YASKAWA SGD7S Product Manual page 505

14.4 Troubleshooting Based on the Operation and Conditions of the Servomotor
Problem
Position
Deviation
(without
Alarm)
14-64
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-
jected to excessive noise
interference.
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.
Confirmation
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
2
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.
Turn OFF the power sup-
ply to the servo system.
Check to see if there is
noise interference on the
I/O signal line from the
encoder or Serial Con-
verter Unit.
Continued from previous page.
Correction Reference
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.
Implement counter-
measures against noise
−
for the encoder wiring
or Serial Converter Unit
wiring.
Continued on next page.