YASKAWA Sigma-7 Series Product Manual page 142

6.3 Troubleshooting Based on the Operation and Conditions of the Servomotor
Problem
Overtravel
Occurred
Improper
Stop Posi-
tion for
Overtravel
(OT) Signal
Position
Deviation
(without
Alarm)
6-54
Possible Cause
The selection of the Servo-
motor stopping method is
not correct.
The limit switch position and
dog length are not appropri-
ate.
The overtravel limit switch
position is too close for the
coasting distance.
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
Check the servo OFF
stopping method set in
Pn001 = n.X or
Pn001 = n.X.
Check the torque control
stopping method set in
Pn001 = n.X or
Pn001 = n.X.
–
–
Check the Encoder Cable
to see if it satisfies speci-
fications. Use shielded
twisted-pair cables or
screened twisted-pair
cables with conductors of
2
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.
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
Select a Servomotor
stopping method other
than coasting to a stop.
*
Select a Servomotor
stopping method other
than coasting to a stop.
Install the limit switch at
the appropriate posi-
–
tion.
Install the overtravel
limit switch at the
–
appropriate position.
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.