YASKAWA SGMJV User Manual page 331

9 Troubleshooting
Problem
Absolute Encod-
er Position Differ-
ence 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.)
9-32
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.
Host controller rotational serial data
reading error
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 to see if the machine is
vibrating.
Also, check the installation condi-
tions of the servomotor (flange face
accuracy, anchoring condition, and
centering).
−
−
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.
Corrective Actions
Use the specified encoder cable.
2
The encoder cable must be no more
than 50 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.
Perform a parity check on the rota-
tional serial data.
Implement measures against noise
and perform a parity check on the
rotational serial data again.
(cont'd)