YASKAWA E-V-MD Series User Manual page 282

10 Maintenance, Inspections, and Troubleshooting
Problem
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.)
Overtravel (OT)
Improper Stop
Position by
Overtravel (OT)
Signal
10-22
Probable Cause
Noise interference due to incorrect
cable specifications of encoder
cable.
Noise interference due to length of
encoder cable.
Noise interference due to damaged
encoder cable.
Excessive noise to the encoder
cable.
FG potential varies because of
influence of machines such as weld-
ers at the servomotor.
SERVOPACK pulse counting error
due to noise interference
Excessive vibration and shock to
the encoder
An encoder fault occurred.
A SERVOPACK fault occurred.
(The pulse count does not change.)
Host controller multiturn data read-
ing error
Forward or reverse run prohibited
signal is input.
Forward or reverse run prohibited
signal malfunctioning.
Incorrect forward or reverse run
prohibited signal (P-OT/N-OT)
allocation (parameters Pn590.3,
Pn591.3)
Improper limit switch position and
dog length
The overtravel limit switch position
is too short for the coasting
distance.
Investigative Actions
The encoder cable must be tinned
annealed copper shielded twisted-
pair or screened unshielded twisted-
pair cable with a core of 0.12 mm
min.
Check the length of the encoder
cable.
Check if the encoder cable is bent
and the sheath is damaged.
Check if the encoder cable is bun-
dled with a high-current line or near
a high-current line.
Check if the machines are correctly
grounded.
Check if there is noise interference
on the I/O signal line from the
encoder.
Check if vibration from the machine
occurred or servomotor installation
is incorrect (mounting surface accu-
racy, fixing, alignment, etc.).
−
−
Check the error detection section of
the host controller.
Check if the host controller is exe-
cuting data parity checks.
Check noise in the cable between
the SERVOPACK and the host con-
troller.
Check the external power supply
(+24 V) voltage for the input signal.
Check if the overtravel limit switch
operates properly.
Check if the overtravel limit switch
is wired correctly.
Check the settings for parameters
Pn590 and Pn591.
Check the fluctuation of the exter-
nal power supply (+24 V) voltage
for the input signal.
Check if the overtravel limit switch
operates correctly.
Check if the overtravel limit switch
wiring is correct. (check for dam-
aged cables or loose screws.)
Check if the P-OT signal is allo-
cated in Pn590.3.
Check if the N-OT signal is allo-
cated in Pn591.3.
−
−
Corrective Actions
Use the specified encoder cable.
2
The encoder cable must be no more
than 10 m.
Replace the encoder cable and cor-
rect the cable layout.
Correct the cable layout so that no
surge is applied.
Ground machines correctly, and
prevent diversion to the FG on the
encoder side.
Take measures against noise in the
encoder wiring.
Reduce vibration from the machine,
or secure the servomotor installa-
tion.
Replace the servomotor.
Replace the SERVOPACK.
Correct the error detection section
of the host controller.
Execute a multiturn data parity
check.
Take measures against noise, and
again execute a multiturn data par-
ity check.
Correct the external power supply
(+24 V) voltage.
Correct the overtravel limit switch.
Correct the overtravel limit switch
wiring.
Correct the settings for parameters
Pn590 and Pn591.
Stabilize the external power supply
(+24 V) voltage.
Correct the overtravel limit switch.
Correct the overtravel limit switch
wiring.
If another signal is allocated in
Pn590.3, allocate P-OT.
If another signal is allocated in
Pn591.3, allocate N-OT.
Install the limit switch at the
appropriate position.
Install the overtravel limit switch at
the appropriate position.
(cont'd)