YASKAWA SGD7S-****20A Series Product Manual page 482

Problem Possible Cause
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.
The Encoder Cable was sub-
Abnormal
jected to excessive noise
Noise from
interference.
Servomotor
There is variation in the FG
potential because of the
influence of machines on the
Servomotor side, such as a
welder.
There is a SERVOPACK
pulse counting error due to
noise.
The encoder was subjected
to excessive vibration or
shock.
A failure occurred in the
encoder.
12.5 Troubleshooting Based on the Operation and Conditions of the Servomotor
Confirmation
Turn OFF the power sup-
ply to the servo system.
Check the Encoder Cable
to see if it satisfies speci-
fications. Use shielded
twisted-pair cables or
screened twisted-pair
cables with conductors of
at least 0.12 mm
(stranded wire).
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.
Check to see if there is
noise interference on the
signal line from the
encoder.
Turn OFF the power sup-
ply to the servo system.
Check to see if vibration
from the machine
occurred. Check the Ser-
vomotor installation
(mounting surface preci-
sion, securing state, and
alignment).
Check the linear encoder
installation (mounting sur-
face precision and secur-
ing method).
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Continued from previous page.
Correction
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.
Turn OFF the power
supply to the servo
system.
Implement counter-
measures against noise
for the encoder wiring.
Reduce machine vibra-
tion. Improve the
mounting state of the
Servomotor or linear
encoder.
Turn OFF the power
supply to the servo
system.
Replace the Servomo-
tor.
Continued on next page.
Reference
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12
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12-63