YASKAWA SGD7S-R70A20A023F40B Product Manual page 200

5.2 FT41 Specification
5.2.7 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)
5-112
Possible Cause
There is a mistake in the allo-
cation of the P-OT or N-OT
(Forward Drive Prohibit or
Reverse Drive Prohibit) sig-
nal in Pn50A = n.X or
Pn50B = n.X.
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 to see if the P-OT
signal is allocated in
Pn50A = n.X.
Check to see if the N-OT
signal is allocated in
Pn50B = n.X.
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 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.
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
If another signal is allo-
cated in Pn50A
*
=n.X, allocate the
P-OT signal instead.
If another signal is allo-
cated in Pn50B
*
=n.X, allocate the
N-OT signal instead.
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.