π × (N)
60 (T
MAX
- T
L
)
t
MIN
=
(J
M
+ J
L
) × 2π × (N)
60( t
AC
)
T
L
+
T
AC
=
(J
M
+ J
L
) × 2π × (N)
60( t
DC
)
T
L
-
T
DC
=
where
t
AC
: Acceleration time [s]
t
DC
: 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 torque [Nm]
T
DC
: Deceleration torque [Nm]
T
MAX
: Max. torque [Nm]
Ｎ : Rotation speed [r/min]
t
MIX
: Shortest acceleration/deceleration time [s]