YASKAWA Sigma-V Series User Manual page 279

8 Troubleshooting
Problem
Abnormal Noise
from Servomotor
(Continued from
previous page.)
Servomotor
Vibrates at
Frequency of
Approx. 200 to
400 Hz.
High Motor Speed
Overshoot on
Starting and
Stopping
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.)
8-30
Probable Cause
Excessive vibration and shock to
the encoder
An encoder fault occurred.
Unbalanced servo gains
Speed loop gain value (Pn100) too
high.
Position loop gain value (Pn102)
too high.
Incorrect speed loop integral time
constant (Pn101)
Incorrect moment of inertia ratio
(Pn103)
Unbalanced servo gains
Speed loop gain value (Pn100) too
high
Position loop gain value (Pn102)
too high
Incorrect speed loop integral time
constant (Pn101)
Incorrect moment of inertia ratio
data (Pn103)
The torque reference is saturated.
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.
A multi-winding drive unit pulse
counting error occurred due to noise
interference.
Investigative Actions
Turn OFF the servo system. Check
if vibration from the machine
occurred or servomotor installation
is incorrect (mounting surface accu-
racy, fixing, alignment, etc.).
−
Check to see if the servo gains have
been correctly adjusted.
Check the speed loop gain (Pn100).
Factory setting: Kv = 40.0 Hz
Check the position loop gain
(Pn102).
Factory setting: Kp = 40.0/s
Check the speed loop integral time
constant (Pn101).
Factory setting: Ti = 20.0 ms
Check the moment of inertia ratio
(Pn103).
Check to see if the servo gains have
been correctly adjusted.
Check the speed loop gain (Pn100).
Factory setting: Kv = 40.0 Hz
Check the position loop gain
(Pn102).
Factory setting: Kp = 40.0/s
Check the speed loop integral time
constant (Pn101).
Factory setting: Ti = 20.0 ms
Check the moment of inertia ratio
(Pn103).
Check the torque reference wave-
form.
Turn OFF the servo system. 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.
Turn OFF the servo system. Check
the length of the encoder cable.
Turn OFF the servo system. Check
if the encoder cable is bent and the
sheath is damaged.
Turn OFF the servo system. Check
if the encoder cable is bundled with
a high-current line or near a high-
current line.
Turn OFF the servo system. Check
if the machines are correctly
grounded.
Turn OFF the servo system. Check
if there is noise interference on the
I/O signal line from the encoder.
Corrective Actions
Reduce vibration from the machine,
or secure the servomotor installa-
tion.
Turn OFF the servo system.
Replace the servomotor.
Execute the advanced autotuning.
Reduce the speed loop gain
(Pn100).
Reduce the position loop gain
(Pn102).
Correct the speed loop integral time
constant (Pn101).
Correct the moment of inertia ratio
(Pn103).
Execute the advanced autotuning.
Reduce the speed loop gain
(Pn100).
Reduce the position loop gain
(Pn102).
Correct the speed loop integral time
constant (Pn101).
Correct the moment of inertia ratio
(Pn103).
Use a mode switch.
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.
• Use a double-shielded encoder
cable.
Ground machines correctly, and
prevent diversion to the FG on the
encoder side.
Take measures against noise in the
encoder wiring.
(cont'd)