9 Troubleshooting
9-28
Absolute
Encoder Position
Difference Error
(The position
saved in the host
controller when
the power was
turned OFF is
different from the
position when the
power was next
turned ON.)
Noise interference due to incorrect
cable specifications of encoder
cable.
The encoder cable must be tinned
annealed copper shielded twisted-
pair or screened unshielded twisted-
pair cable with a core of 0.12 mm
2
min.
Use the specified encoder cable.
Noise interference due to length of
encoder cable.
Check the length of the encoder
cable.
The encoder cable must be no more
than 50 m.
Noise interference due to damaged
encoder cable.
Check if the encoder cable is bent
and the sheath is damaged.
Replace the encoder cable and cor-
rect the cable layout.
Excessive noise to the encoder
cable.
Check if the encoder cable is bun-
dled with a high-current line or near
a high-current line.
• Correct the cable layout so that
no surge is applied.
• Use a double-shielded encoder
cable.
FG potential varies because of
influence of machines such as weld-
ers at the servomotor.
Check if the machines are correctly
grounded.
Ground machines correctly, and
prevent diversion to the FG on the
encoder side.
A multi-winding drive unit pulse
counting error occurred due to noise
interference.
Check if there is noise interference
on the I/O signal line from the
encoder.
Take measures against noise in the
encoder wiring.
Excessive vibration and shock to
the encoder
Check if vibration from the machine
occurred or servomotor installation
is incorrect (mounting surface accu-
racy, fixing, alignment, etc.).
Reduce vibration from the machine,
or secure the servomotor installa-
tion.
An encoder fault occurred.
−
Replace the servomotor.
A fault occurred in the multi-wind-
ing drive unit.
−
Replace the multi-winding drive
unit.
Host controller multiturn data read-
ing error
Check the error detection section of
the host controller.
Correct the error detection section
of the host controller.
Check if the host controller is exe-
cuting data parity checks.
Execute a multiturn data parity
check.
Check noise in the cable between
the SERVOPACK and the host con-
troller.
Take measures against noise, and
again execute a multiturn data par-
ity check.
Overtravel (OT)
Forward or reverse run prohibited
signal is input.
Check the external power supply
(+24 V) voltage for the input signal.
Correct the external power supply
(+24 V) voltage.
Check if the overtravel limit switch
operates properly.
Correct the overtravel limit switch.
Check if the overtravel limit switch
is wired correctly.
Correct the overtravel limit switch
wiring.
Check the settings for parameters
Pn50A and Pn50B.
Correct the settings for parameters
Pn50A and Pn50B.
Forward or reverse run prohibited
signal malfunctioning.
Check the fluctuation of the exter-
nal power supply (+24 V) voltage
for the input signal.
Stabilize the external power supply
(+24 V) voltage.
Check if the overtravel limit switch
operates correctly.
Correct the overtravel limit switch.
Check if the overtravel limit switch
wiring is correct. (check for dam-
aged cables or loose screws.)
Correct the overtravel limit switch
wiring.
Incorrect forward or reverse run
prohibited signal (P-OT/N-OT)
allocation (parameters Pn50A.3,
Pn50B.0)
Check if the P-OT signal is allo-
cated in Pn50A.3.
If another signal is allocated in
Pn50A.3, allocate P-OT.
Check if the N-OT signal is allo-
cated in Pn50B.0.
If another signal is allocated in
Pn50B.0, allocate N-OT.
(cont’d)
Problem
Probable Cause
Investigative Actions
Corrective Actions
