YASKAWA SGD7S-R70A Product Manual page 197

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