YASKAWA SGD7S series Product Manual page 118

4.1 SERVOPACKs with Analog Voltage/Pulse Train References
4.1.7 Troubleshooting Based on the Operation and Conditions of the Servomotor
Problem
Large Motor
Speed
Overshoot
on Starting
and Stop-
ping
Absolute
Encoder
Position
Deviation
Error (The
position
that was
saved in the
host con-
troller when
the power
was turned
OFF is dif-
ferent from
the posi-
tion when
the power
was next
turned ON.)
4-50
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.
The setting of Pn101 (Speed
Loop Integral Time Con-
stant) is not appropriate.
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.
Noise interference occurred
because the Encoder Cable
is too long.
Noise interference occurred
because the Encoder Cable
is damaged.
Replace the Encoder Cable
and correct the cable instal-
lation environment.
There is variation in the FG
potential because of the
influence of machines on the
Servomotor side, such as a
welder.
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%.
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
2
at least 0.12 mm .
Check the length of the
Encoder Cable.
Check the Encoder Cable
to see if it is pinched or
the sheath is damaged.
Check to see if the
Encoder Cable is bundled
with a high-current line or
installed near a high-cur-
rent line.
Check to see if the
machines are correctly
grounded.
Continued from previous page.
Correction Reference
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.
• 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.