YASKAWA SGD7S-180A - Page 197

8.3 Troubleshooting Based on the Operation and Conditions of the Servomotor
8-57
8
Maintenance
Large Motor
Speed
Overshoot
on Starting
and Stop-
ping
The servo gains are not bal-
anced.
Check to see if the servo
gains have been cor-
rectly tuned.
Perform autotuning
without a host refer-
ence.
–
The setting of Pn100 (Speed
Loop Gain) is too high.
Check the setting of
Pn100.
The default setting is Kv =
40.0 Hz.
Set Pn100 to an appro-
priate value.
–
The setting of Pn102 (Posi-
tion Loop Gain) is too high.
Check the setting of
Pn102.
The default setting is Kp
= 40.0/s.
Set Pn102 to an appro-
priate value.
–
The setting of Pn101 (Speed
Loop Integral Time Con-
stant) is not appropriate.
Check the setting of
Pn101.
The default setting is Ti =
20.0 ms.
Set Pn101 to an appro-
priate value.
–
The setting of Pn103
(Moment of Inertia Ratio or
Mass Ratio) is not appropri-
ate.
Check the setting of
Pn103.
Set Pn103 to an appro-
priate value.
–
The torque reference is satu-
rated.
Check the waveform of
the torque reference.
Use the mode switch.
–
The force limits (Pn483 and
Pn484) are set to the default
values.
The default values of the
force limits and Pn483 =
30% and Pn484 = 30%.
Set Pn483 and Pn484
to appropriate values.
–
Absolute
Encoder
Position
Deviation
Error
(The posi-
tion that
was saved
in the host
controller
when the
power was
turned OFF
is different
from the
position
when the
power was
next turned
ON.)
Noise interference occurred
because of incorrect Encoder
Cable specifications.
Turn OFF the power sup-
ply to the servo system.
Check the Encoder Cable
to see if it satisfies speci-
fications. Use a shielded
twisted-pair wire cable or
a screened twisted-pair
cable with conductors of
at least 0.12 mm
2
.
Use cables that satisfy
the specifications.
–
Noise interference occurred
because the Encoder Cable
is too long.
Turn OFF the power sup-
ply to the servo system.
Check the length of the
Encoder Cable.
• Rotary Servomotors:
The Encoder Cable
length must be 50 m
max.
• Linear Servomotors:
Make sure that the
Serial Converter Unit
cable is no longer
than 20 m and that
the Linear Encoder
Cable and the Sensor
Cable are no longer
than 15 m each.
–
Noise interference occurred
because the Encoder Cable
is damaged.
Turn OFF the power sup-
ply to the servo system.
Check the Encoder Cable
to see if it is pinched or
the sheath is damaged.
Replace the Encoder
Cable and correct the
cable installation envi-
ronment.
–
Noise interference occurred
because the Encoder Cable
is damaged.
Turn OFF the power sup-
ply to the servo system.
Check to see if the
Encoder Cable is bundled
with a high-current line or
installed near a high-cur-
rent line.
Correct the cable lay-
out so that no surge is
applied by high-current
lines.
–
There is variation in the FG
potential because of the
influence of machines on the
Servomotor side, such as a
welder.
Turn OFF the power sup-
ply to the servo system.
Check to see if the
machines are correctly
grounded.
Properly ground the
machines to separate
them from the FG of
the encoder.
–
Continued on next page.
Continued from previous page.
Problem Possible Cause Confirmation Correction Reference