Description of Fault Codes
‑77‑
Cause
Confirming Method
Solution
3. The encoder Z signal is
being disturbed.
Check the cable layout on
site: Check whether ambient
devices are generating
disturbance and whether
multiple disturbance
sources such as variable‑
frequency devices are
present inside the cabinet.
Make servo drive stay in
"Rdy" status and rotate
motor shaft
counterclockwise (CCW)
manually and observer
whether H0b.17 (Eelectrical
angle) increases/decreases
smoothly. Turning one circle
corresponds to five 0–360°
(for Z series motors). For X
series motors, turning one
circle corresponds to four
0–360°. If H0b.17 changes
abnormally during motor
rotating, the encoder is
faulty. If no warning is
reported during rotation but
the servo drive reports a
warning during operation,
disturbance may be present.
It is recommended to use
the cables provided by
Inovance. For use of
customized cables, check
whether the customized
cable complies with
specifications and whether it
is a shielded twisted pair
cable. Route the motor
cables and encoder cables
through different routes.
Ensure the servo motor and
servo drive are grounded
properly. Check whether the
connectors at both ends of
the encoder are in good
contact and whether any pin
retracts.
4. The encoder is faulty.
Replace with a new encoder
cable. If the fault no longer
occurs after cable
replacement, the original
encoder cable is damaged.
Keep the motor at the same
position, and power on
several times and check the
value of H0b.17. The
electrical angle deviation
should be within ±30°.
Replace with a new encoder
cable. If the fault persists
after the encoder cable is
replaced, the encoder may
be faulty. In this case,
replace the servo motor.
● E939.0: Motor power cable failure
Cause
Confirming Method
Solution
Motor power cables are
broken or not connected.
Check the wiring of U/V/W
power cables.
1. Check whether the power
cables are disconnected
or in poor contact. Re‑
connect the power cables.
2. Replace the servo motor.
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