YASKAWA JUSP-MD D01A Series User Manual page 316

Problem 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.
Abnormal Noise
Excessive noise to the encoder
from Servomotor
cable.
(Continued from
previous page.)
The FG potential varies because of
influence from machines on the ser-
vomotor side, such as the welder.
A multi-winding drive unit pulse
counting error occurred due to noise
interference.
Excessive vibration and shock to
the encoder
An encoder fault occurred.
Unbalanced servo gains
Speed loop gain value (Pn100) too
high.
Servomotor
Vibrates at Position loop gain value (Pn102)
Frequency of too high.
Approx. 200 to
400 Hz.
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)
High Motor Speed
too high
Overshoot on
Starting and
Incorrect speed loop integral time
Stopping
constant (Pn101)
Incorrect moment of inertia ratio
data (Pn103)
The torque reference is saturated.
9.3 Troubleshooting Malfunction Based on Operation and Conditions of the Servomotor
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 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.
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.
• Use a double-shielded encoder
cable.
Properly ground the machines to
separate from the encoder FG.
Take measures against noise in the
encoder wiring.
Reduce vibration from the machine,
or secure the servomotor installa-
tion.
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.
(cont'd)
9
9-27