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8. CALCULATION METHODS FOR DESIGNING
(4) Continuous effective load torque
If the torque required for the servo motor changes with time, the continuous effective load torque
should be lower than the rated torque of the servo motor. There may be a servo motor torque delay at
the start of acceleration or deceleration due to a delay in the control system. To simplify the
calculation, however, it is assumed that constant acceleration and deceleration torques are applied
during t
psa and tpsd. The following equation is used to calculate the continuous effective load torque in
the following operation pattern. T
LH indicates the torque applied during a servo motor stop. A large
torque may be applied especially during a stop in vertical motion applications, and this must be fully
taken into consideration. During vertical drive, the unbalanced torque TU will become T
LH.
S
e
r
v
o
m
o
t
o
r
s
p
e
e
d
T
i
m
e
S
e
r
v
o
m
o
t
o
r
t
o
r
q
u
e
N
[r/min]
0
Time
0
Time
t
psa
t
c
t
f
(1 cycle)
T
Ma
T
Md
T
d
T
a
T
L
T
LH
tt
psd
Trms
tf
T
Ma
t
psa
T
L
tc T
Md
T
LH
t
222 2
t
psd
.................................................................................(8.14)