Fuji Electric Faldic-a Series, User Manual

Page: 240 / 251

11-6 MHT258a (Engl.)
(e) Calculation of accel./decel. torque and accel./decel. time (shortest)
(i) Accel./decel. torque
For application to soft start/stop operation, etc, accel./decel. torque should be calculated according to the formula below.
・
Accel./decel. torque (T
AC
)
Where,
J
L
: Moment of load inertia after conversion into motor shaft extension [kg
･
m
2
]
J
M
: Moment of inertia motor rotor [kg
･
m
2
]
N
0
: Motor speed before the speed change [r/min]
N
1
: Speed after the speed change [r/min]
t
AC
: Accel./decel. time [s]
T
AC
: Max. accel./decel. (breakdown (max.) ) motor torque
T
L
: Load torque after conversion into motor shaft [N
･
m]
The result of the above calculation should be within the allowable maximum accel. /decel. torque of motor.
(ii) Shortest accel./decel. time
For obtaining the target speed in the shortest time, calculation is required by the formula below.
When T
AC
＋
T
L
: t
AC
: (shortest decel. time)
T
AC
−
T
L
: t
AC
: (shortest accel. time)
(iii) Operation pattern, basic
Accel. torque
(f) Actual torque (Trms) determination
In application to a machine which performs rapid feed frequency, the motor may overheat due to the energy required for accel. and decel..
To prevent this, calculate the actual torque in the following procedure depending on the given repetitive operation pattern and ensure that the
value is not larger than motor rated torque.
Shown below are the formula for actual torque in the typical operation pattern.
( J
M
+ J
L
)
×
2
π ×
( N
1
- N
0
)
60
×
( t
AC
）
±
T
L
[N
・
m]
T
AC
=
( J
L
+ J
M
)
×
2
π ×
( N
1
- N
0
)
[S]
60
×
( T
AC
±
T
L
)
t
AC
=
( T
AC
2
×
t
AC
) + ( T
L
2
×
t
L
) + ( T
DC
2
×
t
DC
)
t
CYC
T
rms
=