YASKAWA SGDS Sigma III Series User Manual page 315

10 Inspection, Maintenance, and Troubleshooting
10.1.5 Troubleshooting for Malfunction without Alarm Display
Symptom
Overtravel An overtravel signal does not change
(OT) {(P-OT (1NC-7) or N-OT (1CN-8) is
at "H"}.
(Movement
over the zone
specified by
the host con-
troller)
The overtravel signal does not
operate normally (P-OT or N-OT
signal sometimes changes).
Incorrect P-OT signal selection
Incorrect servomotor stop method
selection
Improper LS overtravel position
setting
Noise interference due to improper
encoder cable specifications
Noise interference because the
encoder cable distance is too long.
Noise influence due to damaged
encoder cable
Excessive noise interference to
encoder cable
FG varies because machine such as
welder installed on servomotor side.
SERVOPACK pulse count error due
to noise
Excessive vibration and shock to the
encoder
Encoder fault
SERVOPACK fault
Position error Unsecured coupling between
machine and servomotor
(without
alarm)
Noise interference due to improper
input signal cable specifications
Encoder fault (pulse count does not
change)
Servomotor Ambient temperature too high
Overheated
Servomotor surface dirty
Overloaded
10-24
Table 10.5 Troubleshooting for Malfunction without Alarm Display (Cont'd)
Cause
Check if the voltage of input signal external
power supply (+24 V) is correct.
Check if the overtravel limit switch (SW)
operates properly.
Check if the overtravel limit switch (SW) is
connected correctly.
Check the fluctuation of the input signal
external power supply (+24 V) voltage.
Check if the overtravel limit switch (SW)
activate correctly.
Check if the overtravel limit switch wiring
is correct. (check for damaged cables or
loosen screws.)
Check the P-OT signal selection Pn50A.3.
Check the N-OT signal selection Pn50B.0.
Check if "coast to stop" in servo OFF status
is selected.
Check if "coast to stop" in torque control
mode is selected.
The distance to the LS overtravel (OT) is
too short considering the coasting distance.
The encoder cable specifications must be:
Tinned annealed copper twisted-pair or
twisted-pair shielded wire with core 0.12
2
mm (0.0002 in
The wiring distance must be 20 m(65.6 ft)
max.
Check if the encoder cable is bent or its
sheath is damaged.
Check if the encoder cable is bundled with a
high-current line or near high-current line.
Check if grounding of the machine is made
correctly.
Check if the signal line from the encoder is
influenced by noise.
Machine vibration occurred or servomotor
mounting such as mounting surface
precision, fixing, alignment is incorrect.
An encoder fault occurred.
A SERVOPACK fault occurred.
Check if a position error occurs at the
coupling between machine and servomotor.
The input signal cable specifications must
be:
Twisted-pair or twisted-pair shielded wire
with core 0.12 mm
tinned annealed copper twisted wire.
An encoder fault occurred. (pulse count
does not change)
Measure servomotor ambient temperature.
Check visually.
Run under no load.
Inspection
: Turn OFF the servo system before executing operations.
Connect to the external +24 V power supply.
Correct the overtravel limit SW.
Correct the overtravel limit SW wiring.
Stabilize the external +24 V power supply voltage.
Adjust the overtravel limit SW so that it operates
correctly.
Correct the overtravel limit SW wiring.
Correct the setting of P-OT signal selection Pn50A.3.
Correct the setting of N-OT signal selection Pn50B.0.
Check Pn001.0 and Pn001.1.
Check Pn001.0 and Pn001.1.
Correct the LS OT position.
Use encoder cable with the specified specifications.
2
) min.
The encoder cable distance must be within the specified
range.
Correct the encoder cable layout.
Change the encoder cable layout so that no surge is
applied.
Ground the machine separately from PG side FG.
Take a measure against noise for the encoder wiring.
Reduce the machine vibration or mount the servomotor
securely.
Replace the servomotor.
Replace the SERVOPACK.
Secure the coupling between the machine and
servomotor.
Use input signal cable with the specified specifications.
2 2
(0.0002 in ) min. and
Replace the servomotor.
Reduce ambient temperature to 40°C (104 °F) max.
Clean dust and oil from motor surface.
Reduce load or replace with larger capacity servomotor.
Corrective Actions