YASKAWA UAK series User Manual page 300

11 Inspection, Maintenance, and Troubleshooting
Problem
Position Error
(Without Alarm)
Motor Overheated
11-46
Probable Cause
Noise interference due to incorrect
encoder cable specifications
Noise interference due to length of
encoder cable
Noise influence due to damaged
encoder cable
Excessive noise to encoder cable
The FG potential varies because of
influence from machines on the ser-
vomotor side such as the welder.
SERVOPACK pulse count error due
to noise
Excessive vibration and shock to
the encoder
Unsecured coupling between
machine and motor
Noise interference due to improper
I/O signal cable specifications
Noise interference due to length of
I/O signal cable
Encoder failure (The pulse count
does not change.)
SERVOPACK failure
Ambient operating temperature too
high
Motor surface dirty
Motor overloaded
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 its 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 the I/O signal line from the
encoder is influenced by noise.
Check if vibration from the machine
occurred or motor installation is
incorrect (mounting surface accu-
racy, fixing, alignment, etc.).
Check if a position error occurs at
the coupling between machine and
motor.
The I/O signal 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 I/O signal cable length.
−
−
Measure the motor ambient operat-
ing temperature.
Visually check the surface.
Check the load status with monitor.
Corrective Actions
Use the specified encoder cable.
2
The encoder cable must be no more
than 20 m.
Replace the encoder cable and mod-
ify the encoder cable layout.
Change the encoder cable layout so
that no surge is applied.
Properly ground the machines
encoder FG.
Take measures against noise in the
encoder wiring.
Reduce the machine vibration or
mount the motor securely.
Secure the coupling between the
machine and motor.
Use input signal cable with the
specified specifications.
2
The I/O signal cable length must be
no more than 3 m.
Replace the motor.
Replace the SERVOPACK.
Reduce the ambient operating tem-
perature to 40°C or less.
Clean dust and oil from the surface.
If overloaded, reduce load or
replace with larger capacity SER-
VOPACK and motor.
(cont'd)